Dennis J. Eichenberg

Glenn Research Center, Cleveland, Ohio

Development and Testing of the Glenn Research

Center Visitor’s Center Grid-Tied Photovoltaic

Power System

NASA/TM—2009-215847

December 2009
NASA STI Program . . . in Profi le

Since its founding, NASA has been dedicated to the 

advancement of aeronautics and space science. The 

NASA Scientifi c and Technical Information (STI) 

program plays a key part in helping NASA maintain 

this important role.

The NASA STI Program operates under the auspices 

of the Agency Chief Information Offi cer. It collects, 

organizes, provides for archiving, and disseminates 

NASA’s STI. The NASA STI program provides access 

to the NASA Aeronautics and Space Database and 

its public interface, the NASA Technical Reports 

Server, thus providing one of the largest collections 

of aeronautical and space science STI in the world. 

Results are published in both non-NASA channels 

and by NASA in the NASA STI Report Series, which 

includes the following report types:

• TECHNICAL PUBLICATION. Reports of 

completed research or a major signifi cant phase 

of research that present the results of NASA 

programs and include extensive data or theoretical 

analysis. Includes compilations of signifi cant 

scientifi c and technical data and information 

deemed to be of continuing reference value. 

NASA counterpart of peer-reviewed formal 

professional papers but has less stringent 

limitations on manuscript length and extent of 

graphic presentations.

• TECHNICAL MEMORANDUM. Scientifi c 

and technical fi ndings that are preliminary or 

of specialized interest, e.g., quick release 

reports, working papers, and bibliographies that 

contain minimal annotation. Does not contain 

extensive analysis.

• CONTRACTOR REPORT. Scientifi c and 

technical fi ndings by NASA-sponsored 

contractors and grantees.

• CONFERENCE PUBLICATION. Collected 

papers from scientifi c and technical 

conferences, symposia, seminars, or other 

meetings sponsored or cosponsored by NASA.

• SPECIAL PUBLICATION. Scientifi c, 

technical, or historical information from 

NASA programs, projects, and missions, often 

concerned with subjects having substantial 

public interest.

• TECHNICAL TRANSLATION. Englishlanguage translations of foreign scientifi c and 

technical material pertinent to NASA’s mission.

Specialized services also include creating custom 

thesauri, building customized databases, organizing 

and publishing research results.

For more information about the NASA STI 

program, see the following:

• Access the NASA STI program home page at 

http://www.sti.nasa.gov

• E-mail your question via the Internet to help@

sti.nasa.gov

• Fax your question to the NASA STI Help Desk 

at 443–757–5803

• Telephone the NASA STI Help Desk at

 443–757–5802

• Write to:

 NASA Center for AeroSpace Information (CASI)

 7115 Standard Drive

 Hanover, MD 21076–1320
Dennis J. Eichenberg

Glenn Research Center, Cleveland, Ohio

Development and Testing of the Glenn Research

Center Visitor’s Center Grid-Tied Photovoltaic

Power System

NASA/TM—2009-215847

December 2009

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5285 Port Royal Road

Springfi eld, VA 22161

Available electronically at http://gltrs.grc.nasa.gov

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—2009-215847 1 

Development and Testing of the Glenn Research Center 

Visitor’s Center Grid-Tied Photovoltaic Power System 

Dennis J. Eichenberg 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Summary 

The NASA Glenn Research Center (GRC) has developed, installed, and tested a 12 kW DC grid-tied 

photovoltaic (PV) power system at the GRC Visitor’s Center. This system utilizes a unique ballast type 

roof mount for installing the photovoltaic panels on the roof of the Visitor’s Center with no alterations or 

penetrations to the roof. The PV system has generated in excess of 15000 kWh since operation 

commenced in August 2008. The PV system is providing power to the GRC grid for use by all. Operation 

of the GRC Visitor’s Center PV system has been completely trouble free. 

A grid-tied PV power system is connected directly to the utility distribution grid. Facility power can 

be obtained from the utility system as normal. The PV system is synchronized with the utility system to 

provide power for the facility, and excess power is provided to the utility. 

