In the present paper, the finite element method is used to perform an exhaustive analysis of the thermal behavior of encapsulated phase change materials (EPCMs), which includes an assessment of several materials in order to identify the best combination of PCM and shell material in terms of thermal energy storage, heat transfer rate, cost of materials, limit of pressure that they can support and other criteria. It is possible to enhance the heat transfer rate without a considerable decrease of the thermal energy storage density, by increasing the thickness of the shell. In the first examination of thermomechanical coupling effects, the technical feasibility can be determined if the EPCM dimensions are designed considering the thermal expansion and the tensile strength limit of the materials. Moreover, when a proper EPCM shell material and PCM composition is used, and compared with the current storage methods of concentrated solar power (CSP) plants, the use of EPCM allows one to enhance significantly the thermal storage, reaching more than 1.25 GJ/m³ of energy density.

Thermal energy storage systems (TES) are a key component of concentrated solar power (CSP) plants that generally use a NaNO₃/KNO₃ mixture also known as solar salt as a thermal storage material. Improvements in TES materials are important to lower CSP costs, increase energy efficiency and competitiveness with other technologies. A novel alternative examined in this paper is the use of salt mixtures with lithium nitrate that help to reduce the salt’s melting point and improve thermal capacity. This in turn allows the volume of materials required to be reduced. Based on data for commercial plants and the expected evolution of the lithium market, the technical and economic prospects for this alternative are evaluated considering recent developments of Lithium Nitrates and the uncertain future prices of lithium. Through a levelized cost of energy (LCOE) analysis it is concluded that some of the mixtures could allow a reduction in the costs of CSP plants, improving their competitiveness.