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.