OPTIMIZATION OF A GEN3 CONCENTRATING SOLAR POWER SYSTEM WITH A SILICON CARBIDE PRIMARY HEAT EXCHANGER

Abstract

This study evaluates the technical and economic impact of a topology-optimized silicon carbide (SiC) primary heat exchanger on the energy-specific cost and optimized design of Gen3 concentrated solar power (CSP) plants. Gen3 CSP systems aim to replace nitrate salt with solid particles such as silica sand or manufactured ceramics like Carbo HSP 40/70. Particles can operate at temperatures exceeding 1000 °C without material degradation, enabling smaller heat exchangers, reduced parasitics, and higher power-cycle efficiency. However, transferring heat from particles to a working fluid is challenging without direct mixing, which is precluded by extreme pressure differentials between the pressurized working fluid and the particles. Primary heat exchangers in Gen3 CSP systems must tolerate temperatures above 700 °C while resisting continuous abrasive wear. SiC satisfies these requirements and enables operation at elevated temperatures, but higher temperatures do not monotonically reduce energy-specific cost. While efficiency improves, higher temperatures also reduce falling-particle receiver efficiency and increase the cost of turbomachinery, lifts, storage, and piping. These tradeoffs are explored through a detailed techno-economic optimization of a system-level Gen3 CSP model. The model is implemented in a modified version of the National Renewable Energy Laboratory’s System Advisor Model and includes a supercritical CO2 closed Brayton cycle, solar field, receiver, particle lift, thermal energy storage, and primary heat exchanger. Computationally efficient submodels are used for each component in the system. Op-timizations adjust recompression ratio, split fraction, and recuperator conductance to minimize energy-specific cost, while parameters such as turbine inlet temperature are varied parametrically. Results indicate that a topology-optimized SiC primary heat exchanger can reduce energy-specific cost by up to 40% over a baseline. The dominant driver of reduced energy-specific cost is the lower particle flow rate enabled by higher operating temperatures, which increases energy density and reduces parasitic losses.