Design and development of nitrate-nitrite based molten salts for concentrating solar power applications

This study presents new alternative molten salt mixtures as energy storage media in concentrating solar power technologies. The commercial Hitec mixture and new ternary reciprocal mixtures with lithium nitrate were studied. Various techniques were used in order to examine the thermal and rheological properties of the selected salt mixtures. The results show for the new mixtures a decrease of the melting temperature up to 65 degrees C lower than the commercial Hitec. Thermal stability under a nitrogen atmosphere is stable up to at least 600 degrees C for all the mixtures analyzed. With the lithium nitrate addition, the heat capacity is improved and the viscosity at the critical temperature (close to the solidification temperature) is reduced. The evaluation of the melting point, heat capacity, thermal stability and viscosity showed that the new molten salt mixtures have great potential applications in thermal storage systems despite the cost of lithium nitrate. The operational range can be extended since a larger Delta T reduces the salt amount and hence the capital costs of a thermal energy storage system.