High performance metal hydride based thermal energy storage systems for concentrating solar power applications

• The degradation of hydrogen capacity of NaAlH4 and Na3AlH6 were compared.
• The cycling stability of NaAlH4 was enhanced by the addition of ENG and Al additives.
• Costs of two metal hydride pairs were calculated and compared.
• Future direction for high temperature material development is discussed.

Thermal energy storage systems based on metal hydride pairs using high efficiency materials are evaluated. The low temperature metal hydrides NaAlH4 and Na3AlH6 were cycled to determine stability of hydrogen capacity over extended cycling. Addition of aluminum and expanded natural graphite were found to enhance the cycling stability of NaAlH4. Potential high temperature metal hydrides were investigated based on NaMg materials. A techno-economic analysis was performed to evaluate the performance a thermal energy storage system based on two metal hydride pairs: NaMgH3:NaAlH4 and NaMgH2F:Na3AlH6. The resulting analysis suggests that the two systems have the potential to reach low cost and high efficiency performance targets.