Design and Analysis of an Integrated Hydrogen-Thermal Energy Storage System for Cogeneration

At present, the large amount of low-grade waste heat generated by proton exchange membrane fuel cell (PEMFC) cannot be efficiently and economically utilized, so this study proposes an integrated hydrogen-thermal energy storage system for cogeneration, which employs solid thermal energy storage (STES) to generate high-value steam at 573.5 K and 1 MPa. Through establishing a steady state model of the system, this study shows the influence of steam mass flow rate variations on waste heat recovery efficiency, system efficiency, net power output, and STES capacity. Building on thermodynamic results, an economic model assesses market competitiveness through lifecycle cost analysis. Results show that the system achieves maximum efficiency of 97.55 %, which was 27.55 % higher than steam and power cogeneration system of PEMFC coupled high temperature heat pump. Under optimal conditions, waste heat recovery efficiency peaks at 100 %, with net power output minimized at 0.9765 MW and STES capacity maximized at 55.75 MWh. Economic analysis reveals that the payback period for achieving maximum efficiency is minimized 5.97 years when utilizing green hydrogen priced at 30CNY/kg. Substituting blue hydrogen priced at 20CNY/kg reduces the payback period to 4.27 years. The unit hydrogen energy revenue in all efficiency ranges surpasses that of traditional hot water supply systems. Sensitivity analysis shows valley electricity and steam prices drive revenue in high efficiency scenarios, while peak electricity dominates under low efficiency.