51 05-1 61 

Solar Thermal Power Systems Project 

Parabolic Dish Systems Development 

DOE/JPL-1060-89 

Distribution Category UC-62 

:??ASB-cF-175920) SUi'lEAfiY A5SE22MXNT OF 1137-1 2049 

SCLAri TtillbMAL PEhiEECLIC bISH 'IECENOLOGY FOB 

ELEC'IdiCAL PDKEfi GENEEALIth (:et Ecopuisioll 

Lab.) 1Lf: p CSCL 106 Uiiclas 

G3/44 44935 

Assessment of Solar 

Generation 

Dish Technology 

. -. 

'\ 

P.L. Panda - 

T. Fujita 

J.W. Lucas 

September 15, 1985 

Prepared for 

U.S. Department of Energy 

Through an Agreement with 

National Aeronautics and Space Administration 

by 

Jet Propulsion Laboratory 

California Institute of Technology 

Pasadena, California 

JPL Publication 85-55 
5 105-1 6 1 

Solar Thermal Power Systems Project 

Parabolic Dish Systems Development 

DOEIJPL-1060-89 

Distribution Category UC-62 

Summary Assessment of Solar 

Thermal Parabolic Dish Technology 

for Electrical Power Generation 

P.L. Panda 

T. Fujita 

J.W. Lucas 

September 15, 1985 

Prepared for 

US. Department of Energy 

Through an Agreement with 

National Aeronautics and Space Administration 

by 

Jet Propulsion Laboratory 

California Ins ti tu te of Technology 

Pasadena, California 

JPL Publication 85-55 
Prepared by the Jet Propulsion Laboratory, California Institute of Technology, 

for the U.S. Department of Energy through an agreement with the National 

Aeronautics and Space Administration. 

The JPL Solar Thermal Power Systems Project is sponsored by the U.S. 

Department of Energy and is part of the Solar Thermal Program to develop lowcost solar thermal and electric power plants. 

This report was prepared as an account of work sponsored by an agency of the 

United States Government. Neither the United States Government nor any 

agency thereof, nor any of their employees, makes any warranty, express or 

implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process 

disclosed, or represents that its use would not infringe privately owned rights. 

Reference herein to any specific commercial product, process, or service by trade 

name, trademark, manufacturer, or otherwise, does not necessarily constitute or 

imply its endorsement, recommendation, or favoring by the United States 

Government or any agency thereof. The views and opinions of authors 

expressed herein do not necessarily state or reflect those of the United States 

Government or any agency thereof. 
ABSTRACT 

An assessment is provided of solar thermal parabolic dish technology for 

electrical power generation. 

program undertaken by the Jet Propulsion Laboratory for the U.S. Department of 

Energy and covers the period from the initiation of the program in 1976 

through mid-1984. The program was founded on developing components and 

subsystems that are integrated into parabolic dish power modules for test and 

evaluation. The status of the project is summarized in terms of results 

obtained through testing of modules, and the implications of these findings 

are assessed in terms of techno-economic projections and market potential. 

The techno-economic projections are based on continuation of an evolutionary 

technological development program and are anchored to the accomplishments of 

the program as of mid-1984. 

summarized for each major subsystem including concentrators, receivers, and 

engines. The ramifications of these accomplishments are assessed in the 

context of developmental objectives and strategies. 

The assessment is based on the development 

The accomplishments of the development effort are 

iii 
ACKNOWLEDGMENTS 

The authors wish to thank the following individuals, whose contributions 

and comments were greatly appreciated: M. Alper, J. Bowyer, W. Carley, 

W. Gates, V. Gray, H. Holbeck, L. Jaffe, T. Kiceniuk, F. Livingston, 

A. Marriott, B. Nesmith, W. Owen, W. Revere, J. Stallkamp, and T. Thostesen. 

Appreciation also goes to those who managed the Solar Thermal Power 

Systems Project throughout most of its existence at the Jet Propulsion 

Laboratory (JPL): V.C. Truscello, Project Manager, and Assistant Project 

Managers J.C. Becker, J.W. Lucas, and A.T. Marriott. Dr. J.W. Lucas also 

served as Project Manager during the JPL phase-out effort and transition 

activity with Sandia National Laboratories. 

This report was prepared by the Jet Propulsion Laboratory, California 

Institute of Technology, for the U.S. Department of Energy through an agreement with the National Aeronautics and Space Administration (NASA Task RE-152, 

Amendment 327; DOE/ALO/NASA Interagency Agreement No. DE-AM04-80ALl3137). 

iv 
AGT 

DOE 

EPRI 

ESOR 

FACC 

GE 

IPH 

JPL 

LeRC 

NASA 

O&M 

ORC 

PCM 

PCU 

PDC 

PDTS 

PKI 

PON 

RFP 

SABC 

SAGT 

SCSE 

SERI 

SNETCO 

SNLA 

TBC 

TPS 

USAB 

ACRONYMS 

advanced gas turbine 

U.S. Department of Energy 

Electric Power Research Institute 

Experimental Solar-Only Receiver 

Ford Aerospace and Communications Corporation 

General Electric Company 

Industrial Process Heat 

Jet Propulsion Laboratory 

NASA Lewis Research Center 

National Aeronautics and Space Administration 

Operating and Maintenance 

Organic Rankine Cycle 

Phase-Change Material 

Power Conversion Unit or Power Conversion Subsystem (PCS), 

i.e., engine plus alternator and/or rectifier 

Parabolic Dish Concentrator 

Parabolic Dish Test Site 

Power Kinetics, Inc. 

Program Opportunity Notice 

Request for Proposal 

subatmospheric Brayton cycle 

Solarized Advanced Gas Turbine 

Small Community Solar Thermal Power Experiment 

Solar Energy Research Institute 

Southern New England Telephone Company 

Sandia National Laboratories, Albuquerque, New Mexico 

test bed concentrator 

Solar Thermal Power Systems Project at JPL 

United Stirling AB of Sweden 

V 
CONTENTS 

I . INTRODUCTION ............................ 1-1 

A . THE NATIONAL SOLAR THERMAL PROGRAM ............. 1-1 

B . JET PROPULSION LABORATORY’S ROLE .............. 1-1 

C . HISTORY OF SOLAR THERMAL WORK AT JPL ............ 1-2 

D . CURRENT MARKET PROJECTIONS ................. 1-6 

E . PARABOLIC DISH-ELECTRIC SYSTEM DESCRIPTION ......... 1-6 

I1 . COMPONENT DEVELOPMENT STATUS ................... 2-1 

A . CONCENTRATORS ....................... 2-1 

1 . Concentrator Characteristics ............. 2-1 

2 . Concentrator Optics ................. 2-1 

3 . Development Strategy ................. 2-4 

4 . Development of Candidate Concepts .......... 2-7 

a . Test Bed Concentrator .............. 2-8 

b . Parabolic Dish Concentrator No . 1 ........ 2-12 

c . Parabolic Dish Concentrator No . 2 ........ 2-16 

d . Advanco Concentrator .............. 2-20 

e . LaJet Concentrator ................ 2-20 

5 . Other Concepts Tested Under the DOE 

Solar Thermal Program ................ 2-23 

a . Raytheon and General Electric/Shenandoah .... 2-23 

b . Omnium-G .................... 2-23 

c . Power Kinetics. Inc ............... 2-23 

6 . Concentrator Technology Assessment Summary ...... 2-25 

B . RECEIVERS ......................... 2-26 

1 . Receiver Characteristics ............... 2-26 

2 . Optical and Thermal Characteristics ......... 2-26 
3 . Development Strategy ................. 2-28 

4 . Development of Candidate Concepts .......... 2-30 

a . Garrett Air Brayton Receiver .......... 2-31 

b . Garrett Steam Rankine Receiver ......... 2-34 

c . FACC Organic Rankine Receiver .......... 2-37 

d . Fairchild Stirling Receiver ........... 2-39 

e . General Electric Stirling Receiver ....... 2-40 

f . Sanders Air Brayton Receiver .......... 2-42 

g . Experimental Solar-Only Receivers ........ 2-43 

5 . Receiver Technology Assessment Summary ........ 2-44 

C . POWER CONVERSION UNITS ................... 2-46 

1 . Engine Characteristics ................ 2-46 

2 . Strategy for "Solarization" ............. 2-47 

3 . Adaptation and Testing of Principal Engine Cycles . . 2-49 

a . Conceptual Design Studies (Rankine and 

Brayton Cycles) ................. 2-49 

b . Steam Rankine-Cycle Engine ........... 2-49 

c . Organic Rankine-Cycle Engine .......... 2-53 

d . Air Brayton-Cycle Engine ............ 2-58 

e . Subatmospheric Brayton-Cycle Engine ....... 2-62 

f . Stirling-Cycle Engine .............. 2-63 

4 . Engine Technology Assessment Summary ......... 2-65 

D . ENERGY STORAGE ....................... 2-67 

1 . Buffer Storage .................... 2-69 

2 . Battery Storage ................... 2-70 

3 . Thermal Energy Storage ................ 2-70 

viii 
E. TRANSPORT . . . . . . . . . . . . . . . . . . . . . . . . . 2-73 

1. Thermal Transport . . . . . . . . . . . . . . . . . . 2-74 

2. Thermochemical Transport (and Storage) . . . . . . . . 2-75 

3. Electric Transport . . . . . . . . . . . . . . . . . . 2-75 

F. CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . 2-77 

111. CURRENT STATUS OF MODULE DEVELOPMENT . . . . . . . . . . . . . . . 3-1 

A. RANKINEMODULE. . . . . . . . . . . . . . . . . . . . . . . 3-1 

1. Module Description . . . . . . . . . . . . . . . . . . 3-1 

2. System Experiment (Small Community Solar Thermal 

Power Experiment) . . . . . . . . . . . . . . . . . . 3-1 

B. STIRLING MODULE . . . . . . . . . . . . . . . . . . . . . . 3-5 

1. Vanguard Project . . . . . . . . . . . . . . . . . . . 3-5 

2. McDonnell Douglas Dish/Stirling Venture . . . . . . . 3-7 

C. BRAYTON MODULE . . . . . . . . . . . . . . . . . . . . . . . 3-9 

IV. SYSTEM PERFORMANCE AND ECONOMIC PROJECTIONS . . . . . . . . . . . 4-1 

.. 5-1 

APPENDIX: DETAILED ASSESSMENT REPORTS PUBLISHED AT THE CLOSE OF 

THE JPL SOLAR THERMAL POWER SYSTEMS PROJECT . . . . . . . . A-1 

Figures 

1-1. Elements of the Early Solar Thermal Power Systems Project . 1-3 

1-2. Test Bed Concentrators at the Parabolic Dish Test Site . . 1-4 

1-3. TPS Project Engineering Experiments . . . . . . . . . . . . 1-5 

1-4. Principal Components of a Parabolic Dish-Electric Module . 1-7 

1-5. Rendering of a Typical Parabolic Dish-Electric 

Power Plant . . . . . . . . . . . . . . . . . . . . . . . . 1-8 

2-1. Concentrator Configurations . . . . . . . . . . . . . . . . 2-2 

ix 
2.2 . Concentrator Optics ................... 2-3 

2.3 . TBC Mirror Facet ..................... 2-11 

2.4 . Close-up of Flux Mapper from Outer End .......... 2-11 

2.5 . TBCs During Component Testing at the PDTS ........ 2-12 

2.6 . General Electric Concept for a 

First-Generation Concentrator .............. 2-13 

2.7 . PDC-1 Concentrator Panel During Testing in the JPL 

25-ft Space Simulator .................. 2-15 

2.8 . PDC-1 at the Parabolic Dish Test Site .......... 2-16 

2.9 . Diagnostic Photograph of PDC-1 .............. 2-17 

2.10 . Model of Acurex Advanced Concentrator Design (PDC-2) ... 2-18 

2.11 . Cross-Sectional Diagram of Acurex Concentrator Gore ... 2-19 

2.12 . Acurex Cellular-Glass-Type Gores Delivered to JPL .... 2-19 

2.13 . Model of Advanco Concentrator .............. 2-21 

2.14 . LaJet 38-m2 Concentrator ................ 2-22 

2.15 . Other Concentrators Tested under the DOE 

Solar Thermal Program .................. 2-24 

2.16 . Receiver Configurations ................. 2-27 

2.17 . Proposed Air Brayton Receiver Designs .......... 2-32 

2.18 . Proposed Steam Rankine Receiver Designs ......... 2-33 

2.19 . Cross-Sectional Diagram of the Garrett Air 

Brayton Receiver ..................... 2-34 

2.20 . Garrett Prototype Air Brayton Receiver .......... 2-35 

2.21 . Cross-Sectional Diagram of the Garrett Steam 

Rankine Receiver ..................... 2-36 

2.22 . Garrett Prototype Steam Rankine Receiver ......... 2-36 

2.23 . Garrett Receiver Producing Steam During Testing 

at the Focal Plane of a TBC ............... 2-37 

2.24 . Cross-Sectional Diagram of the FACC Organic Receiver ... 2-38 

2.25 . FACC Organic Receiver Prior to Engine Integration .... 2-38 

I X 
2.26 . 

2.27 . 

2.28 . 

2.29 . 

2.30 . 

2.31 . 

2.32 . 

2.33 . 

2.34 . 

2.35 . 

2.36 . 

2.37 . 

2.38 . 

2.39 . 

2.40 . 

2.41 . 

2.42 . 

2.43 . 

2.44 . 

2.45 . 

2.46 . 

2.47 . 

Fairchild ReceiverIStirling Engine Quadrant 

and Burner ....................... 2-40 

GE Heat Pipe Stirling Receiver Concept ......... 2-41 

A 30-deg Sector of Ceramic Honeycomb Matrix ....... 2-42 

Sanders Ceramic Receiver Test Unit ........... 2-43 

ESOR-I11 ........................ 2-45 

Conceptual Steam Rankine Engine Configurations ...... 2-50 

Conceptual Open- and Closed-Cycle Brayton 

Engine Configurations .................. 2-51 

Carter 5-kWe Single-Cylinder Engine Under Test ..... 2-53 

ORC Power Conversion Assembly 

with Detail of the Turbine/Alternator/Pump ....... 2-55 

ORC Qualification Testing at Barber-Nichols ....... 2-56 

The ORC ReceiverIEnginelAlternator Mounted 

on a TBC for Solar Testing ............... 2-57 

Measured Performance of the ORC Test Unit ........ 2-58 

Initial Garrett Air Brayton Engine Concept Based 

on the GTP 36-51 Gas Turbine .............. 2-59 

Conceptual Drawing of the Garrett Solarized Advanced 

c-2~ T-rhifi~ Rrrcpd nn the ACT 101 ............ 2-60 

Garrett Solarized Advanced Gas TurbineISanders Receiver 

Test Unit ........................ 2-61 

Subatmospheric Brayton-Cycle Engine ........... 2-61 

USAB Stirling Engine with 

Integral Receiver .................... 2-63 

Bench Testing of Stirling EngineIAlternator in 

Inverted Position .................... 2-64 

Stirling Engine Generating Electricity 

at the TBC's Focal Plane ................ 2-66 

Stirling Measured Performance .............. 2-67 

Insolation Versus Demand Load .............. 2-68 

Battery Storage System for a Dish-Electric Power 

Plant Using an AC-Link Transport Approach ....... 2-71 

xi 
2.48 . Thermal Storage Concept for a Cluster of 

Dish Collectors ..................... 2-73 

2.49 . Artist's Concept of a Dish Collector Thermal 

Transport System .................... 2-74 

2.50 . Parabolic Dish-Electric Transport Concept ........ 2-75 

2.51 . Conceptual Block Diagram for a Solar Generation 

Unit Using a DC-Link Approach with an AC Generator 

and Rectifier ...................... 2-76 

3.1 . Small Community Experiment Site Selection ........ 3-2 

3.2 . Simplified Hardware Schematic for the Small 

Community Experiment .................. 3-3 

3.3 . Drawing of the Vanguard Dish-Stirling Module 

(Elevation View) .................... 3-5 

3.4 . Fully Assembled Vanguard Module Installed at the 

Rancho Mirage Test Site ................. 3-7 

3.5 . Fully Assembled Brayton Developmental Test Module .... 3-10 

4.1 . Annual Production Rate versus Initial 

Plant Price in $/kWe .................. 4-5 

4.2 . Annual Operation and Maintenance Cost 

for a 5-MWe Plant .................... 4-6 

4.3 . 1990 Market Potential for Cost-Competitive Solar 

Thermal Parabolic Dish Systems in Grid-Connected 

Applications ...................... 4-7 

4. . 1990 Parabolic Dish Breakeven Costs: O&M 

Sensitivity for Medium Fuel-Price Scenario ....... 4-8 

Tables 

1.1 . Solar Thermal Program Laboratory Network ........ 1-1 

2.1 . Concentrator Characteristics .............. 2-5 

2.2 . TBC Key Design Requirements ............... 2-9 

2.3 . Materials Selected for TBC Mirror Fabrication ...... 2-10 

2.4 . Receivers Developed by the TPS Project ......... 2-29 

2.5 . First-Generation Receiver Preliminary Designs ...... 2-31 

xi i 
2-6. 

2-7. 

2-8. 

2-9. 

2-10. 

2-11. 

3-1. 

3-2. 

3-3. 

4-1. 

4-2. 

4-3. 

United Stirling Experimental Solar-Only Receivers 

Tested at the PDTS . . . . . . . . . . . . . . . . . . . 2-44 

Results of ESOR-IIA and IIB Testing with Different 

Concentrator Alignments . . . . . . . . . . . . . . . . . 2-45 

Engines Modified and/or Tested 

for Dish-Electric Modules . . . . . . . . . . . . . . . . 2-48 

Conceptual Design Study Contracts of Rankine- and 

Brayton-Cycle Engines . . . . . . . . . . . . . . . . . . 2-52 

Candidate Storage Media for Dish-Mounted Receivers . . . 2-70 

Cost and Performance of Advanced Electrochemical 

Storage Batteries . . . . . . . . . . . . . . . . . . . . 2-72 

Efficiency and Performance Goals for the Proposed 

Small Community Experiment at Osage City . . . . . . . . 3-4 

Characteristics of the Vanguard Module . . . . . . . . . 3-6 

Vanguard Operating Parameters for June 1984 . . . . . . . 3-8 

Analysis of Performance of Various Parabolic 

Dish Modules for Four Geographic Locations . . . . . . . 4-2 

Breakeven Costs for Early Parabolic Dish 

Installations in California . . . . . . . . . . . . . . . 4-4 

Summary of 5-MWe Plant Characteristics . . . . . . . . . 4-4 

xiii 
SECTION I 

INTRODUCTION 

A. THE NATIONAL SOLAR THERMAL PROGRAM 

Solar thermal technologies produce heat from the sun's radiant energy 

for a variety of uses including electric power generation, process heat for 

industrial and agricultural applications, and photo/thermochemical production. 

The U.S. Department of Energy's (DOE) Solar Thermal Program, to implement 

Congressional legislation enacted in 1974 that established a national solar 

energy policy, instituted specific objectives including (1) completion of 

research and development required to support the near-term needs of industry 

and utilities for electricity, cogeneration, and process heat applications and 

(2) completion of research and development needed to expand the technology 

base of solar thermal energy into new industrial application areas, such as 

the production of fuels and chemicals. The strategy for meeting these objectives is "a program of government-sponsored and cost-shared research and 

development aimed at achieving a sufficient level of technical maturity for 

the various solar thermal technologies [so] that decision makers within the 

private sector will find acceptable risks should they choose to manufacture, 

market, or use the technologies" (Reference 1). 

B. JET PROPULSION LABORATORY'S ROLE 

Technical direction of the Solar Thermal Program is carried out for DOE 

by a network of national laboratories, which manage work done by private 

industry under contract or in cost-shared partnership (Table 1-1). From 

Table 1-1. Solar Thermal Program Laboratory Network (Circa 1983) 

Organization Area of Responsibility 

DOE San Francisco Operations Fuels and Chemicals 

Office, San Francisco, California 

Jet Propulsion Laboratory, 

Pasadena, California 

Parabolic Dish-Electric Module 

Deve 1 o pmen t 

Sandia National Laboratories, Parabolic Trough and Thermal Dish 

Albuquerque, New Mexico Development 

Sandia National Laboratories, Central Receiver Development 

Livermore, California 

Solar Energy Research Institute, Materials and Concentrator Research 

Golden, Colorado 

1-1 
1977 through 1983, the Jet Propulsion Laboratory (JPL) was responsible 

primarily for the development of parabolic dish-electric modules. 

overall assessment document describes and summarizes all activities carried 

out at JPL under the DOE Solar Thermal Program during those years. During 

FY 1984, this work was phased out at JPL and at the direction of DOE was 

transferred to Sandia National Laboratories in Albuquerque (SNLA). This 

document, in addition to approximately 30 detailed reports and a complete 

bibliography, were published by JPL as part of the Project phaseout efforts. 

JPL also will continue to perform related Program tasks for SNLA. 

This 

Specifically, this overall assessment provides a narrative of the 

history and evolution of solar thermal work at JPL (Section I.C,D); a general 

system description (Section 1.E); development and/or testing of dish system 

components including concentrators, receivers, power conversion units, energy 

transport, energy storage, and controls (Section 11); current status of module 

development (Section 111); and system performance and economic projections 

(Section IV). 

C. HISTORY OF SOLAR THERMAL WORK AT JPL 

The Solar Thermal Power Systems (TPS) Project at JPL was initiated in 

1976 to develop solar thermal systems capable of producing thermal and 

electrical energy in a reliable and cost-effective manner. Studies conducted 

during that year under sponsorship of the National Aeronautics and Space 

Administration (NASA) Office of Energy Programs established point-focusing 

distributed receiver systems as a solar thermal approach with the potential 

for producing low-cost energy. From 1977 through the end of 1983, the TPS 

Project continued research and development of this technology as part of the 

national Solar Thermal Program funded by DOE'S Division of Solar Thermal 

Technology. 

The attractiveness of these point-focusing devices (called parabolic 

dishes because of the parabolic shape of the reflector) lies in their inherent 

modularity, the potential for high conversion efficiency via high concentration 

and high operating temperatures, two-axis tracking capability for maximum 

radiation collection, heat production over a wide temperature range, and massproduction possibilities. 

Early Project goals included (1) the demonstration of the potential, in 

mass production quantities, for producing electricity or heat by pointfocusing devices at a cost that is economically competitive with conventional 

alternatives and (2) the development of cost-effective point-focusing 

distributed receiver technology necessary for accelerated market penetration 

of small solar thermal power systems (Reference 2). 

Initial studies indicated the existence of a small near-term market 

(1990 to 2000 time frame), known as the "isolated loads market," where the 

user is isolated from the electric utility distribution grid. 

tion is typical of small municipal Communities, isolated industrial sites, 

other isolated sites (i.e., rural/agricultural communities, islands, and 

military installations), and cottage industries in developing countries. 

Although this market is small (300 to 1000 MWe/year) when compared to the 

grid-connected utility market, up to 10,000 parabolic dishes per year would be 

This applica1-2 
\ 

required to meet this need -- a quantity justifying the use of mass production 

techniques for dish fabrication. 

The projected far-term market for parabolic dishes was the U.S. gridconnected utility market. It was estimated that almost all utilities in the 

continental United States will be connected to an electric distribution grid 

by the end of this decade. For dishes to compete in the low-cost gridconnected market by the year 2000, they were to benefit from the technological 

experience and mass production techniques achievable through the successful 

penetration of the higher-cost isolated markets. 

Because of the fact that two market phases (near- and far-term) were 

envisioned, the TPS Project structured its Technology Development Element 

(Figure 1-1) on the basis of two types of hardware development: firstgeneration and second-generation. First-generation equipment would entail 

fewer developmental risks and would permit the early introduction of dish 

power plants into the isolated loads market. The far-term market would be 

penetrated by dish systems using second-generation technology. These modules 

would benefit from advanced engine technology, improved system efficiency, 

innovative collector design, and increased production volume. 

As shown in Figure 1-1, the Technology Development Element of the early 

TPS Project was complemented by two parallel spheres of activity carried out 

under the Advanced Development Element and the Applications Development 

Element. Advanced Development was oriented toward research and development, 

emphasizing materials, component, and subsystem development. Resulting 

designs were engineered, fabricated, and tested in complete module 

configurations through the Technology Development Element. Power plant 

systems were then to be assembled and demonstrated under the third Project 

<I> THERMAL POWER 

\ SYSTEMS PROJE CT j 

ADVANCED TECHNOLOGY APPLICATIONS 

DEVELOPMENT \ DEVELOPMENT DEVELOPMENT 

COMPONENTS/ 

SUBSYSTEMS 

Feasibility 

Tests 

MODULES 

Technology 

Readiness 

Tests 

SYSTEMS 

System 

Readiness 

Tests 

Figure 1-1. Elements of the Early Solar Thermal Power Systems Project 

1-3 
element through a number of engineering system experiments in a variety of 

user applications. 

