A methodology for the thermal design and integration of fluidized bed heat exchangers in sCO2-based solar tower plants

Next generation solar tower plants aim at increasing the maximum achievable temperature thanks to the adoption of advanced heat transfer media to exploit the higher efficiency of sCO2 cycles. In this context, the Horizon Europe Powder2Power project aims at demonstrating at MW-scale the adoption of fluidized particles as heat transfer medium in CSP plants. This work focuses on the numerical model for the sizing and simulation of the sCO2-particles multistage heat exchanger to be used in the overall plant analysis. The developed model adopts reliable heat transfer correlations available in the literature to size the heat exchanger based on the target thermal duty and pressure losses. A sensitivity analysis is presented to study the effect of the main design parameters on the component size and efficiency. The model is then used in a case study for the complete techno-economic optimization of fluidized particles based solar tower CSP plants. Results show that the temperature differences at the cold- and hot-end of the heat exchanger greatly influence the minimum number of stages, and that an increase in the number of stages leads to a reduction in the total heat transfer surface. The economic optimization highlights that the fluidized bed heat exchanger represents a marginal share of the plant overall cost. Therefore, there is no advantage in adopting a component with a limited number of stages that would penalize the efficiency. Additionally, in real applications, the number of stages is more likely to be constrained by technical aspects related to component manufacturing.