High-temperature thermochemical energy storage using metal hydrides: Destabilisation of calcium hydride with silicon

The thermochemical energy storage properties of calcium hydride (CaH2) destabilised with either silicon (Si) or CaxSiy compounds at various molar ratios, were thoroughly studied by a combination experimental and computer assisted thermodynamic calculations. Particularly, the destabilisation effect Si on CaH2 five different ratios (1:1, 1:2, 2:1, 3:4, 5:3 to Si) was extensively investigated. Theoretical calculations predicted multi-step thermal decomposition reaction between forming varying temperatures, which confirmed in-situ synchrotron X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis mass-spectroscopic measurements. most suitable reactions that meet criteria system for next-generation concentrated solar power (CSP) plants identified. CaSi (in 2:3 ratio CaSi) showed desirable operating conditions temperature 747 ± 33 °C hydrogen pressure 1 bar. Pressure composition isothermal measurements conducted this determine its practical enthalpy form Ca5Si3. calculated value (107.3 kJ mol?1 H2) lower compared experimentally determined (154 4 H2). This mismatch mainly due formation CaO solid solution in addition desired Ca5Si3 phase.