The development by the Project of both first- and second-generation 

technology began at approximately the same time: late 1978 and early 1979, 

respectively. First-generation activities would continue throughout 1983, 

while the evolution of second-generation hardware was to progress toward the 

end of the decade, during which the most promising candidates for advanced 

components and systems would be evaluated and tested. Two test bed concentrators (TBCs), built by E-Systems and installed in September 1979 at the JPL 

Edwards Test Station in the Mojave Desert, California, became the primary test 

vehicles (Figure 1-2) for characterizing and testing components and were also 

the first major pieces of equipment comprising what soon became known as the 

Parabolic Dish Test Site (PDTS). 

During 1980 and 1981, the Advanced Development Element was called the 

Research and Advanced Development Element and was responsible for work on 

advancedl components, including the Acurex advanced concentrator, the United 

Stirling P-40 engine, the Fairchild "hybrid" receiver, and the General 

Electric heat pipe receiver (each discussed in Section 11). This element also 

reported to the Solar Energy Research Institute (SERI) work done at JPL in the 

areas of advanced systems studies and component research and development, 

including transport and materials technology. In 1981, these efforts were 

transferred to SERI and are described in Reference 3. 

Figure 1-2. Test Bed Concentrators at the Parabolic Dish Test Site 

lThe term "advanced" is synonymous with "second-generat ion. I' 

1-4 
Three engineering experiments were the emphasis of the renamed 

Applications and Market Development Element during the early 1980s. 

