Dependence on geographic location of air mass modifiers for photovoltaic module performance models

Air mass modifiers are frequently used to represent the effects of solar spectrum on PV module current. Existing PV module performance models assume a single empirical expression, a polynomial in air mass, for all locations and times. In this paper, air mass modifiers are estimated for several modules of different types from IV curves measured with the modules at fixed orientation in three climatically different locations around the United States. Systematic variation is found in the effect of solar spectrum on PV module current that is not well approximated by the standard air mass modifier polynomial.