Thermodynamic performance analysis of a novel energy storage system consist of asymmetric PEMEC and SOFC combined cycle

Abstract

Accessing energy storage systems at the grid or renewable energy sources can effectively solve the problem of unstable renewable energy generation. Hydrogen is considered as a potential energy storage medium due to its high energy density and environmental friendliness. In this paper, a novel hydrogen energy storage system is proposed to solve the problem of grid volatility caused by renewable electricity. The system consists of asymmetric PEMEC and SOFC. Asymmetric PEMEC produces high pressure hydrogen directly by electrochemical reaction without mechanical compressor. This will simplify the system structure and improve the stability of the system. Hydrogen-fueled SOFC and ORC-sCO2 waste heat recovery systems enable efficient power generation with no carbon emissions. On the basis of the thermodynamic modeling of the system, the energy analysis, exergy analysis and the sensitivity analysis were performed. The results show that the round-trip thermal and exergy efficiencies are 54.29% and 50.34%, respectively, and the energy storage density is 367.92 kWh·m−3. The sensitivity analysis revealed that the PEMEC hydrogen production rate and SOFC operation temperature are the main influencing parameters for the system energy efficiency. Increasing the PEMEC hydrogen production rate will reduce the charging time, but the system energy efficiency will be significantly reduced. SOFC operation temperature increased from 700 °C to 1100 °C, the system round-trip exergy efficiency increased by 12.02%. PEMEC operating pressure has a slight impact on system energy efficiency, so it is not considered as a main influencing parameter. But, increasing the PEMEC operating pressure can significantly increase the system energy storage density, which is beneficial for energy storage system. In summary, the novel hydrogen energy storage system proposed in this paper provides theoretical guidance and new ideas for the practical application of hydrogen energy storage system.