Enhanced models for the evaluation of electrical efficiency of PV/T modules

Recently increasing attention has been paid on photovoltaic/thermal (PV/T) solar systems as these systems allow to generate heat and electricity simultaneously. Thermal and electrical performance of PV/T modules are coupled, so it is crucial to monitor both efficiencies to decide the optimal operating point. In this context, this paper aims to investigate numerically and experimentally the electrical energy performance of PV/T modules suitable to be used for online monitoring and control purposes. This study proposes a novel methodology for the evaluation of the electrical efficiency of PV/T modules as a function of the temperature of the cooling fluid, the solar radiation and the solar incidence angle. The proposed methodology is based on the calculation of the cell temperature of the PV/T module, which is in turn a function of the temperature of the cooling fluid and the specific features of the PV/T module. Models proposed in the literature for the evaluation of the electrical efficiency for PV modules have been redrafted, adapting them to PV/T modules. The proposed methodology has been validated using the experimental data carried out on an unglazed pilot PV/T plant located in Catania (Italy). The comparison between the calculated data by the developed redrafted models and observed data gives rises to a normalized Root Mean Square Error (nRMSE) of 9.73%. It is worth noticing that the accuracy of the models increases taking into consideration of the dependence of the electrical efficiency from the solar incidence angle (nRMSE equal to 8.99%).