Air-cooled photovoltaic roof tile as an example of the BIPVT system - An experimental study on the energy and exergy performance

The air-cooled photovoltaic tile is a subject of presented investigations, which focused on improving the overall system efficiency of PV tiles with heat recovery. The operational efficiency of a PV roof tile, together with the construction optimising the air cooling efficiency, were the main points of plans realized at this research stage. The article describes the experimental research consisting of the assessment of electrical, thermal, and total efficiency, as well as exergy efficiency and parameters of a commercial photovoltaic (PV) roof tile, which back wall was cooled by flowing air. An influence of various cooling duct depths and various volumetric flow rates on the system operation was analysed. During the tests, a solar light simulator and a radial fan, providing the assumed volumetric flow rate of cooling air were used. It has been proven that the depth of the cooling duct and the air volumetric flow rate have a crucial impact on the obtained results. Air cooling the back wall of the PV roof tile, lowered the average surface temperature by a maximum of 6.3 K, while the temperature difference, between the surface next to the cooling air inlet and the surface next to its outlet, was a maximum of 23.4 K. Both values were obtained for air cooling with a volumetric flow rate equal to 4 m 3 /h and a channel depth of 25 mm, with a solar irradiance of 900 W/m(2). The overall efficiency was calculated as a sum of the electrical an thermal efficiencies. Its maximal obtained value was about 32%, wherein the highest thermal efficiency was at the level of 27%. An exergy analysis was performed and the exergy efficiency between 5.08% and 9.94% was determined. These results are promising for future utilization of the system consisted of the PV roof tiles together with the cooling ducts. (C) 2020 Elsevier Ltd. All rights reserved.