The project transfers space technology to terrestrial use via nontraditional partners. GRC personnel 

glean valuable experience with PV power systems that are directly applicable to various space power 

systems, and provides valuable space program test data. PV power systems help to reduce harmful 

emissions and reduce the Nation’s dependence on fossil fuels. Power generated by the PV system reduces 

the GRC utility demand, and the surplus power aids the community. 

Present global energy concerns reinforce the need for the development of alternative energy systems. 

Modern PV panels are readily available, reliable, efficient, and economical with a life expectancy of at 

least 25 years. Modern electronics has been the enabling technology behind grid-tied power systems, 

making them safe, reliable, efficient, and economical with a life expectancy of at least 25 years. Based 

upon the success of the GRC Visitor’s Center PV system, additional PV power system expansion at GRC 

is under consideration. 

The GRC Visitor’s Center grid-tied PV power system was successfully designed and developed 

which served to validate the basic principles described, and the theoretical work that was performed. The 

report concludes that grid-tied photovoltaic power systems are reliable, maintenance free, long life power 

systems, and are of significant value to NASA and the community. 

Introduction 

The NASA Glenn Research Center has a wealth of experience in photovoltaic power systems. The 

work was done under the Hybrid Power Management (HPM) Program. The GRC Electrical and 

Electromagnetics Branch initiated the HPM Program for the GRC Technology Transfer and Partnership 

Office. HPM is the innovative integration of diverse, state-of-the-art power devices in an optimal 

configuration for space and terrestrial applications. The appropriate application and control of the various 

power devices significantly improves overall system performance and efficiency. Applications include 

power generation, transportation systems, biotechnology systems, and space power systems. 

A PV power system can either be a stand alone, off-grid system, or a grid-tied system. An off-grid PV 

system provides local power only. A grid-tied PV system is connected directly to the utility distribution 

grid. Facility power can be obtained from the utility system as normal. The PV system is synchronized 

with the utility system. The PV system provides power for the facility, and excess power is provided to 

the utility. 
NASA/TM—2009-215847 2 

Photovoltaic power systems have tremendous potential. The 89 petawatts of sunlight reaching the 

Earth’s surface is approximately 6,000 times greater than the 15 terawatts of average power consumed by 

the human population. PV generation has the highest power density of renewable energies with a global 

mean of 170 W/m2

 (Ref. 1). PV is entirely pollution free during use. PV system production end wastes 

and emissions are manageable utilizing existing pollution controls. End-of-use recycling technologies are 

under development to minimize negative environmental effects. PV systems can operate with minimal 

operator intervention or maintenance after initial setup. 

Grid-tied PV power systems provide many benefits. Operating costs of a PV power system are low 

compared to conventional power technologies. PV can displace the highest cost electricity during times of 

peak demand in most climatic regions, and thus reduce grid loading. Net Metering is often used, in which 

independent power producers, such as PV power systems, are connected to the utility grid via the 

customers’ main service panel and meter. When the PV power system is generating more power than 

required at that location, the excess power is provided to the utility grid. The customer pays the net of the 

power purchased when the on-site power demand is greater than the on-site power production and the 

excess power that is returned to the utility grid. 

Grid-tied PV power systems can be used locally thus reducing transmission/distribution losses. 

Transmission/distribution losses in the U.S. were approximately 7.2 percent in 1995 (Ref. 2), thus 

providing a potential for significant energy savings. 

Theoretical power generation has been determined for the grid-tied 12 kW PV power system. The 

actual 12 kW PV power system installed at the GRC Visitor’s Center served to validate the theoretical 

work that was performed. 

Analysis 

Predicted Power Generation 

The National Renewable Energy Laboratory has developed a calculator to determine the energy 

production of grid-tied PV power systems throughout the world. The calculator is based upon the work of 

David F. Mennicucci (Ref. 3). 

The calculator creates hour-by-hour performance simulations that provide power estimated monthly 

and annual energy production in kilowatts and energy value. Users can select a location and choose to use 

default values or their own system parameters, for size, electricity cost, array type, tilt angle, and azimuth 

angle. The calculator can provide hourly performance data for the selected location. 