experiments were to demonstrate the technical and economic readiness of dish 

systems in electric power and process heat applications (Reference 2). Market 

sectors for each of the experiments are shown in Figure 1-3. The third 

engineering experiment (EE No. 3) was carried out by JPL up to the operational 

phase: A collector built by Power Kinetics, Inc. (PKI), was prototype tested 

and installed at the process heat user site. At that time, management of the 

experiment was turned over to Sandia National Laboratories in Albuquerque (see 

Section II.A.5.c). EE No. 2 was abandoned due to funding constraints, and 

EE No. 1 became the major thrust of the Applications Element. This latter 

experiment evolved into the Small Community Solar Thermal Power Experiment 

No. 1 (SCSE-1) that was to be installed at Osage City, Kansas, in 1984. JPL's 

participation in this experiment (Section III.A.2) continued until the fall of 

1983 when DOE and Ford Aerospace and Communications Corporation (FACC), prime 

contractor for the organic Rankine-cycle (ORC) module,2 were unable to 

complete contractual arrangements .3 

These 

SMALL COMMUNITIES GOAL 

DISPERSED 

SITINGUTILITY LARGE 

MARKET UTI LlTlES 

BULK ELECTRIC 

REPOWERING 

TECHNICAL, 

AND 

ECONOMIC 

ISOLATED SMALL 

COMMUNITIES OPE RAT1 ONAL EE No. 2 ISOLATED SITES 

MILITARY 

DEVELOPING READ1 NESS 

COUNTRIES 

INDUSTRIAL 

MARKET 

PROCESSHEAT 

FUELS 

CHEMICALS 

0 COGENERATION 

ENHANCED OIL 

EE No. 3 0 TOTAL ENERGY 

RECOVERY 

Figure 1-3. TPS Project Engineering Experiments 

~~~ 

2The ORC module, development of which was managed by the TPS Project, was to 

be deployed as the dish system for SCSE-1. 

3DOE resolicited bids for the experiment in December 1983. 

1-5 
The original Technology Development Element became the TPS Project's 

main vehicle for developing and/or testing dish system components and for 

integrating them into complete dish-electric power modules. 

(i.e., concentrators, receivers, engines, transport, storage, and controls) 

are discussed in detail in Section 11. JPL's efforts to develop dish-electric 

modules based on Rankine-, Stirling-, and Brayton-cycle technology (discussed 

in Section 111) continued until transfer of activities to Sandia National 

Laboratories was completed in mid-1984. 

These components 

D. CURRENT MARKET PROJECTIONS 

Tests conducted through 1984 by the TPS Project of modules employing 

Brayton, organic-Rankine, and Stirling engines indicate that early modules 

achieve efficiencies of 15 to 25% (sunlight to net electricity produced). 

Using these results as a base and projecting improvements in efficiency, 

operation and maintenance, and concentrator design, module costs have been 

determined as a function of production volume (see Section IV). Present TPS 

studies indicate that dish-electric modules now in the test and evaluation 

stage would be competitive in the isolated load markets at production levels 

of 100 units per year and in the small community markets at 1000 per year if 

fossil fuel prices rise to the upper limit presently projected. If 

intermediate fuel price projections are used, further advances in technology 

leading to higher performance and lower cost would be necessary for 

dish-electric modules to be competitive in the energy markets (Reference 4). 

E. PARABOLIC DISH-ELECTRIC SYSTEM DESCRIPTION 

A point-focusing parabolic dish system comprises one or more autonomous 

energy-producing units called modules. Each module includes a collector, 

composed of a dish-shaped parabolic concentrator (that focuses the sun's rays) 

plus a receiver (heat absorber) that is mounted on the dish at its focal 

plane, and a power conversion unit integrally joined to the receiver 

(Figure 1-4). The concentrated sunlight enters the receiver opening 

(aperture) and heats a fluid (heat transfer fluid) circulating through the 

receiver. The hot fluid is used to produce electricity by the power 

conversion unit, which typically consists of a heat engine, alternator, and 

associated controls. A single parabolic dish module can achieve fluid 

temperatures from 300 to 15OOOC (572 to 2732OF) and can efficiently 

produce up to 25 kW of electricity. (Minimizing the cost of power results in 

a system about this size.) Each module is a complete electricityproducing unit, which can function autonomously either as an independent 

system or as part of a group of modules linked by an electrical transport 

network to form a power plant. Dish plants ranging in size from 10 kWe to 

10 We or higher output power could supply cost-effective electricity to 

isolated communities and other small communities that are not connected to 

utility grids and are forced to use high-cost conventional energy supplies. 

typical parabolic dish-electric power plant is shown in Figure 1-5. 

A 

1-6 
ORIGINAL PAGE IS 

OF POOR QUALITY 

POWER CONVERSION 

u N I T/REC E I v ER 

Figure 1-4. Principal Components of a Parabolic Dish-Electric Module 

Figure 1-5. Rendering of a Typical Parabolic Dish-Electric Power Plant 

1-7 
Dish collectors track the sun in two directions (axes) so that the 

reflective surface of the concentrator can continuously face the sun at the 

optimal angle for maximum heat collection. Two-axis tracking is usually 

accomplished by using an azimuth-elevation mount, where the concentrator 

rotates about a vertical axis for alignment in the azimuth direction and about 

a horizontal axis for elevation alignment. 

Two types of energy transport (thermal and/or electrical) can be used in 

dish systems, depending on the output of the plant. Thermal transport piping 

networks carry hot fluid directly from the receivers of a field of dish 

collectors to the end point of use (Reference 5). The collected heat energy 

can be used to power a central generator installed on the ground or it can be 

piped to a nearby industrial plant for a variety of process heat applications. 

Electrical energy is transported from a dish-electric module's engine/alternator 

by a transport system that collects electrical energy and either feeds it 

directly into the utility grid or, in some cases, inverts the output from 

module rectifiers before feeding it into the grid. A cogenerating dish plant 

can make use of both types of transport, thus increasing the versatility of 

dish power systems. 

The control system for a typical solar thermal power plant consists of 

the hardware, software, and facilities needed for operating and monitoring the 

entire power supply system. A central minicomputer or microprocessor performs 

the monitoring and control functions during start-up, shutdown, and operation 

under normal, intermittent, and emergency conditions (Reference 6). Completely autonomous operation is required to reduce operator costs to an 

acceptable level. 

Studies of thermal storage for use with dish systems have centered on 

the concept of latent-heat buffer storage. Buffer storage provides a "buffer" 

between the variations in solar flux and the heat delivered by the receiver to 

the engine, thus reducing the amount of time that the engine must operate under 

part-load conditions and thereby improving engine efficiency and extending 

engine life (Reference 7). This type of storage is integrated with the 

receiver and mounted at the concentrator focal plane. Longer-term storage for 

dish systems includes consideration of ground-mounted batteries 

(electrochemical), thermal storage using large external tanks, and 

thermochemical transport and storage. 

1-8 
SECTION I1 

COMPONENT DEVELOPMENT STATUS 

A. CONCENTRATORS 

1. Concentrator Characteristics 

The concentrator is the largest and most costly component of a 

parabolic dish module. Selection of optical configuration, material, and 

structure for any particular concentrator design is based upon considerations 

of good optical efficiency and ultimately of low installed cost and low 

lifetime cost (Reference 8). 

Two-axis tracking collectors can utilize concentrator configurations 

ranging from the conventional rigid paraboloidal mirror to the Fresnel or 

Cassegrainian (Figure 2-1). 

number of individual facets. However, there is no need to maintain an overall 

paraboloidal shape if small facets are properly oriented. For example, many 

spherical or flat facets can be placed on a flat support to form a Fresnel 

mirror. Other variations include Fresnel lens concentrators that allow the 

receiver to be closer to the ground and secondary concentrators that fold the 

optical path or increase the concentration of the collector. 

secondary and compound concentrators for dish systems is contained in 

Reference 9. ) 

The paraboloidal shape may be segmented into a 

(A discussion of 

The standard optical material for solar thermal concentrators is 

second-surface silver on glass, which is durable, highly reflective, but also 

relatively expensive, heavy, and fragile. Thin, low-iron glass is favored for 

this application because regular glass, which protects the reflective surface, 

also contributes to optical losses by absorbing part of the energy. The use 

of polymeric films is also being assessed. Polymers are attractive because of 

have the reflecting surface sandwiched between two other polymer layers (see 

Reference 8 ) . 

.. . . . ... , LLWIL LUW LIIILL~L ~ust &lid ~64; k ft~~t GGT~GZC, ZCZSZ~--C~TCQCO, c~zted, "r 

The concentrator reflector can be supported by either metal, cellular 

glass, reinforced polymeric material, or wood that is in turn supported by 

trusswork, stiffened by ribs, or sandwiched. In many cases, the reflector may 

be strong enough to support itself between the members of the structural 

framework; alternatively, it can be held in shape by tension and/or 

differential pressure. 

2. Concentrator Optics 

Mirror quality (i.e., surface accuracy and reflectance) is the 

primary contributor to optical efficiency. 

paraboloidal-shaped surface were possible, the beam of energy concentrated 

upon the receiver aperture is always enlarged and weakened. 

the energy striking the surface of the mirror is reflected to the aperture; 

some is scattered and absorbed. 

ratio of sunlight incident upon the concentrator to energy entering the 

Even if a perfect 

Also, not all of 

Thus, the concentrator efficiency (i.e., the 

2-1 
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Figure 2-1. Concentrator Configurations (Reference 10) : (a) rigid 

parabolic reflector; (b) pressure stabilized membrane 

reflector; (c) Fresnel lens concept; (d) Fresnel mirror 

concept; (e) Cassegrainian secondary configuration; (f 

Gregorian secondary configuration. 

2-2 
receiver) will always be less than 100%. 

the efficiency. 

the receiver at a position corresponding to an f/D ratio (the ratio of the 

focal length, f, and the diameter of the concentrator's aperture, D) of about 

0.6 (Figure 2-2 and Reference 11). Adding to beam enlargement is the fact 

that not all the energy is reflected in accordance with idealized optical 

surfaces. Instead, there is an angle of spreading that varies with different 

reflector materials. Plastic films have a large spreading angle; glass, a 

small one. The optical efficiency increases as the spreading angle 

decreases. Pointing errors resulting from inaccurate sun tracking and 

misalignment also can contribute to a reduction in collectable energy. 

As mirror quality improves, so does 

Enlargement of the sun's image can be minimized by locating 

It is true that the highest performance concentrator has the highest 

quality surface. However, the optimal concentrator design must also consider 

cost, including that of the surface, substrate, and structure. A poorer 

quality concentrator having a lower cost might be preferred for certain 

applications, especially those requiring receiver operating temperatures in 

the low to medium ranges. In other words, it is necessary to maximize the 

ratio of thermal energy into the receiver over cost (kWt/$), accounting for 

reradiation and convection losses. 

A method for evaluating reflective surfaces of parabolic dish 

concentrators is an essential part of their development. Criteria for the 

evaluation of second-surface glass mirrors, aluminum, and metallized polymeric 

films are defined in Reference 12. 

SUN'S INCOMING RAY kFOCAL Po"T 

/ / I 

I 

FOCAL PLANE 

\ 

CONCENTRATOR APERTURE DIAMETER (D) 

Figure 2-2. Concentrator Optics (see Reference 11) 

2-3 
3. Development Strategy 

As shown in Table 2-1, ten types of concentrators have been 

designed, built, and/or tested under the DOE Solar Thermal Program. These 

concentrators are being developed for three basic applications: 

process heat (IPH), cogeneration (total energy), and dish-electric power 

plants. 

Laboratories, Albuquerque (SNLA) were both involved in developing 

first-generation thermal dish modules operating in the mid-temperature range 

(315 to 4OO0C, 600 to 7500F) for IPH and cogeneration applications. Four 

concentrators tested under the program were built by General Electric (the 

type used at Shenandoah), Omnium-G, Power Kinetics, and Raytheon, and are 

compared in Table 2-1 and described in Section II.A.5. The thermal module 

work at JPL was transferred to SNLA during FY 1982. 

industrial 

During the late 1970s, the JPL TPS Project and Sandia National 

From its inception, the TPS Project has been concerned primarily with 

the evolution of components and modules that are autonomous electricityproducing units employing dish collectors coupled to high-efficiency heat 

engines. Efficient concentrators, supplying highly concentrated energy to 

receivers and engines, are required for such modules. Fabrication of the 

durable, high-efficiency test bed concentrators (by E-Systems) as vehicles for 

testing receivers and engines was a major step toward achieving the Project's 

goal as well as providing valuable data on concentrator materials, 

fabrication, and characterization (see Table 2-1 and Section II.A.4.a). 

As a result of the Project's first competitive solicitation, three 

preliminary designs of first-generation concentrators were completed. They 

are described briefly below and detailed further in Sections II.A.4.b and c. 

(1) A General Electric Company (GE) design, a rigid paraboloid with 

aluminized polyester (plastic) film on injection molded plastic 

reflective panels, was to emphasize low-cost materials and 

fabrication techniques. A prototype (PDC-1) was installed at the 

Parabolic Dish Test Site (PDTS) and was tested for optical 

performance . 

(2) An original Acurex concept evolved into a more advanced 

concentrator composed of cellular glass gores with a 

second-surface silver/glass reflector. Development of this 

lightweight, self-supporting panel (gore) aimed at producing not 

only a lower-cost concentrator (PDC-2, being paired with an 

organic Rankine-cycle engine/receiver for the Small Community 

Experiment described in Section III), but also advanced techniques 

that could be used in the fabrication of second-generation 

concentrators. 

(3) The Boeing membrane film reflector with protective enclosure was 

not carried past conceptual design until the Solar Energy Research 

Institute (SERI) began research and advanced development of 

polymers for mirrors and mirror enclosures in the early 1980s. 

SERI's work on this concept is described in Reference 3. 
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Two other concentrators by Advanco and LaJet were chosen because of 

their suitability for use in near-term Stirling and Brayton modules, 

respectively. They differ widely in materials and structure as shown in 

Table 2-1 and by the detailed descriptions given in Sections II.A.4.d and e. 

Both feature good optical and performance characteristics as well as low-cost 

fabrication techniques for planned mass production in the near future. 

Other concentrator efforts managed by the TPS Project that are not 

described in detail herein include: 

Entech's (formerly E-Systems Energy Technology Center) preliminary 

design and optical (lens panel) testing of a Fresnel lens 

concentrator (see O'Neill, M. J., "A Transmittance-Optimized, 

Point-Focus Fresnel Lens Solar Concentrator," Proceedings Fifth 

Parabolic Dish Solar Thermal Power Program Annual Review, JPL 

Publication 84-13, DOE/JPL-1060-69, March 1, 1984). 

A 14-m-diameter dome lens concentrator based upon this Fresnel 

lens concept will be fabricated and installed by Entech within the 

next 2 years in Albuquerque, New Mexico, as part of the DOE 

Innovative Concentrator Program managed by SNLA.4 

University of Arizona's concept definition of a Fresnel mirror 

concentrator. 

Boeing's design and optical (panel) testing of a rigid parabolic 

concentrator (see A Conceptual Design Study of Point Focusing 

Thin-Film Solar Concentrators, Final Report, prepared for Jet 

Propulsion Laboratory under Contract 955804 by Boeing Engineering 

and Construction, Seattle, Washington, November 11, 1981). 

University of Chicago's fabrication and testing of several 

secondary (trumpet-type) concentrators at the PDTS (see Winston, 

K., ana U'Gaiiagner, J., nurl-Iluagiiig Secuiiciary ZuuL;cllLLLciLL~iQ ," 

Proceedings Fourth Parabolic Dish Solar Thermal Power Program 

Review, JPL Publication 83-2, DOE/JPL-1060-58, pp. 221-233, 

February 1, 1983). 

.._. 

Development of Candidate Concepts 

During 1977 and 1978, the JPL Solar Thermal Power Systems Project 

proposals for low-cost, efficient parabolic dish concentrators 

(PDCs) capable of producing temperatures in the range of 540 to 815OC (1000 

to 15000F). The Project's selection of candidate concepts was based on the 

idea that first-generation hardware development would emphasize proven 

technology and techniques. This philosophy is seen in the first two 

concentrators developed by the Project: a test bed concentrator based on a 

microwave antenna design and a concentrator to be fabricated by an injection 

molding process used in the production of many commercial products.' 

4Personal communication, Mark O'Neill, Entech, Inc., P.O. Box 612246, 

DFW Airport, Texas 75261, May 15, 1985. 

2-7 
a. Test Bed Concentrator (TBC). In December 1977, a Request 

for Proposal (RFP) was released for design of a test bed concentrator that 

would (1) accommodate JPL-developed mirror facets, (2) provide solar tracking, 

and (3) support an engine/receiver unit at the dish focal plane for testing 

purposes. On September 14, 1978, a contract was awarded to E-Systems of 

Dallas, Texas, for the fabrication of two such concentrators (Reference 14). 

TBC Structural Characteristics. The TBC structure met 

design specifications for stiffness and accurate pointing capability by using 

proven satellite communications antenna technology. The reflector structure 

of a 13-m-diameter communication antenna was adapted for this application with 

a pedestal modification that would enable full sky coverage. 

requirements of the TBC are listed in Table 2-2. 

Key design 

The reflector support structure is a steel space frame consisting of 

eight truss beams radiating from a central hub and interconnected with 

diagonal and intercostal members (Reference 15). The hub, which is unchanged 

from the 13-m antenna configuration, provides exceptionally high stiffness. 

The receiver support structure is a tubular bipod connected to a receiver ring 

and stabilized laterally and torsionally by adjustable rods attached to the 

dish periphery, The pedestal is an elevation over azimuth mount with a wheel 

and track alidade. For azimuth tracking, a 3-hp dc servo motor drives one of 

the three alidade wheels through a 740:l gear reducer; in elevation, an 

identical motor drives a 20-ton screw-type linear actuator through a single 

helical gear box. The control system provides for active sun tracking (via 

two photocell sensors) in addition to program tracking (using a 

microprocessor). 

Mirror Facet Development. After reevaluation of earlier 

work in the areas of material selection, environmental test, optical 

characteristics, and reliability, Foamglas (a soda-lime cellular glass 

insulating material that is lightweight, easily shaped, and durable) was 

selected as the mirror substrate. Subsequently, block size and mirror 

material had to be determined in light of the TBC application and the 

structural characteristics of Foamglas. Analysis showed that block sizes 

greater than 46 cm (18 in.) square would provide satisfactory performance. 

actual block size of 61 x 71 x 5.1 cm (24 x 28 x 2 in.) was chosen, meaning 

that 224 facets would be required to compose the 11-m-diameter concentrator. 

Several materials were then analyzed as candidates for the mirrors, mirror 

adhesive, and sealant coatings for the mirror/substrate interface; those 

materials ultimately selected for mirror fabrication are listed in Table 2-3. 

Prior to assembly at JPL, the optical characteristics of each facet were 

measured in the laboratory using an optical tunnel, a reflectometer, and a 

photometer (Reference 16). A finished TBC mirror facet is shown in Figure 2-3. 

An 

Assembly and Installation. Trial assembly of the reflector 

structures and pedestals at the fabricator's facility ensured their timely 

installation at the Parabolic Dish Test Site (PDTS). Installation and 

operational checkout was completed in October 1979, 2 months after ground 

breaking for the foundations. Attachment of the mirror facets was done by 

fastening three flexure tabs (bonded to the facet substrate) to the reflector 

2-8 
Table 2-2. TBC Key Design Requirements (see References 15 and 17) 

Item Design Requirement 

Physical 

Aperture diameter 

Rim angle 

Focal ratio, f/D 

Focal point load 

Receiver mounting 

Tracking control 

Azimuth 

Travel 

Slew rate (13 m/s wind) 

Elevation 

Travel 

Slew rate (27 m/s wind) 

Tracking accuracy (operating wind) 

Pointing accuracy 

Environmental 

Operating wind 

Survival wind 

Seismic 

Ice 

Snow 

Ref lector 

Nominal diameter 

Mirror facets 

output 

Nwnbe r 

Materia 1 

Nominal size 

Nominal radii of curvature 

Three regions 

Initial reflectance 

Slope error 

Focal length 

11 m (35 ft) 

450 

0.6 

504.4 kg (1100 lb) 

76 cm (30 in.) inside diameter ring 

- +178O 

2028O / h 

0 to 90° 

168O/h 

0.05O 

1 .oo 

13 m/s (30 mi/h) gusting 

45 m/s (100 mi/h) 

0.25 G, any direction 

0.4 kg/m2 (10 lb/ft2) 

.. 

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11 m 

70 kWt at 800 W/m2 insolation 

224 

Second-surface glass 

60.96 x 71.12 cm (24 x 28 in.) 

1320, 1574.8, 1610.4 cm 

(520, 620, 634 in.) 

95% maximum 

1 mrad 

6.6 m (21.65 ft) 

2-9 
Table 2-3. Materials Selected for TBC Mirror Fabrication (see Reference 16) 

I tern Material (Manufacturer) 

Substrate 

Mirror 

Mirror adhesive 

Support tabs 

Support tab adhesive 

Mirror edge seal 

Foamglas sealant 

Paint 

61 x 71 x 5.1 cm (24 x 28 x 2 in.) 

Foamglas High Load Bearing 136.17 kg/m3 

8.5 lbs/f t3 density) (Pittsburgh Corning) 

60 x 70 x 0.15 cm (23-3/4 x 27-3/4 x 0.058 in.) 

Corning Glass Code 0317 (Silvered by Falconer) 

DER 332 - Dow Epoxy Resin 9427 Hardener (Furane 

Plastics) 

0.032 Aluminum with 5.1 x 7.6 cm (2 x 3 in.) 

contact area with Foamglas 

PC-88 two-part adhesive (Pittsburgh Corning) 

Vulkem 116 Urethane Sealant (Nameco) 

Pittcote 404 Acrylic Latex (Pittsburgh Corning) 

Chemglaze I1 A276 White Polyurethane 

structure while it was still on the ground. The entire structure was then 

placed on the pedestal in a single lift by a 45-ton hydraulic crane (see 

Reference 15). 

TBC Characterization. The TBC mirror facets were aligned at 

night using a semi-distant incandescent light source to produce a reflected 

image on the focal point target, which was marked with a series of concentric 

rings 2.54 cm (1 in.) apart (Reference 18). Because only one mirror facet 

could be aligned at a time, covers for individual mirrors were fabricated, 

with Velcro fasteners for easy removal and reattachment to the mirrors. The 

TBC was boresighted to the aimed light source using two sets of cross hairs 

and two aperture disks that were replaced by disks with successively smaller 

apertures. Individual mirror alignment was physically accomplished by 

adjusting the three flexure tabs that attach the facet to the reflector 

structure. 

The TBCs were then characterized using a flux mapper (Figure 2-41 and a 

cold-water calorimeter. The flux mapper uses a Kendall radiometer as the 

sensing device and is mounted on an x-y-z motor-driven positioning mechanism 

for testing. 

peak flux of 1750 W/cm2 at a normalized insolation of 1000 W/m2 within a 

20.3-cm (8-in. )-diameter aperture, resulting in temperatures up to 33OOOC 

(6000OF). 

Results of flux mapper testing show that a TBC can produce a 

Cold-water calorimeter testing has shown that the TBCs can each 

2-10 
Figure 2-3. TBC Mirror Facet 

Figure 2-4. Close-up of Flux Mapper from Outer End 

F. 

2-1 1 
produce a maximum of 82 kWt at an insolation of 1000 W/m2 within apertures 

of 56 cm (22 in.) and 25.4 cm (10 in.) in diameter (Reference 19). During 

component testing, temperature, thermal power level, and flux intensity 

distribution at the concentrator focal plane are routinely controlled by the 

number, location, and alignment of uncovered mirror facets (Reference 20). 

Throughout many years of operation at the PDTS, the test bed 

concentrators (Figure 2-5) have proven to be valuable vehicles for testing 

numerous kinds of receivers and power conversion units (see Sections 1I.B 

and C of this report). In 1984, both test bed concentrators were disassembled 

and reinstalled at the Sandia National Laboratories test facility in 

Albuquerque, New Mexico, where they will be used to test advanced parabolic 

dish-electric subsystems. 

b. Parabolic Dish Concentrator No. 1 (PDC-1). The fabrication 

of PDC-1 was the culmination of TPS Project efforts to develop a firstgeneration low-cost concentrator. Preliminary design contracts were awarded 

to Acurex Corporation, The Boeing Company, and General Electric Company (GE). 

These designs were completed in March 1979. The Acurex design was based on a 

faceted, "compressed" paraboloidal (Fresnel) reflector made up of 33 triangular facets mounted independently on a flat triangular frame (see Reference 17). 

The Boeing design featured an inflated plastic enclosure to protect collector 

components from all environmental loads, thus permitting the use of lightweight, 

less expensive internal structures. The reflector for this design was to be a 

13-m diameter, first-surface metallized plastic film membrane shaped by a 

slight vacuum within the frustrum (refer to Figure 2-lb and Reference 17). 

General Electric's design, featuring an 11-m-diameter reflector made of 

Figure 2-5. TBCs During Component Testing at the PDTS 

2-1 2 
ORIGINAL PAGE IS 

OF POOR QUALITY 

plastic injection molded panels, was selected for further development: 

August 1979, GE was given a contract for detailed design of their concept, and 

in 1981 separate contracts were awarded for panel fabrication, structure 

fabrication and installation, and controls. 

In 

PDC-1 Design Characteristics. The detailed design of the 

General Electric concept (Figure 2-61, later known as Parabolic Dish 

Concentrator No. 1, was completed in mid-1981. For the purpose of engine 

compatibility, the concentrator diameter was increased from 11 m to 12 m in 

order to provide an output of 80 kWt for a receiver operating at 815OC at an 

insolation of 1000 W/m2. It is composed of 12 radial gpres, each comprising 

an inner, center, and outer panel. The 36 panels are attached along their 

radial edges to 12 radial steel ribs located in front of the reflective 

panels. The reflective surface is an aluminized plastic film (Llumar) 

laminated to a plastic sheet and then bonded to a molded fiberglass/balsa 

sandwich panel. The original injection molded plastic panel with integral 

ribs, which was proposed for this concentrator, was abandoned because of 

fabrication difficulties. 

The elevation-over-azimuth mount uses a wheel and track arrangement with 

outboard trunnions to permit stowing in a face-down position and access to the 

engine/receiver unit. The control system, which includes a central computer, 

manual control panel, and sun sensor, enables the concentrator to track the 

sun by first pointing it to a predetermined position calculated from the solar 

ephemeris. When the concentrator is about 1 deg from the sun's position, the 

sun sensor assumes control and maintains alignment of the solar image with the 

receiver aperture. 

4 h 

Figure 2-6. General Electric Concept for a First-Generation Concentrator 

2-13 
Panel Fabrication and Testing. Under a separate 

procurement, Design Evolution 4 began fabrication of the PDC-1 panels in 

