A model was constructed for computation of the maximum power point output of a photovoltaic system from radiation components on the horizontal plane, based on general transposition formulas for beam radiation, the Hay and Davies model for diffuse radiation and assumed seasonal variations in ground reflectance [12]. All radiation components are modified by an incidence angle modifier, expressed by [13], that depends on the effective angles of incidence. The conversion efficiency of the photovoltaic array, dependent on ambient temperature and standard NOCT measurements for solar cells, was modeled from [12]. Standard silicon solar cell parameters were
used and temperature and radiation data were generated for Stockholm with the climate database program Meteonorm 6.0. [14].