The calculator uses typical meteorological year weather for the selected location, and determines the 

incident PV array solar radiation and the PV cell temperature for each hour of the year. The DC energy 

for each hour is calculated from the PV system DC rating and the incident solar radiation, and then 

corrected for the PV cell temperature. The AC energy for each hour is calculated by multiplying the DC 

energy by the overall DC-to-AC derating factor and adjusting for the inverter efficiency as a function of 

the load. Hourly values of AC energy are summed to determine monthly and annual AC energy 

production. 

A PV system is rated upon its nameplate DC power rating. This is determined by adding the PV panel 

power listed on the nameplates of the PV panels in watts (W), and dividing the sum by 1,000 to convert 

the rating to kilowatts (kW). PV panels are rated for standard test conditions of 1,000 W/msolar 

irradiance, and 25 °C PV panel temperature. 

The PV system AC rating is determined by multiplying the nameplate DC power rating by an overall 

DC-to-AC derating factor. The DC-to-AC derating factor accounts for losses from the DC nameplate 

power rating, and is the mathematical product of the derating factors for the components of the PV 

system. The derating factor components includes PV array nameplate DC rating accuracy, inverter and 

transformer losses, mismatch, diode and connection losses, DC wiring losses, AC wiring losses, PV array 

contamination, system availability, and shading. 
NASA/TM—2009-215847 3 

The derating factor for PV array contamination accounts for snow and other foreign matter on the 

surface of the PV array that prevents solar radiation from reaching the solar cells. PV array contamination 

is location and weather dependent. There are greater contamination losses in high-traffic, high pollution 

areas with infrequent rain. Snow reduces energy produced, and the severity is a function of the amount of 

snow and the duration that it remains on the PV array. Snow remains the longest when sub-freezing 

temperatures prevail, small PV array tilt angles prevent snow from sliding off, the PV array is closely 

integrated onto the roof, and the roof, or another structure, in the vicinity facilitates snow drift onto the 

array. 

The tilt angle for a fixed array is the angle from horizontal of the inclination of the PV array. Thus a 

tilt of 0° is a horizontal array, and a tilt of 90° is a vertical array. An array is normally tilted at the 

location’s latitude. This normally maximizes annual energy production. Increasing the tilt angle favors 

energy production in the winter, and decreasing the tilt angle favors energy production in the summer. 

The ballast type roof mount utilized for this application is fixed at a tilt of 25.0° from horizontal. 

The azimuth angle for a fixed array is the angle clockwise from true north that the PV array faces. An 

azimuth angle of 180° (south-facing) is normally used for locations in the northern hemisphere, and 0° 

(north-facing) for locations in the southern hemisphere. This normally maximizes energy production. For 

the northern hemisphere, increasing the azimuth angle favors afternoon energy production, and decreasing 

the azimuth angle favors morning energy production. For the southern hemisphere, decreasing the 

azimuth angle favors afternoon energy production, and increasing the azimuth angle favors morning 

energy production. 

The monthly and yearly energy production estimates are modeled using the selected PV system 

parameters and weather data that are typical or representative of long-term averages. Weather patterns 

vary from year to year, so the model is a better indicator of long-term performance than of performance 

for a particular month or year. PV performance is largely proportional to the solar radiation received, 

which may vary from the long-term average by 30 percent monthly and 10 percent yearly. For these 

variations, and the uncertainties associated with the weather data and model, future months and years may 

have actual PV performance that differs from the model. The variations may be as much as 40 percent for 

individual months, and up to 20 percent for individual years. Long-term performance over many years is 

expected to be accurate within 10 percent. 

There are other factors that affect model accuracy. Nearby buildings, objects, or other PV arrays and 

array structures that shade the PV array will cause a reduction in actual energy production from the 

model. Snow or other contamination of the PV array will cause an inconsistency with the model. There is 

a reduction in power generation over time that is not factored into the model. Aging is due to weathering 

of the PV array, and is typically 1 percent per year. 

