November 2012

NASA/TM–2012-217787 

Preliminary Design of a Solar Photovoltaic 

Array for Net-Zero Energy Buildings at 

NASA Langley 

Stuart K. Cole and Russell J. DeYoung 

Langley Research Center, Hampton, Virginia 
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November 2012

NASA/TM–2012-217787 

Preliminary Design of a Solar Photovoltaic 

Array for Net-Zero Energy Buildings at 

NASA Langley 

Stuart K. Cole and Russell J. DeYoung 

Langley Research Center, Hampton, Virginia 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

Acknowledgements 

This work was performed as a collaboration between the LaRC Science Directorate and 

Research Directorate to fulfill the need for meeting the Center’s sustainability and energy 

conservation goals, furthering technological advances and research, and promoting 

opportunities for inter-departmental working relationships. The NASA HQ funded this 

research through the Climate Adaptation Science Investigator program. 

The use of trademarks or names of manufacturers in this report is for accurate reporting and does not 

constitute an official endorsement, either expressed or implied, of such products or manufacturers by the 

National Aeronautics and Space Administration. 
 1 

Preliminary Design of a Solar Photovoltaic Array for Net-Zero Energy 

Buildings at NASA Langley 

Stuart K. Cole 

 Langley Research Center, Research Directorate, Mail Stop 164D, 

Hampton, Virginia 23681, Phone 757-864-5450 

Russell J. De Young 

Langley Research Center, Science Directorate, Mail Stop 401A, 

Hampton, Virginia, 23681, Phone 757-864-1472 

Abstract 

 An investigation was conducted to evaluate photovoltaic (solar electric systems) systems for a single 

building at NASA Langley as a representative case for alternative sustainable power generation. Building 1250 

in the Science Directorate is comprised of office and laboratory space, and currently uses approximately 

250,000 kW/month of electrical power with a projected use of 200,000 kW/month with additional conservation 

measures. The installation would be applied towards a goal for having Building 1250 classified as a net-zero 

energy building as it would produce as much energy as it uses over the course of a year. Based on the facility’s 

electrical demand, a photovoltaic system and associated hardware were characterized to determine the optimal 

system, and understand the possible impacts from its deployment. The findings of this investigation reveal that 

the 1.9 MW photovoltaic electrical system provides favorable and robust results. The solar electric system 

should supply the needed sustainable power solution espically if operation and maintenance of the system will 

be considered a significant component of the system deployment. 

 
 2 

Introduction and Background 

Climate change is impacting the NASA Centers. These impacts include rising tidal conditions, changing 

weather patterns, intensity of weather patterns, increased ambient temperatures and rising energy demand and 

energy costs. The cumulative effect of these conditions will affect both the near and long term operational 

posture of NASA Langley Research Center (LaRC) and potentially directly, or indirectly, affect the capability 

to meet mission requirements. Also it is now clear that burning of fossil fuels increases carbon dioxide in the 

atmosphere and thus causes increased atmospheric temperatures. The Federal Government has placed 

emphasis on renewable power generation that will mitigate climate change by reducing carbon emissions. 

In particular, LaRC has completed preliminary investigations to ascertain the impacts of the regional 

climate change on the Center and has identified the need for implementing sustainable solutions to address 

climate change impacts including electrical power demands.(1) From this, an alternative sustainable power 

source(s) was identified as one of several significant components to meet the critical need for broadening the 

base of potential energy supply to LaRC. For land based applications, alternative power sources typically 

include: geothermal, hydroelectric, biofuels, wind, concentrating solar power, and photovoltaics (solar electric 

system) which are renewable and sustainable system solutions. 

