A novel route for coal-fired power plants flexibility through the integration of H2/O2 burning and solid oxide electrolysis cells: Design and performance evaluation

The flexible operation of coal-fired power plants (CFPPs) is of significant importance for the penetration of large-scale renewable energy and can enhance the stability and reliability towards the power grid. As an alternative solution, coupled solid oxide electrolysis cells (SOEC) and H2/O2 burning technology allows for both the flexibility of CFPPs and low-cost H2 production. For the integration system proposed in this paper, the extra main steam from CFPPs in extracted for H2 production during the charging process while H2/O2 burning is adopted for additional power generation during the discharging process. For SOEC, a maximum H2 production capacity of 6.1 kg/s with the corresponding unit electrical consumption of 3.328 kWh/Nm3 can be achieved during the charging process. The maximum power generation growth for CFPPs rises from 223 MW to 240 MW with increasing operation temperatures of SOEC during the discharging process. The integration system can achieve a lowest unit load of 14.2 % THA with a maximum round-trip efficiency of 74.65 %. Exergy analysis indicates that the exergy efficiencies of the turbine and extraction system in the discharging process are higher than those in the charging process while the maximum exergy efficiencies of the H2/O2 burner and SOEC are available under 700 °C for SOEC.