Use of cold start-up operations in the absence of external heat sources for fast fuel cell power and heat generation in a hydrogen energy system utilizing metal hydride tanks

Abstract

In this study, cold start-up operations for a stationary hydrogen energy system utilizing metal hydride (MH) tanks, named Hydro Q-BiC™, are conducted for emergency power outages, i.e., when no power from both grid and renewable energy sources are available. Here, cold start-up refers to the heating of cold MH tanks and an increase in desorbing pressures to the minimum required for fuel cell (FC) operation to supply power and heat continuously. Our proposed procedure uses only the existing system components to generate power and heat. No external heat sources are used. Power was supplied from a Li-ion battery, and hydrogen was produced by the electrolyzer (ELY), stored in the MH tanks and used by the FC. Three internal heat sources were used to heat the MH tanks: ELY waste heat, MH reaction heat, and FC heat output. Two H2 storage capacities were tested (75% and 50%) and both supplied ≥30 kWh electricity within 30 min. Although a minor energy loss of 5275 kJ (⇔ 1.97 kWh) was sustained, overall, the procedure yielded an acceptable energy efficiency of 79%.