Photovoltaic Translation Equations: A New Approach; Final Subcontract Report

New equations were developed for the purpose of evaluating the performance of photovoltaic cells, modules, panels, and arrays. These equations enable the performance values determined at one condition of temperature and irradiance to be translated to any other condition of temperature and irradiance. The equations were developed to satisfy the following goals: (1) The equations should moreaccurately translate the short-circuit current and the open-circuit voltage (Voc). In particular, the influence of irradiance on Voc should be more accurately treated. (2) The equations should more accurately and more simply translate the I-V curve of data point pairs, Ii and Vi. (3) The equations should be based on the use of dimensionless coefficients such as alpha and beta and have units ofdeg C-1 and not, for example, amps/deg C or volts/deg C. (4) An equation should be developed for translating the maximum power without involving the translation of Isc, Voc, or any I-V data pairs. The data presented in this report show good agreement between the analytical predictions made with the new equations versus actual test measurements and superior performance when compared to thecurrent translation equations.