Multi-layer thermal models of PV modules for monitoring applications

An essential task in devising photovoltaic power plant energy production capacities is based on the evaluation of a PV module thermal behavior from meteorological conditions in a given place. In this context up to 5 °C error in the operating temperature can be acceptable and so simplified (one-layer) models can be adopted. Multi-layer models (three layers) allow not only to calculate more precisely the PV cell temperature but also to evaluate both front and back layer temperatures. The presented five-layer model is useful to evaluate also the front and back cover superficial temperatures. These two temperatures, especially the back temperature, can be measured during the operation of a PV module, so it is likely to tune on-line the thermal model and calculate very precisely the inner temperature. In this paper five multi-layer models, that differ for the modeling of the convective terms into the heat balance equations, are described and checked against measured data on a glass to glass PV module equipped with temperature sensors. The dynamic models have been compared by means of a numerical code implemented in Matlab environment. The numerical results put also in evidence the uncertainties introduced by the environmental variables (ambient temperature, irradiance, wind speed) measurements.