This investigation was initiated to determine the preliminary design requirements for a Net-Zero Energy 

Building which is defined as a building that produces as much energy as it uses over the course of a year. Netzero energy buildings are very energy efficient, and the remaining low energy needs are typically met with onsite renewable energy. Much focus is placed on energy efficiency as the most cost-effective way to reduce 

energy use in commercial buildings. All net-zero energy buildings must reduce energy use through energy 

efficiency and demand-side renewable energy technologies such as use of skylights, insulation, passive solar 

heating, high-efficiency heating ventilation and air conditioning equipment (HVAC), natural ventilation, 

evaporative cooling, ground-source heat pumps, and ocean water cooling. There is a point at which the cost of 

adding efficiency measures is higher than that of using supply-side renewable energy technologies such as 

photovoltaics (PV). Supply-side renewable energy technologies must be used for a building to be classified a 

net-zero energy building.(2) 

To assess the potential to support renewable power sources, an investigation was conducted to evaluate 

solar photovoltaic electric systems for a single building as a representative case for application. The selection 

of a solar PV system for this investigation was driven based on the familiarity gained by the September 2010 

installation at LaRC of a 39.5 kW system for the Badge and Pass Office. In addition, opportunities for use of 

these PV systems must be investigated routinely as their market cost may make them more attractive. It is 

noted that a “decline has been indicated in the cost of utility scale solar photovoltaic systems. Current cost 

benchmarks for utility-sector solar electric systems are generally at the low-end of the range exhibited by the 

projects sampled for year 2010, with various entities estimating an installed cost of $3.8/W to $4.4/W, 

depending on system size and configuration for utility sector systems installed at the end of 2010 or beginning 

of 2011.”(2) 

This investigation is motivated by the 20 year LaRC Master Plan. At the time of the initial plan 

development it was stated in the Master Plan that: “LaRC's current electricity rates (recently adjusted 

downward) do not drive a compelling business case for on-site renewable energy sources. This was confirmed 

through a NASA wide renewable energy assessment. The Master Plan indicates that LaRC is active in 

renewable energy, and the strategy to address renewable energy goals was identified as: (1) Continue to 

purchase Renewable Energy Credits (REC’s) required to meet goals via the Agency evaluation metric: 

Increase renewable source energy to 7.5% by 2015 (EO 13514); (2) Leverage other investments and 

incorporate as much as possible with available funds; and (3) Research other approaches for reduction in 

energy use.” (3)
 3 

The use of PV electric systems directly supports the Federal Leadership in Environmental, Energy and 

Economic Performance Executive Order 13514 (EO) which sets sustainability goals for Federal agencies and 

focuses on making improvements in their environmental, energy and economic performance. The EO requires 

Federal agencies to submit a 2020 greenhouse gas pollution reduction target within 90 days, increase energy 

efficiency, reduce fleet petroleum consumption, conserve water, reduce waste, support sustainable 

communities, and leverage Federal purchasing power to promote environmentally-responsible products and 

technologies. 

As an example of how a PV system could power a LaRC building, the Science Directorate (Building 

1250) was chosen as a typical installation. The Science Directorate is comprised of office and laboratory space, 

with supporting cooling/heating HVAC infrastructure and currently uses approximately 250,000 kWH/month 

electrical power, but with aggressive conservation could experience an electrical power reduction to 

approximately 200,000 kWH/month. The lower projected electrical demand will be obtained by a detailed 

energy audit, increased energy conservation, online power use monitoring, and use of intelligent energy 

control systems. This level of electric energy use is equivalent to the power consumed by about 314 private 

homes. 

The immediate environs of Building 1250 include asphalt paved parking areas with the edges of the 

developed areas bordered by a dense forest of deciduous trees and intermittent landscaped grassed areas. It is 

well known that direct rainwater runoff from any development supplies of undesired nutrients and 

microconstituents to the Chesapeake Bay. These pollutants in rainwater runoff must be mitigated. (4) 

Solar photovoltaic systems have been used successfully in extremely harsh environments, (5) (6) and in 

terrestrial applications where their use is quite common for commercial application as indicated on Table 1. 
 4 

System and Hardware Description 

A PV system is made up of many photovoltaic solar panels. An individual panel is usually small, 

typically producing about 230 watts of power for each panel as direct current (DC). To boost the power output 

of PV panels, they are connected together to form larger units called modules. Modules, in turn, can be 

connected to form even larger units called arrays, which are also interconnected. The arrays are then co-located 

to form a large power system. The modules are mounted on individual or common foundations and oriented to 

the sun to capture the highest amount of light exposure possible. Spacing of arrays in a commercial system 

becomes a critical design element as land area must be optimized for panel density, maximum sun exposure, 

and access for maintenance. These arrays are monitored by computer systems to indicate failure of any one 

module as well as overall system performance. 

