NBS

Publications

Reference^

:IR 81-2381

lar Industrial Process Heat

Systems -- An Assessment of

Standards for Materials and

Components

NAT'L INST, OF STAND & TECH

ailOb 2ST77Q

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

September 1 981

Prepared for Solar Thermal Technology Division

Office of Solar Heat Technologies

Conservation and Renewable Energy

U.S. Department of Energy —QC Vashington, DC 20585

100

.056

81-2381

1981
Ii:
NBSIR 81-2381 NOV 2 3 1981

r

SOLAR INDUSTRIAL PROCESS HEAT

SYSTEMS -- AN ASSESSMENT OF

STANDARDS FOR MATERIALS AND

COMPONENTS

Walter J. Rossiter, Jr. Walter E. Shipp

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

September 1981

Prepared for Solar Thermal Technology Division

Office of Solar Heat Technologies

Conservation and Renewable Energy

U.S. Department of Energy

Washington, DC 20585

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U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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ABSTRACT

A study was conducted to obtain information on the performance of materials

and components in operational solar industrial process heat (IPH) systems, and

to provide recommendations for the development of standards including evaluative test procedures for materials and components. An assessment of the needs

for standards for evaluating the long-term performance of materials and components for IPH systems was made. The assessment was based on the availability

of existing standards, and information obtained from a field survey of operational systems, the literature, and discussions with individuals in the industry. Field inspections of 10 operational IPH systems were performed. The study

did not address the thermal efficiencies and health and safety considerations

of IPH systems.

The results of the study are presented in this report. It is concluded that

standard test methods are needed for evaluating the long-term performance of

materials and components used in IPH systems operating at high temperatures.

Some standard test methods are available having applicability to materials

and components in low temperature systems. However, in the latter case, data

bases are lacking which demonstrate their applicability. Recommendations are made and priorities assigned for the development of standards for materials and

components.

Keywords: field survey; industrial process heat; materials performance; solar

collector; standards; test methods.

iii
ACKNOWLEDGMENTS

The report was prepared under the sponsorship of the DoE Solar Thermal

Technology Division and was administrated by the Solar Technology Group at NBS.

Special thanks are given to William D. Nettleton, Jr. of the DoE San Francisco

field office for his time and hospitality in providing an overview of the IPH

program and a summary of the status of the IPH field test installations.

The authors express their appreciation for the contributions and technical

assistance provided by their colleagues at the National Bureau of Standards,

namely: Thomas Boone, Elizabeth Clark, Robert Dikkers, F. Eugene Metz,

Leopold Skoda, and Robert Stiehler. Special mention is made of the assistance

of Leslie Suddueth who arranged our visits to the field test installations.

The authors also wish to acknowledge with thanks the representatives of

architectural and engineering firms and collector system manufacturers, as well

as IPH field project site managers, who gave so generously of their time in

discussing the performance, operation, and maintenance of their systems. We

appreciated the opportunity to visit the field test installations and to take

many photographs, some of which appear in this report.
TABLE OF CONTENTS

Page

ABSTRACT ili

ACKNOWLEDGMENTS iv

LIST OF TABLES vli

LIST OF FIGURES viii

1. INTRODUCTION 1

1 . 1 Background 1 1.2 The Solar Industrial Process Heat Program 1 1.3 Objectives 3

1.4 Scope 4

2. FIELD OBSERVATIONS OF MATERIALS PEFORMANCE 5

2.1 Absorptive Materials 7 2.2 Absorber Panels 7 2.3 Containment Materials 8

2.4 Covers/Jackets 8

2.5 Drive Systems 9

2.6 Evacuated Tubes 10

2.7 Flex Hoses/Swlvel Joints 10

2.8 Fluids 10

2.9 Insulation (Thermal) 11

2.10 Pumps II

2.11 Receivers (Line-Focus Systems) 12

2.12 Reflective Surfaces 12

2.13 Seals (Rubber) 13

2.14 Trackers 14

2.15 Troughs (Parabolic) 14

3. ADDITIONAL INFORMATION RELATING TO IPH MATERIALS AND COMPONENTS

PERFORMANCE 32

3.1 The Literature 32

3.2 Discussions with Individuals In the Industry 35

4. STANDARDS FOR MATERIALS AND COMPONENTS OF SOLAR IPH SYSTEMS 37

4.1 Absorptive Materials 37

4.2 Absorber Panels 42

4.3 Containment Materials 43

4.4 Covers/ Jackets 45

4.5 Drive Systems 47

4.6 Evacuated Tubes 47

4.7 Flex Hoses/Swlvel Joints 48

4.8 Fluids 49

4.9 Insulation (Thermal) 50

4.10 Pumps 51

V
TABLE OF CONTENTS

Page

4.11 Receivers (Line- Focus Systems) 52

4.12 Reflective Surfaces 53

4.13 Seals (Rubber) 54

4.14 Trackers 55

4.15 Troughs (Parabolic) 56

5. SUMMARY AND CONCLUSIONS 58

6. RECOMMENDATIONS 59

7. REFERENCES 62

APPENDIX A. SUMMARY OF THE IPH DEMONSTRATION INSTALLATIONS VISITED .. A

APPENDIX B. TEST METHODS FOR MATERIALS COMMONLY USED IN SOLAR

ENERGY SYSTEMS B

vl
LIST OF TABLES

Page

Table 1. Types of Collectors for Solar Industrial Process Heat

Systems and the Operating Temperature Ranges 3

Table 2. Solar Industrial Process Heat Systems Inspected During

the Study 6

Table 3. Components for Solar IPH Systems, Their Function, and

Materials 38

Table 4. ASTM Standards Relating to Solar Materials and

Components 39

Table 5. Federal and Military Specifications Revelwed for

Applicability to Solar IPH Materials and Components 40

Table 6. Summary of Needs for Materlals-Related Standards Development

for IPH Components and the Priority of the Need 60

vii
LIST OF FIGURES

Page

Figure 2.1 Peeling and Cracking of Absorptive Coating and

Moisture on the Underside of the Cover Plate 15

Figure 2.2 Receiver Tube Without Glass Jacket Exposing the

Absorptive Coating to the Weather 15

Figure 2.3 White Deposits on Absorptive Coating of Receiver Tube ... 16

Figure 2.4 White Deposits on Absorber Plate and Rivets, and Moisture

on the Underside of the Cover Plate 16

Figure 2.5 White Deposits on Upper Section of the Absorber

Ducts of an Air System 17

Figure 2.6 Corrosion of an Elbow Fitting Connecting a Metal Flex

Hose and a Receiver Tube 17

Figure 2.7 Crimped Tubing Removed from Collectors 18

Fifure 2.8 Inadequately Sealed Joint Between Cover Plates Allowing

Dust and Dirt Penetration into the Collector 18

Figure 2.9 Metallic Spacer Ring on Absorber Tube 19

Figure 2.10 Spring Clip Holding Jacket on a Receiver Tube and

Moisture on the Underside of the Jacket 19

Figure 2.11 Insulated Receiver Tube Assembly Having a Flat Glass

Cover Plate 20

Figure 2.12 Drive System of a Line-Focus Collector 20

Figure 2.13 Oil Deposit on the Building Roof Under the Collector

Gear Box 21

Figure 2.14 Exposed Gear Mechanism 21

Figure 2.15 Breakage of Evacuated Tubes 22

Figure 2.16 Loss of Vacuum in an Evacuated Tube 22

Figure 2.17 Flex Hose of a Line-Focus System 23

Figure 2.18 Swivel Joint of a Line-Focus System 23

Figure 2.19 Insulated Piping Transporting Heat Transfer Fluid to and

from the Collector Field 24

vlii
LIST OF FIGURES (Continued)

Page

Figure 2.20 Exposed Fibrous Glass Insulation 24

Figure 2.21 Failure of Protective Covering on Insulation 25

Figure 2.22 Punctures in Spray-Applied Polyurethane Foam and its

Protective Coating Due to Vandalism 25

Figure 2.23 Bent Receiver Tube Due to Excessive Temperatures 26

Figure 2.24 Short Section of Uninsulated Receiver Tube 26

Figure 2.25 Desilvering of Exposed Glass Mirrors 27

Figure 2.26 Broken Glass Mirror 27

Figure 2.27 Delamination of a Small Area of Metallized Plastic

Film 28

Figure 2.28 Delamination of a Metallized Plastic Film at the Edge

of a Trough 28

Figure 2.29 Dust and Dirt on the Surface of an Evacuated-Tube

Collector 29

Figure 2.30 Dust and Dirt on the Reflective Surface of a Parabolic

Trough 29

Figure 2.31 0-Rlng Seal at the End of an Absorber Tube 30

Figure 2.32 Cracking of a Sealant Used to Protect Against Moisture

Penetration into Thermal Insulation 30

Figure 2.33 Shadow Band Tracker Having Moisture Within the Housing .. 31

Figure 2.34 Delaminated Plastic Strip at the Edge of a Trough 31
H
1. INTRODUCTION

1.1 BACKGROUND

The use of solar energy in industrial process heat (IPH) applications offers

tremendous potential for a reduction in fossil fuel energy consumption. Industry accounts for about forty percent of the total energy consumed in the United

States, most of which is derived from fossil fuels [1].* Fifty to seventy percent of this industrial energy consumption may be used as heat for industrial

processes [2]. Industrial process heat has been defined as thermal energy used

in the preparation and treatment of goods produced by manufacturing processes.

Twenty-seven percent of industrial process heat has a temperature below 288 °C

(550°F). Supplying this twenty-seven percent of industrial process heat as solar energy is attractive, since solar technology including concentrating collectors is available to collect heat below this temperature. Moreover, the use

of solar energy is currently most cost-effective below 288°C (550®F)[2]. In

addition, it has been estimated that, if solar preheating to 288°C (550°F) is

used in processes which require higher temperatures, approximately 51 percent

of Industrial process heat may be supplied with available solar equipment [2].

1.2 THE SOLAR INDUSTRIAL PROCESS HEAT PROGRAM

The U.S. Department of Energy (DoE) has established the solar industrial process

heat (IPH) program [3]. The IPH program provides direction, funding, and management of solar projects applying the direct conversion of solar energy to

useful thermal energy for industrial process heat systems. The program objectives are to stimulate and demonstrate the use of solar technologies as a replacement for and supplement to fossil fuels presently used for industrial

processes. The program which focuses on experimental and field test projects

provides the means for industry to perform government-funded experiments and

to construct cost-shared prototype solar systems. Specifically, the IPH program

has been designed to:

° assess industrial processes where solar energy may supply a significant

amount of process heat;

° design solar systems which can supply significant amounts of process

heat;

° experiment with various designs to determine the best method of deriving

industrial process heat; and

° demonstrate by the Installation of large scale cost-shared systems, the

capacity of solar energy to provide significant amounts of the process

heat requirements of various industries [3].

* Numbers in brackets indicate references listed in section 7.

1
Solar energy applications for industrial processes were originally categorized

into three [3] depending upon the temperature of the process:

° low temperature applications, below 100°C (212°F);

° Intermediate temperature applications, ranging from 100 to 177 °C (212

to 350°F); and

° high temperature applications, above 177 to 288°C (350 to 550°F).

Thirteen field test projects with prototype operational solar systems are included in the IPH program* and are divided in four cycles [4]. Projects in

the first three cycles (I-III) are designed to supply process heat within three

ranges: hot water, low temperature steam, and intermediate temperature steam.

The collector arrays for projects in Cycles I-III have collector areas about

929 m2 (10,000 ft2) or less in size. Cycle IV projects include processes

which require heat over the range of low to high temperature applications and

have collector arrays which may be as large as 4645 m2 (50,000 ft2).

The low temperature applications in Cycle I provide for Industrial hot water up

to 100°C (212°F). Industrial processes in Cycle I include hot water for can washing, concrete block curing, and textile dyeing. Cycle II field test projects provide low temperature steam up to about 177°C (350°F) in processes

involving gauze bleaching, pasteurization, laundering, and textile drying.

Intermediate temperature steam in the range of 149 to 288“C (300 to 550°F) will

be supplied by Cycle III projects. The Industrial processes for Cycle III projects are latex production, beer brewing, oil refining, and potato processing.

The two Cycle IV processes will provide hot water for the washing of machined

parts and steam for polystyrene production.

Three types of collectors, flat-plate, evacuated-tube , and line-focus, may be

used for generating solar industrial process heat [3]. The type of collector

may be selected depending upon the temperature range of the IPH application.

Table 1 shows the temperature range at which each type of collector normally

operates. As may be seen in table 1, the operating temperature ranges of the

three collector types overlap one with another. Line-focus collectors are used

for the higher temperature processes.

The success of the IPH program is dependent in part on the reliability of the

system materials and components to perform satisfactorily over the long-term.

Standards including test methods to evaluate materials are generally not available to assist architects, engineers, and other designers in the selection and

procurement of materials for use in solar IPH systems. Since these standards

could help assure the design and construction of systems which would reliably

perform, and contribute to the commercialization of the solar IPH industry.

* When the solar process heat program was initiated, it encompassed

agricultural as well as Industrial processes. These two programs are now

separated with thirteen projects classified as Industrial [4].

2
Table 1. Types of Collectors for Solar Industrial Process Heat Systems

and the Operating Temperature Ranges

Type of Operating Temperature Range

Collector °C °F

Flat-Plate 27 - 93 80 - 200

Evacuated-Tube 49 - 177 120 - 350

Line-Focus 66 - 288 150 - 550

the Department of Energy (DoE) requested the National Bureau of Standards (NBS)

to evaluate the need for materials standards for solar IPH systems. It is

essential to assess materials performance in operational IPH systems in order

to identify the needs for standards and to obtain information to aid in the

development of the standards.

A study was conducted in 1977 at the National Bureau of Standards (NBS) to

evaluate the performance of materials in solar systems primarily Intended for

the supply of space heating, cooling, and hot water [5]. A major conclusion

reached in the study was that "the process of selecting materials for specific

applications within solar energy systems is hindered by the lack of an adequate

data base of materials performance under the conditions experienced in solar

systems and subsystems." The report [5] gave Impetus to the Initiation of a number of projects by NBS to assist in developing the technical bases for

standards for materials used in residential and commercial solar systems for

the supply of building heating, cooling, and hot water. For the most part,

these materials standards were developed for flat-plate collectors. Industrial

process heat systems use primarily evacuated-tubes and line-focus collectors

and to a lesser extent, flat-plate collectors. The former types of collectors

may subject materials to conditions not commonly experienced by flat-plate

collectors in residential and commercial systenxs. In particular, operational

parameters such as temperatures, pressures, and liquid flow rates may be

higher. IPH systems may also be located in industrial areas where the environment including atmospheric contaminants may be harsh. In addition, the IPH systems may be larger and more complex than residential and commercial systems.

For these reasons, the existing material standards for solar components may not

be applicable to IPH systems. Existing standards may need to be modified or new standards developed.

1.3 OBJECTIVES

This report presents the results of the DoE-sponsored study to evaluate the

need for materials and component standards for solar IPH systems. The objectives of the study were: to obtain information on the performance of materials

and components in operational solar IPH systems, and to provide recommendations

3
for the development of standards including test methods for the evaluation of

materials and components used in these solar systems.

1.4 SCOPE

Data and information presented in this report were obtained from a field survey

and the published literature. Ten solar installations were inspected during

the field survey. Eight of these systems were field test projects in the DoE

industrial process heat program. Two of the installations were agricultural.

These latter two installations were inspected, since the solar systems were of

the type used for IPH applications.

The project plan addressed only the performance of materials and components in

IPH systems. An assessment of the thermal efficiencies and health and safety

considerations of the operational solar systems to provide industrial process

heat was beyond the project scope. Information from the literature and field

survey was complemented by that obtained in discussions with individuals knowledgeable in the field including architects, engineers, and solar system

manufacturers

4
2. FIELD OBSERVATIONS OF MATERIALS PERFORMANCE

The field inspections were intended to provide observations of materials and

components performance for operational systems. The ten solar IPII systems

inspected during the field phase of the study are listed in table 2. The location of the installation, the type of industrial process, the type of collector

system, the size of collector arrays, operating temperatures and pressures,

system energy outpur. , and the operational status of the system at the time of

c-he visit are also given in table 2. Appendix A presents a summary description

of each system visited.

All installations were DoE-sponsored field test projects. The three types of

collectors currently in use for IPH applications, flat-plate, evacuated-tube

and line-focus (parabolic trough and fixed receiver/tracking mirror), were

included in the inspections. Six of the ten systems were operational at the

time of the inspection. Two other systems were consttucted but not operating

when visited because of failures in key components. The remaining two sites

were under construction which was close to completion. Each of these latter

systems had collected some energy, as the collectors were being checked out in

preparation for becoming operational. The maximum age of the operational systems was about 2 1/2 years which was considered a relatively short time to assess materials performance in service. The systems were located in various

sections of the United States having different climates. A summary of the

status of all IPH projects including those visited has recently been

published [6].

