Assessment of thermal and electrical performance of flat plate air-cooled photovoltaic roof tile – experimental and numerical studies

The current state of development of the solar energy sector necessitates a new form of incentive for entities to invest in photovoltaic (PV) installations. Building-integrated photovoltaic/thermal (BIPV/T) systems are gaining increasing interest. Effective methods for heat recovery from BIPV/T collectors are searched for. Presented research experimentally and numerically considered the influence of cooling conditions on the electrical efficiency and heat recovery potential of PV roof tiles, using air as cooling medium. An experimental system consisted of PV roof tile module, casing and twenty halogen lamps, acting as a sunlight simulator. Temperature of PV roof tile and the casing, together with electrical current and voltage as well as volumetric air flow rate were controlled. Based on the experimental system, a numerical model was prepared in the ANSYS Fluent software. It takes into account two configurations of flow channel height 25 and 50 mm, various values of solar irradiance (from 300 to 900 W/m2), and a set of different volumetric air flow rates (from 4.5 to 7.5 m3/h). An approach based on the SST k-ω turbulence model and Discrete Ordinates (DO) radiation model was proposed. Among all the configurations investigated, the variant with a flow channel height of 25 mm exhibited a higher heat recovery potential. At extreme parameter values (solar irradiance of 900 W/m2, volumetric air flow rate of 7.5 m3/h), the highest heat flux, removed by the air, reached 330 W/m2. The highest thermal efficiency, up to 48.7% and 44.2% for the 25 and 50 mm channel height variants, respectively, was achieved at a solar irradiance of 300 W/m2 and a volumetric air flow rate of 7.5 m3/h. A high correspondence between experimental and numerical results was obtained, indicated by the root mean square percent error (RMSPE) of thermal efficiency at the range from 4.42% to 9.33%. The highest electrical efficiency (5.76%) was achieved for solar irradiance of 600 W/m2 and a volumetric air flow rate of 7.5 m3/h, for the variant with a channel height of 50 mm. These findings contribute to a better understanding of the influence of flow channel geometry and cooling conditions on module performance, supporting the design of more efficient and economically viable BIPV/T systems.