Optimal voltage of direct current coupling for a fuel cell–battery hybrid energy storage system based on solar energy

Abstract

A hybrid energy storage system based on a polymer electrolyte membrane fuel cell and a battery is designed and applied using solar energy in this study. The fuel cell and batteries are connected using a direct coupling method. The optimal DC coupling voltage is examined by turning the fuel cell operation on and off. The voltage difference is first evaluated and it is found that a 2 V difference yields the optimal condition with the longest operating time and transition period without system failure. Various on–off couples are then determined. It is found that an on–off​ couple of 49–51 V presents the best transition period, indicating the good harmonized operation between the fuel cell and batteries. Therefore, an on–off couple at 49–51 V for fuel cell operation is the optimal and suitable DC coupling voltage according to this work system.