The predicted AC energy production for a grid-tied 12 kW DC PV power system located in 

Cleveland, Ohio is shown in Table 1. The assumptions made for this prediction is that the PV array is 

crystalline silicon, the PV array azimuth is 180.0°, and the DC-to-AC derating factor is 0.770. The PV 

system AC energy production was predicted for a PV tilt array of 0.0°, 25.0°, and 41.4°. The predicted 

monthly AC energy production is shown graphically in Figure 1, and the predicted annual AC energy 

production is shown graphically in Figure 2. 

PV arrays are sometimes mounted on rooftops with a tilt of 0.0° for simplicity. There are several 

disadvantages with this mounting configuration. It is obvious from Figure 2 that a PV system installed in 

Cleveland, Ohio will produce significantly less annual energy with an array tilt of 0.0° than at a greater 

tilt angle. Cleveland has significant annual snow accumulation, and a PV array tilt is very helpful in 

clearing the snow. A PV array tilt is also helpful in cleaning the array of contamination. The latitude of 

Cleveland is 41.4°, and although the maximum instantaneous energy produced by a PV system installed 

in Cleveland is with an array tilt of 41.4°, the maximum annual energy produced by a PV system in 

Cleveland is with an array tilt of 30°. A PV system in Cleveland with an array tilt of 25.0° actually 

produces greater annual energy than a system with an array tilt of 41.4°. 
NASA/TM—2009-215847 4 

TABLE 1.—PREDICTED AC ENERGY FOR A GRID-TIED 12 kW DC PHOTOVOLTAIC POWER SYSTEM IN 

CLEVELAND, OHIO FOR VARIOUS ARRAY TILT ANGLES 

Month 0.0° Array tilt 25.0° Array tilt 41.4° Array tilt 

Solar 

radiation, 

kWh/m2

/day 

AC 

energy, 

kWh 

Solar 

radiation, 

kWh/m2

/day 

AC 

energy, 

kWh 

Solar 

radiation, 

kWh/m2

/day 

AC 

energy, 

kWh 

January 1.65 447 2.24 653 2.49 734 

February 2.43 623 3.09 815 3.34 881 

March 3.4 968 3.98 1147 4.09 1174 

April 4.68 1265 5.07 1367 4.94 1329 

May 5.78 1557 5.87 1566 5.48 1461 

June 6.19 1571 6.10 1521 5.56 1387 

July 6.01 1563 6.01 1543 5.55 1424 

August 5.32 1378 5.68 1466 5.47 1411 

September 4.19 1067 4.85 1239 4.90 1249 

October 2.91 769 3.68 998 3.91 1060 

November 1.58 386 2.03 524 2.18 566 

December 1.23 308 1.56 420 1.68 458 

Total annual 3.79 11900 4.19 13260 4.14 13133 

Figure 1.—Predicted Monthly AC Energy for a Grid-Tied 12 kW DC Photovoltaic Power 

System in Cleveland, Ohio for Various Array Tilt Angles. 
NASA/TM—2009-215847 5 

Figure 2.—Predicted Annual AC Energy for a Grid-Tied 12 kW DC Photovoltaic Power System 

in Cleveland, Ohio for Various Array Tilt Angles. 

TABLE 2.—PREDICTED ANNUAL ENERGY FOR A 

GRID-TIED 12 kW DC PHOTOVOLTAIC POWER 

SYSTEM WITH AN ARRAY TILT OF 25

City Solar radiation, 

kWh/m2

/day 

Annual AC 

energy, 

kWh 

Cleveland 4.19 13260 

Tampa 5.37 16353 

Los Angeles 5.60 17584 

Phoenix 6.54 19293 

Las Vegas 6.54 19745 

Anchorage 2.95 9303 

Montreal 4.06 13044 

Berlin 3.05 9372 

Matsumoto 4.50 14166 

Moscow 3.05 9430 

Paris 3.25 10103 

The predicted annual AC energy produced from a grid-tied 12 kW DC PV power system for different 

areas throughout the world are shown in Table 2. The assumptions made for this prediction is that the PV 

array is crystalline silicon, the PV array tilt is fixed at 25, the PV array azimuth is 180.0°, and the DC-toAC derating factor is 0.770. It is interesting to note from the world comparison that Cleveland, Ohio is a 

viable location for PV production, with potentially significantly greater annual energy production than 

Berlin, Moscow or Paris for the same PV system installed at that location. In addition, the potential 

annual energy production from the same PV system installed in Cleveland, Ohio is not significantly less 

than such a system located in Tampa, Florida. 