As determined based on discussions with site personnel and observations made

during the field survey, a wide variability in the performance of the various

IPH installations existed. It is emphasized that this judgment is qualitative,

since measurements relating to system performance were not conducted and were

beyond the scope of the study. On one extreme, at one site personnel indicated

that the operation of the system was successful to the extent that they were considering an increase in the size of the solar system. On the other extreme,

as mentioned above, two systems were nonoperational because of materials

failures. The other sites visited were performing between these extremes.

Some sites had experienced few problems and had operated satisfactorily since

their construction. In one case, the solar system had experienced periods of

inoperation due to leaks in the heat transfer fluid circulating system.

Problems of varying degrees were observed at all the sites. Some problems

concerned unsatisfactory materials performance, while others centered on inadequate design. The emphasis in this section is to report observations concerning

unsatisfactory materials performance; however, reference is oiade to materials

and components which were functioning satisfactorily. Discussions with site

personnel Indicated that in some cases, components had performed Inadequately

and been replaced before the field visits. Reference is made to these replacements in the report.

The observations on materials problems are given for the various components of

the different types of collector systems. These components, given in alphabetical sequence. Include: absorptive coatings, absorber plates, containment

5
Table

2.

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Industrial

Process

Heat

Systems

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[7]
materials, covers/ jackets , drive systems, evacuated tubes, flex hoses/swlvel

joints, fluids, insulation (thermal), pumps, receiver tubes, reflective surfaces, seals, trackers, and troughs (parabolic). The following subsections

present a summary of the observations for each component and make reference to

selected photographs from the field inspections. The photographs may be found

at the end of this section.

2 . 1 ABSORPTIVE MATERIALS

o In one flat-plate system, the black velvet, nonselective absorptive coating

was peeling from a number of the aluminum absorber plates. A representative

of a collector manufacturer indicated that the poor adhesion of the coating

may have been due to improper cleaning and preparation of the aluminum surface combined with the use of a brittle coating. Moisture had penetrated

into some of the collector enclosures. Condensation was present on the

underside of some of the cover plates when observed during mid-morning (fig- ure 2.1). It was not determined whether there was a relationship between

the peeling of the coating and the moisture.

o Black chrome selective coatings were used on the receivers of the six

line-focus systems. For two installations, a black non-selective coating

had been field applied to the receiver tubes reportedly because of degradation of the original black chrome. At one of these Installations, some sections of the receiver tubes had the absorptive coating directly exposed

to the weather, since glass jackets were missing (figure 2.2). The piping

was copper. In another case, deterioration of the selective coating was

observed, even though the system was not fully operational. In this case,

the receiver tube piping was specified as being stainless steel. Low heat

transfer fluid flow rates through the receiver tubes during system check-out

reportedly resulted in excessive heating of the receivers, exposing the

selective coating to temperatures in excess of the design limits. At

another installation the black chrome coating appeared in good condition,

except that some small sections of the receiver tubes had some spotting

and white deposits (figure 2.3). The receiver tube piping was specified as carbon steel.

2.2 ABSORBER PANELS

o White deposits were observed on the upper surfaces of some absorber panels

at the only liquid system inspected having flat-plate collectors. In this

case, the absorber panels, which contained a black velvet, non-selective

coating, consisted of copper tubing sandwiched between two formed aluminum

plates attached with pop rivets. The heads of many rivets visible through

the cover plates had white deposits on them (figures 2.1 and 2.4). Moisture

was condensed on the underside of the cover plates of many collectors where

the white deposits were observed on the absorper panels. It was not determined whether the formation of the white deposits was related to the

presence of the moisture.

o For the one air system inspected, the absorber ducts generally appeared to

be in good condition, although a few small sections contained white deposits

7
(figure 2.5). The absorber ducts consisted of galvanized steel with a black velvet, non-selective coating.

2.3 CONTAINMENT MATERIALS

o A containment material is one which encloses the heat transfer fluid or is

in contact with the heat transfer fluid or storage material or both. Containment materials, as discussed here, primarily concern piping and storage

systems. Specific containment components such as flex hoses, swivel joints

a^jd pumps are discussed in other sections of the report (sections 2.7 and

2.10). Piping for the six line-focus systems Inspected consisted of steel,

stainless steel, or copper. For the three evacuated-tube systems two had

copper tubing and one had stainless steel tubing within the glass shrouds.

o Observations concerning the external appearance of containment materials

iodicatejd few problems. Observations were not made concerning the internal

appearance of the containment materials, since the systems were generally

operational and taking test cuts was beyond the project scope. Corrosion

was observed on some brass elbow fittings connecting copper receiver tubes

and copper flex hoses at one line-focus installation (figure 2.6). Some of

t^ corroded elbow fittings were leaking. A representative for the collectpr manufacturer indicated that the corrosion may have been due to galvanic

eprrosion in addition to inadequate selection of the alloy composition.

The fluid in the system was filtered well water. The corroded elbows were connected to the top of the flex hoses. Similar elbow fittings at the

botto® of the flex hoses were not leaking.

o Leaks in the heat transfer fluid piping systems during collector start-up

wfjre reported hy site personnel for two installations. In one case of an e^scuated-tube system, leakage occurred at the fittings connecting the

coilector tubing and system manifold. Leaks were stopped by tightening of

fittings. In addition, lack of adequate space for movement of the

cdl^e^tpr tubing, due to thermal expansion of the manifold piping, resulted

if| crimping of the tubing (figure 2.7). The tubing was pressed against the

hpqsi^g of the piping manifold when the piping expanded. The problem was

rpjportedly corrected by providing adequate space for expansion in the manifn|4 t^ij^ing. In one other evacuated-tube system, soldered joints between

tip collj^e^itor tubing and manifold piping leaked during start-up. Resoldering

of the joints eliminated the leaks.

o N© matfrials-related problems concerning the storage systems were observed

during the visits or reported by site personnel.

2.4 COVERS/JACKETS

o Cover plates on one of the two flat-plate collector systems were glass. The

second flat-plate system had three types of covers; glass, polycarbonate,

and glass reinforced plastic. No cover plate breakage was observed at

either site. Dust and dirt accumulation was present on the covers at both

installations. A sprinkler system had been installed at one system to wash

the cover plates.

8
o The flat-plate system containing the three types of cover plates was originally constructed using a continuous thin sheet of polycarbonate,

approximately 55 m (180 ft) in length. Replacement of the original polycarbonate was made in the summer of 1980 which was only a few months prior to

the site visit. The long expanses of the originally installed polycarbonate

sheets were replaced because of reported problems of buckling and cracking

associated with lack of adequate provisions for thermal expansion. Glass,

polycarbonate, or glass reinforced plastic were reportedly used as replacement covers on an experimental basis to determine which of these three

materials might perform most satisfactorily at the system location. Site

personnel indicated that when the system was designed, there was reluctance

to use glass covers because of possible breakage due to vandalism. Vandalism

of the replacement glass had not occurred. In general the materials had

been in place too short a time to observe differences in performance. The

replacement polycarbonate cover plates consisted of short sheets joined

together by overlapping. Some of these overlaps were not tight, and dust

and dirt were blown into the joints between sheets and into some collector

enclosures (figure 2.8).

o With one exception, the receiver tubes of the six line-focus collector

systems had circular glass jackets (figures 2.3, 2.9, and 2.10) or flat covers (figure 2.11). In the case of the exception, there was no jacket on

the receiver tube as designed and constructed. Some breakage of the glass

had occurred at four sites. At one site, breakage had been attributed to

inadequate allowance for thermal expansion. Redesign and replacement of the

jacket supports to allow for expansion had corrected the breakage problem,

although not all the broken jackets had been replaced. At another site,

breakage of glass jackets was attributed by site personnel to the use of a metallic spacer ring around the midpoint of the absorber tube (figure 2.9).

The spacer ring was intended as a support for the glass jacket. Upon thermal expansion, the rings scratched the glass, which subsequently broke.

Removal of the spacer rings corrected the glass breakage problem. At a third site, semicircular glass jackets were held on insulated receiver tubes

using spring clips (figure 2.10). Moisture was present within some sections

of the receiver tubes. One small length of a glass jacket, which apparently

had no spring clips holding it in place, broke when it fell from the receiver

tube during focusing of the collector. The flat glass covers were used in an insulated receiver tube assembly (figure 2.11). In addition to some sections of broken glass, moisture was present on the underside of many of

the flat glass covers.

2 . 5 DRIVE SYSTEMS

o The performance of the drive systems of the six line-focus collectors was variable. For three of the six installations, the drive systems were functioning without any reported problems (figure 2.12). Conversely, in the

worst case, all gear boxes of one system were frozen and the collectors

could not be turned from the stow position. Reasons for the failure of the

gear boxes were not reported, although they apparently leaked fluid. Oil

deposits were observed on the roof under the gear boxes (figure 2.13).

Excessive movement of the collectors due to faulty tracking may have also

9
contributed to the failure (section 2.14). At another location, problems

occurred with drive systems having undersized motors which operated inter^-

mittently. These motors are being replaced with those of proper size

operate continuously. At a third site, one gear box was frozen, while

motors on some other gear boxes were described by site personnel as continually blowing fuses. At this site, the gear drive was exposed to the waat^r

(figure 2.14). Site personnel indicated that future installations of this

system were planned to have a housing around the gear drive.

2.6 EVACUATED TUBES

o Three of the sites visited had evacuated-tube collector systems. At two of

the sites, breakage of the glass evacuated tubes was considered extensive;

while §t the third site, it was minor (figure 2.15). At this latter site,

it was indicated during conversations that about 1 percent of the tubes

broke during system start-up and were replaced by the manufacturer. Site

personnel attributed breakage to factors such as thermal shock and scratching of the tubes during installation. In one case, site personnel reported

that tube breakage occurred when the system became operational after brief

interruptions of service for repairs. Vandalism was also a significant

cause of tube breakage at one site.

o A num^jer of tubes at the three sites had lost the vacuum as indicated by the

white oxidized getter at the tips of the tubes (figure 2.16).

o Site personnel indicated concerns with degradation of the copper fins

at;tached to the heat transfer fluid tubing around which the evacuated tubes are placed. The copper fin degradation was reportedly attributed to oxidation at the temperatures reached during system stagnation. The effect of

the fin degradation on the thermal performance of the collectors was not

determined during the site visits.

2.7 FLEX HQSES/SWIVEL JOINTS

o Fle^ hoses (figure 2.17) in the six line-focus systems inspected were operating without problems. At one site, a single flex hose had failed and

been replaced prior to the visit. Reasons for the failure of this flex

hose were not given.

o One system which was not operational at the time of the visit contained

swivel joints (figure 2.18). Some of the swivel joints were reported by

site personnel to have leaked during system start-up, but the cause of the

leakage was not given.

2.8 FLUIDS

o Three types of heat transfer fluids were used among the systems inspected;

water, aqueous glycol, and an aromatic hydrocarbon high temperature oil.

The systems using water operated within the range of 66-177°C (150-350®F).

10
Operating temperatures for the aqueous glycol systems ranged from 57-132°C

(135-270°F). The oil system which was under construction at the time of the

visit was designed to operate at 186°C (367°F). Line-focus collectors should

not stagnate, provided that they de-focus or are placed in the stow position

upon exceeding a predetermined maximum temperature of the receiver tube or heat transfer fluid. An evacuated-tube collector may reach 371°C (700°F)

or higher upon stagnation. One of the evacuated-tube systems used aqueous

glycol as the heat transfer fluid. Information was not available concerning

changes in physical and chemical properties of the glycol solutions. With

one exception, site personnel did not indicate problems with heat transfer

fluids and, as previously discussed, leaks in containment materials were

few (section 2.3). One water system was retrofitted with a filter to remove

particulates which were clogging valves.

2.9 INSULATION (THERMAL)

o Insulation was used in the sites visited on the backsides of absorber plates

and receiver tubes, on transport piping and accessories, and on storage

systems. It was generally not possible to observe the insulation because of

the covering provided to protect it from the effects of weather. Piping was normally insulated with fiberous glass, although some foam was also used.

o The primary concern raised from the field observations centered on the

application which was variable over the sites. Some applications appeared

satisfactory in so far as the insulation was protected from moisture intrusion and other weather effects (figure 2.19). Conversely, other applications

were found to have deficiencies including: missing protective covering

(figure 2.20); improper installation of protective coverings allowing moisture entry into the insulation (figure 2.21); use of sealants which split

and cracked; and lack of insulation on accessory items such as valves and

flex hoses (figures 2.2 and 2.17).

o The one air system in the field inspection had spray-ln-place polyurethane

foam insulation on the exposed air ducts. With the exception of vandalism,

the coating on the foam appeared through visual inspection to be satisfactory

after three years exposure. Vandalism had caused many punctures and splits

in the coating and insulation (figure 2.22). Another site had pre-formed

foam Insulation with a liquid applied coating on manifold pipes. This insulation was not properly protected from the weather, as indicated by its

cracked and crazed surface.

o Receiver tubes on three line-focus systems were insulated on the backside

(figure 2.10). In two of the cases, the insulation was fibrous glass; the

type was not determined in the third case. Since the Insulations could not

be observed because of encapsulation, their condition could not be evaluated.

Concern was expressed as to the thermal stability of the insulations in

contact with receiver tubes.

2.10 PUMPS

o Pump failures had occurred at some of the sites. In one case, the system

was Inoperable because a failed pump had been removed and not replaced. In

11
other cases accounts of pump failures which had been corrected before the

site visits were reported by site personnel. These failures were generally

attributed to the seals, but further information was not provided. In one

case, pump failure occurred because of packing which was too tight.

2.11 RECEIVERS (LINE-FOCUS SYSTEMS)

o At one line-focus Installation, site personnel indicated that bending of some of the metallic receiver tubes had occurred when the receivers were in

focus with low flow rates of the heat transfer fluid. This condition

resulted in excessive receiver temperatures (figure 2.23). The bent receiver

tubes were being replaced at the time of the visit.

o At one site the ends of the receivers were not sealed between the absorber

pipe and glass jackets. Some dirt had blown into the receivers at these

locations

o At another site, receivers of an inoperable line-focus system contained some split copper pipes and broken glass covers. A cause of split pipes may have

been freezing of water which was not drained from the non-operating

receivers

o Receiver tubes at some installations had short uninsulated sections extending

beyond the glass jacket in the vicinity of the supports (figure 2.24).

2.12 REFLECTIVE SURFACES

o Three types of reflective surfaces were used at the six line-focus

installations: two systems had second surface glass mirrors, two had

polished aluminum, and two had metallized plastic film. Two evacuated-tube

systems used polished aluminum, and the third evacuated-tube system had a metallized plastic film. At one site with glass mirrors, desilvering had

occurred and was particularly extensive along the mirror edges (figure 2.25),

perhaps due to moisture penetration at those locations. Breakage of the

mirrors was also evident at this site (figure 2.25). Site personnel indicated that the glass mirrors were to be upgraded with a metallized plastic

film because of the extent of desilvering and breakage. Mirrors at the

other site appeared in good condition.

o The polished aluminum reflective surfaces of both line-focus and evacuatedtube systems were generally in good condition, although dulling had occurred

at some sites. For example in one case, two sections of evacuated-tube

collectors had been removed from the site to determine, by laboratory

measurements, whether the dulling had reduced collector efficiency.

o Visual evidence of abrasion of the front surfaces of the metallized plastic

films was not seen at the three sites having such reflective surfaces. Some

delamination of metallized plastic films was observed at two of the sites.

In one case, small areas of delamination, about 13 mm (1/2 in.) in width,

ran horizontally from one end of the trough to the other (figure 2.27). In

the second case, delamination of the metallized plastic film was from the

longitudinal edge of a single trough toward its center. The film apparently

12
was delaminated when a plastic strip sealing the edge of the collector fell

from the trough and pulled the film from the surface (figure 2.28). Blisters

raised slightly from the substrate were also observed on areas of the trough

surfaces other than the edges. Many of these blisters were located in areas corresponding to screw penetrations on the back of the troughs. It was not

determined whether the screw penetrated the trough surface under the reflective film. At the third site, where construction of the collector system

was essentially completed, the metallized plastic film appeared in good

condition.

o Dirt, dust, and other particulate accumulation on the reflective surfaces was

a problem common to all sites visited (figures 2.29 and 2.30). Reduction in

collector efficiency because of soiling of the reflective surfaces was of

concern to many site personnel. Cleaning procedures such as the use of

hoses, sprinkler systems, and the hiring of professional washers had been

initiated at many sites to remove accumulated particulates from the reflective surfaces. At some locations, site personnel indicated that line-focus

collectors were turned upwards during rain storms to wash the reflective surfaces. It was also indicated that placing the line-focus collectors in the

stow position when not in use reduced the accumulation of dirt and dust.

o Vandalism at one evacuated-tube installation (see section 2.6) had resulted

in punctures and dents in the metallized plastic reflective film and damage

to the troughs and tubes.