Arrays are connected to DC to AC (direct current to alternating current) power converters where the 

required number and size of converters are strategically designed to accommodate the array system voltage and 

also provide needed redundancy. These DC to AC converters are outdoor installations typically with a 95 

percent or greater efficiency, and are connected to metering points at the voltage AC substation. Converters 

consist of utility-grade multi-megawatt platforms on a reinforced concrete foundation that consists of a unit 

Table 1 

INSTALLED SOLAR POWER SYSTEMS

PV SYSTEM 

OWNER LOCATION 

SYSTEM DESCRIPTION Characteristics Date 

3.5 MW by Sunpower 

Corp. 

Inland Empire Utilities 

Agency (IEUA), a 

municipal water agency 

San Bernardino County, 

CA 

18,210 Panels of the 

commercial roof & ground 

system type. PV panels are 

mounted on the patented 

single-axis Trackers at 20° of 

tilt, generating up to 30 % more 

energy than conventional fixedtilt solar power systems. 

 Offsets over 10% of the District’s total electricity demand 

 Provides significant hedge against future rate increases from Southern 

Califomia Edison 

 Reduces carbon emissions by over 230 million pounds over the next 30 

years, which is equivalent to powering 18,350 homes 

 Savings of approximately $500,000 in annual electricity costs 

removing more than 19,000 cars from our roads 

 Contributes to IEUA’s increasing commitment to sustainability and 

environmental practices 

Dec. 

2008 

3.5 MW by Solar 

Power, Inc. Aerojet 

(Division of GenCorp 

Inc.) a space & defense 

contractor 

Sacramento, California 

18,000 Modules consisting of 

SPI 200-watt unit each 

mounted atop 12 tracking 

arrays over 20 acres. 

 During its first year of use, will offset approximately 4,200 tons of CO2

, 

16.7 tons of SO2

 and approx. 6.5 tons of NO2. 

 Is equivalent to planting 976,520 trees or offsets approx. 8,270,000 car 

miles driven. 

Nov. 

2009 

3.5 MW by CME & 

DEGERenergie systems 

Vilanueva de Córdova 

Province of Andalusia, 

Spain 

3,044 Modules consisting of 

single-axis TOPtracker 8.5 

systems installed with a tilt 

angle of 30°. 

 Maximizes the yield of solar power plants with an “intelligent” control 

 MLD tracking is up to 46 % higher yield than that of rigid systems and 

this difference is even more pronounced for peaks 

Feb. 

2011 

3.5 MW by Windaerts 

Energie GmbH 

Bavaria, Germany 

14,208 PV modules by 

Canadian Solar Inc. 

 Supplies 3.7 million KWh annually for 1,200 homes Aug. 

2011 

2.7 MW by SunDurance 

Energy 

William Patterson 

University 

Wayne, New Jersey 

11,856 panels that cover both 

rooftops and elevated parking 

lot canopies. 

 Saves over $3 million in energy costs without any additional capital 

expenditures. Installed over buildings and parking lots. 

 SunDurance took a value engineering approach and determined that 

parking structures over the many existing lots could provide ample solar 

electricity at a discount to the university’s grid rates 

 Funded and operated by Nautilus Solar. Will cut $4.3 million over 15 

Year Purchase Power Agreement. 

 Reduces air pollution and improve air quality, while creating green jobs 

in the region. 

Aug. 

2011 
 5 

with power inverters, integrated step-up transformers, disconnect switches, and power use monitoring 

electronics. Figure 1 shows a schematic of a PV electric system providing power to both the building and the 

power grid, where it grid is used for power storage. 

Figure 1. Solar photovoltaic electric system schematic configuration 

Mounting the PV arrays for Building 1250 will require substantial land area for the PV array. Mounting 

PV arrays therefore was designed to optimize the existing land available including clear spaces, parking areas, 

and building roof tops. The use of PV arrays over parking areas will however provide a unique opportunity for 

additional environmental and cost benefits such as the capture of rainwater, reduction of heat absorption by the 

pavement which may contribute to local micro-climate warming, and affording shade and some overhead 

weather protection to equipment, pedestrians, or automobiles. Electric car charging can be easily 

accommodated in such structures. 

