Effect of air gap on a novel hybrid photovoltaic/thermal and thermally regenerative electrochemical cycle system

Abstract

Electricity efficiency improvement of photovoltaic/thermal (PV/T) collector is still received much attention recently because solar energy is regarded as an effective and promising alternative to fossil fuels. A novel PV/T combined with a thermally regenerative electrochemical cycle (TREC) hybrid system is proposed in this paper to improve the overall electricity efficiency by means of converting the thermal energy from the hot water of the PV/T into electricity. As the heat gathering in the PV/T reduces the electrical efficiency of PV but improves both the thermal efficiency of the PV/T and electrical efficiency of the TREC, mathematic models are developed to assess and compare the performance of PV/T-TREC systems with and without air gap. The effects of heat recuperation as well as various working conditions on the overall electricity performance of hybrid systems are studied and analyzed. The results show that the PV/T-TREC hybrid system with air gap is superior to the one without air gap. Hybrid systems are better than PV/T and PV collector in all scenarios except for large wind velocity scenarios. The maximum improvement of the overall electrical efficiency is up to 1.79% at the solar radiation of 1000 W/m2. Additionally, at the ambient temperature of 5 °C, most cases at water inlet temperature below 15 °C can achieve a peak power generation. This paper may guide the design, optimization and application of the novel PV/T-TREC hybrid system to improve the overall electricity efficiency of solar energy.