2.13 SEALS (RUBBER)

o Rubber seals were not used to any extent in the systems visited. At one

site, rubber o-ring seals were originally Installed at the ends of the

receivers between the absorber tubes and glass jackets to protect against

dirt and moisture entry (figure 2.31). According to site personnel, the

temperature of the o-rings exceeded the design limits due to concentration

of the solar radiation on the seals when the collectors were in focus. The

excessive temperature reportedly resulted in deterioration of the seals. An

expedient temporary correction of the problem was accomplished by installing

reflective tape on the receiver jacket at the o-rlngs to prevent absorption

of the concentrated solar radiation by the seals and excessive temperatures

at those locations. Site personnel indicated that a metal seal was being

designed to replace the o-rings as a permanent correction of the problem.

o At one line-focus installation, pre-formed rubber gaskets were used to seal

the flat glass covers to the insulated receiver assembly (figure 2.11).

Some of the gaskets were seen to be deformed and have buckles, and thus were

not tight against the flat glass covers.

o Sealants were used in many systems to prevent water penetration into thermal

insulations at piping system locations such as joints, couplings, fittings

and valves. In many cases, the sealants were seen to have split and cracked

(figure 2.32).

The term, rubber seal, is used generically to indicate elastomeric materials.

13
2.14 TRACKERS

o In the case of the two operational parabolic trough line-focus systems

visited, the collectors at each individual site were oriented in the same direction towards the sun. Quantative information regarding tracking

accuracy was not obtained during the field survey.

o A concern to site personnel at some line-focus systems having shadow band

trackers was the irregular tracking of the collectors under conditions of

low solar radiation and random cloud cover. Under these conditions, when

the clouds cover the shadow band trackers for short intervals of time, the

collectors rotate in an attempt to find the sun. If the sun is not found,

the collectors may go to the stow position. This irregular behavior of the

tracker was experienced at one site during the field inspections. At

another location, site personnel indicated that excessive searching of the

collectors, due to trackers functioning improperly, may have been responsible in part for failure of the system gear boxes. As previously mentioned

(section 2.5), this system was inoperational because of frozen gear boxes.

o At one site, moisture had entered into the shadow band trackers due to holes

in the tracker housings (figure 2.33). Site personnel indicated concerns

that the entrapped moisture would result in failure of the trackers. The

trackers with moisture were to be replaced. One replacement tracker was installed prior to the site visit and did not show moisture in its interior.

2.15 TROUGHS (PARABOLIC)

o In the case of one line-focus collector having parabolic troughs, plastic

strips used as molding to seal the edges of the troughs (aluminum honeycomb

sandwiches) were delaminating (figure 2.34). These molding strips were brittle. The delamination of the edge moldings exposed the interior of the

troughs to moisture.

o At one site, the back surface of one collector trough was not protected

from hot sparks and solder from welding operations during system construction. The trough had pitted areas where the sparks landed on the rear surface

14
Figure 2.1. Peeling and cracking of absorptive coating and moisture

on the underside of the cover plate

Figure 2.2. Receiver tube without glass jacket exposing the absorptive

coating to the weather

15
i

Figure 2.3. White deposits on absorptive coating of receiver tube

16
Figure 2.5. White deposits on upper section of the absorber ducts

of an air system

Figure 2.6. Corrosion of an elbow fitting connecting a metal flex

hose and a receiver tube

17
Figure 2.7. Crimped tubing removed from collectors

Figure 2.8. Inadequately sealed joint between cover plates allowing

dust and dirt penetration into the collector

18
Figure 2.10. Spring clip holding jacket on a receiver tube and

moisture on the underside of the jacket

19
Figure 2.11. Insulated receiver tube assembly having a flat glass cover plate

Figure 2.12. Drive system of a line-focus collector

20
I

I

Figure 2.13. Oil deposit on the building roof under the collector

gear box

Figure 2.14. Exposed gear mechanism

21
Figure 2.15 . Breakage of evacuated tubes

Figure 2.16. Loss of vacuum In an evacuated tube

22
Figure 2.18. Swivel joint of a line-focus system

23
Figure 2.20. Exposed fibrous glass insulation

Figure 2.19. Insulated piping transporting heat transfer fluid to

and from the collector field

24
Figure 2.21. Failure of protective covering on insulation

Figure 2.22. Punctures in spray-applied polyurethane foam and its

protective coating due to vandalism
Figure 2.23. Bent receiver tube due to excessive temperatures

Figure 2.24. Short section of uninsulated receiver tube

26
Figure 2.26. Broken glass mirror

27
Figure 2.28. Delaminatlon of a metallized plastic film at the edge

of a trough

i

28
Figure 2.29. Dust and dirt on the surface of an evacuated- tube

collector

Figure 2.30. Dust and dirt on the reflective surface of a parabolic

trough

29
Figure 2.31 . 0-ring seal at the end of an absorber tube

Figure 2.32. Cracking of a sealant used to protect against moisture

penetration Into thermal Insulation

30
Figure 2.33. Shadow band tracker having moisture within the housing

Figure 2.34. Delaminated plastic strip at the edge of a trough

31
3. ADDITIONAL INFOR^IATION RELATING TO IPH MATERIALS AND COMPONENTS PERFORMANCE

3 . 1 THE LITERATURE

The dissemination of information regarding the design and in-service

performance of IPH solar systems is an integral part of the IPH program. A

number of proceedings and reports have been published to allow the Industry to

share its experiences and to learn the results of ongoing research and development. A review of the literature was conducted as part of this study to evaluate the need for standards for materials and components for IPH systems. A

summary of the literature considered pertinent to the development of standards

is given in this section of the report. It was beyond the scope of the project

to present a comprehensive review of current research and published papers.

3.1.1 Conferences and Workshops

A series of conferences on solar IPH technology have been held, and the

proceedings have been published [8-12]. The proceedings provide an overview

of the IPH program and Include papers on system design, economic analyses,

potential industrial processes for solar applications, field experiences, and

research results. Descriptions and status reports of the demonstration projects are included in the proceedings. The status reports for operational

systems mention materials and components problems which have occurred in service, and remedial actions taken to correct them. The materials problems

reported in the proceedings were among those observed in the field survey

conducted during this study (section 2).

The proceedings of a workshop on the reliability of materials for solar energy

systems have been published [13, 14]. Some papers addressed materials used

for IPH systems including absorber coatings, mirrors or other reflective surfaces, transport systems and heat transfer fluids. The development of methods

for materials evaluation and the preparation of Industry standards and design

rules for solar technology were among the recommendations listed in the

workshop

A workshop devoted solely to IPH processes was held in 1976 [15]. The theme of

the workshop was the feasibility and potential applications of the use of solar

energy for industrial processes. Papers were presented on the design of the

early IPH field test projects. Many recommendations were made concerning

future research and development needs for the industry with regard to collectors, storage, and systems. However, the proceedings made little reference to

the performance of materials in IPH systems.

In late 1980, a seminar was held on the development of line-focus solar thermal

energy technology [16]. In contrast to the 1976 IPH workshop, the 1980 seminar

included sessions concerned with the development and performance of materials

and components for line-focus collectors. Papers on materials performance were presented on the subjects of black chrome, glass fiber reinforced concrete for

troughs, silvered glass mirrors, and polymer reflectors. The prediction of the

service-life of components was also discussed. It was indicated that accelerated aging studies are needed for making reliable predictions of service-life.

32
since the systems and technology are in the relatively early stages of

development

The proceedings of the second conference on absorber surfaces for solar receivers

has been published [17]. The main topics of the conference were: the development of microstructural models for black chrome selective solar absorbers; the

stabilization of black chrome for applications to 350°C (662°F); and the laboratory development of cermets for application to 600°C (1112°F). Although

intended as a conference topic, the field exposure and durability of absorber

coatings were not discussed. The conference proceedings contained an appended

bibliography of papers related to absorber surfaces.

The performance of solar reflective materials has also been the subject of a workshop [18]. The workshop focused on problems regarding the durability of

superstrates , reflective layers, and protective layers of heliostat mirrors.

The workshop objective was to assess research efforts to understand and control

the degradation process which mirrors have undergone after relatively short

periods of field service. The major topics addressed at the workshop were:

the effects of environmental contamination; glass and mirror production processes; the environmental stability of glass superstrates; analysis of silverglass second surface mirror degradation; the experience with and potential of

polymer mirror systems; and advanced mirror protection concepts. Among the

general conclusions from the workshop, it was indicated that: adhesion mechanisms of dust on mirrors are not well understood; research into glass production processes would improve efficiency and durability; mechanisms for silverglass mirror degradation are mainly speculative; and. Improvements in polymer

technology have shown a potential for using highly specular polymer mirrors

[18].

Another workshop on solar surfaces addressed the problem of soiling of

reflective surfaces by air-borne particulates and aerosols [19]. The magnitude

of the effect of the air-borne contaminants on the reduction of surface reflectivity was dependent upon the design of the optical system, the nature of the

contaminants at the exposure site, the seasonal climate at the site, the material comprising the optical surface, and the method of removal of contaminants

from the surface. Recommendations for research were given including obtaining

data on the rate of dust accumulation for various materials and locations, and

the development of a quantitative method for predicting the soiling effects

on solar concentrators from local pollution and climate data.

3.1.2 Handbooks and Field Experience

Kutscher and Davenport published a report describing the preliminary operational

results of the six low-temperature solar IPH field test installations [20].

Observations from the field showed materials and components problems such as degradation of absorber surfaces and glazings, thermal shock of evacuated tubes,

mirror breakage and desilvering, water seepage into Insulation and overheating

of plastic pipe. The authors considered that the observations would be useful

to the design of future projects. Among their conclusions they indicated that

"problems similar to those encountered in solar heating and cooling of buildings

programs occur in IPH applications [20]."

33
The "Solar Heating Materials Handbook" has been prepared to provide solar

designers assistance in the selection of appropriate materials [21]. Emphasis

is placed on the consideration of environmental and safety factors during materials selection. Solar materials included in the handbook are heat transfer

fluids, glazing, insulation, seals and sealants, thermal storage media, and

absorber materials. Values of properties considered important to performance

are given for specific materials.

A listing of the factors to be considered in each aspect of the design of solar

IPH systems has been given [7]. The factors listed were based on information

learned in the design and operation of the IPH field test installations. The

purpose of the document was to take advantage of the field experiences in order

to help prevent recurrence of past problems in future systems. Factors listed

for consideration during design included the following topics: system application, oyerall system design, design of individual components, instrumentation,

and controls, installation, prediction of the energy delivered, economics, data

acquisitipn, and safety.

A forecast of solar IPH technology in the year 2000 has been prepared by

Prythero and Meyer [22]. They predicted that the selected IPH system will

consist o| line-focus parabolic trough collectors. Material components were predicted to be based upon existing and anticipated future technological

developments. Technologies considered to have significant impact on future IPH

systems include glassmaking, silvering, electroplating, and plastics forming.

3.1,3 Research Related Publications

The National Bureau of Standards has a laboratory research program intended to

aid in providing the technical basis for consensus standards for assessing

performance and durability of solar materials in flat-plate collector systems

[23] . Materials studied include absorptive coatings, metallic and non-metallic

containment materials, cover plates, rubber hose, thermal insulation, and seals.

A number of NBS publications are available from the studies [24-29]. Standards

for some materials such as absorber covers, hoses, seals, and metallic containment materials have been developed by the American Society of Testing and

Materials (see section 4).

>-

The mid-temperature solar system test facility is located at the Sandla National

Laboratories. A status report of the facility’s activities gives a summary of

ongoing research projects for the development of mid-temperature solar technology [30]. Areas of materials research include mirror cleaning, heat transfer

oil aging, black chrome thermal aging, flex hose testing, trough components

life testing,, and long-term evaluation of receivers.

The Solar Energy Research Institute is developing an outdoor test facility for

"Solar Energy Research and Applications in Process Heat" for evaluation of

solar IPH systems [31]. The performance of complete small-scale systems will

be monitored in a closely controlled environment. A primary objective of the

facility is to verify materials performance as part of an operational system.

34
The technical support for solar applications for buildings provided by the Los

Alamos Scientific Laboratory to DoE has been described in a progress report

[32]. Collector and materials projects funded by DoE have been monitored.

Fifteen projects concerned with the development of concentrating collectors,

while twenty-nine dealt with research and development of materials including

absorbers, glazings and coatings, fluids and corrosion, insulating materials,

and sealants. Research at the laboratory was centered on testing of evacuatedtube collectors, and selective coated metal foils for use in these types of

collectors

Finally, the design reports (often called Phase I reports) for the field test

installations in the DoE industrial process heat program should be mentioned.

These reports provide information concerning system design and materials selection. In general, the design reports indicate that standardized evaluative

test procedures were seldom used for the selection of many materials and components in the systems. Subjective value judgments played a major role in the

selection process.

3.2 DISCUSSIONS WITH INDIVIDUALS IN THE INDUSTRY

During this study, discussions were held with solar system manufacturers’

representatives, architects, plant engineers, designers, consultants, and

other individuals in the solar IPH industry. The purposes of the dlscusssions

were to review these individuals* experiences concerning the performance of

materials and components and to ask their opinions concerning the need for

standards for IPH materials and components. With regard to materials performance, the discussions Indicated that many individuals in the Industry were

aware of the problems that had occurred in the field test program. Moreover,

manufacturers were aware of the specific problems with their systems which

were observed in the field survey (section 2).

Most individuals contacted in the Industry Indicated that the development of

standards including materials specifications and evaluative test methods would

be beneficial. However, many of the opinions concerning the benefits of standards development were qualified. Comments from the industry were at times

contradictory, because of the various opinions held by different individuals.

It is of interest to note some of the following industry comments and opinions

concerning standards development:

o Priority in standards development should be given to key materials and

components of the system; for example, reflective surfaces and absorber

coatings for line-focus collectors.

o Although standards development would be beneficial, the time is too early;

the industry is still developing. Preparation of standards for materials

and components under development is not critical.

o Standards development should be initiated for materials and components which

are forecast to be used in the industry for a long time.

33
o For many non-solar specific components, for example, steel support members,

pipes, nuts, and bolts, material standards are available to the solar syste*

designer.

o Standards should be non-restrictive in that they should not preclude the use of materials in situations where they would perform satisfactorily.

o Test method development is not practical at this time, since insufficient

data are available on solar materials and component performance under a variety of environment conditions. Test exposure conditions and criteria

need to be precisely selected, if the test results are to be correlated

reliably with in-service performance.

o A need exists to develop service-life prediction techniques so that

long-term materials performance may be readibly assessed from short-term

tests

o Lack of standards in the industry is detrimental to designers and

manufacturers selling collector systems with warranties. The designers may

select materials which were Inadequately assessed because of the lack of

evaluative procedures. These materials are then incorporated into systems

for which the solar manufacturer, and not materials supplier, has warranty

responsibility.

o The availability of standards for key components would eliminate the use of

marginal materials.

o Standards availability would be of little importance to architecturalengineering firms which specify predesigned and engineered collector systama

from a solar manufacturer. In these cases, the architect-engineer may bas«

the selection of the system on the reputation of the solar manufacturer.

From the discussions, the lack of materials standards including evaluative test

methods was seen to have an adverse effect on the materials procurement process.

Many solar designers indicated that standards would have been useful in seloating solar-specific materials and components. These individuals stated tkat tjMcy

used available standards for the non-solar specific materials and components

included in their systems.

In eases where standards were not available, the designer might prepare a specification for the given material based on his own experience gained from

designing products in technological fields other than solar energy (e.g.,

aerospace). Designers mentioned that in some instances, non-standardized

laboratory tests were conducted on materials considered for solar applications.

One designer indicated that laboratory tests of materials were expensive, timeconsuming, increased the cost of the solar installation, and were not always

successful. In some cases, designers choose trade name products and made value

judgments basing their decision in part on the reputation of the material

manufacturer.

36
4. STANDARDS FOR MATERIALS AND COMPONENTS OF SOLAR IPH SYSTEMS

Standards may be classified into various types including: materials

specifications; test methods for determining materials properties; practices

for evaluating materials performance under given exposure conditions; and

practices for materials applications and use. Test methods for materials

properties and evaluative practices are of major interest within the

scope of this report. In considering the evaluation of materials for IPH

solar applications, the type of material, its use and function in the system,

and the exposure conditions during service must be considered. Test methods

are selected to determine values of key material properties. Standard evaluative practices should expose the materials to conditions simulating those anticipated in-service. After exposure, values of key properties may be remeasured

to determine the effect of the exposure.

Skoda and Masters have previously listed test methods for the common materials

used in solar energy systems: coatings, fluids, glass, insulation, metals,

plastics, and rubbers [5]. The lists of test methods are reprinted in appendix

B, since reference to them is made within this section of the report. It is

not the intent to review the applicability of these test methods to the evaluation of solar materials; this has been accomplished. The key needs identified

by Skoda and Masters regarding standards for materials for solar heating and

cooling systems were the development of accelerated aging tests for the

estimation of long-term servicabillty.