Test Objectives 

The objective of testing the 12 kW grid-tied photovoltaic power system is to validate the theoretical 

analyses and verify long-term system performance. This validation provides confidence in using the 

analyses for developing and optimizing conceptual grid-tied photovoltaic power system designs. 
NASA/TM—2009-215847 6 

Testing of the 12 kW grid-tied photovoltaic power system was performed at the NASA Glenn 

Research Center. Of particular interest is the long-term performance of the system. Power and energy 

were monitored on a regular basis. 

Test Hardware Description 

GRC Visitor’s Center 12 kW Grid-Tied Photovoltaic Power System 

The GRC Visitor’s Center 12 kW grid-tied photovoltaic power system test hardware includes the 

photovoltaic panels, and the DC/AC inverters. The design of the system is based upon the GRC prototype 

2 kW photovoltaic power system that has been operating flawlessly at GRC since 2006 (Ref. 4). The GRC 

Visitor’s Center PV system is configured as four independent units, with four sets of photovoltaic panels, 

and four photovoltaic inverters. The photovoltaic panels are shown in Figure 3 and the photovoltaic 

inverters are shown in Figure 4. The system block diagram is shown in Figure 5. System component 

specifications are included in the Appendix. 

The photovoltaic panels are semiconductor panels that convert energy from sunlight to DC electrical 

power. The panels are unbreakable and maintenance free. The PV system consists of four sets of 

15 panels connected in series. Each panel is rated at 200 W (at 27.1 V), and consists of 54 silicon polycrystalline cells in series. The panel efficiency in providing power from the sunlight is rated at 15 percent. 

Each panel weighs 39 lb, and is 58.5 by 38.6 in. The life expectancy of the PV panels is 25 years or greater. 

The support structure for the panels is a ballast mount to orient the panels southerly with a tilt of 25.0° from 

horizontal. 

An array tilt of 25.0° in Cleveland, Ohio permits the PV system to produce greater annual AC energy 

than an array tilt of 41.4°, which is the latitude of Cleveland. There are many advantages of the ballast 

type roof mount over a fixed mount. A ballast type roof mount provides PV panel installation on existing 

roofs with no alterations or penetrations to the roof. The PV panels and mountings can be easily relocated 

to facilitate roof maintenance. Solar trackers are available to increase the available power from the Sun. 

Under ideal conditions, a tracker can provide up to 50 percent additional daily power from a PV array. In 

temperate latitudes, a tracker can provide an annual 25 percent increase in power from a PV array. 

Numerous technologies are available for trackers, including electric drives and fluid drives. Trackers are 

mechanical devices, and thus have potential life and maintenance issues. To avoid life and maintenance 

issues, a ballast type roof mount was used for the GRC Visitor’s Center 12 kW PV power system. 

Four photovoltaic inverters convert the DC electrical power derived from the photovoltaic panels to 

single phase, 60 Hz, sinusoidal AC power synchronized to the AC utility power system. Each inverter 

integrated into the GRC Visitor’s Center PV power system is rated at 3.3 kW, 208 VAC with an 

efficiency of 94 percent. Each inverter weighs 49 lb, and is 28.5 by 15.9 by 5.75 in. The life expectancy 

of the inverter is 25 years or greater. 

Figure 3.—GRC Visitor’s Center 12 kW System Photovoltaic Panels. 
NASA/TM—2009-215847 7 

Figure 4.—GRC Visitor’s Center 12 kW System 

Photovoltaic Inverters. 

