A study of new method and comprehensive evaluation on the improved performance of solar power tower plant with the CO₂-based mixture cycles

This study provides an exploration on improving the performance of solar power tower (SPT) plant via integrating with the CO₂-based mixture Brayton cycle, and proposes a comprehensive comparison method. The effects of the crucial parameters on the SPT system are firstly revealed. Then, a comprehensive evaluation method is proposed based on 3 performance metrics including exergy efficiency, specific work and temperature difference of the main-heater, which are used to assess the thermodynamic performance and the compatibility between the thermal storage system and power cycle. Finally, the trade-off relationships of these metrics are found. The optimal layout, additive and operating parameters are also pointed out based on the comparative results to meet different design requirements. The findings show that the effects of crucial parameters on the performance of SPT system are not monotonous and individual criterion cannot comprehensively evaluate the system performance. Using xenon as an additive can yield excellent performance with higher exergy efficiency and better compatibility between cycle and thermal storage system than the CO₂ alone. While the ability to generate specific work is decreased to 105–112 kW·kg⁻¹ with xenon-added that compares to the inter-cooling S-CO₂ cycle (121–130 kW·kg⁻¹). When the exergy efficiency is required higher than 33%, the inter-cooling CO₂/xenon cycle is the primarily recommended layout for its large specific work and good compatibility between the thermal storage system and cycle. The findings provide a novel way to improve the efficiency of SPT system as well as the compatibility between the cycle and thermal storage system.