Performance investigation of thermal energy storage systems using metal hydrides adopting multi-step operation concept

• A model is established for metal hydride based thermal energy storage systems.
• The thermal energy storage/release processes of the system were simulated.
• A concept called multi-step charging/discharging operation modes was adopted.
• The system performance can be improved by optimizing the operation mode.

The metal hydride based thermal energy storage (MHTES) technology is an attractive option for concentrating solar power. In this paper, a mathematical model was developed for MHTES systems. The charging and discharging processes of thermal energy were numerically analyzed. As shown in the simulation results, the temporal profiles of the average reacted fraction, the fluid outlet temperature and the hydrogen pressure appear to be repeated in a cyclic manner. The mean value of true temperature boost during the discharging process increases as the flowrate of the heat transfer fluid decreases. When the concept called multi-step charging/discharging operation modes was adopted instead of the conventional one-step reaction operation mode, the outlet temperature fluctuation of the heat transfer fluid of the MHTES system can be weakened. The system performance can be further improved by varying the fluid flow rate and optimizing the operation mode.