Table 3 presents a list of components of solar IPH systems, as well as the

function of each component in the system, and materials from which the component may be fabricated. The components are listed in alphabetical order. An

assessment of available standards for each component is summarized in the

upcoming subsections of the report. Based on the assessment, the needs for

standards development for each component are given. The needs provide in part

the basis for the recommendations in section 6.

The American Society for Testing and Materials (ASTM) has issued a number of

standards for solar energy materials and components, as shown in table 4. The

ASTM also has under consideration draft standards on other aspects of materials

and component performance including polymeric containment materials, covers,

stability of aqueous heat transfer fluids, thermal insulations, and membrane

liners for water tanks. As part of this study, the ASTM approved standards

were examined for their applicability to IPH systems. In addition, some Federal

and military specifications were also reviewed for applicability (table 5).

4.1 ABSORPTIVE MATERIALS

4.1.1 Assessment

The key performance properties of absorptive materials are absorptance,

emittance, and adhesion. Appendix table B.l presents test methods for evaluating many properties of coatings including optical and adhesion properties.

Absorptive materials used in flat-plate and concentrating collectors are

37
Table 3. Components for Solar IPH Systems, Their Function, and Materials

Component Function Materials

Absorptive Coatings 1 Absorb solar radiation, converting it into

1 heat

1

1 Black paint and metallic compounds on metal

1 absorber panels, or on glass or metal tubes

Containment Materials

1

1 Provide enclosure for heat transfer fluids or

1 heat storage materials

1

1 Glass, metals, plastic, rubber

Covers/ Jackets

1

1 Provide environmental protection and reduce

1 thermal losses

1

1 Plastic, glass

Drive Systems

1

1 Move and maintain parabolic trough collectors

1 in the desired position (focus or stow) to

1 provide smooth tracking and stability during

1 gusts of wind

1

1 Electric motors with mechanical or hydraulic

1 drive

Evacuated Tubes 1 Absorb solar radiation and minimize thermal

1 losses from the absorber

1

1 Glass

Flex Hoses/Swivel Joints

1

1 Provide a flexible connection between tracking

1 receiver tubes and stationary piping headers

1

1 Metals, plastics, rubber

Fluids

1

1 Transfer heat from the absorber to storage

1 or use

I

1 Air, water, glycols, hydrocarbons, silicones

Insulations (Thermal)

1

1 Reduce heat loss from components such as

1 collectors, transport systems, and storage

1

1 Mineral, organic fibrous, and cellular

1 materials

Pumps 1 Circulate heat transfer fluids

1

1 Metals, rubber seals

Receiver Tubes

1

1 Provide a surface for the absorptive coating

1 and containment of the heat transfer fluid

1 which may operate at elevated temperature and

1 pressure

1

1 Glass, metal

Reflective Surfaces

1

1 Redirect the solar radiation so that it

1 concentrates on the receiver

1

1 Polished metals, metallized plastic films,

1 glass mirrors (adhesives for bonding)

Seals

1

1 Prevent leakage (air and moisture) into

1 collector or other enclosure

1

1 Rubbers

Tracke rs

1

1 Sense the sun's position in relation to the

1 collector to activate the drive mechanism

1 to maintain focus of the concentrated solar

1 radiation on the receiver tube

1

1 Photocells, heat-flux sensors

Troughs (Parabolic)

1

1 Provide adequate support and a smooth sub1 strate for the reflective surface

1

1 Metals, plastics, composites

38
Table 4. ASTM Standards Relating to Solar Haterlals and Components

Materials/

Components

ASTM

Designation Title of the Standard

Absorber

Panels

B 638 Specification for Copper and Copper-Alloy Solar Heat Absorber Panels

Absorptive

Haterlals

E 744 Practice for Evaluating Solar Absorptive Materials for

Thermal Applications

E 781 Practice for Evaluating Absorptive Solar Receiver

Materials When Exposed to Conditions Simulating

Stagnation In Solar Collectors With Cover Plate(s)

Collector

Assembly

E 823 Practice for Nonoperatlonal Exposure and Inspection

of a Solar Collector

Containment

Materials

E 712 Practice for Laboratory Screening of Metallic Containment

Materials for Use With Liquids In Solar Heating and

Cooling Systems

E 745 Practice for Simulated Service Testing for Corrosion of

Metallic Containment Materials for Use With Heat Transfer

Fluids In Solar Heating and Cooling Systems

Cover

Materials

E 765 Practice for Evaluation of Cover Materials for Flat Plate

Solar Collectors

E 782 Practice for Exposure of Cover Materials for Solar

Collectors to Natural Weathering Under Conditions

Simulating Operational Mode

Optical

Properties

E 408 Test for Total Normal Emlttance of Surfaces Using

Inspection-Meter Techniques

E 424 Test for Solar Energy Transmittance and Reflectance

(Terrestrial) of Sheet Materials

E 434 Test for Calorimetric Determination of Hemispherical

Emlttance and the Ratio of Solar Absorptance to Hemispherical Emlttance Using Solar Simulation

Rubber Hose D 3952 Specification for Rubber Hose Used in Solar Energy Systems

Rubber Seals D 3667 Specification for Rubber Seals Used in Flat-Plate

Solar Collectors

D 3771 Specification for Rubber Seals Used In Concentrating

Solar Collectors

D 3832 Specification for Rubber Contacting Liquids In Solar

Energy Systems

D 3903 Standard Specification for Rubber Seals Used

In Air-Heat Transport of Solar Energy Systems

39
Table 5. Federal and Military Specifications Reviewed for Applicability to

Solar IPH Materials and Components

Material/

Component

Type of

Specification Designation Title of Specification

Absorptive

Materials

Federal QQ-C-320b Chromium Plating

( Elect rodeposited)

Military Mll-C-14538b (MR) Chromium Plating

(Elect rodeposited)

Flex Hoses Military Mll-H-19034a Hose, Metal, Flexible

Reflective

Surfaces

Federal DD-M-00411b Mirrors, Glass

Federal GGG-M-350a Mirrors, Inspection

40
subjected to the degradative effects of elevated temperatures, temperature

cycling, ultraviolet radiation, and moisture. Test procedures for evaluating

the resistance of absorptive materials to aging should include these factors.

In particular, absorptive coatings for line-focus collectors may experience

operating temperatures in excess of 288°C (550°F). A recent report summarizing

studies on black chrome indicated that some of these selective coatings may

have questionable stability, even at temperatures as low as 200°C (392°F)

[33]. Stagnation conditions encountered by evacuated-tube collectors may

subject absorptive coatings in these systems to temperatures as high as 371°C

(700°F), but in the absence of air. With regard to black chrome selective

coatings, it is noted that the control of the electroplating process is important to the performance of the coatings [34]. An assessment of solar-related

standards for absorptive materials for use in IPH systems is summarized as follows

o ASTM Standard Practice E 744 has been prepared for the evaluation of

absorptive materials for thermal applications (table 4). The standard

practice stipulates exposure of the absorptive materials to the primary

factors considered to cause degradation; solar radiation, elevated temperatures, temperature cycles, and moisture. The practice is applicable to

flat-plate and concentrating collectors having a concentration ratio not

greater than 5. The concentration ratio of line-focus collectors in IPH

systems normally exceeds 5. As given in the scope of the standard, the

practice is not intended for evacuated-tube collectors. A heat aging test

is included in the practice whereby the test specimen is to be exposed for

a period of 500 hours to the stagnation temperature expected in service.

This test may be applicable to the higher temperature IPH systems, although

laboratory data are needed to demonstrate the applicability.

o The performance of absorptive materials for flat-plate collectors with cover

plates under conditions of collector stagnation may be evaluated according

to ASTM E 781. In this test, the absorptive material specimen is exposed

outdoors in a sealed insulated box with a transparent cover plate so as to

simulate a flat-plate collector under stagnation. The maximum nonoperational

stagnation temperature for this test is approximately 200°C (392°F). Thus,

by its very nature, the test is not applicable to evaluate absorptive materials used in evacuated-tube collectors or on receivers of line-focus collectors where specimen configurations are different and operation and/or stagnation temperatures may be higher. Moreover, the coatings in evacuated-tube

collectors operate in a vacuum.

o Federal specification, QQ-C-320B, and military specification, Mil-C-14538b (MR)

(table 6) are available for the plating of black chrome primarily on steel

or nickel-plated steel, although other metal substrates may be used. These

specifications were not prepared to be applicable to IPH solar technology.

Requirements for the measurement of the optical properties (l.e., absorptance and emittance) are not included in either specification. In addition,

aging tests to evaluate the effects of ultraviolet radiation, temperature,

and moisture on the plated specimens are not included in either specification. The federal specification requires adhesion testing of the plated

chrome

41
4.1.2 Needs Concerning Standards Development

The needs concerning standards development for absorptive materials for solar

IPH systems are as follows

o Standard methods of test for evaluating aging at maximum expected operating

and/or stagnation temperatures for line-focus and evacuated-tube collectors

should be developed. The role of other prime aging factors such as temperature cycling, ultraviolet radiation, and moisture should be considered in

the test development. Moisture is not expected to play a role in the aging

of a coating in a sealed evacuated tube. Previously developed test methods,

(ASTM E 744 and E 781) for evaluating absorptive materials for use in low

temperature applications may provide a framework for the test methods

development. Current research on selective coatings for high temperature

applications should aid in providing technical basis for standards

development

4.2 ABSORBER PANELS

4.2.1 Assessment

Absorber panels, which may consist of metals or polymeric materials, are components of flat-plate collectors which receive the incident solar radiation

and transfer the absorbed energy to the heat transfer fluid. The panels consist

of sheets which may function as or provide the support for the absorptive

material. In addition, the sheets contain Integral or attached tubes and

headers, and Inlets and outlets for connection to the fluid transport system.

As part of the flat-plate collector, an absorber panel provides two main

functions: it acts as an absorber material and as a containment material.

Thus, in assessing the long-term performance of an absorber panel with regard

to resistance to aging effects, it should be evaluated using standard practices

for absorber materials (section 4.1) and for containment materials (section

4.3). Proper design of absorber panels is also necessary to achieve satisfactory

long-term performance. Factors to consider during design should include

materials compatibility, dimensional stability during temperature cycling, and

the coefficients of linear thermal expansion of component materials. The

following is an assessment of solar-related standards for absorber panels:

o ASTM standard specification B 638 (table 4) is available for copper and

copper-alloy absorber panels. This specification does not contain

requirements for evaluating the resistance of the panels to aging.

o ASTM standard specifications are not available for absorber panels

constructed from other materials such as aluminum and polymers.

4.2.2 Needs Concerning Standards Development

The needs concerning standards development for absorber panels for solar IPH

systems are as follows:

42
o Since the long-term performance of absorber panels may be evaluated using

standard practices for absorptive materials (section 4.1) and containment

materials (section 4.3), no recommendation for development of a specific

materials-related standard is given at this time. It is considered important that guidelines be readily available to solar designers in order to

assist in the proper design of absorber panels.

4 . 3 CONTAINMENT MATERIALS

4.3.1 Assessment

Containment materials may consist of glass, metals, plastics, and rubbers,

although the high temperature applications of IPH solar technology are generally

limited to the use of metallic or glass containment materials. Test methods

for glass, metals, plastics, and rubbers are listed in appendix tables B.3,

B.5, B.6, and B.7, respectively. The applicability of the test procedures to

the evaluation of solar materials and components has been given [5]. The key

concern in evaluating containment materials is the effect of high temperatures

and of heat transfer fluids on the long-term serviceability of the materials.

Containment materials should be thermally stable at anticipated operating and

stagnation temperatures, and compatible with the heat transfer fluid. The

following is an assessment of solar-related standards for containment materials

for IPH systems:

o ASTM has issued standard practice E 712 (table 4) which describes several

laboratory procedures for evaluating the corrosion performance of metallic

containment materials under conditions similar to those that may occur in

solar heating and cooling systems. The practice incorporates six tests:

Practice A

Practice B

Practice C

Practice D

Practice E

Practice F

Basic Immersion Test at Atmospheric Pressure

Heat-Rejecting Surface Test at Atmospheric Pressure

High-Pressure Test

Repeated Dip Dry Test at Atmoshpheric Pressure

Crevice Test at Atmospheric Pressure

Tube Loop Test at Atmospheric Pressure

Although designed for evaluation of metallic components for solar heating

and cooling systems, these six procedures are considered applicable to IPH

systems operating at relatively low temperatures. Test temperatures for

evaluation in these practices may be selected on the basis of service temperatures. With the exception of Practice C, the heating tests are con- ducted using test apparatus open to atmospheric pressure. These test

procedures (A, B, D, E, and F) are not relevent to high temperature IPH

systems where the heat transfer fluid may operate in a closed system above

its normal boiling point or under a nitrogen atmosphere. Practice C, the

high-pressure test, will allow screening of metallic containment materials

at high pressures and temperatures and may be applicable to high temperature

IPH systems. The procedure Involves placement of the metal specimen and

selected heat transfer fluid in an autoclave or similar test apparatus. The

test may be conducted at any selected pressures, temperatures, and times.

Pressures and temperatures may be selected on the basis of anticipated

43
service conditions. A data base on the performance of IPH solar components

subjected to Practice C exposures would be useful, since data on testing

IPH solar components by this practice are not available.

o ASTM standard practice E 745 (table 4) provides test procedures simulating

field service for evaluating the performance under corrosive conditions of

metallic containment materials in solar heating and cooling systems. Three

tests are included in the practice:

Practice A - Laboratory Exposure Test of Coupon Specimens

Practice B - Laboratory Exposure Test of Components or Subcomponents

Practice C - Field Exposure Test of Components or Subcomponents

Practice A uses coupon test specimens and provides laboratory simulation of

various solar system operating conditions. Practice B utilizes a component

or simulated subcomponent for the test specimen, and also provides a laboratory simulation of various operating conditions. Practice C uses a component

or simulated subcomponent as a test specimen, and provides field simulation

of various operating conditions. The three test procedures Involve heating

the test specimen with the heat transfer fluid to determine the effects of

temperature and fluid on the corrosion of the metal. Any fluid and any

metal may be used in the test. Although standard practice E 745 was developed for evaluating metal containment materials used in solar heating and

cooling systems, it may have applicability to IPH systems. The test conditions

(for example, maximum temperature, temperature cycles, periods of stagnation)

are not specified, but are selected on the basis of anticipated operating

conditions. Procedure A, the Laboratory Test, may be conducted with the use of an autoclave to simulate systems operating under pressure above the

fluid boiling point. A data base indicating the performance of IPH metal

containment materials according to this practice would be useful, since the

practice was developed for heating and cooling systems operating at lower

temperatures than normally encountered in many IPH systems.

o Criteria for the evaluation of rubber hoses used to convey liquids in solar

energy systems are provided in ASTM standard specification D 3952 (table 4).

Within the specification, rubber hoses are typed according to the intended

use in cold or warm climates. Three classes of rubber hose are defined

depending upon the intended use with different heat transfer fluids: class

A with aqueous fluids operating at or below 100°C (212°F); class AT with

aqueous fluids above 100°C (212°F); and class N with nonaqueous fluids.

This standard specification may have limited applicability to IPH systems.

Among the requirements in the standard, tests are to be conducted to determine

the resistance of the rubber hose to heating, and to the heat transfer fluid

while heated. The heating tests are performed at 100°C (212°F) for class A

hoses, and at temperatures selected according to those anticipated in service

for class AT and class N hoses. In this latter case, the maximum temperature

is 250°C (482°F). With regard to the heat transfer fluid resistance test,

only class N rubber hoses are evaluated at temperatures depending upon those

anticipated in service. Both class A and AT are tested at 100°C (212°F).

The specification is considered Inadequate for IPH systems (which may operate

higher than 100°C or 212°F) in that the heat transfer fluid resistance of

44
class AT hoses is not tested at anticipated service temperatures. However,

activities have been undertaken by ASTM to revise the specification to

include a heat transfer fluid resistance test above 100°C (212°F) for class

AT hoses.

o A standard practice for laboratory screening of pol 5nneric containment

materials used in solar heating and cooling systems is under consideration

at ASTM. Such a practice may have applicability to those IPH systems operating at relatively low temperatures. It is of course expected that polymeric containment materials would have limited use in IPH systems because of

high temperature requirements.

4.3.2 Needs Concerning Standards Development

The needs concerning standards development for containment materials in solar

IPH systems are as follows:

o A data base to determine the applicability of ASTM standard practices E 712

and E 745 to IPH systems should be developed. If found applicable, these

practices should be revised as necessary to indicate that IPH components

operating at temperatures higher than those encountered in heating and cooling systems may be evaluated using the practices. If laboratory and field

testing indicate that E 712 and E 745 are not applicable, then standard

practices specific to IPH systems should be developed.

o Standard practices for screening and simulated service testing of pol)nneric

containment materials for use in IPH systems should be developed.

