Evaluation of power output for fixed and step tracking photovoltaic arrays

Abstract A computer program, simulating the insolation on a flat plate photovoltaic array and the energy obtained from it, assuming maximum power point operation, is developed. Unlike old models, the diffuse insolation is not considered isotropic and is estimated by a formula derived by Klucher. A correction is made to this formula, to avoid overestimation of the diffuse insolation. The input data are those of the Typical Meteorological Year, available for 26 locations around United States. Using this program the insolation available on fixed arrays, at different orientations and tilts, for Phoenix, Az., Madison, Wi., and Miami, Fl., is evaluated on a monthly basis. Tracking and stepwise tracking arrays are examined and the advantages of various tracking modes are pointed out. The effect of ambient temperature and reflection from the array's surface on the energy is investigated on a quantitative basis. Finally, the energy output from fixed and continuous tracking arrays is correlated to insolation and ambient temperature and an empirical formula is developed.