Experimental study on charging and discharging characteristics of copper finned metal hydride reactor for stationary hydrogen storage applications

Abstract

With the shift in power generation methods from conventional to renewable, the need for energy storage has increased, and hydrogen as a carrier has great potential. The storage of hydrogen is one of the main obstacles to the effective deployment of the hydrogen economy. Since metal hydride offers a higher energy density than conventional methods, it can potentially be used to store and deliver hydrogen. Also, the metal hydride hydrogen storage system is the primary element of the energy storage system that connects hydrogen production and consumption. Therefore, the present study is focused on the development and testing of a metal hydride reactor. In the present experimental study, 9 kg of La0.7Ce0.1Ca0.3Ni5 is loaded in a single tube copper finned reactor attached to an external jacket, and the charging and discharging characteristics related to hydrogen storage are analysed along with variations in its thermal performance under various operating conditions. Also, the effect of HTF temperature on the hydrogen release performance of the copper finned reactor is studied under constant discharge pressure and constant discharge flow rate. Further, a comparison has been made between the copper and aluminium finned reactors. This fabricated copper finned reactor attained volumetric and gravimetric storage densities of 21.78 kg per m3 of H2 and 0.77%, respectively. The results indicated that La0.7Ce0.1Ca0.3Ni5 filled within the copper finned reactor stores 1.45 wt.% (130.7 g) of hydrogen in 680 s, corresponding to 25 bar feed gas pressure. At the HTF temperature of 60 °C, the copper-finned reactor discharged 1.42 wt.% (127.3 g) of hydrogen in 1450 s, showing the release of 98% of the stored mass of hydrogen. Further, the developed copper finned MH reactor could supply hydrogen at a constant rate of 13 lpm with a capability of 90% discharge even at a discharge temperature of 30 °C. Beside this, the comparative results showed that adding copper fins showed a considerable improvement over aluminium fins during discharging compared to the charging process. The copper-finned reactor consumed 20.9% and 23.6% less time to release 1 wt.% of hydrogen than the aluminium-finned reactor at discharge temperatures of 40 °C and 50 °C, respectively.