Operation and maintenance (O&M) of the PV system is a necessary and routine requirement. The 

system must be continuously monitored, and if individual PV panels are found defective they must be 

replaced. The O&M of the system must be operated and managed by qualified personnel and include a 

Computerized Maintenance Management System with scheduled services, cleaning, and snow/debris removal. 

Risk of damage to solar panels could exist from adverse weather including hail or other high winds resulting in 

airborne debris. 

Electrical Demand 

Building 1250 electrical demands generally consist of lighting, HVAC, and electrical mechanical 

systems. Currently, the building has been documented to use approximately 250,000 kWH/month as shown in 

Figure 2. Energy conservation is expected to reduce this demand to 200,000 kWH/month. The demand would 

also include charging stations for electric cars. 
 6 

Figure 2. Building 1250 electric energy demand (Year 2010) 

System Configuration 

The solar electric system configuration consists of PV panels, support structure for the modules, 

converters, wiring, on-line monitoring system, and the space to install the system. The system is tied to both 

the Building 1250 electrical supply and to the LaRC substation. During off peak hours and low demand days 

such as holidays and weekends when the building is unlikely to be occupied, the PV system will supply power 

to the LaRC electrical grid; thus there is no need for electricity storage usually requiring batteries. 

Modules may be fixed or of the type that tracks the sun through the arc of day. Fixed modules are 

permanently mounted and are pointed in a single direction to obtain the largest exposure of light during the 

entire day light hours. There is a slight variation of each module direction based on its physical location in the 

field to optimize the panel exposure to light. Shade from buildings and the tree line must be accounted for in 

the placement of the modules and the installation location. The specifications for a PV system location and 

orientation were based on Norfolk, Virginia, as shown in Table 2. In order to generate the required alternating 

current in kilowatt-hours demand including the de-rating factor of 0.77, a PV system would be sized as a 1.888 

Megawatt DC system.
 7 

Table 2 

Station Identification and System Specifications

City: Norfolk 

State: Virginia 

Latitude: 36.90° N 

Longitude: 76.20° W 

Elevation (meters): 9 

DC Rating: 1,888 kW 

DC to AC Derate Factor: 0.77 

AC Rating: 1,453 kW 

Array Type: Fixed Tilt 

Array Tilt: 36.9° 

Array Azimuth: 180.0° 

This investigation considered fixed array only based on the perception that it was the least costly. Of 

these fixed installations, three types of module installation configurations were considered. The first is a basic 

fixed array that is installed on concrete foundations in open space. The second configuration is a mount on the 

existing building, and the third is a system mounted on an elevated structure that would support the modules 

over a parking area for automobiles. 

One PV system advantage is the unique opportunity for meeting the environmental goal of collecting 

valuable rainwater and storing it for beneficial use. These benefits would also include: the reduction or 

elimination of pollutant runoff from automobile parking areas, runoff volume control, reduction of nutrients in 

the runoff, supplemental irrigation, supplemental cooling tower water, and aesthetic impoundment features for 

attracting waterfowl, and supporting other beneficial flora and fauna. The collection of this valuable rain and 

runoff water as resource would be by construction of an impoundment comprised of an earthen detention pond 

with a spillway, and an outfall weir to control the volume of water. Panels would be equipped with a gutter 

edge material to collect rainwater. Figure 3 provides a schematic and photo of an array installation for a 

parking area where panels collect rain water. 
 8 

Figure 3. Typical Solar panel installation for parking areas. 

The installation of arrays could be mounted in areas where the land is subject to 100 year flooding or is 

otherwise unsuitable for other heavy building construction. The relatively lightweight arrays can be installed 

on fixed pier type screw type anchors which readily allow the installation in soft and unstable soils and thereby 

maximize land use. 

Panel Hardware 

Solar panels are manufactured worldwide and improvements to their output performance and efficiency 

vary. For convenience, a single manufacturer, UNICOR FPI (a U.S. company) was selected from multiple 

panel manufacturers to characterize panel performance. Based on UNICOR’s manufacturing data (2011), the 

following performance data is given in Table 3.

