Environmental and thermophysical pre-selection of low-melting point molten salts for thermal energy storage in concentrated solar power systems

Abstract

Environmental impact, energy efficiency, and cost optimization are key factors during the strategic selection of Thermal Energy Storage materials for concentrated solar power plants, where low-melting point Molten Salts are positioned as one of the preferred alternatives due to their operational stability, high heat capacity, and low vapor pressure. In this study, 12 low-melting point Molten Salts were thermophysically characterized (the traditional Solar Salt, Hitec®, Hitec XL®, and 9 new formulations), and their environmental performance per unit of heat transfer was assessed using SimaPro 10.1 software, the ReCiPe 2016 assessment method, the Ecoinvent 3.11 database, and the “cradle-to-grave” approach. The results show that the LiNO3 Molten Salts, specifically Salt #5, have the best thermophysical properties and the lowest impact values (95.29 mPt/MJ), and achieved the more favorable results in 7 of 22 impact categories and in the three damage areas for intermediate cost values per unit of heat transfer (2.88 €/MJ). Furthermore, it is found that Solar Salt obtained the highest environmental impact score (335.44 mPt/MJ). The novelty of this work lies in the combined thermophysical and environmental pre-selection of low-melting point Molten Salts per unit of heat transfer. The knowledge gained in this study will provide a detailed view of the environmental impacts of concentrated solar power plants, thereby improving decision-making criteria for responsible managers and contributing to the decarbonization of the energy sector.