Performance comparison and evaluation of four compressed CO₂ energy storage systems integrated into tower solar power generation

The compressed CO2 energy storage system has emerged as a promising and efficient technology that has received increasing attention in recent years. However, research on its integration with solar tower power generation remains limited, leading to an insufficient understanding of its operating characteristics, overall performance, and key governing parameters in solar power applications. To address this research gap, the manuscript constructs four compressed CO2 energy storage systems integrated with solar tower technology, namely subcritical, transcritical, liquid, and supercritical configurations. The effects of key design parameters on system performance are examined in a systematic manner, and a comparative evaluation of the four systems is provided. A comparative assessment of the four systems is presented, and a representative day simulation is performed for the most competitive configuration. Results reveal that higher turbine inlet temperature, energy storage pressure, and energy release pressure consistently enhance energy storage density, whereas compressor inlet pressure exerts non-uniform influences. Among the four systems, the liquid CO2 configuration shows distinct advantages in energy storage density while maintaining high energy, thermal, and exergy efficiencies. Under summer solstice conditions, heliostat field efficiency is more sensitive to direct normal irradiance than receiver efficiency, with maxima of 69.41% and 88.20%, respectively. During the winter solstice, shorter duration and lower intensity of solar radiation restrict storage capacity and reduce the discharge period to around 8 h, although rated power output can still be sustained.