Table 3 

PV PANEL PERFORMANCE - UNICOR PV (2011) 

Panel Efficiency 14.3% 

Number of Panels for a 1.9 MW Array Approximately 7,826 

Watts per Panel 230 W 

Guaranteed Life Expectancy 25 Years 

Actual Panel Life Expectancy 40 Years 

Approx. Panel Cost, Each $368 

Operating Module Temperature -40 to 85oC 

Maximum Series Fuse Rating 15 A 

Nominal Voltage 24 V 

Limiting Reverse Current 15 A 

Power output Tolerance -0 /+4.999 watts 

Current Temperature Coefficient 0.04 to 0.08 %/oC 

Voltage Temperature Coefficient -0.45 to -0.36 %/oC 

Power Temperature Coefficient -0.68 to -0.52 %/oC 
 9 

Electrical Power Supply 

A monthly load projection of 200,000 kWh would require a system output of 2,400,000 kWh annually. 

Figure 4 shows the monthly AC energy production per month for the example Building 1250, and Figure 5 

shows the corresponding solar radiation received per month for the Norfolk and Hampton, Virginia region. In 

order to generate the requirement for 200,000 kWh per month including the de-rating factor, a PV electric 

system would be sized at approximately 1.9 MW. It is important to note that the system utilized to produce 

these results assumes a DC to AC de-rating factor of 0.77. This de-rating factor represents the loss in energy 

and inefficiencies when converted from DC to AC. Furthermore, the array could produce more kWh 

depending on the efficiency and performance capabilities of the module provider. Thus the total kWh 

indicated to be required at 1.9 MW is a conservative estimate. 

Figure 4. Projected electric energy supply per month for Building 1250 

(Courtesy Rae Sullivan, UNICOR FPI) 
 10 

SUMMARY TOTAL ENERGY 

PRODUCTION IN ONE YEAR

Month

Solar Radiation 

(kWh/m2/day)

AC 

Energy 

(kWh)

January 3.84 173560 

February 4.53 185493 

March 4.69 205580 

April 5.47 222830 

May 5.40 222490 

June 5.69 220219 

July 5.44 215125 

August 5.61 224918 

September 5.02 199136 

October 4.95 210019 

November 4.04 170351 

December 3.37 150474 

Total Year 4.84 2,400,194 

Figure 5. Summary of incident solar radiation and AC power production. 

(Courtesy Rae Sullivan, UNICOR FPI) 

Land Use Requirements 

Land use within the environs of Building 1250 is a critical system constraint. In consideration of this 

constraint, the arrays would be located contiguous to Building 1250 in open spaces not designated for 

development and above existing parking areas. Based on preliminary sizing calculations, a 1.9 MW ground 

mount system would require about 8 acres of total space, or 348,480 square feet. This is based on the average 

watts per square foot expected to be generated with an array tilt of 37 degrees. A conceptual layout of this 

array is shown in Figure 6 where red boxes indicate the PV array area. As seen in the figure part of the total 

PV array is a large array field and part is designed for use on a car port structure. The final determination of 

how much space would be required would also be accomplished during the final design, as the parking lot 

layout heavily impacts the amount of PV ground area needed. Preliminary estimate for the total area required 

for parking areas would increase total the area by about 1 acre, or 43,560 square feet. 
 11 

Figure 6. Conceptual layout showing area for a 1.9MW PV array. 

The estimated ground area needed for installation of the solar electric system is therefore about nine 

acres. This space need not be contiguous, however long electric lines tying sub-arrays together do increase 

project cost. The optimization of the array spacing was not performed in this investigation. Space utilization 

for the arrays, however, was assumed to take existing large open spaces and encompassing areas near sensitive 

waterways and adjacent to wetlands. These sensitive areas most likely will never be developed as they are 

presently used as buffers. 

The environmental impact of the array installation on trees was considered. Cutting of large stands of 

trees or tracts of foliage was not recommended. Where parking areas were found distinctly attractive for 

application of the arrays, adjacent or perimeter trees could be selectively cut trimmed or topped as identified 

by a professional arborist’s strategic objective for improved tree management, and thus help to improve the 

direct exposure to panels. See Figure 3 for a schematic of the concept and Figure 7 photo for the parking lot 

PV installation. 
 12 

Figure 7. Typical Solar panel installation for parking areas. 

