Performance improvements for green hydrogen-ammonia fueled SOFC hybrid system through dead-end anode recirculation and split transcritical CO2 power cycle

This paper proposes a novel green hydrogen-ammonia fueled solid oxide fuel cell (SOFC) hybrid power system by coupling dead-end anode recirculation with split transcritical CO2 power cycle (STCC). The STCC with dual-temperature heaters adopts split heat absorbing concept to recover cathode off-gas waste heat. The thermodynamic and economic performances of novel system are investigated and compared. Furthermore, the impacts of fuel ammonia mixing ratio, cell stack fuel utilization ratio, STCC CO2 split ratio, fuel price etc. on system performance are revealed. The results show that the introduction of STCC results in a 3.96 % improvement in total system energy efficiency and a 0.6 % reduction in total system levelized cost of electricity (LCOE) compared with standalone dead-end anode recirculated SOFC unit. The extremely high current density is not beneficial to enhance hybrid system thermo-economic performance. For every 0.1 increase in fuel ammonia mixing ratio, total system energy efficiency increases by 0.26–0.85 % and LCOE decreases by 4.6–7.4 %. The optimal STCC CO2 split ratio of recuperator declines with increasing fuel ammonia mixing ratio. Novel hydrogen-ammonia fueled hybrid system offers a high total energy efficiency of 0.7406, and its economic performance advantage over dead-end anode recirculated SOFC declines with decreasing fuel price.