4.4 COVERS/ JACKETS

4.4.1 Assessment

Flat-plate solar collectors contain cover plates which may consist of glass or plastic materials, while line-focus collectors generally have glass jackets on

the receivers. The covers and jackets protect the absorber and receiver,

respectively, against the effects of weather and convective and radiative heat

losses. Evacuated-tube collectors normally do not have covers, unless installed

for a particular reason such as the prevention of tube breakage from vandalism.

Transmittance and impact resistance are key properties for both glass and plastic covers, and glass jackets. In addition, abrasion resistance and embrittlement and warping are important to plastic covers. Both glass covers and jackets

may be subject to breakage, if the collector design does not allow for sufficient expansion of the glass components upon heating. Test methods for glass

and plastic materials are given in appendix tables B.3 and B.6, respectively.

The applicability of these tests to solar technology has been previously

presented [5]. An assessment of solar-related standards for covers and jackets

for use in IPH systems is given as follows:

o ASTM standard practice E 765 (table 4) has been prepared for the evaluation

of flat-plate cover materials. Test methods are included for measurements

of transmittance, dimensional stability, impact resistance, tensile strength.

45
and the effect of dirt retention on solar transmittance. Aging procedures

consider the effects of exposure to heat, natural weathering, and accelerated

weathering. Exposure of cover materials to natural weathering under conditions simulating modes of collector operation at approximate operating temperatures may be conducted according to ASTM standard practice E 782

(table 4). According to the method in the practice, a metal box containing the cover material and an inner black surface to simulate a flat-plate

collector is exposed outdoors. Practice E 782 is not Intended for cover materials for evacuated-tube collectors. These two standard practices

(E 765 and E 782) are applicable only to IPH systems having flat-plate

collectors

o A test method is under draft by ASTM for the effect of outgasslng on cover material transmittance. Such a test would be useful to evaluate line-focus

receiver assemblies having glass covers, insulation, and seals. The test

procedure should allow for evaluation of outgassing at maximum anticipated

exposure conditions, which in the case of a line-focus collector may exceed

288°C (550°F).

o ASTM has under consideration practices for the hail resistance and the

thermal shock resistance of flat-plate collectors. The latter practice is

intended to determine the ability of the collector to withstand thermal

shock such as caused by precipitation. Hail damage and thermal shock to

line-focus receiver jackets is considered less likely to occur than in the case of flat-plate collector covers, and such test methods may have low

priority for line-focus systems. Line-focus, parabolic trough collectors

are generally designed to stow when not receiving solar energy. If the

line-focus system design is such that the collectors will not stow rapidly

enough at the beginning of a rain or hail storm to protect the jackets, or will remain upright due to power failure, then test methods for determining

hail resistance and thermal shock resistance of receiver jackets should be

developed. It is interesting to note that one literature reference indicated that some glass jackets on line-focus collectors survived 19 mm

(3/4 in.) hail without damage [35]. Further details were not given and in

particular it was not mentioned whether the collectors were designed to

stow during the hall storm.

4.4.2 Needs Concerning Standards Development

The needs concerning standards development for covers and jackets for solar IPH

systems are as follows:

o A standard method of test to evaluate the effect of outgassing on the

transmittance of glass covers of insulated, sealed line-focus receiver

assemblies should be developed.

o The development of a hail resistance test and a thermal shock resistance

test for line-focus collectors is desirable, since the collectors may not

stow rapidly enough during storms to be protected.

46
4 . 5 DRIVE SYSTEMS

4.5.1 Assessment

The drive systems on line-focus tracking collectors consist of motors, drive

train and gear boxes whose purpose is to maintain the focus of solar radiation

on the receiver tubes. The drive system should allow the operation of the collectors with precision and accuracy up to the maximum design wind loads at

which the collectors will continue to track. When the maximum design wind load

is exceeded, the collectors are normally designed to stow. At least one solar

designer has indicated that this concept should be evaluated to determine

whether the stow position, or some other position (for example, parabolic

trough back to the wind), is the most suitable collector orientation during

periods of high winds. Selecting proper motors and gear boxes, with consideration to starting and stopping Inertia as well as frictional and flexural

loads, is also of Importance to the performance of tracking collectors. An

assessment of solar-related standards for drive systems used in IPH systems is

summarized as follows:

o Solar-related standards for drive systems are not available.

4.5.2 Needs Concerning Standards Development

The needs concerning standards development for drive systems for line-focus

solar systems are as follows;

o Since a drive system is an engineered component of the solar IPH system,

no recommendation for development of a materials-related standard is given

at this time. It is considered useful that guidelines be readily available

to solar designers in order to assist in the proper selection of drive systems to help prevent recurrence of past failures such as those experienced

in the field test program (see section 2.5). One solar designer has recom- mended that drive systems consist of standard components so that replacement

parts may be readily obtained and installed whenever necessary. It is also

considered Important that the drive system be controlled in such a manner

as to defocus the collectors in case of low flow of heat transfer fluids or power failures.

4.6 EVACUATED TUBES

4.6.1 Assessment

Evacuated-tube collectors are used in IPH solar systems for heat processes up

to about 177°C (350°F) (table 1). Evacuated tubes consist of glass and have

absorptive coatings within the evacuated interior. Test methods for coatings

and glass are given in tables B.l and B.3, respectively. Key concerns with

evacuated-tube collectors are impact resistance, resistances to stresses such

as thermal shock from cold filling and water hammer, and the resistance to

shattering due to defects such as scratches in the glass. Another concern

with evacuated tubes is the effect of the high stagnation temperatures, about

370°C (700°C), on metal components such as heat exchange fins around which the

47
evacuated tube is placed. An assessment of solar-related standards for evacuated tubes for use in IPH solar systems is summarized as follows:

o A standard practice for the evaluation of evacuated tube collectors under

conditions simulating service temperatures is not available.

o ASTM standard practice E 823 for exposing a solar collector assembly in a non-operating mode is applicable to evaluating evacuated-tube collectors

under stagnation conditions. In conducting this practice, metal components

such as heat transfer fins around which the evacuated tubes are placed, if

normally present in the system, should be included in the test.

o ASTM has under consideration a test method for determining the emittance of

evacuated-tube collectors.

4.6.2 Needs Concerning Standards Development

The needs concerning standards development for evacuated tubes for solar IPH

systems should focus on the following:

o A standard practice for the evaluation of evacuated-tube collectors under

conditions simulating service should be developed. Primary factors affecting performance, such as Impact resistance, thermal shock, and the permanency

of the vacuum over time should be Included in the practice.

4.7 FLEX HOSES /SWIVEL JOINTS

4.7.1 Assessment

Flex hoses and swivel joints are flexible couplings or movable connections in

parabolic trough line-focus collectors joining the receiver tubes and piping

headers. These components allow movement of the receiver tubes during collector

tracking while being connected to the stationary piping headers.

Flex hoses and swivel joints normally consist of metals, although flex hoses

for low temperature systems may be polymeric (rubber). Swivel joints may contain rubber seals. Test methods for metals and rubbers are given in appendix

tables B.5, and B.7, respectively. The applicability of these methods to the

testing of solar materials has been discussed [5]. The key properties for flex

hoses and swivel joints are their resistance to high temperatures and high pressures, and compatibility with heat transfer fluids under elevated temperature

and pressure, and resistance to cyclic or fatigue stress under operating conditions. Evaluative test procedures should include these factors.

A summary of the assessment of solar-related standards for flex hoses and

swivel joints is as follows:

o Although flex hoses and swivel joints are classified as containment materials,

the standards E 712 and E 745 for metal containment materials (see section

4.2) are not considered applicable to these components. These two ASTM

standards do not Include the effect of cyclic or fatigue stress which is a

48
primary factor affecting the long-term performance of flex hoses and swivel

joints. Similarly, ASTM standard specification D 3952 (table 4) for rubber

hoses used in solar energy systems is not considered applicable to flex hoses

because a cyclic or fatigue stress test is not included.

o A military specification, Mil-H-19034A, is available for metallic flex hoses

(table 5). This military specification is applicable only to flex hoses

used on air intake and exhaust lines of engines. The specification was not

developed for flexible hoses through which hot fluids are circulated under

pressure. The specification has no applicability to solar technology.

4.7.2 Needs Concerning Standards Development

The needs concerning standards development for flex hoses and swivel joints used

in line-focus collectors are as follows:

o A standard practice for evaluating the performance of metallic flex hoses and

swivel joints under simulated service conditions should be developed. The

practice should include factors affecting degradation such as high temperature, high pressure, fluid compatibility, and cyclic or fatigue stress.

Results of current studies on flex hose performance may provide in part the

technical basis for the standards development. In addition ASTM standard

practices for containment materials may also provide a framework for the

standards development.

o A standard practice for the evaluation of polymeric flex hoses under simulated

service conditions would also be useful. This practice should also include

the key factors which affect degradation of the flex hose, including cyclic

or fatigue fatigue stress. ASTM standard specification D 3952 may provide a framework for the standards development.

4.8 FLUIDS

4.8.1 Assessment

Depending upon the maximum service temperature, a number of heat transfer fluids

are available for IPH systems including water, glycols, hydrocarbons, and silicones. Fluid properties may be measured according to tests given in table appendix

B.2. The key properties of transport fluids have been described [36] and

include density, coefficient of thermal expansion, latent heat of vaporization,

heat transfer (thermal conductivity and heat capacity), flow over a wide temperature range (viscosity), and safety (flash point, autoignition temperature,

toxicity). Heat transfer fluids should be stable at the elevated temperatures

encountered in IPH systems and compatible with other materials (metals, rubbers)

with which they may come into contact at the elevated temperatures. An assessment of solar-related standards for heat transfer fluids for use in IPH systems

is follows;

o Standard practices for evaluating heat transfer fluids under simulated

service conditions are not available. In general, the development of such

practices has not begun, although the ASTM has under consideration a prac49
tice for testing, at normal operating and stagnation temperature conditions,

the stability of heat transfer liquids used as aqueous solutions.

o A standard practice for evaluating heat transfer fluids In service Is not

available and would be useful. The practice would be Intended to provide

data as to whether or not a fluid In service should be replaced. Some manufacturers recommend periodic measurement of values of fluid performance properties (for example, pH of aqueous glycols) after a given length of service.

The standard practice for evaluating a fluid In service should Include

requirements as to which performance properties should be periodically

determined, when they should be determined, and by which test procedures.

4.8.2 Needs Concerning Standards Development

The needs for standards development for heat transfer fluids for solar IPH

systems are as follows:

o Standard specifications for the various types of heat transfer fluids

except air and water for use In IPH systems should be developed. Specifications should Include measurement of key properties previously listed.

Standard methods of test for evaluating the thermal stability of heat transfer fluids and the effect of other materials such as metals and rubber on

the fluid stability under simulated service conditions are also needed.

o A standard practice for evaluating heat transfer fluids In service should

be developed.

4.9 INSULATION (THERMAL)

4.9.1 Assessment

Thermal Insulations are used to reduce heat losses from solar system components

such as absorbers of flat-plate systems, receivers of line-focus systems,

piping, valves, and storage tanks. Thermal conductivity Is the property of

the material which Indicates Its ability to provide resistance to heat flow.

Other key properties of thermal Insulations for IPH systems Include corrosiveness, dimensional stability, hot surface performance, moisture absorption,

resistance to outgasslng, surface burning characteristics, and temperature

stability. Test methods for Insulations Including thermal conductivity are given In appendix table B.4. The applicability of these test methods to solar

technology has been previously reviewed [5]. Insulations used In IPH solar

systems should be resistant to the adverse effects of elevated temperatures

and moisture. For outdoor Installations the Insulation normally contains a covering or coating to provide protection against the effects of weathering.

An assessment of solar-related standards for Insulations for use In IPH systems

Is summarized as follows:

o No solar-related materials standards are available.

o A draft standard practice for evaluating thermal Insulation materials for use In solar collectors Is under consideration by ASTM. For such a standard to be applicable to thermal Insulations for IPH systems, provisions

50
should be included to provide thermal aging tests at temperatures up to

at least 288°C (550°F).

o A standard practice for the installation of insulation and protective

covering is not available.

4.9.2 Needs Concerning Standards Development

The needs for standards development for insulations for solar IPH systems are

as follows:

o A standard practice to evaluate the performance of Insulations used for

IPH systems at maximum anticipated operating temperatures which may reach

288°C (550°F) should be developed.

o A standard practice for the installation of insulation and protective

covering should be developed for the IPH solar industry. The practice would

be intended to insure that piping insulation is properly Installed and sealed

against the effects of weather, particularly moisture intrusion. Experience

gained from other industries using insulated piping outdoors may provide in

part the basis for the standard practice for Installing Insulation in IPH

piping systems.

4.10 PUMPS

4.10.1 Assessment

The key components of pumps used for the circulation of heat transfer fluids

are the seals and rotor. Selecting the proper material for the pump (bronze,

stainless steel, or cast iron) depends on the properties of the heat transfer

fluid. The selection of the seals is also dependent on the type of fluid and

its operating temperature. An assessment of solar-related standards for pumps

used in IPH systems as follows:

o No solar-related standards are available.

4.10.2 Needs Concerning Standards Development

The needs concerning standards development for pumps for solar IPH systems

are as follows:

o Since a pump is an engineered component of the solar IPH system, no recommendation for development of a materials-related standard is given at

this time. It is considered useful that guidelines be readily available in

order to assist solar designers in the proper selection of pumps to help

prevent recurrence of past failures such as those experienced in the field

test program (section 2.10). It is also important that the service conditions (including type of fluid and its operating temperature) under which

the pump will perform be considered at the time of selection.

51
4.11 RECEIVERS (LINE-FOCUS SYSTEMS)

4.11.1 Assessment

Receivers are combinations of components such as pipes, coatings, supports,

and protective jackets which operate as a unit to collect the solar energy in

line-focus systems. The needs for standards development for these components

have been described in other subsections of the report. Proper design is

important to the performance of receivers. Factors affecting receiver performance include effective heat transfer to the fluid, accomodation of linear

thermal expansion, mechanical deflection, optical design, and durability. An

assessment of solar-related standards for receivers for use in IPH systems

is summarized as follows:

o ASTM standard practice E 823 (table 4) provides test procedures for exposing

a solar collector to an outdoor or simulated outdoor environment in a non- operational mode. The outdoor exposure test is conducted for a minimum of

30 days in which, for each day, the cumulative minimum radiant exposure,

measured in the plane of the collector, must be 17,000 kJ/m^^day

(1500 Btu/ft^* day) . It is stated within the document that the practice

applies to all collector types. The test specimen must be a complete collector assembly which may be equipped with self-contained, self-actuated

protective devices. Thus, line-focus collectors, which are normally designed

with protective devices to defocus whenever their temperature exceeds a specified limit, may be tested according to this practice. However, if a line-focus collector were to remain defocused for a significant portion of

the thirty-day test period, it is conceivable that the temperature of the

receiver assembly may not reach high values for periods of time long enough

to cause accelerated aging of the receiver materials. It may be useful to

develop an accelerated aging test which would be specific for receivers for

line-focus collectors.

4.11.2 Needs Concerning Standards Development

The needs concerning standards development for receivers in line-focus solar

IPH systems are as follows:

o Since the performance of components comprising receivers (e.g., absorptive

or containment materials) may be evaluated according to standards developed

for the specific item, no recommendation for the development of a specific

materials-related standard is given at this time.

o A test procedure to evaluate a receiver assembly under accelerated exposure

conditions should be developed. The procedure should incorporate the primary factors considered to affect in-service performance. Current research

on the performance of receivers may provide in part the technical basis of

the standards development.

o Guidelines for the proper design of receivers should be readily available

to assist solar designers to help prevent recurrence of past problems such

as those experienced in the field test program (section 2.11).

52
4.12 REFLECTIVE SURFACES

4.12.1 Assessment

Reflective surfaces are important components of IPH solar systems in that they

concentrate solar radiation on the absorber in both evacuated-tube and linefocus systems. Reflective surfaces may consist of mirrored glass, polished

metals, or metallized plastic film materials. Test procedures, which have been

previously reviewed for their applicability to the evaluation of solar components [5], are listed in appendix tables B.3, B.5, and B.6 for glass, metals,

and plastics, respectively. The primary property of a relectlve surface is

reflectivity. Reflectivity is determined according to ASTM E 424 (table B.3).

Primary factors which may effect the reflectivity of a surface are: abrasion.

Impact, mechanical stress, temperature cycling, and weathering including moisture, ultraviolet radiation, and atmospheric pollutants. Test methods for

evaluating the resistance to aging of reflective surfaces should include the

effect of these factors. In many IPH systems, reflective surfaces are adhesively bonded to substrates. The adhesive should be durable and resistance to

the effects of weathering, particularly moisture, and temperature cycling.

