Peak-Shaving of the Oxy-Fuel Power Plant Coupled with Liquid O2 Storage

Integrating a high proportion of intermittent renewable energy provides a solution for the higher peak-shaving capacity of coal-fired power plants. Oxy-fuel combustion is one of the most promising carbon reduction technologies for coal-fired power plants. This study has proposed a novel oxy-fuel power plant that is coupled with both liquid O-2 storage and cold energy recovery systems in order to adapt to the peak-shaving requirements. The liquid O-2 storage system uses cheap valley electricity to produce liquid O-2 for a later use in the peak period to enhance the peak-shaving capacity. Meanwhile, the cold energy recovery system has been introduced to recover the physical latent energy during the phase change of liquid O-2 to increase the power generation in the peak period. Technical economies of three power plants, i.e. a 330 MW (e) oxy-fuel power plant as reference (Case 1), the same power plant coupled with only liquid O-2 storage system (Case 2), and the same power plant coupled with both liquid O-2 storage and cold energy recovery systems (Case 3), have been analyzed and compared. Thermodynamic performance analysis indicates that the peaking capacity of Case 3 can reach the range of 106.03 to 294.22 MW (e), and the maximum peak-shaving coefficient can be as high as 2.77. Exergy analysis demonstrates that the gross exergy efficiency of Cases 2 and 3 reaches 32.18% and 33.57%, respectively, in the peak period, which are significantly higher than that of 26.70% in Case 1. Economic analysis shows that through selling the liquid O-2 and liquid CO2, combined with carbon trading, the levelized cost of electricity (LCOE) of the three cases have been greatly reduced, with the lowest one of 30.90 USD/MWh shown in Case 3. For a comprehensive consideration, Case 3 can be considered a future reference of oxy-fuel power plant with the best thermodynamic and economic performance.