1981. In their specialized molding facility in Lebanon, Ohio, they used three 

separate tooling masters made by System Resources to mold the inner, center, 

and outer panels. The molding facility's press platten, 7 by 11.5 ft long, is 

one of the largest resin transfer presses in the United States. It is raised 

by six air bags to provide a clamping force of 180 tons. Each panel substrate 

was fabricated by loading the mold bottom half with a mat of continuous strand 

glass fibers, a layer of end grain balsa blocks, and another fiberglass mat. 

The mold was then closed and injected with polyester resin, which flowed 

throughout the cavity and filled the glass fiber mats and all gaps between the 

balsa blocks. The reflective film laminate was bonded to the panel with 

contact cement (Reference 21). 

The first set of Design Evolution 4 panels was optically tested in the 

JPL 25-ft Space Simulator (Figure 2-7). This facility allows use of a single 

zenon arc lamp that provides a high quality collimated beam of light over a 

circular area of almost 6 m (19.7 ft) in diameter. This beam was used to 

measure directly the optical forming characteristics of the panels. Test 

results indicated that, although the performance of a concentrator assembled 

from these panels would be satisfactory, it could be increased by improvements 

in panel manufacturing techniques and the use of higher quality optical 

materials. (Further description of optical testing in this facility is 

presented in Reference 22. ) 

Structure Fabrication and Installation. In the spring of 

1982, site preparation for the installation of PDC-1 at the PDTS was carried 

out by Ashland Construction simultaneously with fabrication of the structure 

by Alco Machine Company of Birmingham, Alabama, for Ford Aerospace and 

Communications Corporation (FACC), the prime contractor. After curing of the 

concrete foundation, Valley Iron installed the track, erected the mount frame, 

and began assembly of the dish structure. A trial of the latter had been 

performed at the Alco factory prior to installation. The 36 reflective panels 

were installed after individual optical testing using a new attachment scheme 

to accommodate large shear loads. Delamination of some of the reflective 

sheet during and after installation led to the consideration of an anaerobic 

contact cement for future panels (Reference 23). Subsequent dish rework 

included reinstallation of the panels, which was warranted after initial 

optical testing of the assembled concentrator (discussed below). The panels 

were reinstalled by redrilling rib attachment holes while each panel was held 

in the proper parabolic contour under close temperature conditions. These 

rework efforts resulted in a threefold reduction in the focal spot diameter 

(see Reference 23). 

in Figure 2-8. 

The completed concentrator is shown erected at the PDTS 

Control System. The control system for PDC-1 as used at the 

PDTS employed sun sensors for primary control and a computed sun ephemeris for 

simultaneous check and cloud passage. 

stop/start motion, and operation was at a 0.05-deg deadband for optical 

characterization. 

before PDC-1 was moved to SNLA. 

including message exchange protocol and basic microprocessor control logic, is 

contained in Reference 24. 

Tracking action was a discontinuous, 

The control system performed well for the brief period 

A detailed description of the system, 

2-14 

- 
ORIGINAL PAGE IS 

OF POOR QUALm 

Figure 2-7. PDC-1 Concentrator Panel During Testing in the JPL 25-ft 

Space Simulator 

2-15 
Figure 2-8. PDC-1 at the Parabolic Dish Test Site 

Optical Testing. Tests for optical accuracy of the fully 

assembled PDC-1 were conducted during October and November 1982. 

of these tests were used for evaluating the performance of the concentrator 

and were instrumental in the development of a succcessful panel installation 

procedure as mentioned above. 

The results 

Two diagnostic techniques were used to determine the relationship 

between the image quality and the mechanical properties of the reflecting 

surface. 

factor distribution, and various image photography techniques were used with a 

point-source configuration to predict the intensity distribution of the 

concentrator when it is pointed at the sun. A diagnostic picture taken 

through a telescope at a distance of 600 to 900 m (2000 to 3000 ft) is shown. 

in Figure 2-9. The intercept factor distribution and the diagnostic pictures 

indicate that PDC-1 will perform satisfactorily when coupled to a suitable 

power conversion unit (References 25 and 26). 

A photo-detector raster scan was used to determine the intercept 

C. Parabolic Dish Concentrator No. 2 (PDC-2) 

Background and Preliminary Design. After reevaluation of 

the low-cost concentrator design proposed by Acurex in March 1979 (discussed 

previously), an alternate concept based on the Acurex advanced cone design was 

selected for development as a backup for PDC-1. The processes used to design 

and fabricate this 11-m-diameter, single-pedestal-mounted concentrator also 

were planned for use in second-generation concentrators (Reference 27). 

2-16 
Figure 2-9. Diagnostic Photograph of PDC-1. (The white areas indicate 

panel regions forming images within a 15-cm-diameter circle.) 

During 1979 and 1980, Acurex was under contract to JPL to complete tasks 

relating to their concentrator concept: (1) preliminary design of a cellularglass-substrate advanced solar concentrator, (2) detailed design of reflector 

gore panel, and (3) a mass production cost estimate (Reference 28). The 

rationale for this design is that a lightweight, self-supporting panel will 

decrease drive and foundation loads and reduce installation labor -- all 

leading to lower cost. Cellular glass is relatively inexpensive and also 

durable, has a high stiffness-to-weight ratio, and matches the thermal 

expansion properties of glass. 

PDC-2 was designed as a two-axis tracking parabolic dish, 11 m in 

diameter, consisting of 24 inner and 40 outer gores attached at three points 

to a steel ring truss support structure (Figure 2-10) The gores act as 

cantilevered beams supporting the reflective surface, which is made of 

back-silvered, low-iron, soda-lime glass drawn to a thickness of 0.7 mm 

(0.028 in.) then bonded and shaped to the cellular glass substrate using a 

pressure-forming technique. The concentrator output was projected to be 

79 kWt through a 24-cm (9.4 in.) aperture to produce receiver operating 

temperatures up to 925OC (17000F) at an insolation of 1000 W/m2. 

Gore Fabrication and Testing. On March 30, 1981, Acurex 

delivered seven paraboloidal reflective panels to JPL for optical testing. - 

Six of the gores- were the cellular-glass- type (Figures 2-11-and 2-12) 

consisting of (1) a contoured cellular glass core with a paraboloidal front 

surface and spar-stiffened rear surface, (2) a large full-surface facet of 

2-1 7 
Figure 2-10. Model of Acurex Advanced Concentrator Design (PDC-2) 

ORIGINAL PAGE IS 

of P08R Qum 2-18 
ORIGINAL PAGE IS 

OF POOR QUAW 

OUTER GORE PANEL (TYPICAL) CE LLULAR 

GLASS CORE 

MIRROR GLASS 

OVER ALL NON-REFLECTING 

SURFACES 

CAP 

GORE SUPPORT 

RING TRUSS 

Figure 2-11. Cross-Sectional Diagram of Acurex Concentrator Gore 

Figure 2-12. Acurex Cellular-Glass-Type Gores Delivered to JPL 

2-1 9 
flexed back-silvered glass mirror bonded to the paraboloidal front surface, 

and (3) a full-length structural glass cap bonded to the spar on the rear 

surface. The cellular glass core is protected by a coating of butyl rubber 

that forms an edge seal around the mirrored face of the gore to prevent 

moisture damage to the reflective silver coating. White siliconelalkyd paint 

shields the butyl rubber from ultraviolet radiation. During laboratory 

testing, these cellular glass gores showed excellent optical quality (see 

Reference 27). 

The seventh panel delivered to JPL is a glass-reinforced developmental 

panel. Initial optical tests indicated structural problems, the resolution of 

which would require additional development (Reference 29). 

Future Plans. A later version of PDC-2, intended for use in 

the Small Community Solar Thermal Power Experiment (see Section 1111, employs 

a 12.2-m-diameter dish. The concentrator was modified to increase the power 

delivered to the receiver to 95 kWt for use with the proposed Barber-Nichols 

25-kWe organic Rankine-cycle power conversion assembly mated to the 

lS-in.-diameter aperture FACC receiver. Construction of the 12.2-m PDC-2 was 

initiated, then suspended when DOE and FACC were unable to finalize contract 

terms. 

d. Advanco Concentrator. An 11-m-diameter concentrator was 

developed and fabricated by Advanco Corporation as part of the Stirling module 

development program at JPL (see Section 111). This concentrator is made up of 

320 facets, each 460 x 610 mm (18 x 24 in.). The individual facets are 

foamglass-backed thin glass, back-silvered mirrors providing a total 

reflective surface area of 89.2 m2 (960 ft2) for the concentrator. The 

mirror facets are attached to flat racks that are in turn attached to a carbon 

steel truss structure with leveling attachments that allow the reflective 

surface to approximate a paraboloid (Figure 2-13). 

The truss is mounted on a pedestal via an exocentric gimbal mechanism 

(developed by Rockwell International), which supports the concentrator 

reflector. The pedestal, which is 750-m (30-in.) carbon steel pipe in a 

poured concrete footing, has an upper joint (elbow) and a lower joint 

(shoulder). The elbow joint consists of a turntable bearing that is rotated 

using a pinion gear, gear reduction, and a small electric motor. This 

rotation (about an axis through the center of mass) reduces torque 

requirements and produces elevation and some azimuth drive. The shoulder 

joint pivots and produces azimuth drive only (see Reference 11). 

control is accomplished with an Electrospace Model 93C-15 antenna controller 

and motors (Reference 30). 

Concentrator 

e. LaJet Concentrator. In 1979, the LaJet Energy Company began 

developing concentrators with plans to market mass-producible collector 

units. 

general configuration in progressively larger sizes: 

of reflective surface area. LaJet's 38-m2 version is shown in Figure 2-14. 

Their 44-m2 concentrator, the LEC 460, was planned for use in the Projects' 

Brayton module development program (see Section 111). 

Since that time, LaJet has fabricated concentrators using the same 

18.81, 38, and 44 m2 

2-20 
ORIGINAL 

s)F: POOR 

PAGE IS 

QUALW 

Figure 2-13. Model of Advanco Concentrator 

Description. The LEC 460 features an open lattice space 

frame, a cantilever truss, and multiple low-cost circular-dish reflectors. 

The open lattice structure is made of lightweight round steel tubing connected 

with specially designed joints that are bolted together with simple fittings. 

The cantilevered design permits sun tracking and adjustments in elevation and 

azimuth via small motors. Each 1.52-m (6O-in.I-diameter mirror consists of a 

shallow, lightweight, cylindrical housing with a closed rigid back and an open 

top. A reflective thin film, which is easily replaceable, is attached to the 

top of the housing. A closed-loop, adjustable mechanism controls the partial 

vacuum forming the concave shape of each individual mirror facet (as in 

Figure 2-lb) and is used to achieve desired concentration ratios and focal 

lengths. The manufacturer-stated efficiency is approximately 70%. 

Optical Testing of a Mirror Facet. In mid-1983, an LEC 460 

The following two 

(1) auto-focus tests with a point source of light at the 

concentrator facet was tested for imaging quality at JPL. 

methods were used: 

facets' radius of curvature and (2) tests with the sun close to the horizon as 

a distant light source. The results of these tests indicated that all of the 

solar image reflected by an LEC 460 made of facets identical to the test 

specimen should fall within a 22.9-cm (9-in.l-diameter if the outer facets are 

carefully adjusted. Such a concentrator would provide acceptable performance. 

These optical tests not only evaluated the imaging characteristics of a 

sample facet, but also demonstrated the kind of tests that can be conducted 

for quality control during facet manufacture and for characterizing a complete 

concentrator. 

in Reference 31.) 

(A detailed description of this testing procedure is contained 

2-21 
Figure 2-14. LaJet 38-m2 Concentrator 

ORIGINAL PAGE IS 

OF POOR QUALITY 

2-22 
5. Other Concepts Tested under the DOE Solar Thermal Program 

In 1980, in response to a DOE request that JPL monitor the Omnium-G 

SNETCO installation, the Omnium-G system at the PDTS was retrofitted to the 

latest configuration. In August 1981, the system (with a new tracking unit 

and elevation drive) operated reliably with no operator intervention during a 

normal diurnal cycle. Refocusing of the mirror petals and adding insulation 

I 

Four other concentrators were tested as part of the DOE Solar 

Thermal Technology Program. These four, manufactured by Raytheon, General 

Electric, Omnium-G, and Power Kinetics, Inc. (PKI), are shown in Figure 2-15 

(a), (b), (c), and (d), respectively. 

a. Raytheon and General Electric/Shenandoah. Sandia National 

Laboratories-Albuquerque (SNLA) began testing the Raytheon and General 

Electric/Shenandoah collectors (a concentrator plus a receiver) under a 

program to develop point-focusing concepts for lower temperature applications 

(315 to 400OC, about 600 to 7SOoF), e.g., irrigation or total energy 

(cogeneration) systems. 

The Raytheon concentrator, 6.7 m in diameter, consists of spherical 

mirror segments (sagged, back-silvered, water-white crystal glass) that are 

hard mounted on an aluminum substructure. The collector tracks in azimuth and 

elevation by computer-controlled dc stepping motors (see Reference 9). 

The General Electric/Shenandoah collector (so named for its use in the 

Solar Total Energy Project located in Shenandoah, Georgia) is 7 m in diameter 

having 21 panels, each made of aluminum sheet that is coated on one side with 

3M's FEK-244 reflective film and die-stamped to the desired parabolic 

contour. The dish's central hub is supported by a concrete counter-weighted 

yoke structure that is held at an angle by two solar-axis bearings and 

supported by a tubular carbon steel tripod mount. Rotation of the yoke about 

its axis provides solar tracking (References 32 and 33). 

I b. Omnium-G. Omnium-G, a company that is no longer in 

h..c:-e-c h..:lt CP.*P~-~ .-nll-.-tn-- :- 107Q --,I 1070 the+ ,..I~IP ;n~t-lleA at 1 

various sites in the United States. Two such sites are the Southern New 

Test Site (PDTS) in California. The 6-m reflector is polished aluminum sheet 

on polyurethane foam supported by trusses. The concentrator is rotated on a 

track by electric drive motors. Testing has shown the optical efficiency to 

be about 0.6 at a geometric concentration ratio of 800 (see Reference 9). 

I England Telephone Company (SNETCO) in Connecticut and JPL's Parabolic Dish 

I 

t 

2-23 
(a) Raytheon 

(b) General Electric 

(c) Omnium-G (d) Power Kinetics, Inc. 

Figure 2-15. Other Concentrators Tested under the DOE Solar Thermal Program 

2-24 
azimuth control; rotating each mirror support assembly around its center of 

gravity provides elevation adjustment. The concentrator focuses sunlight onto 

a cavity receiver producing steam for process heat applications. 

A PKI collector is now in operation at the Capitol Concrete Products 

block plant in Topeka, Kansas. Conception and installation of this system 

experiment was carried out by Applied Concepts Corporation under the direction 

of the JPL TPS Project, who helped transfer management of the experiment's 

operational phase to SNLA in FY 1982. (Reference 35 contains information on 

that phase of the Capitol Concrete system experiment.) 

bought by JPL was installed at Hill Air Force Base in Utah. 

A second PKI collector 

In 1984, a modification of the PKI collector was selected for use in the 

newly contracted Small Community Experiment at Osage City, Kansas. 

Further information about the SNLA thermal dish program is contained in 

References 36, 37, and 38. 

6. Concentrator Technology Assessment Summary 

Concentrators designed, developed, and/or tested as part of the 

TPS Project included rigid parabolic, membrane (pressurized and/or multiple), 

Fresnel mirror or lens, and secondary. Initially, the rigid parabolic and 

Fresnel mirror concentrator concepts were defined by JPL and the University of 

Arizona, respectively. Preliminary designs were prepared by Entech (Fresnel 

lens) and Boeing (pressurized membrane). A Boeing design of a rigid parabolic 

concentrator included tests of a mirror segment; Acurex work on a rigid 

parabolic type included partial detailed design plus tests of several mirror 

panels. Four concentrators were designed, built, and tested: E-Systems/JPL 

rigid Darabolic (TBC). Advanco rigid parabolic, General Electric rigid 

parabolic (PDC-l), and University of Chicago secondary concentrator. 

Concentrators developed by three commercial companies also were tested: 

umnium-G rigia paraboiic, Puwer I(;uc:ti~s IGC. FZ~SGZ? ~trr~r, 2~2 Lz.?~t 

multiple membrane. This work, together with accompanying analysis, led to 

major advances in understanding the characteristics that govern the 

performance and cost of dish concentrators and to increased commercial 

interest in dish concentrator systems. 

Indications are that bringing concentrator costs down to target 

levels will not be easy. Concentrators must be designed from the start for 

low-cost mass production, using good production engineering and cost-effective 

technology. To keep material costs down, concentrators must be lightweight 

and made of inexpensive materials. Nevertheless, the optical elements must 

withstand the weather for years (bare aluminum will not do so), and the 

concentrator must not be damaged by hail or blow away in gusty winds. 

Providing adequate strength to withstand windstorms at minimum cost is 

probably the most challenging problem in engineering concentrators. 

Single-post mounts tend to be lighter and cheaper than mounts using tracks or 

multiple pedestals. Field labor costs are high in the U.S.; therefore, the 

initial design should minimize field assembly and alignment. 

foundations are needed; in the southwestern U.S., for example, pier 

foundations are usually cheaper than concrete pads. 

Inexpensive 

2-25 
B. RECEIVERS 

1. Receiver Characteristics 

The receiver is a critical component of a parabolic dish module 

because it transfers the heat from the concentrated solar beam to a suitable 

medium (water, steam, non-condensing gas, molten salt, or metallic or organic 

liquid) that can produce useful energy. This medium (the working fluid or a 

heat transfer fluid) can supply energy directly for process heat or fuels and 

chemicals applications or can be used to power a heat engine for electricity 

production. Concentrated solar energy enters the receiver through the 

aperture (opening) at one end and strikes the heat-absorbing surface of the 

receiver's inner cavity, which is typically metal or a ceramic material. The 

working fluid circulates through coils (Figure 2-16a) or a matrix structure, 

such as a honeycomb (Figure 2-16b), near the cavity surface and is heated by 

the absorbed solar energy. The inner cavity is surrounded by insulation and a 

protective outer shell, which provides inlet and outlet passages for the 

working fluid and a means for mounting the receiver to a concentrator and/or 

for integrating it to the heat engine. Receivers also may require flow 

controls to prevent catastrophic heating or to smooth out transients (uneven 

heating) during start-up and shutdown (Reference 39). 

Receivers are usually classified according to the working fluid and/or 

the engine for which they provide thermal input. Brayton receivers are either 

open-cycle (using air as a working fluid at below ambient or higher than 

atmospheric pressures) or closed-cycle (using helium or other gases at several 

atmospheres pressure). These receivers require a relatively large heat 

exchanger area within a compact size because of the gaseous working fluid. 

Stirling receivers typically use helium or hydrogen as the working fluid at 

pressures up to 200 atmospheres and require efficient heat exchangers that 

provide minimal volume. Rankine receivers use water/steam or organic fluids 

and may also use liquid metals or molten salts in an intermediate transport 

loop between the receiver and working fluid. 

2. Optical and Thermal Characteristics 

Design of a solar receiver must consider the optical properties of 

the concentrator as well as the orientation of the receiver to the 

concentrator. To evaluate the properties of the solar flux into the receiver, 

models have been developed in which the sun is an extended, finite-size source 

and its radiation is analyzed by using cones (rather than rays) as the basic 

description for energy transport. Such solar simulations (Reference 40) can 

determine the best concentration ratio as a function of the heat flu 

impinging on the heat transfer surface, the concentrator reflectance, the 

local solar insolation, and the collector efficiency. Thermal analysis of the 

receiver can then be performed by entering the cavity wall incident flux 

information into a finite-element, thermal analyzer computer code that 

calculates the multiple reflections and reradiation characteristics. These 

calculations show that minor variations in concentrator performance (e.g., 

slope error of 2 mrad) will not significantly affect receiver cavity 

2-26 
INSULATION 7 

\\ 

CERAMIC 

REFLECTIVE SURFACE 

-CERAMIC TUBE 

- MERMAL 

INERTIA 

SLEEVE 

CERAFORM RlGlDlZED 

INSULATION 

CARBON STEEL TANK 

INLET 

MULLITE STORAGE SEGMENTS 

(b) 

Figure 2-16. Receiver Configurations: (a) coiled tube concept; 

(b) honeycomb pressurized matrix concept by 

Sanders Associates (see Reference 39) 

2-27 
efficiency for the aperture size selected. In addition, determination of 

cavity efficiency as a function of thermal input energy for various aperture 

sizes has shown that the smallest aperture consistent with concentrator optics 

is the most desirable (Reference 41). 

3. Development Strategy 

Development of solar receivers by the TPS Project proceeded along 

two parallel paths: 

other, advanced (second-generation) technology. Overall strategy included 

selection of technically attractive concepts for fabrication and performance 

evaluation. After determination of technical feasibility, suitable receivers 

were chosen for system integration tests where the performance of components 

would be verified while operating as part of a dish module system. Receivers 

developed by the TPS Project are listed and characterized in Table 2-4. 

one emphasizing first-generation technology and the 

Because a receiver must meet the operating requirements of both the 

concentrator and engine to which it is coupled, its design requirements must 

consider the specific application and system configuration. These design 

requirements are determined by the following factors (Reference 42): 

(1) Temperature and pressure needed by the power conversion or thermal 

process subsystem. 

(2) Heat transfer characteristics defined by the working fluid. 

(3) Mechanical configuration of the solar power system that includes 

both size and weight constraints. 

(4) Optical characteristics of the concentrator. 

(5) Available materials. 

The goal of the Project's first-generation technology effort was to 

design, fabricate, and test receivers meeting the requirements listed above 

for various applications and configurations. Two such receivers (one air and 

one steam) were built in 1979-80 by Garrett AiResearch, under contract to JPL, 

for use with Brayton and Rankine power conversion units, respectively. These 

receivers are described in detail in Sections II.B.4.a and b below. Another 

first-generation receiver was designed and built by Ford Aerospace and 

Communications Corporation (FACC) for use with an organic Rankine-cycle engine 

as part of the Small Community Experiment (discussed in Section 111). 

features toluene (an organic liquid) as the working fluid and is detailed in 

Section II.B.4.c. 

It 

Advanced technology efforts emphasized the achievement of hightemperature (816 to 1375OC, 1500 to 25000F) receivers required for 

higher-performance engines. [An advanced technology effort to build even 

higher-temperature receivers (required for some industrial process heat 

applications and fuels and chemicals processes) being carried out at JPL was 

transferred to the Solar Energy Research Institute in 1981 (see Reference 31.1 

2-28 
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2-29 
Second-generation receivers also aim to maximize efficiency, provide a 

lifetime of 20 to 30 years with minimum maintenance, and have an acceptable 

mass production cost (see Reference 42). 

Receiver concepts by Fairchild/Stratos Division and General Electric 

(GE) were evaluated for use with a Stirling engine under the TPS Project's 

advanced technology program. 

encased in a copper slab and operates from either solar or fossil fuel at a 

temperature of 816OC (15000F). 

storage as well as hybrid operation. A Sanders Associates receiver, suited 

for use with a Brayton engine and based on a ceramic honeycomb matrix heated 

through a quartz window, was evaluated for operation between approximately 

1100 and 1375OC (2000 and 2500OF) for a thermal output of 75 kW. These 

three advanced receivers are discussed in Sections II.B.4.d, e, and f. 

The Fairchild receiver consists of a metal tube 

The GE heat pipe receiver features thermal 

In a special test program funded jointly by DOE and United Stirling, the 

feasibility of a commercial solar receiver was demonstrated. Five United 

Stirling experimental solar-only receivers were successfully operated with a 

Stirling-cycle engine at the focus of a test bed concentrator. These 

receivers and the results of the test program are described in Section 

II.B.4.g. 

4. Development of Candidate Concepts 

During 1977 and 1978, the goal of the TPS Project's receiver 

development task was to provide efficient, cost-effective receivers for use 

with compatible concentrators and power conversion units as required for the 

development of various types of dish modules. During this time, the Project 

let six contracts to industrial firms for conceptual designs of firstgeneration receivers: Four gas receivers suitable for use with an open-cycle 

Brayton engine (having a turbine inlet temperature of 816OC, or 1500°F) 

and two steam receivers (once-through to superheated steam at 54OoC, or 

10000F, and up to 14 MPa, or 2000 psi) for use with a Rankine-cycle engine. 

Table 2-5 lists the contractors and corresponding receiver types and 

configurations selected. Cross-sectional drawings (also listing receiver 

characteristics) are shown for the Brayton and Rankine designs in Figures 2-17 

and 2-18, respectively. 

To facilitate effective management and technical support of these design 

contracts, a JPL design team analyzed steam Rankine and air Brayton receiver 

parameters, including fluid flow, heat transfer, and material stress. The 

geometrical distribution of solar energy on the interior surfaces of the 

receiver cavity is a critical variable influencing receiver design. 

Therefore, the JPL-developed flux mapper (see Section II.A.4.a) was used 

during receiver prototype testing to measure the concentrated flux in three 

dimensions and to determine its geometrical distribution. In addition, a 

computer simulation model, HEAP, was developed in order to aid in receiver 

characterization (Reference 44). 

By December 1978, the contractors completed their preliminary designs, 

which incorporated ten-minute buffer storage and included complete parametric 

analyses, estimates of initial production costs, and proposals for final 

2-30 
Table 2-5. First-Generation Receiver Preliminary Designs 

Contractor Type Configuration 

Garrett AiResearch, 

Los Angeles, CA 

Air Brayton Plate fin 

Steam Rankine Tubular with steam drum 

Boeing Engineering and Air Brayton Tubular 

Construction, Seattle, WA 

Sanders Associates, 

Nashua, NH 

Air Brayton Ceramic core 

Dynatherm Corporation, Air Brayton Heat pipe 

Cockeysville, MD 

Fairchild/Stratos Division, Steam Rankine Coil 

Manhattan Beach, CA 

designs and fabrication of prototypes. 

were submitted the following January, two were selected for development: one 

for an open-cycle air Brayton receiver and the second for a steam Rankine 

receiver. 

