PV Temperature Prediction in BIPV, BAPV, BIPV/T During any Day Based on a Generalized Expression of the Ross Coefficient

Abstract

The PV temperature, Tpv, in a BIPV and BIPV/T structures was studied experimentally and theoretically. For this a holistic formula was used based on the Ross coefficient prediction under any environmental conditions accounting additionally for the building thermal parameters. It was shown that the slope of the PV temperature,Tpv, vs the solar radiation, IT, on the BIPV modules corresponds to a generalized expression of the Ross coefficient, f, which must account for the BIPV thermal conditions, too. The profiles of the Ross coefficient for BIPV/T, BAPV and free standing PV operating in the same site were determined, compared and discussed. The theoretical and experimental analysis of a BIPV/T test cell disclosed that Tpv vs IT is a linear function in all cases from sunrise till solar noon with a practically constant slope and coefficient of determination, R2>0.96. Correspondingly, from noon to sunset the linearity still holds but with a lower slope which depends on the insulation of the building and the increased ambient temperature during sunset compared to sunrise, which is the usual case. An improved version of a Tpv prediction holistic formula was developed to take into account the building thermal parameters, the ratio of the PV surface over the building surface, and the environmental parameters. This new and improved methodology for the f and Tpv prediction for both morning to noon and noon to sunset periods was tested against measured Tpv vs IT and the predicted results confirmed its validity.