Explicit empirical relation for the monthly average cell-temperature performance ratio of photovoltaic arrays

An empirical relation is derived that allows accurate estimates of the influence of cell temperature variations on the output of a photovoltaic array. Monthly average cell-temperature performance ratios, PRT, can be calculated from the latitude of the site and monthly average values of solar irradiance, air temperature and wind speed. The derivation of the empirical relation for PRT is based on intermediate empirical relations and approximations established by the analysis of a database from stations located at various latitudes and having diverse climatic characteristics. The accuracy of the relation is tested against PRT calculations from short-interval data available in the database. Copyright (C) 2006 John Wiley & Sons, Ltd.