mid-1979 (see Reference 17). 

Of the six final design proposals that 

Contracts for both designs were awarded to Garrett AiResearch in 

Description. The Garrett air receiver was designed to 

operate from an input of 85 kWt, supplied by solar tlux rrom a disn concentrator, to heat the working gas of a highly recuperated open-cycle gas turbine 

Brayton engine from a temperature of 565 to 816OC (1049 to 1500OF). 

metallic (Inconel 625) plate-fin heat transfer surface, shown in Figure 2-19, 

is used to effect this energy transfer. The inner receiver cavity is composed 

of the transfer surface (a single-sandwich panel) surrounded by an inner 

cylindrical assembly with approximately 0.11 m (4.5 in.) of insulation between 

the panel and the housing. The panel contains a high-density offset fin 

matrix having 4.72 fins per centimeter (12 fins per inch) that are brazed to 

the two metal sheets. Air (at 565OC) from the Brayton engine recuperator is 

ducted to a toroidal manifold at the bottom of the panel where it flows up the 

annular passage that defines the vertical walls of the inner cylindrical 

assembly and is heated to a temperature of 816OC. This high-temperature air 

is then collected in another toroidal manifold at the top of the receiver 

cavity and is ducted to the engine's turbine inlet at a pressure of 0.25 MPa 

(37 psia). 

approximately 0.76 m (30 in.) in diameter by 1.71 m (46 in.) long. 

receiver aperture end is a silicon carbide cone assembly that forms a circular 

opening through which concentrated solar energy enters during operation. 

Brackets on the surface of the case are used to mount the receiver at the 

concentractor focal plane by attachment to a mounting ring (see Reference 41). 

A 

The cavity assembly is enclosed in an outer cylindrical case 

The 

2-31 
GARRETT PLATE FIN DESIGN 

6 

CAPACITY: 62 kWth 

WEIGHT: 325 Ibs WITH INSULATION 

MATER I AL: HAST E LiOY 

INSULATION: MIN-K 2000 

STORAGE TYPE: INTEGRAL OR SEPARATE 

WEIGHT OF STORAGE: 325 Ibs 

THERMAL EFFICIENCY: 84% 

MOLTEN SALT (NoCI) 

BOEING ENG AND CONST. 

ABT 60 TUBES 

1/4" DIM4 - 4" INSULATION 

CAPACITY: 90 kWth 

WEIGHT: 300 Ibs 

MATERIAL: INCONEL 617 

INSULATION: KAOWOOL BLANKET 

STORAGE TYPE: 0 SENSIBLE HEAT 

AND BLOCK 

IN REFRACTORY 

@ sBPAHT:"E'R"uOR 

WEIGHT OF STORAGE: lo00 Ibs 

@ 50 Ibs 

THERMAL EFFICIENCY: 87.4% (NOT COUNT I NG 

SPILLAGE) 

77 8Yo WITH 

11% SPILLAGE 

DYNATHERM CORP. 

47 HEAT PIPES -J 

CAPACITY: 100 kWth 

WEIGHT: 700 Ibs INCLUDING STORAGE 

MATERIAL: STAINLESS STEEL OR SUPERALLOY 

INSULATION: NOT SPECIFIED 

STORAGE TYPE: INTEGRAL MOLTEN 

SALT (LiF/NoF/MgF) 

WEIGHT OF STORAGE: INCLUDED IN ABOVE 

THERMAL EFFICIENCY: 95% 

SANDERS ASSOCIATES 

p- 38.5"l 

CERAMIC 

6" IN LET 

AND 

OUTLET 

CAPACITY: 80 kWth 

WEIGHT: 150 Ibs 

MATERIAL: STAINLESS STEEL 

INSULATION: THERM0 12 

STORAGE TYPE: SEPARATE SENSIBLE 

HEAT IN REFRACTORY 

BLOCKS 

WEIGHT OF STORAGE: 300 Ibs 

THERMAL EFFICIENCY: 86% 

Figure 2-17. Proposed Air Brayton Receiver Designs (see Reference 14) 
FAIRCHILD STRATOS 

1" DIA. HOLES 

WINDBREAK COLLAR TEMPERATURE: l20O0 F 

CAPACITY: 90 kWth 

PRESSURE: 1500 psi 

TUBE MATERIAL: STAINLESS STEEL 

FLOW RATE: 2.5 Ibs/hr kWth 

WEIGHT: 75 Ibs 

TYPE: ONCE THROUGH TO SUPERHEAT 

REHEAT CAPABILITY: WITH MINOR MODS 

THERMAL E FFl Cl E NCY: 8O-9OO% 

GARRETT AIRESEARCH 

_- 

SECTION 

I llm 

A\ MANIFOLD CAPACITY: 50-90 kWth 

PRFSSIJRE: ls00 psi 

TEMPERATURE: 1200°F 

TUBE MATERIAL: STAINLESS STEEL !J I1 I 

FLOW RATE: 2.5 Ibs/hr kWth 

WEIGHT: 200 Ibs 

TYPE: SEPARATE BOILER/~~lPFRHFATFR 

I [FiN-%& "' 

CYCLONE 

CCDhDhTnD DFUCAT TAPARII ITV. WI 

SECTION I 

\WA~~LCI;CULATION 

WATER 

INLET /' 

I- DEFLECTOR 

SKIRT 

MANIFOLD 

Figure 2-18. Proposed Steam Rankine Receiver Designs (see Reference 14) 

2-33 
SUPPORT 

BRACKET 

Figure 2-19. Cross-Sectional Diagram of the Garrett Air Brayton Receiver 

Test and Evaluation. After delivery to the Parabolic Dish 

Test Site in December 1980, the completed air receiver (shown in Figure 2-20) 

was instrumented and installed at the focal plane of a test bed concentrator. 

During testing, which was completed in May 1981, the receiver's operating 

range (including temperature, pressure, and flow rate) was established. Even 

though performance goals were met, it was determined that high thermal 

gradients in the Inconel heat exchanger produced stresses that would decrease 

its lifetime significantly. Solutions to this problem were formulated that 

could be applied in the fabrication of future units (see Reference 42). 

b. Garrett Steam Rankine Receiver 

Description. The steam receiver by Garrett AiResearch is 

designed to supply process heat as well as energy for powering a steam Rankine 

power conversion unit. The latter application can utilize the reheat option. 

In each case, the receiver operates from a peak solar input of 85 kWt at a 

maximum pressure of 14 MPa (2000 psi) and a temperature of 704OC (1300OF). 

Two helical tube coils form the interior cavity walls. 

coil is located adjacent to the aperture and is an 1.11-cm (0.44-in.) tube 

with a coil diameter of 0.43 m (17 in.) and a length of 0.371 m (14.6 in.). 

The reheat coil is a 1.8-cm (0.75-in.) tube with a coil diameter of 0.43 m 

(17 in.) and a length of 0.175 m (6.9 in.). 

347 stainless steel that are brazed separately and then mechanically joined 

The pre-heat boiling 

Both coils are Inconel 625 or type 

2-34 

~ 
Figure 2-20. Garrett Prototype Air Brayton Receiver 

together. The cavity heat transfer surfaces are separated from the 0.76-111 

(30-in.I-diameter outer case by approximately 10.1 cm (4 in.) of insulation. 

The top of the receiver cavity is an uncooled metal plate of RA 330 steel that 

can be adjusted in the axial direction by a screw on the exterior case (see 

paragraph below). 

as the Garrett air Brayton receiver described immediately above. A drawing 

showing the steam receiver‘s principal components is shown in Figure 2-21 (see 

Reference 41). 

The aperture assembly and mounting provisions are the same 

The Garrett steam receiver‘s movable top end plate makes it possible to 

rebalance the fluid temperature to 704OC when significant variations in the 

flux distribution occur within the receiver cavity. 

toward the aperture 4 cm (1.6 in.) shields the reheat section and provides 

reradiation from the top plate to the rest of the cavity, thus creating the 

rebalancing effect. 

Repositioning the plate 

Test and Evaluation. A prototype steam receiver (shown in 

Figure 2-22) was tested at the PDTS in early 1981. 

stable, uniform operation over the full performance range with no evident flow 

instabilities, even at very low mass flow rates. 

receiver generating steam on solar flux from a test bed concentrator. 

from the receiver frequently was used to produce fuels and chemicals (e.g., 

furfural) in an experimental test setup at the PDTS. The receiver also was 

The receiver demonstrated 

Figure 2-23 shows the 

Steam 

2-35 
REHEAT - 

BOILER 

REHEAT 

TOP PLATE 

FLUX 

Figure 2-21. Cross-Sectional Diagram of the Garrett Steam Rankine Receiver 

Figure 2-22. Garrett Prototype Steam Rankine Receiver 

2-36 
Figure 2-23. Garrett Receiver Producing Steam During Testing 

at the Focal Plane of a TBC 

used to test heat engines and could be used for developing aperture and cavity 

designs that are especially resistant to thermal shock (see Reference 42). 

C. FACC Organic Rankine Receiver. Design of a first-generation 

receiver using toluene (an organic liquid) as the primary working fluid was 

approved by the TPS Project in June 1980. Ford Aerospace and Communications 

Corporation (FACC), the designer, proceeded to fabricate the receiver as part 

of their organic Rankine-cycle (ORC) module planned for use in the Small 

Community Experiment (discussed in Section 1II.A). 

Description. The organic receiver, designed for a 30-year 

lifetime, is a direct-heated, once-through, single-tube toluene boiler capabl 

of operating at sub- or super-critical pressures (Figure 2-24). Its 

cylindrical copper shell cavity is heated by a thermal input of up to 95 kW, 

vaporizing and raising the temperature of the toluene to 399OC (7500F) at 

5.5 MPa (790 psia) as it flows through the stainless steel tubing brazed to 

the outer surfaces of the cavity. The thick copper-plate shell acts as 

"buffer" storage that inhibits flow and boiling instabilities by evenly 

distributing heat entering the receiver. The cavity assembly (core) is 

supported by eight struts, insulated with high-temperature refractory ceramic 

wool, and enclosed by a weather-proofed aluminum casing. The receiver 

aperture, 38 cm (15 in.) in diameter, is formed by a plate and lip ring made 

of copper (Reference 45). The qualification test receiver is shown in 

Figure 2-25. 

! 

2-3 7 
Figure 2-24. Cross-Sectional Diagram of the FACC Organic Receiver 

Figure 2-25. FACC Organic Receiver Prior to Engine Integration 

2-38 
Test and Evaluation. In early 1981, FACC began testing the 

ORC receiver under steady-state conditions, using a test loop to simulate the 

Rankine heat engine. 

toluene pressures and thermal outputs between 25 and 100 kWt. 

these successful qualification tests, the receiver was integrally attached to 

the ORC engine, then shipped to the PDTS for solar testing that took place 

from November 1981 to March 1982 (see Reference 42). The complete ORC power 

conversion assembly operated successfully over a complete range of operating 

conditions, and a receiver efficiency of 95% was measured. These tests 

verified the compatibility of the receiver with other ORC module components. 

The receiver was subjected to sub- and super-critical 

Subsequent to 

d. Fairchild Stirling Receiver. The Stirling receiver designed 

and fabricated by FairchildIStratos Division resulted from an effort by the 

Project in 1979 to develop an advanced receiver suitable for use with a USAB 

(United Stirling AB) engine. 

receiver by General Electric (discussed below). Both the Fairchild and GE 

designs feature a hybrid capability that allows thermal augmentation by a 

gaseous fossil fuel to provide continuous power and eliminate the need for 

storage. Stirling receivers also should be designed so that the engine-cycle 

dead space is minimal. 

This effort also included the design of a 

Description. The Fairchild Stirling receiver uses helium as 

the working fluid and operates on 76.5 kWt from a dish concentrator or on 

70.0 kWt from fossil fuel combustion. The surface of the receiver's cavity is 

a copper conical plate with integral spaces through which the helium passes. 

The passages are formed by tubes made of Inconel 617 embedded in a copper 

matrix that is, in turn, encapsulated by an Inconel 617 sheet. The conical 

plate is heated by solar radiation and also by combustion gas on the back 

surface and the regenerator tubes. The receiver's design operating ranges are 

&Kn tn Ql&Op (13nn tn lWnoUl and ln.5 tn I& MPn (1500 tn 3000 nsil when 

directly coupled to the cylinders and regenerator housings of a Stirling 

engine (Figure 2-26 ) . 

Test and Evaluation. Combustion and heat transfer tests 

were conducted at Fairchild by JPL, Fairchild, and the Institute of Gas 

Technology. After reliable cold-start performance, full design output power, 

and turndown capability were demonstrated (Reference 461, the receiver was 

shipped to JPL in December 1980 for combustor and preheater tests. Fully 

integrated testing of the receiver and the power conversion unit at United 

Stirling in Sweden resulted in leaks in the heater heads. The heads were 

subsequently repaired by the manufacturing subcontractor, Solar Turbines 

International. 

In September 1981, the complete Stirling engine/receiver power 

conversion assembly (PCA) was installed on a test bed concentrator by 

personnel from JPL, United Stirling AB of Sweden, and Advanco Corporation, 

which was responsible for PCA integration and functional testing. The PCA 

operated in a hybrid mode at heater head temperatures of up to 77OOC 

(14200F), mean engine pressures of 11 MPa (1625 psia), and solar thermal 

inputs up to 20 kW with 25% of the TBC facets uncovered. 

terminated after the PCA generated 15 kWe (which were fed into the Southern 

California Edison 

Testing was 

2-39 
Figure 2-26. Fairchild Receiver/Stirling Engine Quadrant 

and Burner 

distribution grid) from 509, of the TBC mirror facets. 

caused failures in the receiver heater head when hot combustor gas impingement 

caused the braze joint on the outermost heater head tube to open. Funds have 

not been available for the redesign and repair required to enable further 

performance testing of the hybrid system (see Reference 36). 

This thermal input 

e. General Electric Stirling Receiver 

Description. The General Electric preliminary design of a 

heat pipe Stirling receiver featuring energy storage is shown in Figure 2-27. 

It consists of fourteen primary heat pipes and one secondary heat pipe, all 

containing sodium for high-temperature operation. The secondary heat pipe is 

embedded in sodium-fluoride/magnesium-fluoride (NaF-MgF2) eutectic salt that 

provides latent heat storage. A natural gas combustor with a set of tertiary 

heat pipes for transporting heat to the large secondary heat pipe allows 

hybrid (fossil-fuel/solar) operation. 

with a 24-kWe Stirling engine at a temperature of approximately 83OOC 

(1520OF) and to provide 48 minutes of thermal storage. 

The receiver is designed to operate 

Preliminary Testing. A modular experiment was conducted at 

General Electric on a single primary heat pipe and a secondary heat pipe 

containing three standard design salt containers and a heat extraction coil to 

simulate a Stirling engine. The test apparatus performed successfully at all 

2-40 
2-4 1 
operating angles and modes (Reference 47). 

defining the operating characteristics of the thermal transport and storage 

systems (see Reference 27). 

precluded fabrication of a complete test unit. 

These tests also provided data for 

Funding reallocations by the Department of Energy 

f. Sanders Air Brayton Receiver 

Description. Early in 1980, Sanders Associates was 

contracted to design and build a high-temperature (137OoC, 2500OF) air 

receiver using a ceramic honeycomb and operating at 2 atmospheres. 

Figure 2-16b.) 

heats the honeycomb matrix (shown in Figure 2-28). Air (or another suitable 

gas) flows through the honeycomb, extracts the energy, then passes through a 

short-term (buffer) ceramic storage matrix before exiting the receiver. The 

directly heated matrix is made from sintered beta-silicon carbide; the storage 

matrix is made from mullite. The cavity assembly is encased in a carbon steel 

housing that is 1.2 m (47.2 in.) long and 0.75 m (30 in.) in diameter. The 

first test unit of this type of receiver is shown in Figure 2-29. 

(Refer to 

Solar energy passes through a fused silica window and directly 

Test and Evaluation. Upon completion of fabrication in 

September 1980, Sanders conducted in-house testing before delivery to the PDTS 

for solar performance and interface compatibility tests. 

testing at different power levels from one quarter (25% of TBC mirror facets 

uncovered) to full power, or about 20 to 80 kWt input, and at various inlet 

and outlet temperatures. 

The latter included 

At full power, receiver outlet temperatures of from 

Figure 2-28. A 30-deg Sector of Ceramic Honeycomb Matrix 

2-42 
O$IG[T4j4. PkGE :s 

OF P08R qUkln 

870 to 1425OC (1600 to 2600OF) were achieved (see Reference 34). Estimates 

of efficiency are 60% at 120OOC (2200OF) and 70% at 8700F (16000F), 

accounting for aperture losses (see Reference 29). 

Results of the Sanders receiver test program demonstrated the 

feasibility of this concept for system configurations requiring exit air 

temperatures above those attainable with state-of-the-art metal designs. A 

modified version of this ceramic receiver is used in a parabolic dish module 

employing a recuperated subatmospheric Brayton-cycle engine (Reference 48) 

(see Section 111). 

g. Experimental Solar-Only Receivers. Five United Stirling 

experimental solar-only receivers (ESORs) were successfully operated with a 

Stirling-cycle engine at the JPL Parabolic Dish Test Site from 1982 to 1984 

under a test program funded jointly by DOE and the receiver manufacturer. 

Objectives of the test program were to gain practical operating experience, to 

improve the performance of the Stirling power conversion unit (PCU), and to 

establish the feasibility of fabricating commercial solar receivers. 

The experimental solar-only receivers, which differ primarily in 

construction of the tube-manifold of the heater, are described in Table 2-6. 

All were operated for many hours with no failures although burnout of three 

receivers occurred because of operator error. The damaged receivers were 

repaired by brazing in replacement tubes (Reference 49). 

Figure 2-29. Sanders Ceramic Receiver Test Unit 

2-43 
Table 2-6. United Stirling Experimental Solar-Only Receivers 

Tested at the PDTS (see Reference 49) 

Receiver Designation Description 

ESOR-I Standard combustion system heater 

ESOR-I IA Solar-only receiver with manifold 

ESOR-I IB Solar-only receiver with only single tubes 

ESOR-I I I Solar-only receiver with only single tubes 

but with increased diameter and tubes 

of the "hair pin" type 

ESOR-IV Optimized receiver for solar application 

with consideration of production cost 

A comparison of data collected during testing of ESOR-IIA and IIB, 

operating with helium (He) and hydrogen (H2) and with different concentrator 

alignments, is presented in Table 2-7. Results of this comparison show that 

concentrator alignment produces a first-order effect on Stirling PCU 

performance, i.e., efficiency of the PCU improves with increasing thermal 

input from the concentrator (Reference 50). 

During subsequent testing, ESOR-I11 (shown in Figure 2-30) performed 

better than ESOR-IIA or IIB. Because ESOR-111's tube length was optimized in 

relation to the outer receiver diameter, a lower operating pressure was 

achieved for the same output power. It was shown that, with ESOR-111, the 

highest dish/Stirling power subsystem output can be attained with a working 

gas pressure of no more than 20 MPa (see Reference 50). 

The Stirling engine test program at the PDTS was terminated before data 

from testing of ESOR-IV could be evaluated. 

5. Receiver Technology Assessment Summary 

The TPS project paid particular attention to solar receivers. 

Even though receivers are much less costly than concentrators or engines, they 

are the essential link in the power cycle between the dish and engine, 

providing the variability in the power chain that allows optimization of the 

more costly components. 

several prototypes built and tested to provide empirical proof of the design 

methods. These included water/steam boilers, both single-phase and boiling 

liquid heaters, and metal and ceramic gas heaters. Temperatures ranged from 

around 150°C (300°F) to the 1425°C (2600°F) outlet temperature of the Sanders 

high-temperature solar receiver. Pressures ranged from below atmospheric 

pressure air up to the over 14-MPa (2000-psia) steam outlet of the Garrett 

A number of receiver concepts were developed and 

2-44 
8iiilGB;dAL PAGE E5 

OF POOR QUALITY 

Table 2-7. Results of ESOR-IIA and IIB Testing with Different 

Concentrator Alignments (see Reference 50) 

Work- Engine Max. Gas Insola- Ef f iReceiver Date ing Output, Pressure, Temp., tion, Input, ciency, 

Type (1982) Gas kWe MPa OC W/m2 kWt % 

ESOR-IIA March He 19.5 17.3 700 915 68.6 28.4 

ESOR-IIB March H2 20.7 15.3 680 980 73.5 28.2 

March He 19.5 17.0 6 90 973 73.0 26.7 

ESOR-IIA July H2 24.2 19.7 704 960 72.0 33.6 

July He 20.7 19.4 700 906 67.9 30.5 

ESOR-IIB June H2 22.4 17.6 699 898 67.3 33.2 

June He 20.6 18.6 691 922 69.2 30.0 

Figure 2-30. ESOR-I11 

2-45 
steam receiver. Heat transfer fluids included water, organic liquids, and a 

variety of gases. Special heat exchangers were developed to accommodate 

system requirements such as (1) the need for symmetry and low volume for the 

Stirling cycle, (2) low pressure drop at high temperatures for the Brayton, 

and (3) two-phase flow in boiling Rankine systems. This wide variety of 

operating needs proved that highly efficient solar receivers were practical 

and attainable with careful design methods. 

on thermal engineering problems unique to solar receivers. 

need to emphasize cavity dynamics for balancing convective and radiative 

losses from the cavity aperture. Another element receiving concentrated 

effort was the development of passive aperture plate materials of reasonable 

cost that could withstand the intense heat of solar "walk-off" (Reference 51). 

Also included was work on methods to accommodate the non-uniform heat 

distribution on the cavity walls by enhancing axial conduction and providing 

superior forced cooling in regions of high flu. Thus, by combining a variety 

of advanced heat transfer techniques into the cavity receiver, long-lived, 

highly efficient solar receivers were proven practical and cost-effective. 

Experimental work centered mainly 

This included the 

C. POWER CONVERSION UNITS 

1. Engine Characteristics 

Engines for parabolic dish-electric modules have characteristics 

that distinguish them from automotive or any other off-the-shelf engine. A 

parabolic dish engine must be relatively small: As engine size and power 

increase, so does the dish area required to provide the optimal solar flux for 

engine operation. It has been determined that power converters in the range 

of 15 to 25 kWe are suitable for use with dish concentrators of about 11 m in 

diameter. Engines larger than automotive-size require such large dishes that 

the resultant manufacturing, transportaton, and maintenance costs for the 

concentrator would offset the gain in engine efficiency. Engine weight is 

also an important consideration because it affects overall system weight and 

the dynamics of tracking control. All engines are inherently subjected to 

temperature variations and mechanical stress. In dish modules, engine stress 

is increased because of uneven thermal input, non-horizontal operation, and 

start-up and shutdown. Adequate engine lubrication and cooling are problems 

aggravated by the variable attitudes imposed on the engine by dish mounting. 

Brayton-, Rankine-, and Stirling-cycle engines -- some available and 

others undergoing development -- offer the most promise for dish systems. 

Available small reciprocating Rankine engines operate on a simple steam cycle 

without reheat and have relatively low efficiency. 

the use of an organic working fluid are attractive Rankine-cycle alternatives 

for dish power converters. Small Brayton engines considered adaptable include 

unregenerated Brayton units (that drive a generator and require the addition 

of a recuperator for acceptable efficiency), the automotive advanced gas 

turbine, and the subatmospheric Brayton cycle (SABC). Future Brayton engines 

employing ceramic parts could operate at higher temperatures (above 87OoC, 

or 1600OF) and corresponding higher efficiencies. Stirling-cycle engines 

require some modification for solar use, e.g., changes to the lubrication 

system to allow inverted engine operation. 

concept and its high thermal efficiency make the Stirling-cycle engine an 

attractive candidate. 

Compound steam cycles or 

The use of an external heat supply 

2-46 
2. Strategy for "Solarization" 

Efficiency, reliability, and cost are the critical issues in 

modifying heat engines for parabolic dish-electric modules. A highly 

efficient power conversion unit (heat engine plus alternator and associated 

controls) can reduce the size of the concentrator required, but also must 

operate at high temperatures. Therefore, the reliability of the engine's many 

moving parts must be assured as they operate in this extreme environment. The 

engine also represents a significant part of the total module cost; hence, a 

trade-off exists between cost (including operation and maintenance) and 

efficiency (see Section IV, "System Performance and Economic Projections"). 

The JPL program to adapt suitable engines for dish-electric modules 

began in 1978 with consideration of small (15-kWe) engines designed for this 

purpose in conjunction with the NASA Lewis Research Center (LeRC) heat engine 

evaluation program. The engines that were subsequently modified for use in 

dish-electric solar power modules are listed in Table 2-8. 

Engines considered by the JPL TPS Project as first-generation were the 

Rankine and air Brayton cycles, which were expected to operate at efficiencies 

of 25 to 35% for applications in the early 1980s and for which considerable 

technology was available (see Reference 14). Design studies of turbine and 

reciprocating Rankine engines in addition to open- and closed- cycle Brayton 

engines are discussed in Section II.C.3.a below. Two Rankine cycles were 

subsequently tested by the Project for use in dish modules aimed at the 

near-term small community market: (1) two simple-cycle steam engines by Jay 

Carter Enterprises: 

to be the only available small steam engine suitable for use with a 25-to-SO 

m2 dish concentrator, and a 15-kWe two-cylinder steam engine suitable for 

larger concentrators; (2) an organic Rankine-cycle engine/ alternator capable 

nf nneratinm at hipher efficiencies than steam Rankines, yet at moderate 

temperatures (400OC, 7500F). These two engines are described in Sections 

II.C.3.b and c, respectively. An open-cycle Brayton engine by Garrett 

AiResearch was selected ror detaiiea aesign ana Eabricaiiuu uui U; thG six 

initial design studies completed for the TPS Project. The Garrett design is 

to include a hybrid capability (i.e., can operate on both solar and 

fossil-fuel input) and is based on the automotive advanced gas turbine (AGT) 

being developed under the LeRC program. The "solarization" of the AGT and 

also of the recuperated subatmospheric engine (another promising Brayton 

concept) are described in Sections II.C.3.d and e. 

a 5-kWe single-cylinder steam engine, which was believed 

Engines considered as second-generation (advanced) were Stirling engines 

and higher-temperature (above 870OC, 1600OF) Brayton engines that could 

achieve efficiencies of 35 to 45% and be used in dish-electric applications by 

1985. An automotive Stirling engine was modified and tested in a solar mode 

at an efficiency of 40% (engine only, not accounting for parasitics). 

JPL program to adapt a United Stirling of Sweden engine and the following 

extensive test series are covered in Section II.C.3.f. Ceramic Brayton 

engines, being pursued under the automotive advanced gas turbine engine 

program, could result in high-efficiency Brayton-dish modules. 

This 

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2-48 
3. Adaptation and Testing of Principal Engine Cycles 

a. Conceptual Design Studies (Rankine and Brayton Cycles). 

During 1979, conceptual design study contracts were completed for the purpose 

of identifying small engines (Rankine and Brayton cycles) in the 10- to 20-kWe 

range that could be modified for first-generation dish-electric applications 

by 1982 (see Reference 17). 

and 2-32 and described in Table 2-9. The studies were limited to available 

engines or those that could be modified using available technology. Following 

parametric studies, design points were selected for each engine configuration, 

and conceptual designs were evolved. 

The engines studied are depicted in Figures 2-31 

Steam Rankine Designs. The Rankine engines studied would 

require modest development to achieve goals for performance and lifetime 

(100,000 hours). The Sundstrand two-stage, reentry turbine (Figure 2-31a) 

would have required verification of a design life of 100,000 hours for bearing 

and seal designs and for overall operation at 73OOC (13500F). A Jay Carter 

Enterprises' reciprocating engine (Figure 2-31b) would have required development from their simple steam cycle operating at 540% (10000F) to the compound cycle designed under the study contract. This engine could be designed 

for a 30-year lifetime with major overhauls at 10-year intervals. The FosterMiller Associates engine design (Figure 2-31c) used "counterflow" (versus 

uniflow in the Carter engine), which means that heat transfer between the 

inlet and exhaust must be essentially eliminated in order to achieve high 

performance. Additional modifications to the Foster-Miller design required to 

meet design goals were (1) the use of graphite rings to eliminate lubricating 

oil and (2) hydraulic operation of the valves. 

A: P Rrs-rtnn neci onc - The onen- and closed-cycle Brayton 

