Measured Impact of a Rooftop Photovoltaic System

Published

August 1, 2003

Author(s)

Arthur H. Fanney, E R. Weise, K R. Henderson

Abstract

A 35-kilowatt roof top photovoltaic system has been installed at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland. The system, located on a the roof that connects NIST s Administration Building to its adjoining conference and cafeteria facilities, produced NIST s first site-generated renewable energy on September 14, 2001. In addition to providing electrical energy and reducing monthly peak electrical loads, the rear surface of each module is laminated to 51 mm of extruded polystyrene enhancing the thermal performance of the roof. A unique ballast system secures the photovoltaic system, eliminating the need for roof penetrations. An instrumentation and data acquisition package was installed to record the ambient temperature, wind speed, solar radiation, and the electrical energy delivered to the grid. Additional solar radiation instruments were installed after it was found that the original solar radiation sensor was influenced by reflections from the south-facing wall of the Administration Building s tower.NIST s electric utility billing schedule includes energy and peak demand charges. The generation charges vary significantly depending upon the time interval - off-peak, intermediate, and on-peak - during which the energy is consumed. The schedule is divided into summer billing months (June-October) and winter billing months (November-May). During the winter billing months, the distribution, transmission, and generation peak demand charges are based on the greatest power demand imposed by the site on the grid. During the summer billing months an additional demand charge is imposed to capture electrical demand during the on-peak time interval.This paper summarizes the monthly and annual measured performance of the photovoltaic system. The monthly energy produced by the system is tabulated. Conversion efficiencies - computed using solar radiation measurements from a single photovoltaic cell radiation sensor, four thermopile-based radiation sensors lA 35-kilowatt roof top photovoltaic (PV) system has been installed at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland. The system, located on the flat roof that connects NIST s Administration Building to its adjoining conference and cafeteria facilities, produced NIST s first site-generated renewable energy on September 14, 2001. In addition to providing electrical energy and reducing monthly peak electrical loads, the rear surface of each module is laminated to 51 mm of extruded polystyrene enhancing the thermal performance of the roof. A unique ballast system secures the photovoltaic system, eliminating the need for roof penetrations. An instrumentation and data acquisition package was installed to record the ambient temperature, wind speed, solar radiation, and the electrical energy delivered to the grid. Additional solar radiation instruments were installed after determining that original solar radiation sensor was influenced by reflections from the south-facing wall of the Administration Building s tower. NIST s electric utility billing schedule includes energy and peak demand charges. The generation charges vary significantly depending upon the time interval - off-peak, intermediate, and on-peak - during which the energy is consumed. The schedule is divided into summer billing months (June-October) and winter billing months (November-May). During the winter billing months, the distribution, transmission, and generation peak demand charges are based on the greatest power demand imposed by the site on the grid. During the summer billing months an additional demand charge is imposed to capture electrical demand during the on-peak time interval.This paper summarizes the monthly and annual measured performance of the photovoltaic system. The monthly energy produced by the system is tabulated. Conversion efficiencies - computed using solar radiation measurements from a single photovoltaic cell ra

Citation

Journal of Solar Energy Engineering-Transactions of the Asme

Volume

125

Issue

No. 3

Pub Type

Journals

Download Paper

Local Download

Keywords

building integrated photovoltaics, NIST, photovoltaic cells, renewable energy, single-crystalline, solar energy

Citation

Fanney, A. , Weise, E. and Henderson, K. (2003), Measured Impact of a Rooftop Photovoltaic System, Journal of Solar Energy Engineering-Transactions of the Asme, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860903 (Accessed December 16, 2024)