Energy, exergy and sustainability analysis of a photovoltaic-thermal solar system with nano-enhancement and thermal energy storage integration

Abstract

As a result of using various energy sources such as fossil fuels, harmful gases emerge and endanger the world's future. The search for different energy sources is to diminish the dangers that may arise in the future. Renewable energy sources are also the most basic for a sustainable future. This study aims to increase the performance of photovoltaic thermal collectors (PVT), which are used to obtain thermal energy from solar energy and produce electrical energy. The novelties of this experimental work are the analysis of a combination of a solar air heater and thermal energy storage via a phase change material technology and surface modifications on absorber plates, including a nanotechnological amendment. Furthermore, the adverse impacts on the environment of the manufactured systems were taken into account with the help of such parameters as waste exergy ratio and sustainability index. Initially, PVT with a V-grooved absorber surface (V-PVT) was built. In the second stage, nano-enhanced V-grooved PVT (NE/V-PVT) was produced, in which the absorber plate was coated by graphene nanoparticles. Then, a thermal energy storage entity was mounted onto the system, and the V-grooved PVT with the thermal energy storage entity (TS/V-PVT) was developed. 40 W absorber fans were used to provide airflow in these manufactured collectors. In addition, Styrofoam insulation material was used for the collector case, and a low-cost system was designed. Simultaneous experiments for each PVT were carried out. The waste exergy ratio (WER) and the sustainability index (SI) were also considered. Based on the experimental results, thermal efficiency was calculated as 40.60%, 54.01%, and 53.90% for V-PVT, NE/V-PVT, and TS/V-PVT, respectively. Furthermore, the coefficient of performance (COP) values were obtained as 2.67 for V-PVT, 4.28 for NE/V-PVT, and 3.49 for TS/V-PVT. The findings illustrated that nano-coating and V-grooved modifications on solar collectors substantially increased the system performance.