(Photo Courtesy of Andrew T. Nekus P.E., SunDurance Energy, anekus@SunDuranceEnergy.com, 

www.SunDuranceEnergy.com, A Conti Group Company) 

Estimated Cost 

PV power generation cannot compete directly with current utility power generation cost. While cost is 

continuing to lower for PV arrays, it will be a considerable time before cost is comparable to central station 

utility power cost. An approximate cost is projected here with the assistance of UNICOR FPI for the 

assumptions above and is given in Table 4.

Table 4 

SOLAR ELECTRIC SYSTEM COST - BUILDING 1250

PV Panel and Installation Costs $8 to $9 Million 

AC/DC Inverters $3 to $4 Million 

O&M (5 Years) $1 Million 

TOTAL $12 to $14 Million 
 13 

The use of PV power generation does allow for other cost reduction scenarios to be accomplished which 

include: 

1. Rent car parking spaces with electric car charging hook up 

2. Water runoff and reuse 

3. Black out and brown out protection 

4. Power agreement with Dominion Virginia Power for sale of excess power generation 

5. Dominion Virginia Power cost sharing to meet renewable energy portfolio energy 

requirements 

6. No need for Center to buy renewable energy certificates 

A report by Ernest Tucker, U.S. DOE, Office of Energy Efficiency and Renewable Energy on 

September 23, 2011 stated, “Installed Cost of Solar PV Systems in the U.S. Declined. The installed cost of 

solar photovoltaic power systems in the United States fell substantially in 2010 and into the first half of 2011.” 

Tucker also cited a report released on September 15 by DOE's Lawrence Berkeley National Laboratory where 

the average installed cost of residential and commercial PV systems completed in 2010 fell by roughly 17 

percent from 2009, and by an additional 11 percent within the first six months of 2011.”(8) This gives hope 

that PV cost will eventually be lowered to the point that it can be used for utility scale electric generation. 

A study by Lawrence Berkeley National Laboratory shown by Figure 8 revealed that the cost of 

commercial PV systems is in a downward trend, and the cost of these systems makes them more attractive for 

deployment. Strategies should be developed to look for opportunities to install PV systems from commercial 

vendors as an alternative power system at reasonable cost for Building 1250. 

Figure 8. Installed cost trends over time for behind the meter PV, by PV system size (5)
 14 

Risks

Project risks are complex and difficult to quantify, but the following are potential risk that must be 

considered when incorporating PV systems. The first is the risk of potential damage to the facility within the 

40 years potential lifespan due to inclement weather. Hampton Roads is subject to hurricanes, tornados, and 

other adverse weather, and such weather could damage some PV panels. The advantage of PV arrays is that 

damaged panels can be isolated and quickly replaced thus preventing the entire system from being 

decommissioned. The second project risk is component malfunction and single point failure. This risk can be 

minimized by having adequate redundancy. If redundancy is not provided for the DC/AC inverters, then the 

replacement period for either repair or re-manufacture of an individual inverter can be 12 to 16 months. The 

loss of a sole inverter will cause the entire solar electric system to be off line. Another risk is that advancing 

PV technology may create breakthroughs that significantly improve performance over the current installed PV 

system. While this may happen a unique advantage of PV power generation is the component nature of the 

technology. For instance newer higher efficiency panels can be interchanged with the older panels over time 

without a major new system cost. The component nature of PV system makes it relatively insensitive to 

technology maturation. 

Conclusions

Climate change will impact NASA installations, requiring them to reduce energy cost and carbon 

footprint. These impacts will affect both the near and long term operational posture of the center and influence 

the capability to meet mission requirements. LaRC has completed preliminary investigations to ascertain the 

impacts of localized changing environmental conditions and has identified the need for improving solutions to 

address electrical power demands. An investigation was conducted to evaluate solar photovoltaic systems for a 

single building (Building 1240) as a representative case for a sustainable power source application. The PV 

system would achieve the goal of having Building 1250 classified as a net-zero energy building as it would 

produce as much energy as it uses over the course of a year. 

Based on the facility’s electrical demand of 200,000 kWh per month, a PV system of 1.9 MW would 

provide sufficient power. While current PV installation cost is high, the cost for large PV system is decreasing. 

The PV system would supply the needed solution for sustainability given that operation and maintenance is a 

significant component of the overall system deployment. 

The project will provide a robust system for supply of alternative power. A 1.9 MW solar electric power 

system will be required. The project will provide the desired net-zero supply using on-site renewable energy as 

a solar PV system. Operation and maintenance of the system must be included with the installation. 

