Experimental optimization of the heating element for a direct-coupled solar photovoltaic water heater

Abstract

In the last few years, the price of photovoltaic (PV) modules has decreased significantly. As a result, solar PV has become an interesting option for water heating. In a direct-coupled PV water heater (DPVWH) system, the PV array is directly connected to the heating element. Therefore, the optimization of the heating element resistance value is an essential step to design a DPVWH system. This research aims to optimize the resistance value of the heating element for different climatic conditions (Montreal and Bagotville in Canada, and Fez in Morocco). Simulation models were developed using MATLAB/Simulink and TRNSYS software to evaluate the performance of a PV system directly connected with the heating element over a one-year period. This simulation model was validated with an experimental setup. The coefficient of determination (R2) ranges from 98.75% to 99.89%. The results of the experimental optimization indicate that in areas with high incident solar irradiation, the optimal resistance value is low, while the opposite is true for areas with lower solar irradiation. Furthermore, it is found that a direct-coupled PV water heater with a capacity of 3000 Wp achieves an average annual solar fraction of 41% in Montreal, and 73% in Fez. Additionally, the simulation results show that the use of an MPPT (Maximum Power Point Tracking) controller could increase the PV energy production by 29% in average. However, a direct-coupled PV solar water heater system is recommended for a remote and cold region, due to its robustness, its low operating cost, and its simplicity.