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Building Environment Division
NIST’s Solar Photovoltaic System
A portion of the energy used at the NIST campus in Gaithersburg, MD is being provided by renewable energy. A solar photovoltaic system is being installed on the roof that connects the main Administration Building to its adjoining conference and cafeteria facilities. The solar system will reduce the quantity of electricity purchased to power the NIST campus and reduce the monthly peak demand charges.
The system consists of 234 photovoltaic modules and associated electronics. Each module, containing 72 monocrystalline photovoltaic cells, produces up to 4.8 amps of direct current electricity at 34 volts under ideal solar conditions. The individual modules are interconnected with the resulting electrical output converted to alternating current by means of an inverter. The system will power the lights in four floors of the Administration Building, approximately 600 lights. Extruded polystyrene insulation panels, on which the modules are mounted, provide additional roof insulation reducing the heating and cooling loads to the building.
The system is projected to generate approximately 33,000 kilowatt hours of electricity on an annual basis, enough energy to meet the total electrical needs of three to four average residences. During nighttime conditions, the building receives all of its electrical power from the local utility in a normal manner. No batteries are used in this grid-interconnected system.
Cross-section of Photovoltaic Module
NIST Contacts
Plant Division –
Mark E. Kuklewicz
301) 975 – 6918
E-mail mark.kuklewicz@nist.govHeat Transfer and Alternative Energy Systems Group –
A. Hunter Fanney
(301) 9755864
E-mail hunter.fanney@nist.govFrequently Asked Questions
How much did the system cost and who provided the funds?
The NIST Plant Division provided the funds for this project, $240,000, using funds earmarked for energy conservation projects.
What was the incentive to install the system?
NIST is committed to reducing energy consumption at both its Gaithersburg and Boulder sites and the use of advanced technology.
How large is the system, and how much of the sunlight is converted into electricity?
The area of the photovoltaic system is 173.6 m2 (1869 ft2). The individual cells on each module convert 13.3% of the sunlight into electricity at standard rating conditions.
What are the environmental benefits of using this photovoltaic system?
Over the projected 30-year lifetime of the system it is estimated that over 2,100 lbs of NOx, 6,100 lbs of SOx, and 756 tons of carbon dioxide will be avoided.
Would the system perform better if it were tilted towards the sun?
Performance enhancement from tilting depends on the latitude and climate. Improvement from tilting is relatively small, since tilting the panels increases the energy collected during the winter at the expense of energy collected during the summer months. Tilting the panels also requires spacing between the panels to avoid inter-row shading.
Are photovoltaic systems available for residential applications?
Yes, several manufacturers are offering complete systems for residences. The array for a typical residence provides 2 to 4 kW compared to the 28 kW used in this installation.
Do the panels need to be cleaned regularly to operate properly?
No, it has been found that soiling has a marginal effect on the performance of the solar cells.
How is the photovoltaic system attached to the roof?
The extruded polystyrene sheets to which the photovoltaic modules are mounted are interconnected to each other using a tongue and groove construction. The outer perimeter of the panels is connected to a concrete ballast. No penetrations through the roof were required to install the photovoltaic system.
Does NIST have other installations of photovoltaic panels?
Yes, the Building and Fire Research Laboratory at NIST has a research program underway to develop models that can accurately predict the annual energy production of building integrated photovoltaics. As part of this program, panels using various photovoltaic cell technologies have been installed in the south wall of the Building Research Laboratory.
More information available ...
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Date created: 8/10/2001
Last updated: 11/17/2003
