Simplified method for predicting photovoltaic array output

A simplified procedure for predicting the long term, monthly average electrical output of photovoltaic arrays is presented. It is restricted to passively cooled, max-power tracked arrays, but is applicable to both south facing, fixed flat arrays and 2-D tracked concentrators. The procedure combines basic parameters characterizing the array with the local monthly mean temperature and the monthly KT (ratio of the total radiation on the horizontal to the extraterrestrial radiation) to yield a monthly average array efficiency which, when multiplied by the monthly array insolation gives the electrical energy output.