NIST logo

Publication Citation: A Comparison of Predicted to Measured Photovoltaic Module Performance

NIST Authors in Bold

Author(s): Arthur H. Fanney; Brian P. Dougherty; Mark W. Davis;
Title: A Comparison of Predicted to Measured Photovoltaic Module Performance
Published: June 27, 2007
Abstract: Computer simulation models to accurately predict the electrical performance of photovoltaic modules are essential. Without such models, potential purchasers of photovoltaic systems have insufficient information to judge the relative merits and cost effectiveness of photovoltaic systems. The purpose of this paper is to compare the predictions of a simulation model, developed by Sandia National Laboratories, to measurements from photovoltaic modules installed in a vertical wall facade in Gaithersburg, MD. The photovoltaic modules were fabricated using monocrystalline, polycrystalline, tandem-junction amorphous, and copper-indium diselenide cells. Polycrystalline modules were constructed using three different glazing materials - 6 mm low-iron glass, 2 mm ethylene-tetrafluoroethylene copolymer (ETFE), and 2 mm polyvinylidene fluoride (PVDF). In order to assess the simulation model's ability to predict photovoltaic module performance, measured solar radiation data in the plane of the modules is initially used. More comparisons are made using horizontal radiation measurements. The ability of the model to accurately predict the temperature of the photovoltaic cells is investigated by comparing predicted energy production using measured versus predicted photovoltaic cell temperatures. The model was able to predict the measured annual energy production of the photovoltaic modules, with the exception of the tandem-junction amorphous modules, to within 6% using vertical irradiance measurements. The model overpredicted the annual energy production by approximately 14% for the tandem-junction amorphous panels. Using measured horizontal irradiance as input to the simulation model, the agreement between measured and predicted annual energy predictions varied between 1% and 8%, again with the exception of the tandem-junction amorphous silicon modules. The big difference between measured and predicted results for the tandem-junction modules is attributed to performance degradation
Proceedings: Energy Sustainability 2007
Pages: 15 pp.
Location: Long Beach, CA
Dates: June 27-30, 2007
Keywords: computer simulation; photovaltaic module; specifications; parameters; irradiance; temperature; radiation measurements
Research Areas: High Performance Buildings
PDF version: PDF Document Click here to retrieve PDF version of paper (287KB)