Figure 5.—GRC Visitor’s Center 12 kW Grid-Tied Photovoltaic System 

Block Diagram. 
NASA/TM—2009-215847 8 

The GRC Visitor’s Center PV system was designed per the National Fire Protection Association 

(NFPA) 70, the National Electrical Code (NEC). The system concurs with all articles of the NEC, and in 

particular addresses Article 690, Solar Photovoltaic Systems. In addition, the system was designed to be 

completely in concurrence with the NASA GRC Safety Manual. The PV panels meet the requirements of 

Underwriters Laboratories Standard for Safety UL-1703 concerning flat-plate PV modules and panels. 

The PV panels are fused to provide overcurrent protection. The PV panels, and the entire PV system, are 

bonded and grounded per the NEC. Each PV inverter includes an NEC compliant DC and AC disconnect 

switch to provide complete system isolation whenever the disconnect switch is opened. The inverter is 

configured to automatically open the inverter circuits whenever utility power is lost to prevent power 

from the PV system from feeding back into the utility power system, thus preventing a potential safety 

hazard. 

Instrumentation 

The GRC Visitor’s Center 12 kW grid-tied photovoltaic power system contains an internal 

instrumentation system. Each of the four photovoltaic inverters include an integral backlit 2-line, 

16-character, liquid crystal display (LCD). The display provides instantaneous inverter output power, 

daily and lifetime inverter output energy, PV array voltage and current, utility voltage and frequency, 

time online, and fault messages. 

Test Procedures 

The tests described in this report were conducted at the NASA Glenn Research Center in Cleveland, 

Ohio. The lifetime energy production of the GRC Visitor’s Center 12 kW grid-tied photovoltaic power 

system is monitored at the PV inverters. The measured monthly energy production is compared to the 

analytical monthly energy production. 

Test Results 

System Performance 

Table 3 summarizes the monthly and annual energy production results for the first year of use of the 

GRC Visitor’s Center 12 kW grid-tied photovoltaic power system, along with the analytical results. 

Figure 6 indicates the monthly energy production, and Figure 7 indicates the total energy production. 

TABLE 3.—GRC VISITOR’S CENTER 12 kW DC 

GRID-TIED PV POWER SYSTEM PERFORMANCE 

Month Predicted 

AC energy, 

kWh 

Measured 

AC energy, 

kWh 

January 653 297 

February 815 76 

March 1147 712 

April 1367 1464 

May 1566 1546 

June 1521 1828 

July 1543 1702 

August 1466 1731 

September 1239 1780 

October 998 1239 

November 524 976 

December 420 242 

Total annual 13260 13593 
NASA/TM—2009-215847 9 

Figure 6.—GRC Visitor’s Center 12 kW DC Grid-Tied PV Power System Monthly AC Energy. 

Figure 7.—GRC Visitor’s Center 12 kW DC Grid-Tied PV Power System Total AC Energy. 
NASA/TM—2009-215847 10 

Discussion 

The objective of testing the GRC Visitor’s Center 12 kW grid-tied photovoltaic power system is to 

validate the theoretical analyses, and verify long-term system performance. The analytical model 

effectively predicts the annual AC energy produced by a grid-tied photovoltaic power system. 

The rather large monthly variation in energy production of the GRC Visitor’s Center 12 kW PV 

power system shown in Figure 6 indicates the large seasonal variation in sunlight in Cleveland, Ohio. A 

grid-tied PV power system is advantageous in regions, such as Cleveland, in which utility power is 

essential in times of limited sunlight to meet the power requirements of the load. The significant power 

produced by the PV power system in the summer months is extremely valuable in meeting the high utility 

system power demand at that time. 

The monthly energy production of the GRC Visitor’s Center 12 kW PV power system shown in 

Figure 6 over the past year indicates very consistent long-term performance. No effort has been made to 

clean the PV panels, or to clear them of snow for these tests. Providing cleaning and snow clearing of the 

PV panels would improve PV system performance, but the test results obtained without cleaning or snow 

clearing indicate the excellent performance attainable from this system under no maintenance conditions. 