engines designed by Garrett AiResearch were based on available engines in different development stages or on existing technology optimized to meet required 

performance. The Garrett open-cycle near-term (baseiinej concepi was a iurhcompressor (Figure 2-32A) developed for a military generator for an auxiliary 

power (30-kWe) unit. The closed-cycle Brayton (Figure 2-32B) was based on a 

Pacific Fruit Express engine (15-20 kWe) to power a commercial transportation 

refrigeration unit. The second open-cycle unit (Figure 2-32C), an optimized 

turbocompressor based on technology developed for the Brayton Rotating Unit 

turbine (using gas bearings and an integral, permanent magnet alternator), 

would require more time to develop than the baseline design. 

b. Steam Rankine-Cycle Engine. A simple Rankine-cycle steam 

engine was selected by the TPS Project for "solarization" and testing because 

it was the only available steam engine suitable for use with a small (6-m) 

parabolic dish. A 5-kWe single-cylinder steam engine (Figure 2-33) built by 

Jay Carter Enterprises was purchased by JPL in 1981 for use as a dish module 

power converter. Prior to this procurement, Jay Carter completed a 

preliminary design study based on one of their Rankine-cycle engines (with a 

two-cylinder expander) for this application. The study determined that for a 

15-kWe engine/induction alternator unit, a single-cylinder expander was 

optimum for a simple cycle and two cylinders were optimum for a reheat cycle. 

Verification of this model through testing of the two-cylinder engine resulted 

2-49 
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2-52 

~ 
ORiGtMAL PAGE IS 

OF POOR QUALm 

Figure 2-33. Carter 5-kWe Single-Cylinder Engine Under Test 

in predictions of thermal-to-electric efficiencies of 26% for the simple cycle 

and 30% for the reheat cycle at an operating temperature of 677OC (1250OF) 

and a 15-kWe power level (Reference 52). 

Solarization of the 5-kWe Carter engine required (1) modifying and refurbishing the piston, piston rod, and crankshaft; (2) machining a new cylinder 

head; and (3) replacing several small parts. 

Test Site utilized a net concentrator aperture area of 87.6 m2, a Garrett 

steam receiver, and a transport line to supply steam to the engine, which was 

located on the ground. 

for these preliminary tests. 

399OC (750OF) and pressures to 7.7 MPa (1100 psi). 

a peak thermal efficiency of 12.7%, which is between 90 and 95% of the 

calculated efficiency for the engine operating at the reduced conditions of 

the test (see Reference 34). 

this engine at peak steam design conditions of 566OC (1050OF) and 14 MPa 

(2000 psi) should be 12 to 15%, which is excellent for small, single-expansion 

steam engines. 

Testing at the Parabolic Dish 

A bypass valve was used to control steam conditions 

Steam temperature was limited to approximately 

Test results indicated 

Therefore, the predicted thermal efficiency of 

c. Organic Rankine-Cycle Engine. The organic Rankine-cycle 

(ORC) power conversion unit was selected for first-generation dish-module 

applications because it had the potential for high efficiencies at moderate 

operating temperatures (around 4OOOC). Ford Aerospace and Communications 

2-53 
Corporation, the system contractor for the ORC module field experiment (see 

the Small Community Experiment described in Section 111), subcontracted with 

the Barber-Nichols Engineering Company early in FY 1980 to design and 

fabricate an ORC engine assembly (see Reference 27). 

Description. The ORC engine uses toluene as the working 

fluid at a maximum operating temperature of 399OC (7500F). Toluene 

(CgHgCH3) yields high performance at lower temperatures and pressures 

than does steam. To avoid leakage and contamination of the working fluid, the 

ORC engine assembly is hermetically sealed (i.e., has no moving seals) with no 

external dynamic seals. The toluene lubricates the bearings, cools the 

alternator and pumps, and operates the hydraulic actuator of the control valve 

(Reference 53). The engine has a design power output of up to 20 kWe at rated 

conditions of 75.6 kWt input and 28OC (82OF) ambient air temperature and 

is designed to operate at all solar-related elevation angles from 5 to 90 deg 

above the horizon. 

The complete ORC power conversion unit, shown in Figure 2-34, consists 

of the FACC organic receiver (described in Section II.B.4.c), the 

Barber-Nichols ORC engine assembly, and a permanent magnet alternator and 

rectifier by Simmonds Precision. The components of the engine assembly are a 

fan-driven, air-cooled condenser, a centrifugal feed pump, a regenerator (heat 

exchanger), and a single-stage axial flow turbine. The feed pump and turbine 

are mounted on the alternator shaft, which carries the permanent magnets and 

rotates at speeds between 50,000 and 60,000 rev/min. 

speed makes it possible for the turbine/alternator/pump assembly to be of a 

compact size and also allows the main feed pump to supply full system flow at 

pressures up to 5.9 MPa (855 psi) with a centrifugal impeller only 33 mm 

(1.3 in.) in diameter (see Reference 53). 

This high operating 

During operation, the toluene flows in a closed loop and is expanded 

through the turbine. The exhaust vapor then passes through the regenerator to 

preheat the toluene entering the receiver then through the condenser and 

finally the pump. The permanent magnet alternator converts the mechanical 

output of the engine to high-frequency, three-phase alternating current (ac), 

which is converted to direct current (dc) by a ground-mounted rectifier. An 

inverter by Nova changes the dc output of the rectifier to three-phase, 60-Hz 

current at 480 V that can be fed directly into an electric utility distribution grid. Additional ground-mounted equipment includes the overspeed brake 

controller and relays. 

Fabrication and Qualification Testing. Barber-Nichols 

fabricated the turbine wheel using an electrochemical machining technique and 

completed fabrication and testing-of the condenser core, boost-pump, and start 

pump prior to qualification testing of the engine/alternator/rectifier subsystem that took place in May 1981. The subsystem was tested at Barber-Nichols 

for 28 hours at elevation angles of 5, 45, and 90 deg (Figure 2-35). 

Efficiencies as high as 23.5% (net dc electric output divided by thermal input 

and accounting for parasitic losses) were demonstrated. The subsystem was 

then shipped to FACC and integrated with an electric resistance heater, 

receiver, inverter, and control system for testing that resulted in successful 

operation for 27 hours under stable operating conditions for steady-state, 

2-54 
7 CONDENSER VAPOR HEADER 

CONDENSER TUBES 

*/-=REEN 

VUOR THROTTLE VALVE 

7 RECEIVER CORE 

RECEIVER WTER SMELL 

APERTURE PLATE REOENERATOR 

TURI)O.ALTERNATOR 

POWER CONVERSION ASSEMBLY 

UIFRYFATFn HIGH PREP 

IULUCNC LlUVlY 

VAPOR IN 

TURB INE-ALTERNATOR-PUMP (TAP) 

CORE 

Figure 2-34. ORC Power Conversion Assembly with Detail of the 

Turbine/Alternator/Pump (see Reference 53) 

2-55 
Figure 2-35. ORC Qualification Testing at Barber-Nichols 

transient, cold and hot start-up, and normal and emergency shutdown modes at 

various thermal input levels. Grid-connected solar testing, begun in January 

1982, is described below. 

Solar Testing and Evaluation. The program for testing the 

ORC power conversion unit at the focal plane of a TBC at the Parabolic Dish 

Test Site (Figure 2-36) included determination of performance, stability, and 

efficiency in all operating modes as well as verification of subsystem 

compatibility (see Reference 29). On thermal input from the test bed 

concentrator, the ORC unit operated for a total of 33.6 hours at an insolation 

level of 950 W/m2. Operation was smooth throughout the test series that 

included the following conditions: variable insolation levels and cloud 

passages, planned and random start-ups and shut-downs, various inverter input 

voltage settings, and all control modes. Measured outputs of the subsystems 

under test and the corresponding calculated efficiencies are shown in 

Figure 2-37. From a thermal input of 70.8 kW, the ORC engine/alternator/ 

rectifier generated 16 kWe at an efficiency of 23% after accounting for 

parasitic losses (References 54 and 55). 

In March 1982, the ORC test unit was removed from the TBC. Subsequent 

disassembly and inspection of the turbine/alternator/pump revealed three 

problems: (1) electrical arcing from the stator winding to the housing, 

2-56 
ORIGINAL PAGE IS 

OF POOR QUALITY 

Figure 2-36. The ORC Receiver/Engine/Alternator Mounted on a 

TBC for Solar Testing 

2-5 7 
SYSTEM 

COMPONENT 

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Figure 2-37. Measured Performance of the ORC Test Unit 

(2) rubbing of the feed pump impeller, and (3) higher-than-predicted bearing 

wear. It also was discovered that alternator and feed pump efficiencies were 

lower than expected. The most promising method for increasing the alternator 

efficiency is to change the number of stator poles and to wire the armature 

portions in series instead of in parallel. Changes in the contour of the 

diffuser are expected to lessen performance problems caused by the feed pump. 

An extensive test program was initiated to solve the problems of the 

internal arcing and of the excessive bearing wear. It was determined that the 

arcing was the result of inadequate quality control during fabrication and 

assembly. The bearing wear was finally diagnosed as being caused by a 

combination of rotor dynamic and electrodynamic effects. An externally fed, 

pressure-lubricated, five-pad Waukesha bearing solved the dynamics problem. 

Mounting this bearing in an electrically insulated carrier eliminated all 

detectable bearing wear. A successful 100-h "hot" test of the ORC power 

conversion system confirmed the effectiveness of these solutions 

(Reference 56 1. 

d. Air Brayton-Cycle Engine. Open-cycle air Brayton engines 

offer higher efficiencies than the organic Rankine-cycle engine and also offer 

potential cost benefits from the automotive gas turbine development program 

being conducted at the NASA Lewis Research Center in conjunction with Garrett 

and Ford. 

2-58 
Early in FY 1980, a contract was awarded to the Garrett Turbine Engine 

Company for detailed design and fabrication of the baseline, open-cycle 

Brayton engine that was conceptualized under the study program described in 

Section II.C.3.a above. The concept subsequently was extended to include a 

fossil-fuel combustion capability for hybrid operation as well as coupling to 

the Sanders ceramic receiver described in Section II.B.4.f. 

Description. The initial engine design used an existing 

turbocompressor from the Garrett GTP 36-51 gas turbine engine (Figure 2-38, 

Reference 57). The upgraded hybrid unit, however, is based on the Garrett 

automotive advanced gas turbine (AGT 101). The "solarized" version of the 

all-metal AGT, called the SAGT, operates on either solar and/or fossil-fuel 

thermal input using a hybrid combustor. Solar input to a Brayton receiver at 

85 kWt heats the air from the recuperator [at 58OOC (1075OF) and 0.25 MPa 

(37 psia)] to a temperature of 87OOC (1600OF) for input to the turbine, 

which rotates at a speed of 80,000 rev/min. A mechanical drive reduces the 

speed to about 1800 rev/min to power a conventional electric generator. Under 

these conditions, the mechanical shaft output power of a production engine is 

estimated to be 15 kWe at an efficiency of about 32%. A later version of the 

SAGT using a permanent magnet alternator instead of a mechanical shaft drive 

is depicted in Figure 2-39. 

The SAGT has the same internal configuration as the AGT 101, with the 

exception of two specially designed ducts that channel the air flow between 

the engine and the Sanders receiver and allow for thermal expansion. Engine 

controls using a microprocessor were easily modified for performing necessary 

Figure 2-38. Initial Garrett Air Brayton Engine Concept Based on the 

GTP 36-51 Gas Turbine 

2-5 9 
Figure 2-39. Conceptual Drawing of the Garrett Solarized Advanced 

Gas Turbine Based on the AGT 101 

solar operational requirements. The induction generator is a commercially 

available, high-efficiency, 60-Hz unit that can be connected directly to the 

ac grid, thus eliminating the need for a separate power conditioning unit 

(Reference 58). Assembly of the SAGT power unit with a Sanders receiver was 

completed in July 1982 and is shown in Figure 2-40. 

Test and Evaluation. Bench testing late in 1982 of the 

metal AGT included runs to 100,000 rev/min under load and pointed to the 

following development problems: (1) interference on re-start due to thermal 

expansion caused by soak back, (2) intermittent dynamic stability problems 

from 75,000 to 100,000 rev/min, and (3) excessive leakage in the rotating 

ceramic regenerator seals and in other joints. Solar testing of the SAGT/ 

receiver unit on a test bed concentrator are planned when these problems have 

been adequately resolved (see Reference 30). 

Future Plans. Late in FY 1981, JPL planned a systems 

contract for design and integration of a parabolic dish-electric module that 

would incorporate the SAGT as the power conversion unit (see Reference 30). 

This contract was not awarded at that time because another Brayton engine (the 

subatmospheric engine described below) was chosen for incorporation into an 

experimental dish-electric module. However, testing of the SAGT was resumed 

in 1985 (see Section 1II.C). 

2-60 
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Second-generation versions of the SAGT incorporating ceramic parts are 

thought to be capable of turbine inlet temperatures up to 1370OC (2500OF). 

The shaft power of such engines has been estimated to be as high as 71 kWe at 

efficiencies up to 48% (see Reference 29). 

feasibility of ceramic materials for an all-ceramic gas turbine (Brayton) 

engine is described in Reference 3. 

SERI's work on the technical 

e. Subatmospheric Brayton-Cycle Engine. A gas-fired heat pump 

system, developed by the Garrett AiResearch Manufacturing Company for the Gas 

Research Institute, features a subatmospheric Brayton-cycle (SABC) engine 

(Figure 2-41) driving the centrifugal compressor of a reversible vaporcompression heat pump. As part of the JPL dish project, an SABC engine was 

adapted by Garrett for use in a dish-electric module. In the solarized 

subatmospheric engine, air is heated in a solar receiver to a temperature of 

870OC (16000F) at ambient pressure, passes first through the turbine, is 

cooled by the recuperator, and drawn into the vacuum created by the 

compressor. The air is then compressed (back to ambient pressure), passed 

through the recuperator again, and then returned to the receiver for heating. 

Late in 1981, a contract was initiated with Sanders Associates to design 

and integrate a dish module consisting of a concentrator, air receiver, and 

Brayton-cycle gas turbine engine (see Reference 36). The baseline subsystem 

being planned uses a Garrett recuperated subatmospheric Brayton engine, a 

Sanders ceramic air receiver, and a LaJet dish concentrator. 

Figure 2-41. Subatmospheric Brayton-Cycle Engine 

2-6 2 

ORIGINAL PAGE IS 

OF POOR QUAlf'lT 
ORIGINAL PAGE IS 

OF POOR QUALITY 

At the beginning of 1984, the unimproved SABC Mod IIIA engine was 

assembled, bench tested, and qualification fuel tested at Garrett AiResearch. 

These preliminary tests indicated low performance, but it is not clear whether 

this was due to the engine itself, the passive solar receiver used for 

testing, the load cell permanent magnet alternator, or the test calibration 

(Reference 59). 

Associates for integration into the Brayton developmental test module as 

described in Section 111. 

In April 1984, the Mod IIIA engine was delivered to Sanders 

f. Stirling-Cycle Engine. The decision to modify a Stirlingcycle engine for second-generation dish application was based on the engine's 

high efficiency and reasonable cost (Reference 60). In 1980, JPL awarded a 

contract to United Stirling AB of Sweden (USAB) to modify a Stirling engine 

for use in a dish-electric module. Their Model 4-95 was found to be the ideal 

choice because its thermal energy requirement is 65 kWt, which is consistent 

with the established baseline design for the Stirling engine subsystem based 

on a 10-m-diameter concentrator with a focal length of 0.6. 

Description and Modification. The USAB Model 4-95 Solar 

Mk I engine (shown in Figure 2-42 with an integral receiver) is a 

four-cylinder (95-cm3 displacement per cylinder), double-acting kinematic 

machine with a drive shaft and two crankshafts. Throughout 150,000 hours of 

testing on 16 unmodified engines, the 4-95 was found to be clean, efficient, 

and durable. A new rod seal, a critical element, demonstrated high 

reliability with no failure modes (Reference 61). 

Figure 2-42. USAB Stirling Engine with Integral Receiver 

2-6 3 
ORGINAL PAGE IS . W P08R QUALITY 

Modifications to the 4-95 for solar use are necessary principally 

because of the inverted operating position required. Changes to the 

lubrication system included machining numerous holes to form oil drainage 

passages in the crankcase bulkheads and gas compressor housing to provide 

adequate drainage by gravity alone. To further assure “dry sump” operation 

under dynamic conditions, an external scavenging pump was installed with an 

external pressure lubrication pump adjacent to it. An external oil’tank was 

installed below the lowest drainage point and connected to the crankcase 

outlets by short pipes. USAB also attached a General Electric induction 

alternator to the engine and fabricated a steel frame for mounting the 

engine/alternator to a test bed concentrator (Reference 62). 

Testing in the Inverted Position. Early in 1981, testing of 

the 4-95 Stirling engine in the inverted position using helium as the working 

fluid took place at USAB in Sweden (Figure 2-43). Under simulated dish module 

orientation, the engine operated successfully for a total of 350 hours at 1500 

rev/min with a heater-head temperature of 71OOC (1310OF) and a coolant 

temperature of 5OoC (122OF). The maximum power output was 22 kWe at an 

overall efficiency of 31.5%. 

oil flow were solved by increasing the drainage pipe area. 

mined that the piston rod sliding seals were capable of functioning well in 

the inverted position (see Reference 62). 

engine/alternator was coupled to the Fairchild hybrid receiver (described in 

Section II.B.4.d) then shipped to the PDTS for solar testing. 

Minor problems that occurred during testing with 

It was also deterIn June 1981, the Stirling 

Figure 2-43. Bench Testing of Stirling Engine/Alternator in 

Inverted Position 

2-64 
Hybrid and Solar Testing. Upon its arrival at the solar 

test site, initial tests were conducted on the Stirling engine/receiver unit 

by Advanco Corporation, the system integrator, prior to concentrator 

mounting. Personnel from JPL, USAB, and Advanco installed the Stirling test 

unit on a TBC for hybrid operation at heater-head temperatures of up to 

770% (14200F), mean engine pressures to 11 MPa (1625 psia), and solar 

thermal inputs to 20 kWt using only 25% of the TBC mirror facets. After 

generating 15 kWe, brazing failures in the heater head precluded further 

testing of the unit in the hybrid mode. 

Solar testing of the Stirling engine continued using five similar USAB 

experimental solar-only receivers (see Section II.B.4.g). During a series of 

sunrise-to-sunset tests using hydrogen as the working fluid (Figure 2-44), the 

power output was in excess of 25 kWe at an insolation level of 1000 W/m2, 

resulting in a solar-to-electric conversion efficiency of 29%, not accounting 

for parasitic losses. The electricity generated was fed directly into the 

Southern California Edison Company distribution grid at 60 Hz and 480 V by the 

induction alternator, with no special power processing required. Measured 

performance of the Stirling engine resulting from a range of solar tests is 

summarized in Figure 2-45. 

Future Plans. During 1983 and 1984, Advanco Corporation 

fabricated and tested a Stirling module (consisting of the 4-95 Mk I1 Solar 

SE, and a receiver and concentrator by Advanco) as the result of a DOE Program 

Opportunity Notice. This Stirling module development program is discussed in 

Section 111. 

Late in 1983, McDonnell Douglas Corporation entered into an agreement 

with United Stirling AB of Sweden to purchase 4-95 Mk I1 engines for the 

purpose of mass producing dish-electric modules for the near-term market. Th-4- .rr-n-n-n 4” -1”- rl4nn..rrnrl 4- Cant:nn 111 -“ 

4. Engine Technology Assessment Summary 

A number of heat engines have been tested at the PDTS to help 

ascertain their readiness for widespread deployment by better understanding 

their performance and operating and maintenance (O&M) costs. Engines tested 

included three steam engines (two Carters and the Omnium-GI, the 

Barber-Nichols organic Rankine-cycle engine, and the USAB Stirling-cycle 

engine. While not tested by JPL at the PDTS, two Brayton-cycle engines (the 

solarized advanced gas turbine manufactured by the Garrett Turbine Engine 

Company and the subatmospheric Brayton-cycle engine built by Garrett 

AiResearch Manufacturing Compan as well as a fourth steam engine (the Bank 

program. All of these engines were run successfully, yielding considerable 

performance data and some O&M figures. As might be expected, each of these 

engines showed strengths and weaknesses that, when combined with the large 

uncertainties in their mass production costs and particularly their long-term 

engine from the United Kingdom) x were included in the JPL engine assessment 

5Built by David D. Banks, 681 Preston Old Road, Feniscowles, Blackburn 

BB2-5EN, Lancashire, England. 

2-65 
ORIGINAL PAGE 63 

'POOR QUALITY 

Figure 2-44. Stirling Engine Generating Electricity at the TBC's 

Focal Plane 

2-66 
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 MODULE^ 26 

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Figure 2-45. Stirling Measured Performance (Receiver efficiency 

is an estimated value) 

O&M costs, make the clear choice of a single winner impossible. Efficiencies WP~P ac eynet-teA- with the Stirling engine the highest (regularly near 40% for 

the engine only), the ORC and Brayton in the mid-20% range, to the small steam 

engines in the teens. But even with this rather clear range of performance 

known, the final economic outcome is stili uncerrain uniii exiuugii 1uiig-LeL111 

O&M data can be gathered to assess plant operating costs and until pilot-scale 

rather than the current hand-built prototype production costs are developed. 

However, the pioneering work done thus far clearly demonstrates the technical 

feasibility of the small heat engine as a solar power conversion device and 

strongly indicates that continuing work will demonstrate the economic 

viability of this type of engine for many applications. 

D. ENERGY STORAGE 

The use of storage with parabolic dish-electric power plants can greatly 

reduce the problem of mismatch between the outgoing power produced solely from 

insolation and the electric power demanded by users (Figure 2-46). Hybrid 

modules, operating from both solar and fossil fuel, can provide a more even 

match between supply and demand. Or, a dish-electric plant may not require 

storage when connected to a conventional plant via a distribution grid. The 

conventional plant modulates its output so that the solar plant provides fuel 

displacement (but not capacity displacement). In this case, the conventional 

plant would take the place of a storage system (Reference 63). 

2-6 7 
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Figure 2-46. Insolation Versus Demand Load (see Reference 63) 

2-68 
To date, the many types of storage considered by the JPL TPS Project can 

be classified as either focal-mounted or ground-mounted. 

is usually called buffer storage and is integrated with the solar receiver. 

Ground-mounted systems include battery (electrochemical) storage, thermal 

storage using large external tanks, and thermochemical storage (see section on 

thermochemical transport and storage, p. 2-75). A dish power plant could 

employ hybrid modules as well as a combination of focal- and ground-mounted 

storage systems. Determination of the storage modes to be used for a 

particular plant would depend on site-specific factors that include demand, 

rate structure, and cost of capital. A methodology for evaluating the cost 

effectiveness of a thermal storage system for a specified solar power plant 

with a given demand profile is described in Reference 64. 

Focal-mounted storage 

1. Buffer Storage 

Buffer storage helps provide a constant heat input to the engine 

and also minimizes the number of start/stop cycles, thus extending engine 

life, improving engine efficiency, and reducing control requirements. Each 

type of power conversion unit would require a different amount of thermal 

buffering to handle short-term (1 hour or less) variations in solar flux. 

During 1979 and 1980, the TPS Project awarded contracts to General Electric, 

Ford Aerospace and Communications Corporation, and Garrett AiResearch for the 

purpose of evaluating latent-heat buffer storage systems for the Stirling-, 

Rankine-, and Brayton-cycle engines, respectively. 

In a related contract, a heat pipe solar receiver concept by GE 

(described in Section II.B.4.e) that incorporates latent heat thermal energy 

storage was demonstrated during modular testing on a full-scale (2.5-cm, 

1-in.-diameter) heat pipe and three full-scale (5.1-cm, 2-in.-diameter) +harms1 ctnr-uo pnntainorc- The following conclusion was drawn from the 

testing: In this design, heat pipe thermal transport and latent heat storage 

provide a near-isothermal and self-regulating heat source for stable operation 

of solar-powered engines (Keterence b5j. 

In-house efforts to develop latent heat buffer storage included (1) an 

investigation of candidate salt-containment combinations (shown in Table 2-10) 

and (2) the formulation of a computer program to simulate a parabolic dish 

receiver having buffer storage capability. 

Of the candidates listed in Table 2-10, the phase-change material 

selected for a detailed system study was NaF-MgF2 (66.9%-33.1% by weight) 

eutectic salt mixture. The analysis assumed use with a Stirlin 

converter with an output of 25 kWe at an insolation of 1.0 kW/m . Preliminary results indicated that the heat transfer characteristics within 

the phase-change material (PCM) and at the PCM/solid surface interface are 

critical factors affecting subsystem performance and that the effects become 

more severe as the storage capacity increases. It was also shown that these 

effects can be alleviated by PCM heat transfer enhancement techniques such as 

the use of fins, bulk additives, mini heat pipes, metallic meshes, and screens 

(Reference 66). 

f power 

2-69 
Table 2-10. Candidate Storage Media for Dish-Mounted Receivers 

(see Reference 27) 

Salt 

Composition Me 1 t ing Containment 

Application Temperature by Weight % Point Mat e r ial 

Rankine 42 7-454OC 61 KC1-39 MgC12 436OC 316 & 321 SS 

(800-8500F) (8160F) Cr/Mo alloy steel 

Steam Rankine 538-566OC 25.9 Na2C03-38.8 557OC 316 & 321 SS 

(L000-1050°F) NaC1-35.3 NaF (1035°F) Cr/Mo alloy steel 

Brayton, 802-728'C 66.9 NaF-33.1 MgF2 813OC 316 & 321 SS 

Stirling (1475-1525OF) (1495OF) 

Brayton, 788-829OC 75 NaC1-25 NaF 7 9 5oc 321 SS 

Stir 1 ing (1450-1525°F) (1463OF) 

Bray ton, 802-829Og 100 NaC1 802:C 9 Cr/l Mo 

Stir ling (1475-1525 F) (1475 F) alloy steel 

A computer model, called High Temperature Energy Storage (HTES), 

predicts the performance of the receiver under varying solar flux, ambient 

temperatures, various amounts of latent-heat buffer storage, and different 

thermal control techniques (see Reference 27). 

2. Battery Storage 

Surveys conducted by the Project in 1981 showed that existing 

battery manufacturers would be able to produce enough capacity by 1990 for 

several solar thermal power plants (see Reference 63). The battery systems 

for these plants would include a bidirectional converter/inverter to couple 

the system to the distribution grid (Figure 2-47). The 16 battery types 

evaluated by the Project are listed in Table 2-11 and discussed in detail in 

Reference 67. The results of the study showed that lead-acid and Fe-Cr Redox 

batteries are the most attractive storage systems for use with dish-electric 

power plants. The specific type of lead-acid battery suitable for solar 

thermal applications is one that is designed for repetitive, deep discharges 

