Coal-based semi-closed CO₂ power generation system temperature-pressure matching variable operating strategy

The large-scale integration of renewable energy into the grid has led to an increasing demand for peak-shaving in power systems. The semi-closed CO₂ cycle, with its advantages of flexible response such as low thermal inertia in direct-fired systems and compact equipment, provides a viable technical path for the development of power sources capable of regulating over a wide load range. This study conducts the one-dimensional design of the compressors which are the key components of the semi-closed CO₂ cycle. Based on the part-load performance of the compressors, operating strategies for the semi-closed CO₂ cycle under variable operating conditions are investigated, analyzing the operating range and performance of the system under different operating strategies. The results indicate that lowering the turbine inlet temperature and increasing the turbine backpressure can prevent regenerator overheating and main compressor stall, respectively. Through temperature-pressure matching, the system can operate within a load range of 30% to 100%, with the net power generation efficiency of 27.0% to 51.6%, and the system’s net power generation load rate can be reduced to as low as 15.7%. Finally, the zone operating strategy based on temperature-pressure matching is proposed, providing a theoretical basis and technical support for variable-condition operation of semi-closed CO₂ cycles.