Abstract:
Although the metal hydride CaH2 possesses a remarkably high hydrogen-based energy storage density, its application in thermal energy storage systems for next-generation concentrated solar power plants presents a challenge due to its 1100 °C decomposition temperature. These plants are expected to operate within a range of 600 to 800 °C, which makes CaH2 unsuitable for use as a reversible hydrogen storage medium. To mitigate the limitations of calcium hydride’s thermal stability, this research uses advanced computational modeling to explore the impacts of calcium vacancy formation on decomposition temperature. Computations were conducted using the Korringa-Kohn-Rostoker method alongside the coherent potential approximation used to model disordered systems. The findings reveal that increasing the concentration of calcium defects in the material correlates with a significant rise in formation enthalpy from −184.5 kJ·mol−1H₂ at 0% calcium defect concentration to −106.9 kJ·mol−1H₂ at 15% calcium defect concentration, along with a marked reduction in decomposition temperature from 1127 °C (0%) to 538 °C (15%). The findings also reveal a significant increase in storage capacity of CaH2 as Ca vacancies are increased, from 4.789 (0%) to 5.586 wt% (15%). Moreover, increasing concentrations lower the activation energy, which enhances hydrogen diffusion and facilitates efficient hydrogen release.
Soufiane Bahou, Improving the thermal energy storage performance of calcium hydride via vacancy defects for next-generation concentrating solar power, Journal of Energy Storage, Volume 153, Part A, 2026, 120885, ISSN 2352-152X, https://doi.org/10.1016/j.est.2026.120885
