Design and integrated performance estimate of a solar-nuclear hybrid energy power generation system

Abstract

In order to promote the global green energy transition and improve the availability of intermittent renewable energy, a thermodynamic power generation system with hybrid solar and nuclear energy is designed in this paper. The hybrid energy system includes a tower solar concentrating thermal module, a High Temperature Gas-cooled Reactor module and a recompression Brayton cycle power generation module. The sodium nitrate-potassium nitrate molten salt is utilized for heat transfer and storage. The EBSILON simulation software is used for model simulation and operational analysis of the system. The effects of different working fluids (S-CO₂, He, He-Xe, N₂, Air) and solar radiation parameters on the power generation performance of the system are investigated. The results show that the power generation efficiency increases with the elevation of turbine inlet pressure, but the efficiency gain is lower with the increase of pressure due to amplified exergy loss. The power generation efficiency of the system increases proportionally to the increase of turbine inlet temperature. Comparative analysis confirms the utilization of S-CO₂ can achieve higher efficiency than the other four fluids and its optimal split ratio is 0.279. As the maximum pressure of the cycle increases, the optimal split ratio of S-CO₂ decreases gradually. When the working conditions of the main compressor is near the supercritical point of S-CO₂, the power generation efficiency reaches the maximum. The system is more sensitive to the change of isentropic efficiency of turbine, and the power generation efficiency of the system increases by 0.7 % for every 1 % increase in isentropic efficiency. With the increase of solar irradiance and solar altitude angle, the concentrated heat collection power and efficiency of the solar thermal field increase. With the increase of solar irradiance, power generation efficiency and the output electric power of the system increases first and then decreases, peaking at 750 W/m²and 800 W/m² respectively. The optimal operating temperature of the Brayton cycle module increases from 512 ℃ at 600 W/m² to 640℃ at 750 W/m² and then drops to 610 ℃ with DNI elevation. In the process of decreasing the proportion of solar energy in the total input energy from 36 % to 16 %, the cycle efficiency of the system decreases continuously.