ENEA research and innovation on thermal energy storage for CSP plants

Thermal Energy Storage is a key factor for efficiency, dispatchability and economic sustainability of Concentrating Solar Power plants. Since 2001 ENEA has developed new CSP plants concepts using molten salts as heat transfer fluid, in which TES is a crucial component. Starting from its experience, to reduce the cost of solar energy, ENEA has been continuing to study innovative solutions for TES systems, increasing energy density, reducing volumes and costs, and maintaining a high heat exchange efficiency. The storage cost reduction, together with the solar field cost decrease, would make the CSP energy competitive compared to fossil sources. The study of new storage materials and new and efficient solutions for heat exchange are the basis of today research. Two different TES concepts have being developed: the first one is based on particular concretes used as sensible heat storage medium. The second one envisages new types of latent heat TESs in which the phase change materials can be mixed with a small amount of nanoparticles to increase their thermo-physical characteristics. First results are very interesting for energy storage amount, charging/discharging times and cyclability, and permit, in a short-medium time perspective, to develop modular TESs concepts. In a long time perspective, ENEA aims to set up a new research topic on thermochemical storage systems to increase energy density and storage period. This allow the realization of TES with large thermal capacity and seasonal utilization avoiding plants oversizing or fossil thermal backups, contributing to solar plant cost reduction and green-energy amount increasing.