Creep is important, if sustained loads are applied to the surface. Reflective

surfaces are not expected to be subjected to temperatures significantly above

ambient, since they reflect solar radiation. If the surfaces become appreciably

soiled, then they may absorb greater amounts of solar radiation. Reflective

surfaces which become soiled are normally cleaned. Periodic cleaning should not cause significant loss of reflectivity. An assessment of solar-related standards for reflective surfaces for use in IPH systems is summarized as follows;

o Standard practices for evaluating the long-term performance of reflective

surfaces under simulated and in-service exposure conditions are not

available.

o Federal specifications, DD-M-00411b and GGG-M-350a, are available for glass

wall mirrors and inspection mirrors, respectively (table 5). These specifications are specific to mirrors used Indoors. They contain no requirements

for evaluating mirrors exposed outdoors and have no applicability to solar

IPH technology.

4.12.2 Needs Concerning Standards Development

The needs concerning standards development for reflective surfaces for solar

IPH systems are listed as:

o Standard practices for evaluating the long-term performance of reflective

surfaces should be developed. These practices should include tests to

determine the resistance of the reflective surface to the primary factors

affecting performance including the effect of cleaning on ref lectivitiy

The research and development activities which have been conducted may provide in part the technical basis for the standards development. Development

of standard evaluative test procedures should not await the completion of

current research projects on reflective surfaces since the period of time

to develop draft standard methods of test may be lengthy.

53
o A standard practice for evaluating the performance of adhesives for bonding

reflective surfaces to substrates should be developed. The practice should

include the effect of the primary factors which may affect adhesive degradation: moisture, temperature, temperature cycling, and stress. The standard

practice may be based in part on existing test methods for adhesives. Current research concerning adhesive bonding of reflective surfaces should also

aid in providing technical basis for standards development.

4.13 SEALS (RUBBER)

4.13.1 Assessment

Seals are nonrigid elastomeric materials set in joints between components to

prevent air and water leakage, and dust and dirt penetration into the collector

and other enclosed areas. Seals are also used to accommodate differences in

thermal movement of connected system components. In addition, seals may be

incorporated in the heat transfer fluid circulation system. Examples of the use of seals in IPH systems are:

° to seal a flat glass protective cover over a receiver tube,

° to seal the space between the absorber and jacket at the end of a receiver tube, and

° to seal evacuated tubes to the pipe manifold housing.

Test methods for rubber materials are given in appendix table B.7, and have

been reviewed previously for their applicability to solar technology [5]

The

primary factors affecting the aging of rubber seals are temperature, temperature cycling, contact with heat transfer fluids, weathering, and atmosphere

pollutants. An assessment of solar-related standards for rubber seals for use

in IPH systems is given as follows:

o ASTM standard specifications D 3667, D 3771, and D 3903 are available for

rubber seals used in flat-plate collectors, concentrating collectors, and

air-heat transport solar systems, respectively (table 4). These specifications have requirements to subject rubber seals to many of the factors

considered to affect their performance including resistance to heating,

ozone, and low temperatures. Test temperatures for determining heat resistance may be selected based on anticipated service conditions. None of

these specifications contains a requirement to determine the ultraviolet

light resistance of rubber seals receiving such exposure in service. It is

stated in the specifications that the seals are to be made from rubber compounds which are impermeable to ultraviolet light. A requirement in the

specifications to determine the ultraviolet resistance of seals which are exposed to sunlight in service would be useful.

o A data base is lacking to indicate the performance of rubber seals used in

IPH systems when subjected to the test requirements described in the ASTM

specifications D 3667, D 3771, and D 3903. Development of such a data base

is needed.

54
o ASTM standard specification D 3832 provides the general requirements for

materials used in preformed rubber seals that contact the heat transfer

fluid in solar energy systems. The specification may have limited applicability to IPH systems. Requirements are Included to determine the compression set of rubber seals upon heating, and to measure their resistance to

heating, ozone, low temperature, and the heat transfer fluid used in service.

The test for resistance to the heat transfer fluid may be conducted at

temperatures selected according to the type of fluid and the anticipated

maximum service temperature. However, this test procedure does not provide

for evaluating the rubber seals in a pressure vessel with the heat transfer

fluid at a temperature above its normal boiling point at atmospheric pressure.

Thus, the specification is not considered adequate to evaluate rubber seals

used in IPH collectors having pressurized heat transfer fluid systems.

4.13.2 Needs Concerning Standards Development

The needs concerning standards development for seals for solar IPH systems are given as follows:

o A test procedure to determine the ultraviolet light resistance of rubber

seals exposed to sunlight in service should be developed for Incorporation

in ASTM standard specifications D 3667, D 3771, and D 3903.

o A data base should be developed to indicate the performance of rubber seals

used for IPH systems, when subjected to the test requirements in ASTM

standard specifications D 3667, D 3771, and D 3903.

o ASTM standard specification D 3832 should be revised to include a test

requirement for the determination of the resistance of rubber seals to heat

transfer fluids operating in pressurized systems above their normal boiling

point at atmospheric pressure.

4.14 TRACKERS

4.14.1 Assessment

Trackers are used in line-focus systems to sense the position of the sun relative to the collector. The tracker activates the drive mechanism to maintain focus of the concentrated solar radiation on the receiver tube. Two types

of trackers are presently in use [22]. The first incorporates two photocells

separated by a shadow band. If one cell senses less light than the other, the

concentrator is moved to equalize the light sensitivity incident on both cells.

The concentrator is thus kept normal to the sun. The second type of tracker

uses a heat flux sensor consisting of a fine wire on the receiver tube. Temperature fluctuations in the wire due to varying heat flux result in changes in the

resistance of the wire to activate the drive mechanism. The key property of

the tracker is its ability to track the sun’s position reliably. An assessment

of solar-related standards for trackers for use in IPH systems is summarized as follows

55
o A solar-related standard for trackers is not available. Materials used in

trackers are not exposed to outdoor conditions differing appreciably from

conditions which building materials are normally exposed. The evaluation

of materials used for trackers should follow normally accepted design

practices for selecting materials used outdoors.

4.14.2 Needs Concerning Standards Development

The needs concerning standards development for trackers for IPH line-focus

systems are as follows:

o Since a tracker is an engineered component of the solar IPH system, no recommendation for development of a materials-related standard is given at

this time. It is important that trackers be designed to function reliably

as intended. Guidelines should be readily available to assist solar

designers in tracker selection in order to help prevent recurrence of past

problems such as those experienced in the field test program (section 2.14).

4.15 TROUGHS (PARABOLIC)

4.15.1 Assessment

Parabolic troughs are important components of line-focus collector systems.

The key functions of troughs have been described [22]: the trough should provide firm support and a smooth distortion-free substrate for the reflective

surface; and it should provide adequate rigidity under torque to maintain collector accuracy. Materials from which troughs are generally constructed include

metals, plastics, and composites such as metal skins on honeycomb cores. Tests

for metals and plastics are given in appendix tables B.5 and B.6, respectively.

Troughs have peripheral members such as support pilons which may be coated to

protect the member against the effects of weather. In general, the troughs

and protective coatings on peripheral members would be subjected to exposure

conditions normally experienced by building materials, although the configuration and operation of the troughs may give rise to stress conditions not

encountered by buildings. Existing aging test procedures for metals and plastics may be applicable to troughs. However, the reliability of correlating

in-service performance of materials with accelerated aging tests is questionable [37]. Accelerated aging tests for troughs, incorporating the key degradation factors such as moisture, temperature, ultraviolet radiation, pollutants,

and impact, and also simulating specimen configuration and operating conditions

may be useful. Future troughs may consist of plastic materials having innovative designs. Traditionally, the durability of plastics has been difficult to assess using accelerated aging procedures. An assessment of solar-related

standards for troughs for IPH systems is given as follows:

o No standard practice for evaluating the long-term performance for troughs

under simulated-service conditions is available.

4.15.2 Needs Concerning Standards Development

The needs concerning standards development for troughs for IPH line-focus

solar systems are:

56
o Since troughs using innovative materials and/or construction techniques

are under development, a standard practice for their evaluation either

under in-service or simulated-service conditions should be developed.

Degradation factors incorporated in the standard practice should Include:

temperature, moisture, ultraviolet radiation, pollutants, and stress. In

the case of sandwich panels used for troughs, the standard method of test

should Include evaluation of the adhesive bond between the core and the

skin of the panel. Factors effecting the bond performance Include moisture,

temperature, stress, and temperature cycles.

57
5. SUMMARY AND CONCLUSIONS

This study was conducted to assess the need for standards development for

materials and components of solar IPH systems. Emphasis was placed on standards

to evaluate materials performance under service conditions. The assessment was based on the availability of existing standards and their applicability to IPH

materials and components. A field survey of ten field test projects was con- ducted to observe the performance of materials in operational systems. Information from the literature and discussions with individuals in the IPH industry

complemented that obtained from the field survey. From the results of the

study, the following conclusions are made:

o Materials problems have occurred to some degree at each of the IPH field

test project sites visited. In worst cases, materials failures have occurred

resulting in inoperation of the system, or costly replacement of components.

The problems have been associated with inadequate system design, or selection of materials which were not fully evaluated for the anticipated service

conditions (section 2). Field observations of inadequate materials performance provide supportive evidence that evaluative test procedures are needed

to assist in the selection of materials.

o Material failures and design deficiencies have been described in the

literature reports (section 3) and at round table discussions at solar IPH

conferences. Research and development is underway to correct problems and

improve material performance and system design.

o Maximum temperatures encountered by IPH systems have at times been

underestimated by designers (section 2).

o Some standard methods of test for evaluating components for solar heating and

cooling systems have been developed (table 4). These methods are applicable

to IPH systems employing flat-plate collectors. Some of the standard methods

may be applicable to concentrating systems operating at low temperatures

(section 4)

o In cases where standards developed for flat-plate collectors for heating and

cooling applications may be applicable to low temperature IPH systems, data

bases are lacking to demonstrate the applicability (section 4).

o Standard methods of test for evaluating the long-term performance of key

components of line-focus and evacuated-tube collector systems operating at

high temperatures (including low flow rates or stagnation conditions) are needed (section 4).

o Lack of standard methods of test has had an adverse effect on material

procurement by solar architects-englneers (section 3). Materials are often

selected according to availability, manufacturers’ specifications, or brand

name without evaluation of long-term performance according to standardized

test procedures which consider the in-service conditions of use.

58
6 . RECOMMENDATIONS

As concluded in section 5, standard methods of test are needed to evaluate

long-term performance of IPH materials and components. The test methods should

incorporate the primary factors effecting degradation of the materials, and

exposure conditions should be based upon anticipated service conditions. The

exposure of materials to high temperatures and high pressures experienced in

concentrating collector systems is of particular importance. It is equally

Important that reflective surfaces be durable and maintain their reflectivity.

In section 4, the needs for standards development were identified for individual IPH materials and components. These needs are summarized in table 6.

It is recommended that standards be developed for those components, as outlined

in table 6. The development of the standards should draw on the experience

gained from current research studies on materials and component performance

(section 3). In cases where laboratory test data are lacking or considered to

be insufficient to support standards development, laboratory studies should be

initiated to provide a data base. Accelerated aging tests Incorporated in

standards should be based upon laboratory data which may be related to the performance of materials in service, as observed from field studies of operational

systems.

The availability of standards for the solar IPH industry could be beneficial

in a number of ways. First, the solar IPH industry is in the early stages of

development and premature material failures have occurred in many of the field

test installations. Standards for materials evaluation during system development would assist in preventing the recurrence of in-service failures. The

standards may be based in part on the experiences gained in the IPH field tests

Second, standards provide means for evaluating Innovative materials used as replacement for conventional materials in future IPH installations. Thirdly,

standards availability would contribute to the commercialization of a developing industry. Standards would instill user confidence that selected materials

and components have been satisfactorily evaluated for long-term performance.

A priority for the needs for standards development has been assigned to each

component, as given in table 7. Priority ratings assigned to each component

are high, medium, and low. The priorities relate to the Importance of having

available standards for evaluating the in-service performance of each component

Criteria for assigning priorities are similar to those previously developed by

Skoda and Masters [5] and are as follows:

o The importance of the component to the performance of the system.

o The availability of existing standards to estimate the in-service

performance of the component.

o The incidence of problems observed for the component during the field survey

o The potential for developing useful consensus standards for the component.

39
Table 6. Summary of Needs for Materlals-Related Standards Development for IPH Components

and the Priority of the Need

Component Needs for Materlals-Related Standards Development Priority

Absorptive Coatings 0 Standard practice for evaluating aging at maximum

conditions expected In service for line-focus and

evacuated-tube collectors

High

Containment Materials

(Metallic )

0 Evaluate the applicability of ASTM standard practices

E 712 and E 745 to metallic containment materials at high

temperatures experienced In IPH systems

High

Containment Materials

(Polymeric)

o Standard practices for screening and simulated service

testing of polymeric containment materials

High

Evacuated Tubes o Standard practice for the evaluation of evacuated tubes

under conditions simulating those expected In service

High

Flex Hoses/Swlvpl Joints

(Metallic and Polymeric)

0 Standard practices for evaluation of metallic and

polymeric flex hoses and swivel joints under conditions

simulating those expected In service

High

Fluids 0 Standard methods of test for the stability of IPH heat

transfer fluids under conditions expected in service

High

0 Standard practice for determining changes In properties

of heat transfer fluids under conditions expected

In service

High

Insulation o Standard practice for the installation of insulation and

protective covering on heat transfer fluid pipes and

related accessories

High

Reflective Surfaces 0 Standard practice for evaluating reflective surfaces of

concentrating collectors under antlclpted service and

environmental conditions

High

o Standard practice for evaluating adhesives for reflective

surfaces for line-focus collector systems

High

o Standard practice for cleaning reflective surfaces High

Seals (Rubber) 0 Revision of ASTM standard specification D 3832 for

applicability to seals used In pressurized IPH systems

High

Covers/Jackets o Standard method of test to evaluate the effect of out- gassing on the transmittance of glass covers of Insulated,

sealed receiver assemblies

Medium

Fluids 0 Standard specifications for the various types of heat

transfer fluids used in IPH collector systems

Medium

Insulation (Thermal) o Standard practice to evaluate Insulations under conditions

simulating those expected In service

Medium

Seals (Rubber) o Method of test to determine the ultraviolet light

resistance of seals exposed to sunlight in service

Medium

0 Development of a data base to determine the applicability

of ASTM standard specifications D 3667, D 3771, and D 3903

to seals used In IPH systems

Medium

Troughs

(Parabolic)

o Standard practice for the evaluation of troughs for

line-focus collectors under simulated and service

conditions

Medium

Covers/Jackets o Standard practices for the determination of hail

resistance and thermal shock resistance of jackets for

line-focus collectors

Low

60
The development of standards for materials and component evaluation may be a rather lengthy process. In the meantime, solar designers need to select

materials for construction of IPH systems. In the absence of standards for

evaluating materials, the solar designer should carefully consider the selection of materials. Experience gained from the IPH field test projects as to

which components have performed satisfactorily may be useful for materials

selection but is limited. The IPH field test projects have been operational

for only short lengths of time. Guidelines to aid in the selection of materials

for use in solar energy systems have been presented [5, 7]. These guidelines

provide a valuable framework of the factors to be considered in the materials

selection process, and should be consulted by the solar designer considering

the use of untried materials.

61
7.

REFERENCES

1. Energy Research and Development Association, Division of Solar Energy,

Solar Energy for Agricultural and Industrial Process Heat, Program Summary,

ERDA 77-72, 91 pages (June 1977).

2. Solar Energy Research Institute, Putting the Sun to Work in Industry,

2nd Edition, 9 pages (September 1979).

3. U.S. Department of Energy, Solar Energy for Agricultural and Industrial

Process Heat, Program Summary, DoE/CS-0053, 93 pages (September 1978).

4. William D. Nettleton Jr., Department of Energy, Personal Communication.

5. Skoda, L. F., and Masters, L. W. , Solar Energy Systems - Survey of

Materials Performance, National Bureau of Standards (U.S.), Report

NBSIR 77-1314, 113 pages (October 1977).

6. Kearney, D. W., Status of Current IPH Applications, Solar Energy Research

Institute, SERl/TP-632-1123 , 6 pages (March 1981).

7. Design Considerations for Solar Industrial Process Heat Systems, Kutscher,

Charles F., Editor, Solar Energy Research Institute, SERl/TR-632-783

54 pages (March 1981).

8. U.S. Department of Energy, Proceedings of the Solar Industrial Process

Heat Symposium, September 19-20, 1977, CONF-770966, 218 pages (June 1978).

9. U.S. Department of Energy, Proceedings: Volume 1, Solar Industrial Process

Heat Conference, October 18-20, 1978, SERl/TP-49-065 , Organized by the

Idaho National Engineering Laboratory and the Solar Energy Research

Institute, 204 pages.

