A Review of High-Temperature Molten Salt for Third-Generation Concentrating Solar Power

Abstract

Current concentrating solar power (CSP) systems operate below 550°C, achieving annual electricity generation efficiencies of 10%–20%, which primarily employs nitrate molten salts as heat transfer fluids (HTFs). However, nitrate salts decompose at temperature exceeding 600°C, rendering them unsuitable for next-generation CSP systems, which aim to operate above 700°C. This review presents the first comprehensive analysis of high-temperature molten salts for third-generation CSP systems. This highlights the potential of carbonates, chlorides, and sulfates as HTFs due to their extended operational temperature ranges. Guided by phase diagrams, multicomponent molten salts are systematically engineered to achieve desirable thermal properties. The review provides a detailed synthesis of compositions and working temperature ranges for these molten salts, with a particular focus on underexplored sulfate-based salts. It consolidates critical data on the melting points and phase compositions of multicomponent sulfates and examines advancements in thermal property enhancements, including the integration of nanoparticles. By summarizing the latest progress and identifying future research directions, this work offers invaluable insights into the design and application of high-temperature molten salts in next-generation CSP systems.