Experimental investigation on annular metal hydride reactor for medium to large-scale hydrogen storage applications

Abstract

In the present study, an annular metal hydride reactor equipped with internal radial fins was designed, fabricated and experimented for absorption and desorption characteristics under different operating conditions. The reactor was filled with 9 kg LaNi5 powder. The alloy absorbed 105.57 g of hydrogen in 1184 s under a supply pressure of 10 bar while the inlet temperature and flow rate of the heat transfer fluid were maintained at 25°C and 2.5 lpm, respectively. At the same time, for a fixed absorption mass of 111 g of hydrogen, the alloy desorbed 110 g of hydrogen in 1590 s at an inlet temperature of 60°C. The developed metal hydride reactor offered a system gravimetric and volumetric storage densities of 0.73% and 20.4 kg of H2 per m3, respectively. Further, the performance of the new reactor was compared to published results for an embedded cooling tube reactor with an outer cooling jacket. The comparison results suggested that the internal heat transfer enhancement of the metal hydride bed resulted in a significant improvement in the absorption (about 56%) and desorption (about 44%) performance than the reactor with multiple cooling tubes. The results also revealed better absorption and desorption rates with the water flow rate of 2.5 lpm (annular metal hydride reactor) instead of a very high flow rate of 20 lpm (embedded cooling tube reactor with an outer cooling jacket), saving a significant amount of pumping power. Finally, a modular design based on the annular metal hydride reactor is proposed for medium to large-scale hydrogen storage applications.