Material Challenges and Alloy Selection for Particle/s‐CO₂ Heat Exchangers in Concentrated Solar Power Systems

Combining supercritical CO 2 (s‐CO 2 ) cycles with particle‐based heat transfer media for concentrated solar power (CSP) plants offers great potential if the material challenges can be overcome. The core challenge in integrating these systems is the particle/s‐CO 2 heat exchanger, which must handle extreme conditions, such as high temperatures, high pressures, and erosion from both CO 2 and hot particles. The mechanical requirements for such a heat exchanger are exceedingly high, demanding materials that can resist CO 2 ‐corrosion and high stresses due to the operating conditions in the supercritical fluid. In addition, the heat exchanger material must also withstand severely erosive conditions due to the hot heat‐carrying particles sliding on the outside of the tube walls. The best selection of an appropriate heat exchanger alloy is discussed, considering cross‐references from supercritical and ultrasupercritical steam boilers and supercritical CO 2 cycles in nuclear power applications. A method is shown to estimate the mechanical requirements, as well as the challenge of determining the corrosion and erosion allowance. Ultimately, the material requirements and challenges are summarized for creating a practical and durable heat exchanger to support the integration of supercritical CO 2 ‐based cycles with CSP plants. Future research and material testing are defined to overcome the final hurdles.