Consistent long-term PV system performance is obvious from the total PV system energy production 

shown in Figure 7. Long-term system performance has been excellent over the past year with no system 

failures, no down time, and no required system maintenance. 

Concluding Remarks 

The NASA Glenn Research Center has successfully designed, developed, analyzed, installed, and 

tested a 12 kW DC grid-tied photovoltaic power system at the GRC Visitor’s Center. The goals of the 

project include reducing the Nation’s dependence on fossil fuels, and reducing the production of harmful 

emissions. The objective of this work is to develop a viable 12 kW DC grid-tied photovoltaic power 

system to validate the theoretical analyses, and to verify long-term system performance. 

Theoretical analyses have been performed successfully to predict the energy produced by a grid-tied 

PV system in Cleveland, Ohio. Empirical test results obtained from the experimental hardware 

successfully validated the basic principles described, and the theoretical work that was performed. Of 

particular value, are the analytical tools and capability successfully used under this project. Performance 

predictions can be made confidently for grid-tied PV systems of various scale. 

The GRC Visitor’s Center 12 kW DC grid-tied PV system has provided consistent long-term 

performance over the year with no system failures, no down time, and no required system maintenance. 

From the analyses and empirical test results, it is apparent that grid-tied PV systems are viable in 

Cleveland, Ohio. 

The report concludes that the implementation of grid-tied photovoltaic power systems can provide 

significant improvements in power system performance, reduce dependency on fossil fuels, and reduce 

the production of harmful emissions. The GRC Visitor’s Center system has been efficient, reliable, and 

maintenance free. The GRC Visitor’s Center grid-tied PV power system has been of great value to GRC 

and to the local community. 
NASA/TM—2009-215847 11 

Appendix—Equipment Under Test Summary Data Sheet 

GRC Visitor’s Center 12 kW Photovoltaic Power System 

1.0 Photovoltaic Panels 

1.1 Type Silicon Poly-Crystalline 

1.2 Peak Power (Wp) 200 W 

1.3 Max Power Voltage (Vmp) 27.1 V 

1.4 Max Power Current (Imp) 7.4 A 

1.5 Open Circuit Voltage (Voc) 34 V 

1.6 Short Circuit Current (Isc) 7.8 A 

1.7 Short Circuit Temp Coefficient 5.6 mA/°C 

1.8 Open Circuit Voltage Coefficient –0.12 V/°C 

1.9 Max Power Temp Coefficient –0.5%/°C 

1.10 Max Series Fuse 15.0 A 

1.11 Normal Operating Cell Temp (NOCT) 45.0 °C (113 °F) 

1.12 Width 98.1 cm (38.6 in.) 

1.13 Length 148.5 cm (58.5 in.) 

1.14 Depth 5.5 cm (2.2 in.) 

1.15 Weight 17.7 kg (39.0) 

 
NASA/TM—2009-215847 12 

2.0 Inverter 

2.1 Type Sine Wave 

2.2 Max AC Power Output 3300 W 

2.3 Nominal AC Output Voltage 208 VAC 

2.4 AC Output Voltage Range 183 to 228 VAC 

2.5 Nominal AC Frequency 60 Hz 

2.6 Max Continuous Output Current 18 A 

2.7 Max Total Harmonic Distortion 3% 

2.8 Power Factor >0.9 

2.9 DC Input Voltage Range 195 to 600 VDC 

2.10 Peak Power Tracking Voltage Range 195 to 550 VDC 

 2.11 Peak Inverter Efficiency 94.7% 

 2.12 Night Time Power Consumption 1 W 

 2.13 Output Overcurrent Protection 25 A 

 2.14 Operating Temperature Range –25 to 65 °C (–13 to 149 °F) 

2.15 Enclosure Type NEMA 3R (outdoor rated) 

2.16 Disconnect PV/Utility disconnect 

2.17 Cooling Convection 

2.18 Communications One RS 232 and two RJ45 ports 

2.19 Display Liquid Crystal Display 

2.20 Width 40.3 cm (15.9 in.) 

2.21 Height 75.5 cm (28.5 in.) 

2.22 Depth 14.6 cm (5.7 in.) 

2.23 Weight 22.2 kg (49.0 lb) 

 
NASA/TM—2009-215847 13 

References 

1. Smil, Vaclav, “Energy at the Crossroads: Global Perspectives and Uncertainties,” The MIT Press, 

November 1, 2003. 

