Current concentrated solar power (CSP) plants that operate at the highest temperature use molten salts as both heat transfer fluid (HTF) and thermal energy storage (TES) medium. Molten salts can reach up to 565°C before becoming chemically unstable and highly corrosive. This is one of the higher weaknesses of the technology. Solid particles have been proposed to overcome current working temperature limits, since the particle media can be stable for temperatures close to 1000°C. This work presents a review of solid particles candidates to be used as HTF and TES in CSP plants in open receivers. In addition, the interactions between solid particles with major system components are described in this review, for example, with TES system or heat exchanger. The parameters and properties of solid particles are identified from the material science point of view explaining their nature and the relation to the power plant efficiency and lifetime durability. Finally, future development is proposed; such as material selection according to each specific design, materials characterization, or durability test.

Thermal Energy Storage Materials (TESMs) may be the missing link to the “carbon neutral future” of our dreams. TESMs already cater to many renewable heating, cooling and thermal management applications. However, many challenges remain in finding optimal TESMs for specific requirements. Here, we combine literature, a bibliometric analysis and our experiences to elaborate on the true potential of TESMs. This starts with the evolution, fundamentals, and categorization of TESMs: phase change materials (PCMs), thermochemical heat storage materials (TCMs) and sensible thermal energy storage materials (STESMs). PCMs are the most researched, followed by STESMs and TCMs. China, the European Union (EU), the USA, India and the UK lead TESM publications globally, with Spain, France, Germany, Italy and Sweden leading in the EU. Dissemination and communication gaps on TESMs appear to hinder their deployment. Salt hydrates, alkanes, fatty acids, polyols, and esters lead amongst PCMs. Salt hydrates, hydroxides, hydrides, carbonates, ammines and composites dominate TCMs. Besides water, ceramics, rocks and molten salts lead as STESMs for large-scale applications. We discuss TESMs’ trends, gaps and barriers for commercialization, plus missing links from laboratory-to-applications. In conclusion, we present research paths and tasks to make these remarkable materials fly on the market by unveiling their potential to realize a carbon neutral future.