10. U.S. Department of Energy, Solar Industrial Process Heat Conference

Abstracts, October 31 - November 2, 1979, SERl/SP-333-443 , Sponsored by

the Solar Energy Research Institute, 86 pages.

11. U.S. Department of Energy, Solar Industrial Process Heat Conference

Proceedings, October 31 - November 2, 1979, SERl/TP-333-429 , Sponsored by

the Solar Energy Research Institute, 524 pages.

12. U.S. Department of Energy, Solar Industrial Process Heat Pre-Conference

Proceedings, December 16-19, 1980, SERl/CP-632-951 , Sponsored by the

Solar Energy Research Institute, 290 pages.

13. U.S. Department of Energy, Proceedings of the Workshop, Reliability of

Materials for Solar Energy, December 18-20, 1978, Volume I, Summary and

Recommendations, SERl/TP-31-248 , Sponsored by the Solar Energy Research

Institute, 158 pages (October 1979).

62
14. U.S. Department of Energy, Proceedings of the Workshop, Reliability of

Materials for Solar Energy, December 18-20, 1978, Volume II, Part I,

Workshop Proceedings, SERl/TP-31-248 , Sponsored by the Solar Energy

Research Institute, 660 pages (October 1979).

15. Energy Research and Development Administration, Division of Solar Energy,

Proceedings of the Solar Industrial Process Heat Workshop, College Park,

MD, June 28-29, 1976, CONF-760655, 73 pages (August 1976).

16. Proceedings of the Seminar, Line-Focus Solar Thermal Energy Technology

Development, Albuquerque, NM, September 9-11, 1980, Sponsored by the

Department of Energy and the Sandia National Laboratories, 489 pages.

17. Proceedings of the Second Annual Conference on Absorber Surfaces for Solar

Receivers, January 24-25, 1979, SERl/TP-49-182 , Sponsored by the

Department of Energy and the Solar Energy Research Institute, 214 pages.

18. Proceedings of the Second Solar Reflective Materials Workshop, February 12-

14, 1980, San Francisco, CA, Solar Energy Materials, Lind, M. A., Guest

Editor, Volume 3, Numbers 1 and 2, 346 pages (September 1980).

19. Call, Patrick J., Summary of Solar Experience with the Soiling of Optical

Surfaces, SERl/TP-334-478 , the Solar Energy Research Institute, 12 pages

(February 1980).

20. Kutscher, Charles F., and Davenport, Roger L., Preliminary Operational

Results of the Low-Temperature Solar Industrial Process Heat Field Tests,

SERl/TR-632-385 , Solar Energy Research Institute, 42 pages (June 1980).

21. U. S. Department of Energy, Solar Heating Materials Handbook,

DoE/TIC-11374, UC-11-59-59C (January 1981).

22. Prythero, Ted, and Meyer, Richard T., Preliminary Definition and

Characterization of a Solar Industrial Process Heat Technology and Manufacturing Plant for the Years 2000, DoE/EV-0100, U. S. Department of

Energy, 27 pages (September 1980).

23. Raufaste, Noel, and Olmert, Michael, Editors, Building Technology

Project Summaries 1979-1980, NBS SP 446-4, 77 pages (July 1980).

24. Masters, L., Seiler, J., Embree, E., and Roberts, W. E., Solar Energy

Systems - Standards for Absorber Materials, National Bureau of Standards

(U.S.), Report NBSIR 81-2232 (January 1981).

25. Brown, P. W., and Grimes, J. W. , Evaluation of a Proposed ASTM Standard

Guide to Assess the Compatibility of Metal-Heat Transfer Liquid Pairs in

Solar Heating and Cooling Systems, National Bureau of Standards (U.S.),

Report NBSIR 79-1919 (November 1979).

63
26 . Clark, E. J., Roberts, W. E., Grimes, J. W., and Embree, E. J., Solar

Energy Systems - Standards for Cover Plates for Flat Plate Solar

Collectors, National Bureau of Standards (U.S.), Technical Note 1132

(December 1980)

27. Stiehler, R. D., and Michalak, J. L., Solar Energy Systems—Standards for

Rubber Hose, National Bureau of Standards (U.S.), Report NBSIR 79-1917

(November 1979).

28. Godette, M. , Lee, J., and Fearn, J., Solar Energy Systems: Test Methods

for Collector Insulations, National Bureau of Standards (U.S.), Report NBSIR

79-1908 (October 1979).

29. Stiehler, R. D., Hockman, A., Embree, E. J., and Masters, L. W., Solar

Energy Systems - Standards for Rubber Seals, National Bureau of Standards

(U.S.), Report NBSIR 77-1437 (March 1978).

30. Otts, John V., Midtemperature Solar System Test Facility Program Status

Report, SAND 80-1681, 94 pages (August 1980).

31. Castle, James, and Su, Wen, SERAPH Facility Capabilities, SERl/RR-632-702

the Solar Energy Research Institute, 58 pages, (June 1980).

32. Reisfeld, Sherry K. , and Neeper, Donald A., Solar Energy Research at

LASL, October 1, 1979 - March 31, 1980, LA-8450-PR, 53 pages (November

1980).

33. Driver, P. M., An Electrochemical Approach to the Characterization of

Black Chrome Selective Surfaces, Solar Energy Materials, Volume 4, p. 179

(1981).

34. Pettit, R. B., and Sowell, R. R. , Black Chrome Solar Selective Coating, in

Proceedings of the Seminar, Line-Focus Solar Thermal Energy Technology

Development, op. cit., p. 389.

35. Treadwell, George, Non-Evacuated Receivers, ibid., p. 360.

36. Parts, Leo, Miller, David R. , Leffingwell, James W., and Thompson,

Quentin E., Superior Heat Transfer Fluids for Solar Heating and Cooling

Applications, U.S. Department of Energy Report, ALO-35356-2, p. 2

(September 1980).

37. Frohnsdorff, Geoffrey, Masters, Larry W., and Martin, Jonathan W., An

Approach to Improved Durability Tests for Building Materials and

Components, National Bureau of Standards (U.S.), Technical Note 1120,

35 pages (July 1980)

64
APPENDIX A. SUMMARY OF THE IPH FIELD TEST INSTALLATIONS VISITED

Ten IPH field test installations were visited during the study to observe the

performance of materials under operational conditions. This appendix presents

a summary description of the solar system and industrial application at each

site. The summary descriptions presented in the following pages are based in

part on information by Kutscher [Al] and Shingleton [A2].

REFERENCES FOR APPENDIX A

AlDesign Considerations for Solar Industrial Process Heat Systems, Kutscher,

Charles F., Editor, Solar Energy Research Institute, SERl/TP-632-783,

54 pages (March 1981).

A2. Shingleton, Jefferson, Mueller Associates, Inc., Personal Communication.

A
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A.l SITE NO. 1 IPH SYSTEM

The industrial process at site no. 1 uses both hot water and steam to wash cans

in its Sacramento, California, soup canning plant. Solar energy first contributed hot water at 66“C (150°F) to this process in June of 1978. This solar

energy system was one of the first solar Industrial process heat systems in the

field test program to begin operation.

The system has both flat-plate and line-focus collectors. Filtered well water

flows through the flat-plate array under plant water pressure. Flat-plate collectors are used in an array of 414 m^ (4,455 ft^) net area. The collectors are mounted on an existing plant roof at an angle of 25° with due south orientation.

The flat-plate collectors preheat water before entry to the array of concentrating collectors. Six groups of parabolic trough concentrators are connected in

parallel. Each group has eight collectors in series. The trough axis is

east/west and the concentrator array area is 268 m^ (2,880 ft^). This is a one-pass system with no return piping to the collectors from storage. Solar

heated water is stored in a 64,900 L (17,150 gal) tank. Upon demand, water is

pumped through a steam heat exchanger to the can washing process.

• COLLECTOR TYPE: Liquid flat-plate and tracking, parabolic trough concentrator

• APPLICATION: Can washing

• SITE SPECIFIC FEATURE: Roof-mounted collector array

• STORAGE: Hot water tank

• FREEZE PROTECTION: Recirculation
A. 2 SITE NO. 2 IPH SYSTEM

The textile plant at site no. 2 is located in LaFrance, South Carolina. Solar

energy is utilized in a 132 ®C (270®F) maximum temperature water/glycol loop

which produces 88®C (190®F) water for use in a dye beck. A dye beck is a special vat in the batch process dyeing operations of a textile plant. The

solar energy system is ground mounted and retrofitted to the existing process

equipment.

The system utilizes 396 evacuated-tube collectors which provide a net area of

621 m^ (5,680 ft^). The collectors are arranged in 11 rows having 36 collectors.

The solar storage tank and pumps are located in a protected outside area. The

controller and data acquisition systems are located in a separate room in the

plant adapted for that purpose.

• COLLECTOR TYPE: Evacuated tube

® APPLICATION: Textile dyeing

• SITE SPECIFIC FEATURE: Ground-mounted collector array

• STORAGE TYPE: Water

• FREEZE PROTECTION: Ethylene glycol

A-2
A. 3 SITE NO. 3 IPH SYSTEM

Solar energy is utilized in a low temperature water loop which produces hot

water used in the concrete block curing process. The concrete block plant at

site no. 2 is located in Middletown, Pennsylvania. The solar energy system was installed from May 1978 to August 1978 at the time the plant was constructed.

The system utilizes 135 line-focus concentrating collectors which provide an effective area of 856 m^ (9,216 ft^). The collectors are single-axis tracking,

with tracking provided by 0.3 m (1 ft) wide mirror strips, mounted in parallel

rows on the 15® sloped roof of the building. The collectors have a 24:1 con- centration ratio with an a stationary steel tube receiver without a glass cover

at their focus. They are mounted on an east-west axis with altitude tracking.

One tracking motor is provided for every vertical row of collectors.

The collectors are arranged in 5 horizontal rows with 7 collector modules per

row. The absorbers are five 76 m (250 ft) continuous steel pipes that are piped in parallel. The absorbers are piped through flexible hoses to the system

supply and return piping.

The solar system is designed to provide 57®C (200“F) water/glycol solution to a heat exchanger located in the boiler room of the plant. At the heat exchanger,

water is supplied to the rotoclave for the curing process. The only storage is

in the rotoclave. All of the mechanical equipment for the solar system is

enclosed in the boiler room except the solar rotoclave pump.

• COLLECTOR TYPE: Tracking mirror, fixed-receiver concentrator

• APPLICATION: Curing of concrete blocks

• SITE SPECIFIC FEATURE: Roof-mounted collector array

• STORAGE TYPE: Storage provided by process rotoclave

• FREEZE PROTECTION: 50/50 solution of water and ethylene glycol

A-3
A. 4 SITE NO. 4 IPH SYSTEM

The site no. 4 IPH system is constructed at a food processing plant in Gilroy,

California which dehydrates onions and garlic. The collector array, designed

to provide 99°C (210°F) water, consists of evacuated-tube modules with an aperture area of 553 m^ (5,950 ft^). The collector bank is supported by wooden

trusses built on a low-sloped warehouse roof. The existing roof required minor

modification for collector installation. The collector array location was some distance from the process heat exchanger, which necessitated long expanses of

pipe to transport the collected energy to the dehydrator. The array is oriented

due south at a tilt of 22° off horizontal. This tilt angle maximizes energy

collected during the peak drying season.

Water is passed through the collector modules in parallel and supplied to one

of two continuous-operation belt dehydrators. A liquid-to-air heat exchanger

delivers solar energy to the drying air stream. An in-line natural gas burner

then heats the air to operating temperature. The outlet water from the heat

exchanger is pumped back to the collector array. Storage is not provided in

the system. When heat is not required by the primary process, the solar energy

is used to preheat the feed water for the plant steam boiler.

• COLLECTOR TYPE; Evacuated tube

• APPLICATION: Dehydration of onions and garlic

© SITE SPECIFIC FEATURES: Roof-mounted collector array

© STORAGE : None

© FREEZE PROTECTION: Recirculation

A-4
A. 5 SITE NO. 5 IPH SYSTEM

The solar IPH system at site no. 5 is used to dry fruit, chiefly grapes, at a Fresno, California location. In August 1978, solar energy was first utilized

in one of twelve dehydration process lines.

The collector array has an aperture area of 1,951 m^ (21,000 ft^), oriented

due south and tilted 36“ of horizontal. The 30 panels of the array measure

1.2 m (4 ft) X 55 m (180 ft) and are connected in parallel. The supply duct

size balances the flow in each collector panel. Duct runs are relatively short

and take a direct route to and from equipment, although a driveway at the plant

had to be spanned overhead. Solar-heated air at the design temperature of 63 “C

(145“F) is blown to the drying process, to storage, or both. The solar-heated

air may reach temperatures in the collectors greater than 93“C (200“F). When

necessary, ambient air is mixed with the solar-heated air to achieve process

temperatures. Natural gas burners in the drying tunnel also augment the solarheated air to operating temperatures whenever necessary. Exhaust air is vented

through the heat recovery wheel, which in turn, warms the ambient make-up air.

The storage consists of a 396 m^ (14,000 ft^) bin filled with rocks. It is

constructed on grade and supplies heat during the second work shift at the

plant. The interior of the bin and exterior of the ducts are insulated with

spray-in-place polyurethane foam.

• COLLECTOR TYPE; Air flat-plate

• APPLICATION: Dehydration of fruit (grapes and plums) • SITE SPECIFIC FEATURES: Heat recovery wheel, site built, ground-mounted

collector array

• STORAGE; Rock bin • FREEZE PROTECTION: None required

AA. 6 SITE NO. 6 IPH SYSTEM

The site no. 6 IPH system is located in Pasadena, California. The 603

(6,496 ft2) array contains 406 solar collectors, each 0.6 m (2 ft) x 2.4 m

(8 ft). The parabolic trough reflectors are oriented north/south with azimuth

tracking. A stationary, selective coated absorber pipe is encapsulated in a glass jacket. The entire array rests on a space frame which spans the existing

laundry roof.

In normal operational mode, water is circulated in a closed loop through the

collector array and then through U-tubes in a kettle type boiler to generate

saturated steam at 0.72 MPa (105 lb/in.2). The outlet water temperature of the

collector array must exceed the boiler shellside water temperature by a minimum

of 5.5°C (10°F) before flow through the boiler tubes is permitted. The concept

of thermal storage at this plant has been abandoned. If there is no demand for

steam, the power to the sun-tracking device will be turned off automatically

when the collector outlet temperature exceeds a limit of 199°C (390°F). The

tracker power is restored when the circulating water temperature drops to 199°C

(390°F).

Volumetric changes in the fluid are accommodated by an expansion tank and the

loop pressure (1.72 MPa or 250 lb/in.2) is maintained by nitrogen blanket in

that tank.

Since this array is located in southern California, no freeze protection mode

has been designed into this system.

• COLLECTOR TYPE: Tracking parabolic trough concentrators

® APPLICATION: Steam generation for commercial laundry

o SITE SPECIFIC FEATURE: Space frame which supports the collectors bridges

the entire laundry building

• STORAGE : None

• FREEZE PROTECTION: None

A-6
A. 7 SITE NO. 7 IPH SYSTEM

The IPH system at site no. 7 supplies steam for a gauze bleaching process. The

system, located at Sherman, Texas, has been in operation since January 1980.

Parabolic trough concentrators are used to generate the steam. The collectors

are arranged in four parallel loops with 48 reflectors in each loop, totaling

1,070 m2 (11,520 ft^) of aperture area. The array is ground-mounted and has an orientation northeast/southwest to align with the plant building. For aesthetic reasons, the entire array was constructed in an shallow pit below the

surrounding natural terrain.

In normal operation, high temperature and pressure water is stored in the

189,250 L (50,000 gal) flash boiler. A 25 horespower pump circulates the water

through the collector array at 3.8 L/s (60 gal/min). When the solar-heated

water from the collectors is hot enough, it flashes to steam after passing

through a throttling valve in a flash boiler. This steam is applied directly

to the plant's steam main. Freeze protection is accomplished by circulating

boiler water in a reverse flow at a reduced rate through the collectors. The

throttling valve is bypassed in this mode.

• COLLECTOR TYPE: Tracking parabolic trough concentrators

• APPLICATION: Gauze bleaching

• SITE SPECIFIC FEATURE: Ground-mounted collector array

• STORAGE: Flash boiler

• FREEZE PROTECTION: Recirculation
A. 8 SITE NO. 8 IPH SYSTEM

Solar energy is collected in a high temperature water loop that feeds a steam

generator to provide steam to an orange juice pasteurizing process. The process

plant for site no. 8 is located in Bradenton, Florida. The solar energy system

was field erected from June of 1979 through September of 1980.

The system utilizes 336 compound parabolic concentrating (CPC) evacuated-tube

collectors which provide an effective aperture area of 929 m^ (10,000 ft^).

The concentration ratio is 3:1. The collectors are mounted on a single-axis

and may be seasonally adjusted for tilt angle.

