1. High-temperature thermochemical energy storage using metal hydrides: Destabilisation of calcium hydride with silicon.
- Author
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Griffond, Arnaud C.M., Sofianos, M. Veronica, Sheppard, Drew A., Humphries, Terry D., Sargent, Anna-Lisa, Dornheim, Martin, Aguey-Zinsou, Kondo-Francois, and Buckley, Craig E.
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HEAT storage , *ENERGY storage , *HYDRIDES , *ENERGY consumption , *CALCIUM , *DIFFERENTIAL scanning calorimetry , *SILICON - Abstract
The thermochemical energy storage properties of calcium hydride (CaH 2) destabilised with either silicon (Si) or Ca x Si y compounds at various molar ratios, were thoroughly studied by a combination of experimental and computer assisted thermodynamic calculations. Particularly, the destabilisation effect of Si on CaH 2 at five different molar ratios (1:1, 1:2, 2:1, 3:4, 5:3 CaH 2 to Si) was extensively investigated. Theoretical calculations predicted a multi-step thermal decomposition reaction between CaH 2 and Si forming Ca x Si y at varying temperatures, which was confirmed by in-situ synchrotron X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis and mass-spectroscopic measurements. The most suitable destabilisation reactions between CaH 2 and Si or Ca x Si y that meet the criteria of a thermal energy storage system for the next-generation of concentrated solar power (CSP) plants were identified. The CaH 2 and CaSi system (in a 2:3 molar ratio of CaH 2 to CaSi) showed desirable operating conditions with a decomposition temperature of 747 ± 33 °C at a hydrogen pressure of 1 bar. Pressure composition isothermal measurements were conducted on this system to determine its practical enthalpy of decomposition to form Ca 5 Si 3. The calculated value (107.3 kJ mol−1 H 2) was lower compared to the experimentally determined value (154 ± 4 kJ mol−1 H 2). This mismatch was mainly due to the formation of CaO and a CaSi solid solution in addition to the desired Ca 5 Si 3 phase. ga1 • Calcium hydride has been thermodynamically destabilised with silicon. • A multistep decomposition pathway was determined by theoretical calculations. • The experimental thermal decomposition pathway and thermodynamics were established. • The Ca–Si system is a viable thermal energy storage material. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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