A photovoltaic module thermal model using observed insolation and meteorological data to support a long life, highly reliable module-integrated inverter design by predicting expected operating temperature

Accurate prediction of photovoltaic (PV) module temperature is needed to understand the expected electrical performance, lifetime, and reliability of photovoltaic cells. A photovoltaic AC module (PVAC) integrated the inverter directly with the PV module which exposes the power electronic circuitry to the thermal environment of the PV module. This has been reported to impose additional requirements on component selection and circuit design. However, a worst-case stack up analysis can lead to the conclusion that module-integrated inverters require industrial grade components or expensive thermal management. This paper presents a detailed thermal model for the PV module that uses real-world operating conditions, based on observed data from the National Renewable Energy Laboratory (NREL) to calculate PV module temperature. Results from the model confirm that the peak PV module temperature can reach over 80degC, which was expected from other techniques, but that these peak temperatures occur on average for only 8 minutes per year in locations similar to Tucson, Az. Since the PV module temperature is found to be less than 70degC for 99% of the operation hours, thermal management is not onerous and that the use of lower cost, commercial grade components will provide a mean time between failure (MTBF) to support an inverter warranty equivalent to that of the PV module itself.