The ground-mounted collectors are arranged in 42 rows of 8 collectors, placed

in 2 side-by-side arrays of 21 rows each. The collector modules are mounted in

such a way that the heaters provide parallel fluid flow between each module.

The solar system is designed to provide 177°C (350°F) water at 1.03 MPa

(150 lb/in.2) to a steam generator located in the solar mechanical building.

The steam is sent to a frozen juice block crusher when the solar system exceeds

0.69 MPa (100 lb/ln.2) boiler pressure. If the crusher is not operating, the

steam is used for a glycol concentrator at 0.14 MPa (20 lb/ln.2). A third

option is to send steam to preheat the water to the crusher boiler if the solar

system cannot make sufficient steam when the crusher is operating.

• COLLECTOR TYPE; Seasonally adjusted, concentrator with evacuated-tube receiver

• APPLICATION: Orange juice pasteurization

® SITE SPECIFIC FEATURE: Ground-mounted collector array

® STORAGE : None

® FREEZE PROTECTION: Glycol solution

A-8
A. 9 SITE NO. 9 IPH SYSTEM

Solar energy is utilized in a high temperature water loop which produces steam

used in a textile drying process. The textile plant with site no. 9 is located

in Fairfax, Alabama. The solar energy system was retrofitted from October 1977

through September 1978 to the existing wooden frame building.

The system utilizes concentrating parabolic trough collectors which provide an array size of 772 m^ (8,313 ft^). The collectors are in parallel 24 m (80 ft) rows on the low-sloped roof of the building and have a 40:1 concentration ratio.

They are mounted on an east-west axis with altitude tracking. A tracking

mechanism is installed on each row.

The collectors are arranged in 24 rows, each consisting of one collector erected

in four 6 m (20 ft) sections. The four 6 m (20 ft) absorbers are piped in

series. The 24 rows are piped in parallel. The absorbers are connected through

rotary joints to the collector supply and return piping.

The solar system is designed to provide 158°C (317°F) water at 0.59 MPa

(85 lb/in.2) to a steam generator located in a penthouse building on the existing roof. The steam generator produces steam for the textile drying process. A

pump returns the condensate to the steam generator. No storage is provided for

this system. All of the mechanical equipment for the solar system is enclosed

in the penthouse including pumps, steam generator, expansion tank and control

equipment

o COLLECTOR TYPE: Tracking parabolic trough concentrator

• APPLICATION: Textile drying

• SITE SPECIFIC FEATURE: Roof-mounted collector array

o STORAGE TYPE: None

• FREEZE PROTECTION: Immersion heaters and recirculation

A-9
A. 10 SITE NO. 10 IPH SYSTEM

Solar energy is used to generate Industrial process steam at site no. 10

located in Dalton, Georgia. In September 1978, construction began on this

field-mounted system that was retrofitted to the existing process equipment

and was essentially completed in January 1981.

This system utilizes 15 rows of parabolic trough collectors in a north-south

orientation, with 10° tilt, facing south. The system has an area of 923 m^

(9,930 ft^) and is designed to provide 186°C (367°F) steam at 1.14 MPa

(165 lb/in.2).

The heat transfer fluid circulates through the collectors and boils water in a kettle boiler to produce steam. An accumulator tank connected to the fluid

loop serves as an expansion tank and dump tank. No overnight freeze protection

is required.

• COLLECTOR TYPE: Parabolic trough tracking collectors

o APPLICATION: Latex manufacturing

• SITE SPECIFIC FEATURE: Ground-mounted collector array

• STORAGE : None

« FREEZE PROTECTION: None

A-10
APPENDIX B. TEST METHODS FOR MATERIALS COMMONLY USED IN SOLAR ENERGY SYSTEMS

This appendix presents tables of test methods for materials commonly used for

solar energy systems: coatings, fluids, glasses. Insulation, metals, plastics,

and rubbers. The test methods were originally compiled by Skoda and Masters

[Bl] in conjunction with their survey of materials perfotToance of solar collector systems. The test methods have been developed by standards organizations

such as ASTM (American Society for Testing and Materials), ANSI (American

National Standards Institute), and ISO (International Organization for Standardization), by the Federal government (Federal and military standards and

specifications), and by trade associations (industrial standards). Because

many of these test methods are considered applicable to the development of

standards for materials and components for solar industrial process heat systems, the tables have been reproduced here. The tables were reviewed to eliminate reference to any test methods which have been withdrawn since the

original tables were published.

REFERENCE FOR APPENDIX B

Bl . Skoda, L. F., and Masters, L. W., Solar Energy Systems - Survey of

Materials Performance, National Bureau of Standards (U.S.), Report

NBSIR 77-1314, 113 pages (October 1977).

B

Table B. 1 Existing Test Methods for Coatings

Type of Test

Abrasion, resistance to

Adhesion

Type of Test

Abrasion, resistance to

Adhesion

Test Designation

ASTM D658, D968, Fed. Std. 141a

ASTM B571,C633, D2197, D3359, ISO 2819

Atmospheric pollutants,

resistance to

ASTM B117, B287, D1543, D1654, D3129, G1

G33, Fed. Std. 141a, Fed. Specs. TT-P-31D,

TT-P-103B, TT-C-530A, TT-C-00498A, TT-E-516A,

TT-E-522A, TT-P-102D

Cleanability ASTM C756, D2486

Color change ASTM D1535, D1543, D1729, D2244, D2616, G45

Corrosion resistance ASTM B117, D1014, D1654, D2933, G1 , ISO 1462

Flammability ASTM D1360, E162, E286

Flexural strength ASTM B571, D522, D1737, Fed. Std. 141a

Fungus resistance ASTM D3129, D3272, D3273, G21, Mil. Std.

810C, Fed. Std. 141a, Fed. Specs. TT-P-31D,

TT-P-51D, TT-P-61E, TT-P-71E, TT-P-81E,

TT-P-19C, TT-P-55B

Gloss ASTM D523

Impact resistance ASTM D1474, D2794, D3170, SAE J400

Moisture, resistance to ASTM DIOIO, D1187, D1735, D2246, D2247,

D2366, D2932, Mil. Std. 810C, Fed. Specs.

TT-P-641F, TT-C-1079A

Optical properties ASTM E97, E424, E434

Permeability ASTM C355, D1653, E96

Physical Integrity

checking ASTM D660

cracking ASTM D661

Scratch resistance ASTM D2197

Surface uniformity ASTM El 36

Tensile strength ASTM D522, D1737, D2370

B-1
Table B.l, (Continued)

Thermal aging, resistance to ASTM D2246, Mil. Std. 810C

Thickness ASTM B567, D1005, D1186, D1400, E376,

ISO 2178, 2360, 2361

Weathering, resistance to ASTM D822, D1006, D1014, D2620, G7, G23,

G24, G26, Mil. Std. 810C, Fed. Std. 141a,

Fed. Specs. TT-P-31D, TT-P-61E, TT-P-71E,

TT-P-81E, TT-C-530A, TT-P-19C, TT-P-55B,

TT-P-95B, TT-P-1181A, TT-C-00498A,

TT-E-516A, TT-E-522A, TT-P-37C, TT-P-102D

B-2
Table B.2. Existing Test Methods for Fluids

Type of Test

Ash content

Autoignition temperature

Boiling point

Color

Corrosivity

Expansion coefficient

Fire point

Flash point

Foaming

Freezing point

pH

Reserve alkalinity

Specific gravity, density

Specific heat

Thermal conductivity

Ultraviolet absorbance

Vapor pressure

Viscosity

Water content

Test Designation

ASTM D482, D1119

ASTM E659

ASTM Dll 20

ASTM D807, D2688, D2776, D3263

ASTM D1903

ASTM D92

ASTM D56

ASTM D1881

ASTM D1015, D1177

ASTM D1287

ASTM D1121

ASTM D941, D1122

ASTM D2766

ASTM D2717

ASTM D2008

ASTM D323

ASTM D445

ASTM D1123, D1744

B-3
Table B.3. Existing Test Methods for Glasses

Type of Test Test Designation

Analyzing stress ASTM F218

Annealing point, strain point ASTM C336, C598

Atmospheric pollutants, resistance to ASTM C724, C777, ISO 1776

Coefficient of expansion ASTM C824, E228, E289

Creep Fed. Spec. DD-G-1403

Density ASTM C693, C729

Fatigue

Flatness ASTM C314

Flexural strength ASTM C158

Impact strength ANSI Z97.1 , Fed. Std. 406

Indentation hardness ASTM C730

Optical properties ASTM E424

Softening point ASTM C338

Thermal aging, resistance to ANSI Z97.1

Thermal conductivity ASTM C177, C408

Theirmal shock ASTM C149

Young’s modulus, shear modulus. ASTM C623

Poisson’s ratio

B-4
Table B.4, Existing Test Methods for Insulation

Type of Test

Atmospheric pollutants, resistance to

Biodeterioration

Breaking strength

Compressive strength

Deflection

Density

Dimensional stability

Expansion

Flame spread

Flexural strength

Impact resistance (by dropping)

Indentation hardness

Mechanical stability

Moisture absorption

Moisture, resistance to

Parting strength

Properties at abnormal temperature

Racking load

Specific heat

Tensile strength

Thermal aging, resistance to

Thermal conductivity

Thermal resistance

Test Designation

ASTM D3273 , G21, G22

ASTM C446

ASTM C165

ASTM C209

ASTM C167, C209, C302, C303, C519

ASTM C548, D1042

ASTM D1037

ASTM E84

ASTM C203

ASTM C487

ASTM C569

ASTM C421

ASTM C209

Mil. Std. 810C

ASTM C686

ASTM D759

ASTM E72

ASTM C351

ASTM C209

ASTM C356, C411, C447, D794, Mil.

ASTM C177, C236, C335, C518, C745

ASTM C653, C687

, C520

Std. 810C

, D2326

B-5
Table B .4 (Continued)

Type of Test Test Designation

Thermal transference

Thickness

Transverse strength

Vapor permeability

Weathering, resistance to

ASTM C691

ASTM C167, C209

ASTM C209

ASTM C355, E96

ASTM G7

B-6
Table B .5

Existing Test .Methods for Metals

Type of Test Test Designation

Acetic acid, resistance to ASTM B287, B368

Atmospheric pollutants, resistance to ASTM B537, G33

Compression ASTM E9, E209

Density and open porosity ISO 2738

Corrosion, resistance to ASTM C464, DUO, D538, D849, D930,

D1280, D1374, D1384, D1616, D1654,

D2247, D2251, D2570, D2649, D2809,

D2933, D2966, G3, G4, G31, G32, G46,

G48, AWPA M-14-72, NACE TM-01-71,

TM-02-70, TM-02-74, TM--01-69

Creep ASTM El 39

Creep at elevated temperature ASTM E150

Ductility ASTM B489

EMF ASTM E189

Fatigue ASTM E466

Fracture toughness ASTM E399

Grain size ASTM El 12

Hardness ASTM ElO, E18, E103, EllO, E384, E448

Impact, resistance to ASTM E23

Oil content ISO 2737

Salt spray, resistance to ASTM B117, G44, Fed. Std. 151b

Stress corrosion ASTM G30, G35, G37 , G38

Tensile strength ASTM E8

Thermal expansion ASTM B95, E80

B-7
Table B .6 . Existing Test Methods for Plastics

Type of Test Test Designation

Abrasion, mar, resistance to ASTM D673, D1044, D1242

Atmospheric pollutants, resistance to ASTMB117, B287, D543, D1149, D1712,

Gl, G33, Fed. Std. 406

Blister-delamination ASTM C363

Burst strength ASTM D774

Cleanability AIMA-7

Coefficient of expansion ASTM D696, D864, D1204

Color change ASTM D1729, D1925, D2244, D2616,

D3134, G45, Fed. Std. 141

Creep ASTM D2552, D2990, D2991, Fed. Std. 406

Deflection ASTM D621, D648

Density ASTM D792, D1505

Embrittlement ASTM D1790

Fatigue ASTM C394, D671, SAE J783

Flammability ASTM D635, D658, D876, D1929, D3014,

E84, E136

Flatness ASTM D1604, Fed. Spec. DD-G-1403,

Mil. Spec. 3787

Flexural strength ASTM C393, D747, D790

Fungus resistance ASTM G21, G22, G29, Fed. Std. 406,

Fed. Spec. L-P-380C

Impact strength ASTM D256, D1790, D1822, D3029,

D3099, D3420, ANSI Z97.1,

Fed . Std . 406

Indentation-hardness ASTM D785, D2240, D2583, Fed. Std. 406

.Modulus of elasticity ASTM D638, D695, D882

Moisture, resistance to ASTM D756, D2126, D2383,

Mil. Std. 810C, Fed. Spec. L-P-380C

B-8
Table B.6. (Continued)

Type of Test Test Designation

Optical properties ASTM E424, E434, Fed. Spec. DD-G-451

Permeability ASTM

Fed

C355, D1434, E96, F372,

Std. 406, TAPPI T-482

Refractive index ASTM D542

Scratches, defects Fed

Spec. DD-G-1403

Tensile strength ASTM C297, D638, D882

Thermal aging, resistance to ASTM D648, D793, D1299, D2115,

D2126, D2288, D2445, D2951, D3045,

Mil. Std. 810C

Thermal conductivity ASTM C177, C518

Thickness ASTM D374, D1777

Ultimate elongation ASTM D638, D882

Warping, bowing ASTM D709

Weathering, resistance to ASTM

G23,

Fed

D1435, D1499, D1501, D2565, G7,

G24, G26, Fed. Spec. L-P-508f,

STd. 406, ANSI Z97.1

Wind, resistance to ASTM E330

B-9
Table B.7. Existing Test Methods for Rubber Materials

Type of Test Test Designation

Adhesion/cohesion ASTM C719, C766

Adhesion, peel ASTM C794, D413, D429, D903, D1781,

D1876, D2630

Atmospheric pollutants, resistance to ASTM D518, D1149 (ozone)

Brittleness point ASTM D2137

Compression-recovery ASTM F36

Compression set ASTM D395, D1229

Creep resistance ASTM D1390, D1456, D1780, D2293,

D2294, F38

Extrusion rate ASTM C603

Flexural strength ASTM D1184

Flow properties ASTM C639

Fungus resistance ASTM D1286, D1877

Impact strength ASTM D950

Hardness ASTM C661, D1415, D2240

Low temperature flexibility ASTM C711, C734, C765, D797, D1053,

D1329, D2137

Moisture or liquid immersion,

resistance to

ASTM D471, DllOl, D1151, D1460,

D3137

Sealability ASTM D1081, F37, F112

Shear strength ASTM D905, D1002 , D2919, D3165

Staining ASTM D925, D2203

Tear resistance ASTM D624

Tensile strength ASTM D412, D897, D906 , D2095,

D2295, F152

Thermal aging, resistance to ASTM C771, C792, D573, D865, D1870

B-10
Table B.7. (Continued)

Type of Test Test Designation

Ultimate elongation ASTM D412

Weathering, resistance to ASTM C718, C732, C793, D904 , D1171,

Young * s modulus

D1183, D1828, D2559, ANSI A116.1,

AAMA 802.2, 804.1, 805.2, 806.1,

807.1, 808.1, Fed. Specs. TT-G-410E,

TT-S-00227E, TT-S-00230C, TT-S-001543A,

TT-S-001657

ASTM D797

B-11
NBS-H4A (REV. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

1. PUBLICATION OR

REPORT NO,

2. Performing Organ. Report No. 3. Publication Date

SHEET (See Instructions) NBSIR 81-2381 October 1981

4. TITLE AND SUBTITLE

Solar Industrial Process Heat Systems - An Assessment of Standards for Materials

and Components

5. AUTHOR(S)

Walter J. Rossiter; Walter E. Shipp

6. PERFORMING ORGANIZATION (If joint or other than MBS. see in struction s) national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State. ZIP)

Office of Solar Applications for Buildings

Department of Energy

Forrestal Building

Washington, D.C. 20585

10. SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here) A Study was conducted to obtain information on the performance of materials and

components in operational solar industrial process heat (IPH) systems, and to provide recommendations for the development of standards including evaluative test

procedures for materials and components. An assessment of the needs for standards

for evaluating the long-term performance of materials and components of IPH systems

was made. The assessment was based on the availability of existing standards, and

information obtained from a field survey of operational systems, the literature,

and discussions with individuals in the industry. Field inspections of 10 operational IPH systems were performed. The study did not address the thermal efficiencies

and health and safety considerations of IPH systems.

The results of the study are presented in this report. It is concluded that standard

test methods are needed for evaluating the long-term performance of materials and

components used in IPH systems operating at high temperatures. Some standard test

methods are available having applicability to materials and components in low

temperature systems. However, in the latter case, data bases are lacking which

demonstrate their applicability. Recommendations are made and priorities assigned

for the development of standards for materials and components.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitall ze only proper names; and separate key words by semicolon s) Field survey; industrial process heat; materials performance; solar collector;

standards; test methods.

13.

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