of 5 to 10 hours on a daily basis at moderate to high power densities. 

Advanced lead-acid batteries now being developed for utility and electric 

vehicle applications are expected to cost less and provide better performance 

than batteries now in use (see Reference 27). 

3. Thermal Energy Storage 

Large thermal energy storage systems for solar thermal power 

plants are being studied and evaluated under the DOE Central Receiver Program 

2-70 
SOLAR 

INCIDENCE COLLECTOR 

AND 

RECEIVER rl CONVERTEV 

INVERTER 

ELECTRIC 

OUTPUT 

XFORMER POWER 

FILTER 

AC 

A * AND 

- STIRLING + AC t ENGINE GENERATOR 

BAITERY 

SYSTEM 

Figure 2-47. Battery Storage System for a Dish-Electric 

Power Plant Using an Ac-Link Transport 

Approach (Reference 68) 

managed by Sandia National Laboratories-Livermore (SNLL) (Reference 69). In 

1975, Sandia developed storage systems for both 10- and 100-MWe water/ 

steam-cooled central receiver power plants. As a result of these studies, * -- f? \ - 7 L nm.14- l. +.. n -0tq-e researcn experiiiie:11Lb WCLC ~CLLU~..~~~ -,. -..- yJy- --..-- ,-, - -. . - 

sensible heat storage system using oil and Hitec (an inorganic nitrate salt) 

-.-- --A (7) 2 4-fldt-h storage system that works on the thermocline principle using 

oil and rock/sand in a single tank. The latter was chosen for the 10-MWe 

Central Receiver Pilot Plant that is operating near Barstow, California. The 

pilot plant storage system operates over a temperature range of 218 to 304OC 

(425 to 5800F) and can deliver up to 7 MWe over a 4-h period. SNLL 

identified the following as promising storage applications: (1) a latent heat 

storage unit that can be integrated with a saturated steam receiver and (2) a 

process heat system requiring saturated steam. 

- 

According to SNLL (see Reference 691, high-temperature storage [815OC 

(15000F) and above] for use with central receiver plants employing Brayton 

or Stirling engines would require new system configurations and low-cost 

containment approaches. Studies conducted by the TPS Project identified a 

molten salt (NaOH) storage system as an attractive candidate for 

high-temperature (815%) dish applications (see Reference 63). 

A storage concept consisting of a cluster of dish collectors supplying 

heat (up to 815OC, 15000F) to ground-based thermal storage and power 

conversion units was analyzed at JPL (Figure 2-48) (Reference 70). In this 

study, three sensible heat systems [molten salt (NaOH), liquid sodium, and 

checker stone (discussed in next paragraph)] and one latent heat system 

[molten salt (NaF-MgF2)I were paired with Stirling and Brayton engines for 

2-71 
Table 2-11. Cost and Performance of Advanced Electrochemical 

Storage Batteries (see Reference 27) 

Battery I Cycles Battery Throughput Projected Probability of 

Type Initial Cost1 At 80% DOD Efficiency% EfficiencyX4 Availability Availability2 

Adv. 

Pb-Acid 

Na-S 

(FORD) 

Na-S 

(FORD) 

Na-S 

(DOW 

Fe-Cr 

Redox 

(LeRC) 

Zn-Cl2 

(EDA) 

(Argonne) 

Zn-Br2 

(Gou Id) 

Zn-Br2 

(Exxon) 

Zn-Br2 

(GE) 

Fe-Air 

(We s tg ) 

Ni-Fe 

(West g 1 

(EP) 

Ni-Hz 

(ERC) 

Ni-Zn 

(Could) 

Hz-Cl2 

( BNL ) 

Ni-Fe 

$116-$13O/kWeh 4000 80-85 

$4 31 We h . 2500 76 

$4 3 / kWe h 2500-5000 75 

$33/kWeh 3000 90 

10000 

2500-3 500 

3000 

2500 

2500-5000 

2000 

1000 

2000 

2000 

10000 

2000~ 

- 

75 

71-74 

85 

70 

80 

75 

50 

60 

65-70 

60-70 

90 

65 

73-78 

70 

69 

83 

69 

65-88 

78 

45 

74 

69 

46 

55 

60-65 

55-65 

83 

60 

1985 

1985 

1985 

1990 

1990 

1985 

1990 

1990 

1990 

- 

1985 

1985 

1990 

1990 

1985 

- 

0.95 

0.95 

0.80 

0.20 

0.80 

0.95 

0.70 

0.70 

0.70 

- 

0.60 

0.70 

0.70 

0.20 

0.60 

- 

1Updated to mid-1979 dollars: costs are based on 80% depth of dtscharge (DOD) and are for battery 

only (not Balance of Systems). Also batteries are overdesigned so that they will deliver full 

rated capacity at end of indicated number of cycles. 

‘Predicated upon EPRI data, vendor data, and best engineering judgment 

4Throughput efficiency (product of battery and inverter/converter ef f iciencies) 

340% DOD 

2-72 
RISER AND 

DOWNCOMER 

- 

THERMAL STORAGE- 1 A - I*- - 

- 

TOR 

Figure 2-48. Thermal Storage Concept for a Cluster of Dish Collectors 

detailed examination as 6-hour storage devices. 

energy costs in the same range as mar: or aisri ua~~ery sys~rm LL.~., ACUUA 

(FeCr), sodium sulfur, zinc chlorine, and zinc bromine], the following thermal 

(1) sensible heat systems employing molten-salt (sodium hydroxide) storage and 

transport for use with either Brayton or Stirling engines, and (2) latent heat 

systems using (a) an engine-powered (Stirling) concept of direct contact, 

scraped tube, passive, and polished tube and (b) a direct-contact Brayton 

concept. 

Based on the achievement of 

-&----- ----*--- 0-- the --.-.c nrnmi~in~ fnr rlich r11rctcl.r nrrnngmnents: uc"r.agL O,OC\-...U UL" *I._ ...- y- r---..----- 0 --- -~-- 

A unique storage concept developed by Sanders Associates under contract 

to JPL is the "checker stove" -- similar to a scaled-down version of large 

storage/regenerator systems used in the glass and steel industry. 

checker stove, designed for use with a gas turbine engine, uses cordierite 

ceramic honeycombs as the storage material (see Reference 7). 

The solar 

E. TRANSPORT 

Transport systems for parabolic dish power plants are of three types: 

thermal, thermochemical, and electric. Thermal transport systems carry heated 

transfer fluid from a field of dish collectors (with distributed, focalmounted receivers) to a ground-mounted turbine/generator for electricity 

production or directly to the point of use requiring process heat (Figure 2-49). 

2-73 
Thermochemical transport is a type of thermal transport where energy is 

absorbed in the receiver using an endothermic reaction, transported to its 

point of use at lower temperatures, then released by an exothermic reaction. 

An electric transport system collects electricity from dish modules (with 

distributed, focal-mounted enginelreceiver units), processes it as required, 

and delivers it to the load (Figure 2-50). 

1. Thermal Transport 

During 1980 and 1981, the TPS Project examined cost-effective 

thermal transport for dish collectors. Earlier studies had shown that 

transport losses from networks (including pumping requirements and thermal 

losses) using hot water (93OC, 20O0F) and steam (51OoC, 9500F) were 

generally less than 10% of the total output of a field of collectors producing 

up to 30 MWt. Optimized, low-cost transport systems, achievable through 

automated factory fabrication and semi-automated field installation, would 

cost 45% less than systems built using conventional labor-intensive 

techniques. 

than 10% even up to plant sizes of 100 MWt (see Reference 5). 

Transport losses from these optimized systems would also be less 

A computer optimization code was developed at JPL to evaluate thermal 

transport concepts and to determine the most cost-effective thermal transport 

layout. The code incorporated data on dish collector spacing, operating 

temperatures, heat losses, fabrication techniques, pumping losses, and costs 

(see Reference 29). 

Figure 2-49. Artist's Concept of a Dish Collector Thermal 

Transport System (see Reference 5) 

2-74 
SMALL HEATENGl NEIGENERATOR CAVITY r SMALL HEATENGl NEIGENERATOR 

COLLECTOR 

FIELD 

ELECTRIC EXTERNAL TRANSMISSION 

COLLECTION STORAGE GRID 

Figure 2-50. Parabolic Dish-Electric Transport Concept 

(see Reference 67) 

2. Thermochemical Transport (and Storage) 

The use of reversible chemical reactions was also studied as a 

means for transporting (and storing) thermal energy. These reactions are 

utilized to decompose and synthesize the working (or transfer) fluid ana are 

usually aided by catalysts. Because the temperature of the transport line 

would be close to ambient, thermal losses and piping/insulation costs would be 

minimized. The most promising candidate reactions for dish applications are 

sulfur trioxide (SO3) decomposition, carbon dioxide reforming of methane, 

and steam reforming of methane. A JPL study (Reference 71) of these three 

candidates recommended that the use of reversible reactions for energy storage 

not be considered further. For transport-only systems, further analysis is 

recommended if cost projections for chemical transport systems are 

substantially lower than those for thermal transport systems. 

3. Electric Transport 

Most dish-electric applications require that utility-grade power 

be delivered directly to the distribution grid. This can be accomplished 

either by (1) constant-speed operation with synchronous generation, or 

(2) variable-speed operation with variable-speed, constant-frequency 

generation (Reference 72). 

Project for variable-speed, constant-frequency generation schemes: 

The following approaches were evaluated by the TPS 

2-75 
a. DC-Link Approach. In this approach, either a dc generator 

or a permanent-magnet variable-frequency alternator with a rectifier is used 

to generate dc power (Figure 2-51). In either case, the power is fed into an 

inverter to obtain a constant-frequency, constant voltage output for the 

distribution grid. 

rectifier was planned for use with the organic Rankine-cycle module for the 

Small Community Experiment and also with a Brayton system, both described in 

Section 111. 

A dc-link approach using a permanent-magnet alternator and 

b. AC-Link Approach. A conventional ac generation system is 

used with the Stirling-cycle module (Section 111). 

Figure 2-47 with the addition of battery storage. 

systems also have been considered for dish-electric plants: 

used in conjunction with a high-frequency generator and a field-modulated 

generator. Field modulation and demodulation techniques use an 

electromagnetic modulator, in which the rotating field coil is excited with 

alternating current at the required low frequency. Output is obtained by 

demodulation employing either a high- or a low-frequency switching scheme. 

Studies conducted by the TPS Project showed that field-modulated generation 

for dish-electric transport is most suitable when (1) the rotational speeds of 

the heat engine are high (such as is typical of Brayton-cycle engines), (2) the 

heat engine is operated in a variable speed mode, and (3) utility-grade ac 

power is required for feeding into the grid without an intermediate storage 

and reconversion system (see Reference 72). 

This approach is shown in 

a cycloconverter 

Two special ac generation 

SOLAR 

ENERGY INPUT 

CONTROL 

CENTER 

THERMAL 

STORAGE 

AND 

TRANSPORT 

PROTECT ION 

HEAT BATTERY AND I 

ENGINE SYNCHRO 

4 t 

CONVENTIONAL AC VA DC/AC HARMONIC - INVERTER - FILTER DC AC GENERATOR - 

J 

I 

- LINE 

I 

1 

Figure 2-51. Conceptual Block Diagram for a Solar Generation Unit 

Using a DC-Link Approach with an AC Generator and 

Rectifier (see Reference 67) 
F. CONTROLS 

The control system for a dish-electric power plant is required to 

provide completely autonomous operation. The system consists of the hardware, 

software, and facilities needed for operating the entire electric power supply 

system (see Reference 6). 

and controls plant functions during start-up, shutdown, and normal operation, 

as well as during intermittent operation and emergency situations. Control 

functions are provided for individual modules so that each is selfsufficient. A two-way data link allows direct communication between the 

module processors and the central plant processor. 

A central microprocessor or minicomputer monitors 

Three major subsystems comprising the control system assure not only 

accurate plant monitoring, but also maximum plant efficiency and safety. 

These three subsystems are (1) concentrator pointing (tracking) control, 

(2) fluid temperature control, and (3) power output control. 

a. Concentrator Pointing Control. Studies conducted by the TPS 

Project show that pointing errors can reduce significantly the efficiency of a 

parabolic dish collector and that on/off tracking control systems inherently 

produce time varying pointing errors (Reference 73). Therefore, accurate sun 

tracking, provided by module processors, is a critical factor in maintaining a 

high concentrator efficiency. 

allows the concentrator to acquire and track the sun using stored data, 

ephemeris data, and/or sun sensors and also moves the concentrator to a stow 

position when the module is not operating. 

The computer-controlled tracking mechanism 

b. Fluid Temperature Control. A dish module engine's cycle 

efficiency is optimized by maintaining the maximum allowable temperature of the 

in Section II.D.l above) can provide this constant heat input, or the flow 

rate of the working fluid can be varied, for example, by a controllable vapor 

valve, as used in the organic Rankine-cycle module (Reference 74). 

--- -*-!-- I1 13 -L LL- ---- -..el-& T-t,-e Lent L..CCfiw rt~rorrn (Aoe~vihaA ..--_-_._ ~- - 

C. Power Output Control. Dish power plants and solar thermal 

power plants, in general, must supply electrical power in a controlled manner 

for various types of loads: utility distribution grids, stand-alone loads, or 

industrial loads. The collection, distribution, and management of electrical 

power that are required by a parabolic dish-electric transport system 

(described in Section 1I.E) are usually monitored by a power output control 

subsystem. This subsystem oversees the following specific functions that 

ultimately result in the distribution of grid-compatible ac power (see 

Reference 67): 

(1) Power processing that includes collection, inversion and 

conversion, and routing. 

(2) Utility interfacing that includes protection, synchronization, and 

operating procedures for transferring power generated by the dish 

plant to the utility bus. 

e-a 2-77 
(3) Power management that includes a manual or automatic system at the 

dispatch center where transmitting and distributing decisions are 

made based on load demand and available power. 

The power output control subsystem designed for the organic-Rankine 

module plant uses individual rectifiers (one per module) to change the ac 

output to dc and eliminate the requirement for synchronous operation of the 

alternator with the grid and permit the variation of turbine speed for control 

purposes. The modules are controlled to the optimal efficiency by maintaining 

a constant turbine inlet temperature. Turbine speeds are allowed to drift 

within a range of values by selecting the appropriate values of alternator 

impedance and by designing the inverter to maintain a constant voltage drop 

across its input circuit. Therefore, active control of individual alternators 

is not required in this scheme (see Reference 74). 
SECTION I11 

CURRENT STATUS OF MODULE DEVELOPMENT 

A major goal of the TPS Project is the design and fabrication of 

prototype modules, each based on a prime solar engine-cycle concept (i.e., 

Rankine, Stirling, and Brayton), for eventual mass production and deployment 

by the private sector as a cost-effective energy source. 

comprising the modules were selected on the basis of their individual 

technical merit and ultimate marketability as well as their compatibility with 

other elements of the dish module system. Engines with integral receivers 

were developed by the Project as one package or developed separately then 

matched for incorporation into a module. These engine/receiver units were 

paired with suitable concentrators to make up the dish-elecric module. 

addition of controls, transport, power processing, and possibly storage 

constitutes the module system that then can be demonstrated in single-module 

or multi-module system experiments. 

The components 

The 

All components used in the Project’s developmental prototype modules 

have been discussed in detail in the previous section of this report. The 

three prototype modules and the corresponding system experiment, where 

applicable, are summarized below. 

A. RANKINE MODULE 

1. Module Description 

Rankine module development was initiated in December 1979 with a 

JPL contract to FACC for design and fabrication of the Rankine power 

conversion assemoiy, wnicn consiscs or a11 rnbb receiveL, a DdLUI=L-1YILlIUlb 

organic Rankine-cycle engine, and a Simmonds Precision permanent magnet 

Acurex design (PDC-2). 

12.2-m-diameter dish to increase the power delivered to the receiver (to 95 

kWt) for use with a proposed Barber-Nichols 25-kWe organic Rankine-cycle 

engine integrated with a 15-in.-diameter aperture FACC receiver. 

-1 +----e-- The nn-naotrntnr c..heon-tantlir celortpd fer the rnndllle Wac an a------J ---- U*-”L..U-”r. *..- w-.---.------- ----- 

The PDC-2 design was changed in late 1983 to a 

2. System Experiment (Small Community Solar Thermal Power Experiment) 

The U.S. Congress appropriated funds in 1977 to build an experimental solar power plant to meet the near-term energy requirements of the small 

community sector (see Reference 30). 

first-generation Rankine-engine technology to be used for what became known as 

the Small Community Solar Thermal Power Experiment. While this work was in 

progress, DOE conducted siting activities (Figure 3-1) that resulted in the 

selection of Osage City, Kansas, as the prime site and Molokai, Hawaii, as the 

alternate site. Osage City is representative of a large number of small U.S. 

cities, capable of generating its own power but purchasing it under certain 

conditions. Construction funds were allocated in 1982, and during 1983 DOE 

negotiated with Osage City for participation in site-related activities for 

the Small Community Experiment. 

FACC was selected to develop the 

3-1 
a 

al 

&I 

3 

w 

e a 

3-2 
Until late 1983, the module systems contractor for the experiment, FACC, 

worked to complete all tasks necessary to deploy the system at the Osage City 

site. Reference 54 contains a detailed description of the requirements that 

were established for the design and development of the 100-kWe, multi-module 

plant. Efficiency and performance goals for the plant are presented in 

Table 3-1. Figure 3-2 shows schematically the Rankine power conversion 

assembly with the power processing equipment (rectifier and inverter) and 

controls (the remote control interface assembly and the master power 

controller) needed to supply three-phase ac power to the city's utility grid. 

However, the above-mentioned activities, as well as those by Acurex to 

build the 12.24 PDC-2, were suspended when FACC and DOE were unable to 

finalize contractual arrangements for carrying out the experiment. DOE 

resolicited bids for the Small Community Experiment in December 1983, and 

Barber-Nichols was awarded the contract in 1984. An ORC engine and modified 

PKI collector will comprise the module for the Experiment, which still is to 

be installed at Osage City, Kansas. 

TO OTHER- - -1 

RCIAS 

SERIAL DATA LINK 

I 4 CENTRAL PROCESSOR 

I------------ (MINICOMPUTER) LOCAL - COMMANDS 

CONTROLLER 

( hl IC R 0 P R 0 C E SSO R 

DATA - 

r----- 

I I 

I DATA 

SWITCHBOARD I I CHANNELS 

/VAPOR VALVE 

R ECTl F I ER 

I -# --:- ne 3000 HZ ACk t . 

TO IlTlLlTY 

2 ,-GRID 

b - 

OTHER INVERTER 

MODULES 

- 4 

CENTRAL EQUIPMENT FOR 

CONTROL AND POWER DISTRIBUTION POWER MODULE 

Figure 3-2. Simplified Hardware Schematic for the Small Community Experiment 

3-3 
Table 3-1. Efficiency and Performance Goals for the Proposed 

Small Community Experiment at Osage Citya 

Efficiency or Performance Parameter 

Cornponent/Item Goa 1 Minimuma 

Concentrator Produce 101 kWt 98.2 kWt through 

through a 37.95-cm the aperture 

(14.94-in.) aperture 

Receiver 9 7% 96% 

PCS (engine/alternator/ 30.2% 

rectifier), based on 

gross output and 427OC 

(8000F) turbine inlet 

temperature 

Energy Transport Subsystemb (cables, 

switchboard, and 

inverter; transformer 

not included 

91.6% 

Module parasitic losses 0.92 N kW 

(N = no. of modules) 

27.5% 

88.7% 

1.2 N kW 

P 1 ant output 110 kWe at rated 

conditions 

100 kWe at rated 

conditions 

aMinimum values at rated conditions. 

bBased on a subscale inverter efficiency of 90% (minimum) or 93% goal. 

An energy transport system efficiency of 96.5% is predicted for a 

full-size plant. 
B. STIRLING MODULE 

1. Vanguard Project 

A dish-electric module, employing a United Stirling 4-95 Mk I1 

Solar SE power conversion unit (engine with solar-only receiver), was designed 

and built by a team of industrial contractors as the result of a DOE Program 

Opportunity Notice (PON) issued in 1981. Advanco Corporation is the 

industrial contract manager (receiving technical assistance from JPL) and is 

also the concentrator supplier. The balance of the module includes a control 

system by Electrospace, Inc. and a generator by Onan, Inc. Modern Alloys 

served as the general contractor, and Rockwell International, the system 

integrator. By November 1983, the fully-integrated module (named "Vanguard") 

had been installed at the user site, the Southern California Edison Company's 

Regional Service Center at Rancho Mirage near Palm Springs, California. A 

drawing of the Vanguard module is shown in Figure 3-3 and its features listed 

in Table 3-2. Figure 3-4 is a photograph of the completed Vanguard power 

module at the Rancho Mirage site. 

Extensive testing of the module in 1984-85 proved its technical 

readiness. Operating parameters for a full month (June 1984) of 

sunrise-to-sunset testing are presented in Table 3-3. The best efficiency was 

achieved on June 21, when the gross electricity generated was 258 kWe-h and 

the net electricity was 238 kWe-h, resulting in a net daily conversion 

efficiency of 25.2% (Reference 75). 

INDUCTION GENERATOR 

- RADIATOR /FAN 

STIRLING ENGINE - UNITED STIRLING 

4-95 SOLAR MK I1 1 

SOLAR RECEIVER 

bUCAL lLANt / 11 \\ , ELECTRIC LIN t RUU AND 1 I Nb GAS 

FACETED REFLECTIVE SURFAC 

FACET RACKS (16) 

DISH SUPPORT TRUSS EXOCENTRIC 

/GIMBAL / PEDESTAL 

F 

- 

OVERALL MODULE FEATURE^ DIAMETER II m HEIGHT 12 m I 

WEIGHT 7980 kg 

SYSTEM EFFICIENCY 25.4% 

ELECTRICAL POWER 20.8 kW4 

HYDROGEN GAS 

CONTROL BOX, 

gure 3-3. Drawing of the Vanguard Dish-Stirling Module, 

Elevation View (see Reference 30) 

3-5 
Table 3-2. Characteristics of the Vanguard Module (see Reference 30) 

Feature De tai 1 s 

Reflective surf ace 

Dish structure 

Dish articulation 

Dish control 

Dish pedestal 

Stirling enginelreceiver 

Genera tor 

Cooling 

Working fluid 

Stirling engine control 

Module 

320 facets, 460 x 610 mm (18 x 24 in.) foamglass-backed thin glass, back-silvered mirrors 

with 89.2 m2 (960 ft2) total surface area 

Carbon steel space frame 

Rockwell elevated-shoulder exocentric gimbal 

design 

Electrospace Model 93C-15 antenna controller 

and motors 

750-mm (30-in.) carbon steel pipe in poured 

concrete footing 

United Stirling 4-95 Solar Mark 11, 

four-cylinder with integral, solar-only 

re c e ive r 

40-kW, 30-hp induction generator 

Dish-mounted radiator/fan combination 

Gaseous hydrogen 

Mean effective pressure variation controlled 

by remote supply and return system 

Rated average power of 20 kWe at 480 Vac, 

60 Hz at 850 W/m2 direct normal insolation. 

Net power produced from 250 to 1100 W/m2 

insolation at temperatures from -25 to 5OoC 

(-13 to 122OF) and wind gusts up to 13 m/s 

(30 mi/h). 

(90 mi/h). 

Survive wind speeds up to 40 m/s 

3-6 
Figure 3-4. Fully Assembled Vanguard Module Installed at the 

Rancho Mirage Test Site 

The Vanguard team also completed market assessment and sales 

implementation plan tasks in preparation for full-scale production and 

commercialization. Sales strategy would take advantage of Federal and State 

tax incentives to encourage venture capitalists to enter into purchase power 

agreements with established utilities with the object of building solar power 

plants using proven Vanguard-type modules. 

In 1985, DOE plans to conduct a series of tests with the Vanguard 

module, including non-destructive quality assurance tests, system reliability 

tests, and a preventive maintenance demonstration. The Electric Power 

Research Institute (EPRI) has also engaged the Energy Technology Engineering 

Center of Rockwell International to observe Vanguard testing and document test 

results, to evaluate the overall Vanguard project, and to recommend further 

tests of interest to the electric utility community (see Reference 50). 

2. McDonnell Douglas Dish/Stirling Venture 

In November 1983, McDonnell Douglas Corporation announced an 

exclusive cooperative agreement with United Stirling AB (USAB) to develop, 

manufacture, and market a new solar-powered electric generating plant. Each 

3-7 
Table 3-3. Vanguard Operating Parameters for June 1984 (see Reference 75) 

Gross Net 

Daily Daily 

Cumulative Ef f i- Ef f i- Dish 

Date kWe-h kWe-h kWe-h/m2 % % Hours tance 

Gross, Net, Insolation, ciency, ciency, Running Reflec611 to 

6/13 

6/14 

6/15 

6/16 

6/17 

6/18 

6/19 

6/20 

6/21 

6/22 

6/23 

6/24 

6/25 

6/26 

6/27 

6/28 

6/29 

Total 

a 

220 

22 7 

213 

210 

204 

221 

236 

258 

24 9 

2 28 

0 

39 

20 2 

205 

96 

a 

2808 

a 

200 

20 7 

193 

189 

184 

199 

216 

238 

227 

208 

24 

181 

184 

77 

a 

-8 

2519 

9.97 

9.89 

9.57 

9.57 

9.33 

10.10 

10.55 

10.88 

10.69 

9.89 

1.38 

3.96 

8.93 

8.99 

5.26 

a 

128.96 

25.5 

26.5 

25.7 

25.3 

25.2 

25.2 

25.8 

27.4 

26.9 

26.6 

0.0 

11.4 

26.1 

26.3 

21 .o 

a 

25. lb 

a 

23.1 

24.1 

23.3 

22.8 

22.7 

22.7 

23.6 

25.2 

24.5 

24.3 

7.0 

23.4 

23.6 

16.9 

a 

-6.7 

22. gb 

4.9 

11.2 

10.5 

12.9 

13.0 

13.1 

13.25 

13.25 

13.25 

13.05 

11.8 

0.2 

4.3 

12.85 

12.55 

9.1 

3.25 

172.45 

a 

0.900 

0.880 

0.875 

0.876 

0.860 

0.860 

0.856 

0.920 

0.898 

0.894 

0.861 

0.858 

0.923 

0.898 

0.894 

a 

0.884 

aThis datum was not included but is available. 

bThese averages were calculated by dividing total power production by 

total input insolation for the month. 

module consists of a USAB Model 4-95 Mk I1 Solar SE Stirling power conversion 

unit mounted on a McDonnell Douglas concentrator, made of 82 spherically 

curved glass mirrored facets, that allows access to the engine by lowering it 

to the ground. In December 1984, the first prototype unit was completed at 

the McDonnell Douglas facility in Huntington Beach, California. Their 

immediate plans call for installation of two units near their facility; one at 

the Southern California Edison Solar One central receiver site near Barstow, 

California; one at the Georgia Power total energy dish plant in Shenandoah, 

Georgia; one at Nevada Power; and others at sites to be specified (see 

Reference 50). 
C. BRAYTON MODULE 

The Brayton module developed by the TPS Project uses the 

near-term6 baseline design formulated by Sanders Associates under a contract 

initiated in 1981. Sanders is also responsible for (1) integrating all 

subsystems, plus controls, necessary to complete the module and (2) conducting 

enginelreceiver feasibility tests in 1984. Their efforts included 

consideration of the subatmospheric Brayton-cycle engine, the solarized 

advanced gas turbine, and other available Brayton engine designs. After 

completing trade studies of module configurations employing various candidate 

engines and concentrators -- all using a Sanders ceramic receiver -- an 

AiResearch Mark I11 subatmospheric Brayton-cycle engine and a LaJet LEC 460 

concentrator were selected for the module. 

After qualification testing at Garrett AiResearch, the SABC Mod 

IIIA engine was delivered to Sanders in April 1984 for integration into the 

developmental test module. Earlier in the year, modifications to the LaJet 

concentrator were made to allow for a higher focal point weight. 

Characterization of the concentrator using a flux rake was performed in 

April. By this time, Sanders had completed assembly of two receivers, taking 

into account the specific requirements (i.e., power, pressure, and aperture 

size) of the SABC Mod IIIA. By May, the Brayton developmental test module 

(Figure 3-5) was fully assembled and integrated with an inverter and controls 

(see Reference 59). 

Preliminary testing of the module indicated poor efficiencies for 

the major subsystems, e.g., an engine efficiency of about 13% and a receiver 

efficiency of 72%. In light of these test results, Sanders recommended 

consideration of alternate Brayton engines for the module, and JPL recommended 

that all aspects of the Brayton module be addressed before proceeding in a new 

direction. 

In early 1985, DOE/SNLA made a decision to terminate the existing 

Brayton module contract with Sanders Associates and to begin testing the 

