Performance optimization of water-based PVT collector with dual tanks: A Staircase Cooling Method

The photovoltaic/thermal (PVT) collector integrates photovoltaic and solar thermal technologies, offering an innovative solution for full-spectrum solar energy utilization. The rising module temperature and poor heat transfer efficiency significantly reduce system energy output. The aims of this study propose a dual-tank water system structure to achieve staircase cooling for PVT modules with the graphite-embedded structure. The thermal and electrical performances of various comparative modules are experimentally analyzed under outdoor conditions in Beijing. The results show that the dual-tank system reduces the average cell layer temperature by 12.3 °C under the radiation intensity of 572 W/m2, resulting in a relative increase in electrical efficiency of 8.2 % compared to the PV module. Additionally, the graphite-embedded PVT module achieves a daily average thermal efficiency of 34.41 %, corresponding to a 57.1 % improvement over the tube-and-sheet module of 21.34 % under the radiation condition of 458W/m2. Moreover, the whale algorithm is employed to determine the optimal dual-tank volume for 30 operating conditions during the experiment. The optimized dual-tank configuration achieves a relative increase in daily energy output of 5–20 % compared to a fixed-volume tank. Meanwhile, a third-order polynomial model is established between the optimal tank volume and radiation. This study can provide a reference for the structural optimization of PVT collectors and a feasible practice for enhancing solar energy utilization.