Metal hydride based thermal energy storage system requirements for high performance concentrating solar power plants

High temperature concentrating solar power plants require suitable thermal energy storage systems to produce electric power efficiently. Thermochemical energy storage based on metal hydrides represents a very appealing prospect for low cost and high efficient solar storage systems. The objective of the paper is to assess the properties required by the metal hydride systems to achieve the U.S. Department of Energy's SunShot techno-economic targets. A simplified model has been developed to evaluate the cost and the exergetic efficiency of hydride-based storage systems. Results demonstrate that metal hydride materials, operating at temperatures higher than 650 °C, with reaction enthalpy on the order of 95-110 kJ/molH2, raw material cost on the order of 1.4-2 $/kg, weight capacities on the order of 3-4% and operating pressures on the order of tens of bars have the potential to closely approach the targets. Selected sensitivity analyses have also been carried out showing that the raw material cost, the material weight capacity and the metal hydride reaction enthalpy are the properties that strongly affect the performance of the storage system.