Experimental study on embedded cooling tube type metal hydride reactor for hydrogen storage, space heating and cooling applications

Metal hydrides offer high energy storage density and are among the safest methods for hydrogen storage and distribution. They exhibit thermal effects during hydrogen absorption and desorption, with heat generation in exothermic reaction and cooling effects in endothermic reaction. The performance of metal hydride reactor depend primarily on factors such as reactor design, alloy composition, and operating conditions. However, experimental studies on novel MH reactor designs, the behavior of MH alloys, and their potential for heating or cooling applications remain limited in the existing literature. In this perspective, the present study focused on analysing the hydrogen storage behaviour and the heating and cooling characteristics of a newly developed La0.7Ce0.3Fe0.75Ni4.25 filled in a embedded cooling tube type metal hydride reactor. A parametric study is conducted to understand the impact of different operating conditions on hydrogen storage capacity, and the rate of heating and cooling outputs. Moreover, the performance of La0.7Ce0.3Fe0.75Ni4.25 is compared with other AB5 alloys reported in the literature. The results revealed that the alloy absorbed 1.45 wt.% (50.7 g) of hydrogen in 858 s with a cumulative heating output of 698.9 kJ at a supply pressure of 20 bar. A slight improvement of 5.7 % in storage capacity and a reduction of 19.3 % in absorption time were observed when the supply pressure was increased from 20 bar to 30 bar. During desorption process, the alloy desorbed 1.02 wt.% (36 g) of hydrogen in 1826 s. Furthermore, at desorption temperature of 25 degrees C, maximum and average rate of cooling output were 0.52 kW and 0.31 kW, resulting in a cumulative cooling output of 532.8 kJ. Further, La0.7Ce0.3Fe0.75Ni4.25 exhibited higher absorption capacity with moderate reaction rates and demonstrated superior cooling rates compared to La0.8Ce0.2Ni5 and La0.7Ce0.1Ca0.3Ni5. This present study is vital for advancing the development of commercial-scale metal hydride-based heating and cooling systems, which have significant potential applications in the automotive sector, commercial buildings, and residential water heating.