Techno-Economic Analysis and Optimal sCO2 Power Cycle Configuration for Novel CSP Plants Adopting Tubular Fluidized Particles Central Receivers

Concentrating Solar Power (CSP) plants, thanks to the use of cost-competitive Thermal Energy Storage (TES), can provide back-up power guaranteeing a zero-emission alternative to conventional power plants and offer of balancing services on the electrical grid. Current state-of-the-art solar tower plants are based on conventional steam Rankine cycles and adopt solar salts both as heat transfer and storage fluid in a direct 2-tanks TES system. However, the 2022 average CSP levelized cost of electricity, equal to 0.118 $/kWh, is still remarkably higher than other renewable technologies. Next generation CSP solar towers are expected to employ novel high-temperature receivers able to reach temperatures above 700°C, leading to improved efficiency of the power block and thus to more competitive technoeconomic performances. In this context, the Horizon Europe Powder2Power project aims at demonstrating at the MW-scale the operation of an innovative tubular solar receiver adopting fluidized particles that will allow to reach temperature as high as 750°C while ensuring intra-week storage capacities at reduced cost, thereby increasing the flexibility and the competitiveness of CSP generation and its value for the grid. For such a high temperature and high flexibility application, the adoption of sCO2 Brayton cycles as power conversion systems is the most recommended option thanks to their high efficiency, compactness of turbomachinery, simple plant arrangement, no water consumption, and fast transients in operation. This work aims to confirm the potential advantages of this power block technology for next generation CSP plants based on tubular fluidized particles solar receivers. A MATLAB+REFPROP V10 numerical model is developed to calculate the system overall efficiency and the capital cost for different cycle configurations, and it is employed to identify the optimal techno-economic solutions which can minimize the specific cost of the overall CSP plant. The model implements ad-hoc routines for the component sizing and uses referenced cost correlations for each component of the power block (compressor, heat rejection unit, recuperators, and turbine) and of the solar field (heliostat, tower, and receiver). Results allow selecting the optimal sCO2 power cycle configuration and nominal design parameters, also considering the tradeoff on the solar-to-electricity efficiency and the total investment cost of the system.