solarized advanced gas turbine mated to a Sanders ceramic receiver on a TBC at 

the SNLA test site. At the time of this writing, no test data were available. 

6A far-term Brayton module proposed by Sanders for fabrication in the late ~ 1980s would use an all-ceramic engine, now being developed under the 

automotive advanced gas turbine program. i 

3-9 

I 
Figure 3-5. Fully Assembled Brayton Developmental Test Module 

3-10 
SECTION IV 

SYSTEM PERFORMANCE AND ECONOMIC PROJECTIONS 

A. SYSTEM PERFORMANCE 

In a recent JPL study (Reference 4), the performance of three dish 

module types (Stirling, organic-Rankine, and Brayton) was analyzed for four 

geographic areas (Albuquerque, New Mexico; Fresno, California; Dodge City, 

Kansas; and Fort Worth, Texas) using available test data or performance 

estimates. The methodology used to calculate the results is described in 

Reference 76. Note that while the Stirling and organic-Rankine modules have 

been demonstrated in at least prototypic form, the ceramic Brayton module 

analyzed is still in the conceptual phase. 

assumptions used in the analysis is contained in Reference 4. 

summarized in Table 4-1 for each geographic location and for each type of 

5-MWe plant and the corresponding typical module. 

A detailed description of 

The results are 

B. ECONOMIC PROJECTIONS 

Potential market sizes for parabolic dish systems in different market 

sectors were also estimated in the study (Reference 4) by comparing breakeven 

costs (demand side) with dish system costs as a function of production volume 

(supply side). 

The market sectors considered fall into two major categories: 

(1) isolated loads (non-grid-connected), which include islands, agricultural 

irrigation, military applications, and stripper wells, and (2) grid-connected 

nnnl;elt;nnc whirh inrliirle inv~ctnr-nwned utilities. municiDa1 utilities, and 

third-party-owned systems. 

-- 

Breakeven costs were determined by a value anaiysis merhodoiugy 

(Reference 77) for each market sector. This methodology uses a computer 

simulation model to calculate the value of fuel and operation and maintenance 

(O&M) expenses displaced by parabolic dish systems having different capacities. 

The following assumptions were used in the simulation to calculate the 

breakeven costs: 

(1) Insolation Levels: Albuquerque, New Mexico, was used to represent 

the above-average insolation region, Fresno, California, the 

average insolation region, and Dodge City, Kansas, the 

below-average region. 

(2) Fuel Price Projections: Energy Information Administration average 

national price projections were used to formulate low, medium, and 

high fuel-price scenarios. 

(3) Utility System Characteristics: The Electric Power Research 

Institute (EPRI) has modeled various synthetic utilities that 

provide a consistent set of data covering all aspects of utility 

power generation and energy demand (Reference 78). 

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4- 2 
(4) Financial Parameters: Financial parameters for municipal 

utilities, investor-owned utilities, and third-party-owned systems. 

(5) Inter-Technology Competition: It was assumed that conventional 

technologies of the 1990s represent the best available alternative 

to dish systems at that time (i.e., inter-technology competition 

with other new technologies is not included). 

(6) Time Frame: Implicit in the demand projections for 1990 parabolic 

dish installations is the assumption that no installations were 

made prior to that year. In this context, the total market demand 

projected to be viable by 1990 is being estimated. 

The breakeven costs for parabolic dish systems installed in California 

are shown in Table 4-2. Note that early dish installations are expected to 

replace the most valuable alternative fuels and least efficient conventional 

capacity. 

The economics of supplying dish systems are governed by the initial 

installed price and the cost of operation and maintenance (O&M). Based on a 

5-MWe plant having the characteristics summarized in Table 4-3, the initial 

installed price and the O&M cost are plotted respectively in Figures 4-1 and 

4-2 as functions of annual production rates for Brayton, Stirling, and ORC 

modules. 

to determine the actual cost data.) In determining the initial installation 

price as a function of annual production rate, it is assumed that the 

production facilities will operate at the specified annual production rate for 

five years. 

(Reference 4 contains a detailed description of the methodology used 

Now that a range of values has been estimated for both supply and A----A +h- art:mc,enc ran he cnmnarerl tn PxAmine the 1990 economic market 

potential for parabolic dish systems. As shown in Figure 4-3, the demand 

curves give the relationship between market price ($/kWe) and cumulative 

parabolic dish capacity. The cost curves (reier to Figure 4-1; show iuarkri 

price versus annual production rate. Even though the units of comparison are 

different, the 1990 economic market potential can be discussed with reference 

to the two figures. They indicate that the market for dish-electric systems 

in the early 1990s is likely to be small, and volume production is unlikely. 

Dish installations will be limited to a few specific applications where unique 

conditions make dish systems attractive. Under the most favorable conditions 

(high fuel prices and low dish prices), dish systems could penetrate the 

electric utility market when the Brayton module becomes commercially available. 

b 

1 

I 

1 

Factors having a significant impact on the market potential of parabolic 

systems include system costs, future fuel prices, the high incidence of coal 

displacement observed in the analysis, and parabolic dish O&M costs. For 

example, small variatians in OdM costs can have a large impact on breakeven 

reduced to 2% of capital costs, incremental values (breakeven costs) increase 

by 35%. 

can vary widely depending on how these factors vary over time. 

1 

1 costs for parabolic dish systems as shown in Figure 4-4. [If O&M costs are 

If O&M costs increase to 8% of capital costs, incremental values ~ 

1 decrease by 20%.] Therefore, the market potential of parabolic dish systems 

I 

I 

4-3 
Table 4-2. Breakeven Costs for Early Parabolic Dish Installations 

in Californiaa 

Inves to r - 

Fuel Type Fue 1 Municipal Owned Third 

Market Displaced Pricesb Utility Utility Party 

Isolated LoadsC Medium 1350 1000 1075 

Oi 1 

Low-High 925-2125 700-1550 825-1450 

Grid-Connected Mixture Medium 1275 950 1025 

Appl icat ionsd (Oil, Coal, 

Nuclear) Low-High 875-2100 650-1500 800-1375 

aThis table provides the incremental values, in $/kWe, for 1990 

installations expressed in 1984 dollars. These figures represent the 

breakeven costs for the first parabolic dish systems installed. 

bMedium fuel-price scenario corresponds to the EIA medium scenario of 

$39/barrel (1990 price in 1984 dollars). Low and high scenarios 

correspond to a range of $30/barrel to $48/barrel, respectively (1990 

price in 1984 dollars). Post-1990 annual rates of escalation -- 0, 2, 

and 4% for low, medium, and high scenarios, respectively. 

CMarket limited to non-grid connected applications currently using 

oil-fired capacity only. 

dBased on a dish system penetration equivalent to 1% of peak demand 

(equal to approximate 400 MWe in California in 1990). 

Table 4-3. Summary of 5-MWe Plant Characteristics 

Concentrator 

Sys t em Size, m 2 Number of Modules 

Bray t on 131 138 

ORC 105.8 214 

S t irl ing 102 167 

4-4 
100,000 

10,000 

1 000 

1 I Ill I 1 I I1 I I II 

- 

- 

ORC 

BRAYTON 

ST I RLI N G 

--- 

- -----...- 

- 

1 00 lo00 10,000 100,000 

ANNUAL PRODUCTION RATE, units/yr 

Figure 4-1. Annual Production Rate versus Initial Plant 

Price in $/kWe (1984 dollars) 

4-5 
1 o8 

1 o6 

-- ORC 

----- BRAYTON 

STIRLING 

100 1000 10,000 25,000 50,000 100,000 

ANNUAL PRODUCTION RATE, units/yr 

Figure 4-2. Annual Operation and Maintenance Cost for a 5-MWe Plant 

(1984 dollars) 

4-6 
2500 

2000 Y 

e3 

\ 

W3 

J 

4 

J 1500 

i nnn 

A \\ 

LOW FUEL PRICE 

I I I I I 1 

10,000 20,000 30,000 40,000 

SOLAR THERMAL ELECTRIC CAPACITY, MWe 

Figure 4-3. 1990 Market Potential for Cost-Competitive Solar Thermal 

Parabolic Dish Systems in Grid-Connected Applications 

(1984 dollars) 

4-7 
1 

Iz 

W 

H 

W 

(I 

0 

z 

I 

a 

- 

v, 

n 

0 

0 

(I 

a 

0 

a 

a 

- 

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m 

a 

a 

7 

s 2000 Y 

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Wa 

3 

> 

1500 , 

1000 

500 - 

10% O&M 

2% O&M 

5% O&M 

8% O&M 

10,000 20,000 30,000 40,000 

PARABOLIC DISH CAPACITY, MWe 

Figure 4-4. 1990 Parabolic Dish Breakeven Costs: O&M Sensitivity for 

Medium Fuel-Price Scenario. 

initial capital cost in 1984 dollars.) 

(O&M expressed as percentage of 

4-8 
C. CONCLUSIONS 

The following conclusions were drawn from the 1985 study (Reference 4): 

(1) If fuel price escalation occurs at a rate near the upper bound of 

the range used in the study, evolutionary engineering development 

of the modules currently being designed and/or tested could 

achieve the breakeven costs needed to penetrate utility markets. 

(2) If fuel price escalation occurs at nominal or intermediate values 

within the range, technology advancements beyond evolutionary 

engineering development of current modules would be required to 

achieve breakeven costs. 

4-9 
SECTION V 

REFERENCES 

1. Fiscal Year 1984 Annual Operating Plan, Solar Thermal Technology Program, 

U.S. Department of Energy, Solar Thermal Technology Division, 1984. 

2. Truscello, V. C., and Williams, A. N., "Heat and Electricity from the 

Sun Using Parabolic Dish Collector Systems," Jet Propulsion Laboratory, 

September 1979. 

3. Solar Thermal Technology (STT) Research Program: FY 1977-FY 1983 

Activity and Accomplishments, Solar Energy Research Institute, Golden, 

Colorado, October 26, 1984, to be published. 

4. 

5. 

6. 

7. 

8. 

9. 

I 

10. 

11. 

12. 

13. 

14. 

Fujita, T., Bowyer, J., Revere, W., Gates, W., and Jaffe, L., Projected 

Techno-Economic Characteristics of Solar Thermal Parabolic Dish-Electric 

Power Systems, JPL Publication 85-87, DOE/JPL-1060-93, September 15, 1985. 

Biddle, J., Revere, W., and Fujita, T., "Low-Cost Thermal Transport 

Piping Networks for Solar Industrial Process Heat Applications," Solar 

Process Heat Conference, Houston, Texas, December 1980. 

Marriott, A. T., "Parabolic Dish Systems at Work: Applying the 

Concepts," Sunworld, Vol. 5, No. 3, pp. 86-89, 1981. 

Truscello, V. C., "Parabolic Dish Collectors: A Solar Option," 

Sunworld, Vol. 5, No. 3, pp. 80-85, 1981. 

Jatte, L. U., Ulsh concentracors Lor DO~~K- iue~iiia~ IXICL~Y. ;CaLUY a**; 

Technology Development, JPL Publication 81-43, DOE/JPL-1060-48, T __._-I_. 1 inoq dauua~y A, A~VL. 

Truscello, V. C., "Status of the Parabolic Dish Concentrator," Proc. 

Soleras Conference, Denver, Colorado, April 1983. 

Jaffe, L. D., and Poon, P. T., Secondary and Compound Concentrators for 

Parabolic Dish Solar Thermal Power Systems, JPL Publication 81-27, 

DOE/JPL-1060-43, April 15, 1981. 

Truscello, V. C., The Parabolic Concentrating Collector, A Tutorial, JPL 

Publication 79-7, DOE/JPL-1060-79/1, 1979. 

Bouquet, F., Criteria for Evaluation of Reflective Surfaces for 

Parabolic Dish Concentrators, JPL Publication 80-81, DOE/JPL-1060-39, 

July 15, 1980. 

Jaffe, L. D., "Dish Concentrators for Solar Thermal Energy," J. of 

Energy, Vol. 7, No. 4, p. 304, July-August 1983. 

Thermal Power Systems Point-Focusing Distributed Receiver Technology 

Project - Annual Technical Report FY 1978, JPL Publication 79-1, 

DOE/JPL-1060-7, March 15, 1979. 

5-1 
15. 

16. 

17. 

18. 

19. 

20. 

21. 

22. 

23. 

24. 

25. 

26. 

27. 

28. 

Goldberg, V. R., (E-Systems), "Test Bed Concentrator (TBC)," Proc. First 

Semiannual Distributed Receiver Systems Program Review, JPL 

Publication 80-10, DOE/JPL-1060-33, April 15, 1980. 

Solar Thermal Power Systems Point-Focusing Distributed Receiver 

Technology Project - Annual Technical Report FY 1979, JPLPublication 79-112, DOE/JPL-1060-30, April 1, 1980. 

Argoud, M. J., "Test Bed Concentrator Mirrors," Proc. First Semiannual 

Distributed Receiver Systems Program Review, JPL Publication 80-10, 

DOE/JPL-1060-33, April 15, 1980. 

Starkey, D. J., "Initial Test Bed Concentrator Characterization," Proc. 

First Semiannual Distributed Receiver System Program Review, JPL 

Publication 80-10, DOE/JPL-1060-33, April 15, 1980. 

Starkey, D. J., "Characterization of Point Focusing Test Bed 

Concentrators at JPL," Proc. Parabolic Dish Solar Thermal Power Annual 

Program Review, JPL Publication 81-44, DOE/JPL 1060-46, May 1, 1981. 

Ross, D. L., and Panda, P. L., "Testing with High-Intensity Radiant 

Energy," Color Brochure, JPL 400-154, 1982. 

Sobczak, I. F., and Pons, R. L., (Ford Aerospace) and Thostesen, T., 

"Development Status of the PDC-1 Parabolic Dish Concentrator," Proc. 

Solar Thermal Power Annual Program Review, JPL Publication 82-66, 

DOE/JPL-1060-52, July 15, 1982. 

Dennison, E. W., and Argoud, M. J., "Solar Concentrator Panel and Gore 

Testing in the JPL 25-Foot Space Simulator," AIAA 2nd Terrestrial Energy 

Systems Conference, Colorado Springs, Colorado, December 1-3, 1981. 

Sobczak, I. F., (Ford Aerospace) and Thostesen, T., "Parabolic Dish 

Concentrator (PDC-1) Development," Proc. Fourth Parabolic Dish Solar 

Thermal Power Program Review, JPL Publication 83-2, DOE/JPL-1060-58, 

February 1, 1983. 

Stallkamp, J. A., Control System for Parabolic Dish Concentrator No. 1, 

JPL Publication 85-40, DOE/JPL-1060-86, March 15, 1985. 

Dennison, E. W., and Argoud, M. J., "PDC-1 Optical Testing," Proc. 

Fourth Parabolic Dish Solar Thermal Power Program Review, JPL 

Publication 83-2, DOE/JPL-1060-58, February 1, 1983. 

Dennison, E. W., and Thostesen, T. O., Development and Testing of 

Parabolic Dish Concentrator No. 1, JPL Publication 85-4, 

DOE/JPL-1060-81, December 15, 1984. 

Solar Thermal Power Systems Parabolic Dish Project - Annual Technical 

Report FY 1980, JPL Publication 81-39, DOE/JPL-1060-45, May 15, 1981. 

Bedard, R., and Bell, D., (Acurex) *'A Cellular Glass Substrate Solar 

Concentrator," Proc. First Semiannual Distributed Receiver Systems 

Program Review, JPL Publication 80-10, DOE/JPL-1060-33, April 15, 1980. 

5-2 
29. 

30. 

31. 

32. 

33. 

34. 

35. 

36. 

37. 

38. 

39. 

40. 

41. 

42. 

43. 

Solar Thermal Power Systems Project - Annual Technical Report FY 1981, 

JPL Publication 82-22, DOE/JPL-1060-51, March 15, 1982. 

Solar Parabolic Dish Annual Technology Evaluation Report Fiscal Year 

1982, JPL Publication 83-73, DOE/JPL-1060-63, September 15, 1983. 

Dennison, E. W., and Argoud, M. J., JPL Tests of a LaJet Concentrator 

Facet, JPL Publication 83-92, DOE/JPL-1060-64, November 15, 1983. 

Zimmerman, J. A., and Hunke, R. W., The Shenandoah Solar Total Energy 

Project, SAND80-2560C, Sandia National Laboratories, Albuquerque, New 

Mexico, 1980. 

Shenandoah Solar Collector, SAND80-7002, Sandia National Laboratories, 

Albuquerque, New Mexico, 1980. 

Selcuk, M. K., Parabolic Dish Test Site: History and Operating 

Experience, JPL Publication 85-18, DOE/JPL-1060-84, February 15, 1985. 

Harley, E. L., and Stine, W. B., Solar Industrial Process Heat Project 

Technical Report, October 1982-September 1983, SAND84-1812, Sandia 

National Laboratories, Albuquerque, New Mexico, November 1984. 

Solar Thermal Technology Annual Evaluation Report Fiscal Year 1982, 

Vols. I and 11, JPL Publication 83-60, DOE/JPL-1060-61, July 1983. 

Solar Thermal Technology Annual Evaluation Report Fiscal Year 1983, 

SERI/PR-253-2188, Solar Energy Research Institute, Golden, Colorado, 

August 1984. 

Solar Thermal Technology Annual Evaluation Report Fiscal Year LY64, 

Solar Energy Research Institute, Golden, Colorado, April 1985, to be 

published. 

Kudirka, A. A., and Leibowitz, L. P., "Advanced Solar Thermal Receiver 

Technology," 18th AIM Aerospace Sciences Meeting, Pasadena, California, 

January 14-16, 1980. 

Wen, L., Huang, L., Poon, P., and Carley, W., "Comparative Study of 

Solar Optics for Paraboloidal Concentrators," J. Solar Energy 

Engineering, Vol. 102, p. 305, November 1980. 

Greeven, M., (Garrett) "The Development of an Air Brayton and a Steam 

Rankine Solar Receiver," Proc. First Semiannual Distributed Receiver 

Systems Program Review, JPL Publication 80-10, DOE/JPL-1060-33, 

April 15, 1980. 

Solar Thermal Technology Annual Technical Progress Report FY 1981, 

Vols. I and 11, JPL Publication 82-60, DOE/JPL 1060-53, June 1982. 

Kudirka, A. A., and Smoak, R. H., "Ceramic Technology for Solar Thermal 

Receivers," J. Solar Energy Engineering, Vol. 105, p. 73, February 1983. 

5-3 
44. 

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46. 

47. 

48. 

49. 

50. 

51. 

52. 

53. 

54. 

55. 

56. 

Lansing, F. L., HEAP: 

Simulating Solar Receivers, JPL Publication 79-3, DOE/JPL-1060-13, 

January 15, 1979. 

Heat Energy Analysis Program, A Computer Model 

Pons, R. L., (Ford Aerospace) "Development Status of the Small Community 

Solar Power System,'' Proc. Solar Thermal Power Annual Program Review, 

JPL Publication 82-66, DOE/JPL-1060-52, July 15, 1982. 

Haglund, R. A., (Fairchild) "Non-Heat Pipe Receiver/P-40 Stirling 

Engine, Proc. Solar Thermal Power Annual Program Review, JPL 

Publication 81-44, DOE/JPL 1060-46, p. 47, May 1, 1981. 

Zimmerman, W. F., (General Electric) "Heat Pipe Solar Receiver with 

Thermal Energy Storage," Proc. Solar Thermal Power Annual Program 

Review, JPL Publication 81-44, DOE/JPL 1060-46, p. 51, May 1, 1981. 

Davis, S. B., "Near-Term Brayton Module Status," Proc. Fifth Parabolic 

Dish Solar Thermal Power Program Annual Review, JPL Publication 84-13, 

DOE/JPL-1060-69, March 1, 1984. 

Livingston, F. R., "Stirling Module Development Overview," Proc. Fifth 

Parabolic Dish Solar Thermal Power Program Annual Review, JPL 

Publication 84-13, DOE/JPL-1060-69, March 1, 1984. 

Livingston, F. R., Activity and Accomplishments in Dish/Stirling 

Electric Power System Development, JPL Publication 85-8, 

DOE/JPL-1060-82, January 15, 1985. 

Jaffe, L. D., Solar Tests of Aperture Plate Materials for Solar Thermal 

Dish Collectors, JPL Publication 83-68, DOE/JPL-1060-62, August 15, 1983. 

Nesmith, B., "Jay Carter Enterprises, Inc., Steam Engine," Proc. 

Parabolic Dish Solar Thermal Power Annual Program Review, JPL 

Publication 81-44, DOE/JPL 1060-46, May 1, 1981. 

Boda, F. P., (FACC) "The SCSE Organic Rankine Engine," Proc. Parabolic 

Dish Solar Thermal Power Annual Program Review, JPL Publication 81-44, 

DOE/JPL 1060-46, May 1, 1981. 

Kiceniuk, T., Development of an Organic Rankine-Cycle Power Module for a 

Small Community Solar Thermal Power Experiment, JPL Publication 85-3, 

DOE/JPL-1060-80, January 15, 1985. 

Clark, T. B., Test Results of an Organic Rankine-Cycle Power Module for 

a Small Community Solar Thermal Power Experiment, JPL 9950-995, 

DOE/JPL-1060-83, prepared for the Jet Propulsion Laboratory by Ford 

Aerospace and Communications Corporation (Contract 955637), Newport 

Beach, California, January 15, 1985. 

Nesmith, B., Bearing Development Program for a 25-kWe Solar-Powered 

Organic Rankine-Cycle Engine, JPL Publication 85-81, DOE/JPL-1060-92, 

September 15, 1985. 

5 -4 
I 

I 

57. 

58. 

59. 

60. 

61. 

62. 

63. 

64. 

65. 

66. 

67. 

68. 

69. 

Six, L., and Elkins, R., (Garrett) "A Hybrid Brayton Engine Concept," 

Proc. First Semiannual Distributed Receiver Systems Program Review, JPL 

Publication 80-10, DOE/JPL-1060-33, April 15, 1980. 

Anson, B., (Garrett) "Solar Advanced Gas Turbine Brayton Power 

Conversion Assembly," Proc. Fourth Parabolic Dish Solar Thermal Power 

Program Review, JPL Publication 83-2, DOE/JPL-1060-58, February 1, 1983. 

Holbeck, H., Development of a Brayton-Cycle Dish-Electric Module, JPL 

Report No. 5105-158, to be published. 

Stearns, J. W., et al, "Solar Stirling System Development," Proc. AIAA 

Terrestrial Energy Systems Conference, Orlando, Florida, June 4-6, 1979. 

Stearns, J. W., and Haglund, R., (Advanco) "High Performance Solar 

Stirling System," Proc. AIAA 2nd Terrestrial Energy Systems Conference, 

Colorado Springs, Colorado, December 1-3, 1981. 

Nelving, H. G., (USAB) and Percival, W. H., (United Stirling, Inc.) 

"Modifications and Testing of a 4-95 Stirling Engine for Solar 

Applications," Proc. Solar Thermal Power Annual Program Review (December 

8-10, 19811, JPL Publication 82-66, DOE/JPL-1060-52, July 15, 1982. 

Steele, H. L., and Wen, L., 'Tomparison of Electrochemical and Thermal 

Storage for Hybrid Parabolic Dish Solar Power Plants," ASME Winter 

Annual Meeting, Washington, D.C., November 15-20, 1981. 

Wen, L., and Steele, H., "Thermal Storage Requirements for Parabolic 

Dish Solar Power Plants," ASME Winter Annual Meeting, Chicago, Illinois, hln-rernh-r 16%-31 198n 

Narayanan, R., (GE), Zimmerman, W. F., (GE), and Poon, P. T. Y., 

Experimental Simulation ot Latent iieac inermai Zriergy Strjioge ziiid 

Heat Pipe Thermal Transport for Dish Concentrator Solar Receiver," 

ASME Winter Annual Meeting, Washington, D.C., November 15-20, 1981. 

1) 

Wu, Y. C., "Effects of Thermal Buffer Storage Performance on Parabolic 

Dish Solar Power Systems," Alternative Energy Sources 111, Vol. 3, Solar 

Energy 3, 1983. 

Bahrami, K. A., Krauthamer, S., and Das, R. L., "Power Processing, Power 

Management, and Utility Interface for Advanced Dispersed Solar Thermal 

Systems," Focus on Solar Technology, Denver, Colorado, November 15-17, 

1978; Advanced Subsystems Development Second Semiannual Progress Report, 

JPL Publication 79-24, DOE/JPL-1060-6, pp. 4-1 to 4-35, November 15, 1978. 

Krauthamer, S., and Frank, H., Electrochemical Energy Storage Systems 

for Solar Thermal Applications, JPL Publication 79-95, DOE-JPL-1060-30, 

Rev. 1, March 1, 1980. 

Mavis, C. L., and Smith, P. N., A Description and Assessment of Solar 

Central Receiver Systems Technology, SAND82-8023, Sandia National 

Laboratories, Livermore, California, to be published. 

5-5 
70. 

71. 

72. 

73. 

74. 

75. 

76. 

77. 

78. 

Fujita, T., Birur, G. C., Schredder, J. M., Bowyer, J. M., and Awaya, 

H. I., 'Tomparison of Advanced Thermal and Electrical Storage for 

Parabolic Dish Solar Thermal Power Systems," 17th Intersociety Energy 

Conversion Engineering Conference, Los Angeles, California, August 1982. 

Schredder, J. M., Performance and Cost of Energy Transport and Storage 

Systems for Dish Applications Using Reversible Chemical Reactions, JPL 

Publication 84-77, DOE/JPL-1060-79, October 15, 1984. 

Ramakumar, R., and Bahrami, K., "Dispersed Solar Thermal Generation 

Employing Parabolic Dish-Electric Transport with Field Modulated 

Generator Systems," Solar Energy, Vol. 27, pp. 7-11, 1981. 

Hughes, R. O., "Effects of Tracking Errors on the Performance of Point 

Focusing Solar Collectors," Solar Energy, Vol. 24, pp. 83-92, 1980. 

Fulton, D. G., (FACC), "Control System Development for the Small 

Community Solar Power System," Proc. Fourth Parabolic Dish Solar Thermal 

Power Program Review, JPL Publication 83-2, DOE/JPL-1060-58, February 1, 

1983. 

Washom, Byron J., Vanguard I Solar Parabolic Dish-Stirling Engine 

Module, Final Report, DOE-AL-16333-2 (84-ADV-5), Advanco Corporation, 

September 30, 1984. 

Bowyer, J. M., Jr., A Program for the Calculation of Paraboloidal-Dish 

Solar Thermal Power Plant Performance, JPL Publication 85-36, 

DOE/JPL-1060-85, April 15, 1985. 

Gates, W. R., Solar Thermal Technology Development: Estimated Market 

Size and Energy Cost Savings, JPL Publication 83-14, February 1983. 

The EPRI Regional Systems, EPRI P-1950-SR, Electric Power Research 

Institute, Palo Alto, California, July 1981. 
APPENDIX 

DETAILED ASSESSMENT REPORTS PUBLISHED AT THE CLOSE OF THE 

JPL SOLAR THERMAL POWER SYSTEMS PROJECT 

Bowyer, J. M., Jr., The Kinematic Stirling Engine as an Energy Conversion 

Subsystem for Paraboloidal Dish Solar Thermal Power Plants, 

JPL Publication 84-30, DOE/JPL-1060-73, Jet Propulsion Laboratory, 

Pasadena, California, April 15, 1984. 

Bowyer, J. M., Jr., A Program for the Calculation of Paraboloidal-Dish Solar 

Thermal Power Plant Performance, JPL Publication 85-36, DOE/JPL-1060-85, 

Jet Propulsion Laboratory, Pasadena, California, April 15, 1985. 

Dennison, E. W., and Argoud, M. J., JPL Tests of a LaJet Concentrator Facet, 

JPL Publication 83-92, DOE/JPL-1060-64, Jet Propulsion Laboratory, 

Pasadena, California, -November 15, 1983. 

Dennison, E. W., John, S. L., and Trentelman, G. F., Concentrator Optical 

Characterization Using Computer Mathematical Modelling and Point Source 

Testing, JPL Publication 84-75, DOE/JPL-1060-77, Jet Propulsion Laboratory, 

Pasadena, California, September 15, 1984. 

Dennison, E. W., and Thostesen, T. O., Development and Testing of Parabolic 

Dish Concentrator No. 1, JPL Publication 85-4, DOE/JPL-1060-81, Jet 

Propulsion Laboratory, Pasadena, California, December 15, 1984. 

Dennison. E. W., and Trentelman, G. F., View-Limiting Shrouds for Insolation 

Radiometers, JPL Publication 85-54, UwE/JrL-Lubu-uu, Jet rropuisiou 

Laboratory, Pasadena, California, May 15, 1985. 

Fujita, T., Bowyer, J. M., Jr., Gates, W. R., Jaffe, L. D., and Revere, W., 

Projected Techno-Economic Characteristics of Solar Thermal Parabolic DishElectric Power Systems, JPL Publication 85-87, DOE/JPL-1060-93, Jet 

Propulsion Laboratory, Pasadena, California, September 15, 1985. 

I 

I Jaffe, L. D., CONC/11: A Computer Program for Calculatinp the Performance of 

Dish-Type Solar Thermal Collectors and Power Systems, JPL Publication 84-9, 

February 15, 1984. I DOE/JPL-1060-68, Jet Propulsion Laboratory, Pasadena, California, 

Kiceniuk, T. Development of an Organic Rankine-Cycle Power Module for a Small 

Community Solar Thermal Power Experiment, JPL Publication 85-3, 

1 DOE/JPL-1060-80, Jet Propulsion Laboratory, Pasadena, California, 

I January 15, 1985. I 

I Livingston, F. R., Activity and Accomplishments in Dish/Stirling Electric Power 

System Development, JPL Publication 85-8, DOE/JPL-1060-82, Jet Propulsion 

Laboratory, Pasadena, California, February 15, 1985. 

A- 1 
Miyazono, C., Overview of Software Development at the PDTS, JPL Publication 85-56, 

DOE/JPL-1060-90, Jet Propulsion Laboratory, Pasadena, California, 

July 15, 1985. 

Miyazono, C., Software Used with the Flux Mapper at the Solar Parabolic Dish 

Test Site, JPL Publication 84-76, DOE/JPL-1060-78, Jet Propulsion 

Laboratory, Pasadena, California, September 15, 1984. 

Moynihan, P. I., Second-Law Efficiency of Solar-Thermal Cavity Receivers, JPL 

Publication 83-97, DOE/JPL-1060-65, Jet Propulsion Laboratory, Pasadena, 

California, October 1, 1983. 

Nesmith, B., Bearing Development Program for a 25-kWe Solar-Powered Organic 

, Rankine-Cycle Engine, JPL Publication 85-81, DOE/JPL-1060-92, Jet 

Propulsion Laboratory, Pasadena, California, September 15, 1985. 

Owen, W. A., The JPL Flux Mapper, JPL Publication 85-95, DOE/JPL-1060-95, 

Jet Propulsion Laboratory, Pasadena, California, September 15, 1985. 

Panda, P., Gray, V., and Marsh, C., Publications of the JPL Solar Thermal Power 

Systems Project, 1976 through 1985, JPL Publication 85-52, DOE/JPL-1060-87, 

Jet Propulsion Laboratory, Pasadena, California, September 1, 1985. 

Roschke, E. J., Wind Loading on Solar Concentrators: Some General 

Considerations, ~~ ~~ JPL Publication 83-101, DOE/JPL-1060-66, Jet Propulsion 

Laboratory, Pasadena, California, May 1, 1984. 

Schredder, J. M., Performance and Cost of Energy Transport and Storage Systems 

for Dish Applications Using Reversible Chemical Reactions, JPL Publication 

84-77, DOE/JPL-1060-79, Jet Propulsion Laboratory, Pasadena, California, 

October 15, 1984. 

Selcuk, M. K., and Fujita, T., A Nomographic Methodology for Use in Performance 

Trade-off Studies of Parabolic Dish Solar Power Modules, JPL Publication 

84-39, DOE/JPL-1060-74, Jet Propulsion Laboratory, Pasadena, California, 

June 15, 1984. 

Selcuk, M. K., Parabolic Dish Test Site: History and Operating Experience, JPL 

Publication 85-18, DOE/JPL-1060-84, Jet Propulsion Laboratory, Pasadena, 

California, February 15, 1985. 

, Stallkamp, J. A., Control System for Parabolic Dish Concentrator No. 1, JPL 

Publication 85-40, DOE/JPL-1060-86, Jet Propulsion Laboratory, Pasadena, 

California, March 15, 1985. 

Stine, W. B., Survey of Manufacturers of High-Performance Heat Engines 

Adaptable to Solar Applications, JPL Publication 84-46, DOE/JPL-1060-75, 

Jet Propulsion Laboratory, Pasadena, California, June 15, 1984. 

Won, Y. S., Voecks, G. E., and McCrary, J. H., Experimental and Theoretical 

Study of a Solar Thermochemical Receiver Module, JPL Publication 84-53, 

DOE/JPL-1060-76, Jet Propulsion Laboratory, Pasadena, California, 

July 15, 1984. 

A- 2