2. Department of Energy, “U.S. Climate Change Technology Program: Technology Options for the 

Near and Long Term,” DOE/PI-0002, November, 2003. 

3. Mennicucci, David F., “Photovoltaic Array Simulation Models,” Solar Cells, 1986, pp. 383–392. 

4. Eichenberg, Dennis J., “Development and Testing of a Prototype Grid-Tied Photovoltaic Power 

System,” NASA Technical Memorandum 2009–216062, 2009. 
REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the 

data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this 

burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. 

Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB 

control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

01-12-2009 

2. REPORT TYPE

Technical Memorandum 

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Development and Testing of the Glenn Research Center Visitor’s Center Grid-Tied 

Photovoltaic Power System 

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Eichenberg, Dennis, J. 

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

WBS 069746.02.03.0485.02 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field 

Cleveland, Ohio 44135-3191 

8. PERFORMING ORGANIZATION 

 REPORT NUMBER

E-17113 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

Washington, DC 20546-0001 

10. SPONSORING/MONITOR'S 

 ACRONYM(S)

NASA 

11. SPONSORING/MONITORING 

 REPORT NUMBER

NASA/TM-2009-215847 

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited 

Subject Category: 44 

Available electronically at http://gltrs.grc.nasa.gov 

This publication is available from the NASA Center for AeroSpace Information, 443-757-5802

13. SUPPLEMENTARY NOTES

14. ABSTRACT

The NASA Glenn Research Center (GRC) has developed, installed, and tested a 12 kW DC grid-tied photovoltaic (PV) power system at the 

GRC Visitor’s Center. This system utilizes a unique ballast type roof mount for installing the photovoltaic panels on the roof of the Visitor’s 

Center with no alterations or penetrations to the roof. The PV system has generated in excess of 15000 kWh since operation commenced in 

August 2008. The PV system is providing power to the GRC grid for use by all. Operation of the GRC Visitor’s Center PV system has been 

completely trouble free. A grid-tied PV power system is connected directly to the utility distribution grid. Facility power can be obtained 

from the utility system as normal. The PV system is synchronized with the utility system to provide power for the facility, and excess power 

is provided to the utility. The project transfers space technology to terrestrial use via nontraditional partners. GRC personnel glean valuable 

experience with PV power systems that are directly applicable to various space power systems, and provides valuable space program test 

data. PV power systems help to reduce harmful emissions and reduce the Nation’s dependence on fossil fuels. Power generated by the PV 

system reduces the GRC utility demand, and the surplus power aids the community. Present global energy concerns reinforce the need for 

the development of alternative energy systems. Modern PV panels are readily available, reliable, efficient, and economical with a life 

expectancy of at least 25 years. Modern electronics has been the enabling technology behind grid-tied power systems, making them safe, 

reliable, efficient, and economical with a life expectancy of at least 25 years. Based upon the success of the GRC Visitor’s Center PV 

system, additional PV power system expansion at GRC is under consideration. The GRC Visitor’s Center grid-tied PV power system was 

successfully designed and developed which served to validate the basic principles described, and the theoretical work that was performed. 

The report concludes that grid-tied photovoltaic power systems are reliable, maintenance free, long life power systems, and are of significant 

value to NASA and the community. 

15. SUBJECT TERMS

Photovoltaic conversion; Energy conversion; Electric power 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

 ABSTRACT

UU 

18. NUMBER

 OF 

 PAGES

19 

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email:help@sti.nasa.gov) 

a. REPORT

U 

b. ABSTRACT

U 

c. THIS 

PAGE

U 

19b. TELEPHONE NUMBER (include area code)

443-757-5802 

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18