The following benefits will be incurred by implementation of a PV system: 

 Sustainability goals established by Executive Order may be achieved 

 Environmental benefits by removal of pollutants from rainwater/parking area runoff and beneficial 

reuse of rainwater 

 Use of electrical powered transportation will be encouraged by charging stations 

 Beneficial use of lands not available for other uses 

 An alternative electric power system provides a strategic additional level of redundancy to the existing 

electric power system 

 Sale of unused electricity output 

 Reduced carbon footprint 
 15 

Nomenclature 

A Amps 

AC alternating current 

DC direct current 

DOE Department of Energy 

EO Executive Order 

HVAC heating ventilation and air conditioning equipment 

kW kilowatt 

kWH kilowatt hours 

LaRC Langley Research Center 

MW megawatt 

NASA National Aeronatic and Space Administration 

O&M operation and maintenance 

PV photovoltaics 

REC Renewable Energy Credits 

V Volts 

W         Watt

References 

1. Climate Change Impacts for NASA Langley Research Center and the Hampton Roads Region of 

Virginia, Alycia Bean and Russell De Young, NASA TP, 2011. 

2. http://www1.eere.energy.gov/buildings/commercial_initiative/printable_versions/zer_energy_options.ht

ml

3. Langley Research Center, New Town Master Plan. 

4. Code of Virginia, Title 10.1 Conservation, Chapter 21 Chesapeake Bay Preservation Act, as adopted by 

the Virginia General Assembly in 1988. 

5. Tracking the Sun IV Contents An Historical Summary of the Installed Cost of Photovoltaics in the 

United States from 1998 to 2010 Environmental Energy Technologies Division, Lawrence Berkeley 

National Laboratory, Primary Authors: Galen Barbose, Naïm Darghouth, Ryan Wiser, Joachim Seel. 

6. Photovoltaic Power for Future NASA Missions, Landis, G. A., Bailey, S. G., NASA John Glenn 

Research Center, AIAA-2002-0718, 2002. 

7. Photovoltaic Cell Operation on Mars, Landis, G. A., Kers, T., 19th European Photovoltaic Solar Energy 

Conference, Paris France, June 7-11 2004. 

8. http://www.renewableenergyworld.com 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

Preliminary Design of a Solar Photovoltaic Array for Net-Zero Energy 

Buildings at NASA Langley

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Cole, Stuart K.; DeYoung, Russell J.

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

NASA Langley Research Center

Hampton, VA 23681-2199

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

National Aeronautics and Space Administration

Washington, DC 20546-0001

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

L-20190

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 31

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

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

14. ABSTRACT

An investigation was conducted to evaluate photovoltaic (solar electric systems) systems for a single building at NASA Langley as a 

representative case for alternative sustainable power generation. Building 1250 in the Science Directorate is comprised of office and 

laboratory space, and currently uses approximately 250,000 kW/month of electrical power with a projected use of 200,000 kW/month with 

additional conservation measures. The installation would be applied towards a goal for having Building 1250 classified as a net-zero energy 

building as it would produce as much energy as it uses over the course of a year. Based on the facility’s electrical demand, a photovoltaic 

system and associated hardware were characterized to determine the optimal system, and understand the possible impacts from its

deployment. The findings of this investigation reveal that the 1.9 MW photovoltaic electrical system provides favorable and robust results. 

The solar electric system should supply the needed sustainable power solution especially if operation and maintenance of the system will be 

considered a significant component of the system deployment. 

15. SUBJECT TERMS

Photovolatics; Power; Solar array

18. NUMBER

 OF 

 PAGES

20

19b. TELEPHONE NUMBER (Include area code)

(443) 757-5802

a. REPORT

U

c. THIS PAGE

U

b. ABSTRACT

U

17. LIMITATION OF 

 ABSTRACT

UU

Prescribed by ANSI Std. Z39.18

Standard Form 298 (Rev. 8-98)

3. DATES COVERED (From - To)

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

509496.02.08.03.69

11. SPONSOR/MONITOR'S REPORT

 NUMBER(S)

NASA/TM-2012-217787

16. SECURITY CLASSIFICATION OF:

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- 11 - 2012