Lightweight reactor design by additive manufacturing for preheating applications using metal hydrides

Thermal energy storage systems based on metal hydrides can be a solution for preheating fuel cells (FCs). They can provide thermal energy at temperatures below ?20 °C during startup, while heat at 50 °C during operation is sufficient for regeneration. The challenge of such a system in mobile applications is the final weight specific thermal power. In this study, a reactor design based on additive manufacturing techniques for ~300 g of metal hydride is presented. Here, a reactor (passive) to hydride (active) mass ratio of 0.97 is realized, still reaching high weight specific thermal power of up to 2.1 kW/kg_MH at ?20 °C and 8 bar (LmNi_4.91Sn_0.15). Considering the example of preheating a FC from ?20 °C in ~120 s, the performance of LaNi₅ and LmNi_4.91Sn_0.15 is studied. While LaNi₅ requires higher regeneration temperatures than LmNi_4.91Sn_0.15 (>40 °C compared to >20 °C), its performance is less sensitive to operative variations due to its nearly ideal thermodynamic characteristic.