Comprehensive evaluation of proton exchange membrane fuel cell-based combined heat and power system with Lithium-ion battery under rule-based strategy

The proton exchange membrane fuel cell-based combined heat and power (PEMFC-CHP) system can recycle waste heat generated by PEMFC and improve energy utilization. With the electrical and thermal demand curves as input, the PEMFC-CHP system (1 kW) with a Lithium-ion battery operating under a rule-based strategy is studied to analyze the electrical and thermal output characteristics. Efficiency, matching degree, economy, hydrogen consumption, and carbon emission are comprehensively studied. The input power of the PEMFC-CHP system is the electrical demand and the operation time of each case is three days. Results show that with the rule-based strategy, the PEMFC and Lithium-ion battery can be properly operated and the electrical demand can be well satisfied. However, there is a thermal deficit that can be alleviated yet still exist even if the rule-based strategy is improved. Compared to the original system, the difference between the maximum and minimum value of T_tank decreases from 14.77 K to 13.52 K for the improved strategy and the PEMFC can be operated with reduced fluctuation. Therefore, the CHP system with an electrical heater added is further explored, which can meet the electrical and thermal demand perfectly leading to the matching degree as 100 %. Finally, the PEMFC-CHP systems are compared with traditional system in terms of economy and carbon emission. The off-grid PEMFC-CHP system can reduce carbon emission by 52.47 % but with an additional daily cost of 2.43 $. Considering the implementation of the carbon tax, the hydrogen price below 1.98 $ kg⁻¹ can render the PEMFC-CHP system overwhelming the traditional system.