Design of metal hydride reactor for medium temperature thermochemical energy storage applications

The performance of a metal hydride (MH)-based TES system depends on its energy and power densities, i.e., the total energy storage capacity and the rate at which it can be charged/ discharged, which are highly influenced by reactor design and material properties. The present study focuses on design of the MH reactor by considering critical parameters such as discharging time, energy and power densities. Firstly, the discharging behavior of the tubular reactors is analyzed and compared. Secondly, an annular MH reactor is proposed to enhance the dis-charging power and reduce the discharging time of the tubular reactors. The results elucidated that the annular MH reactor reduced the discharging time of a 2.5-inch tubular reactor (i.e., 396 min) by 70 %, with only a 16 % reduction in energy storage density. The average specific discharge power of 2.5-inch tubular reactor is increased by similar to 2.5 times with the annular MH reactor. Further, it is found that the number of reactors can be reduced with the annular MH reactor for the equivalent storage capacity and performance. Thirdly, performance of the annular MH reactor is evaluated by applying the conditions experienced by the reactors near the outlet section of a MH reactor array. Finally, radial fins are added to the annular MH reactor to reduce the discharging time for the reactors near the MH array outlet section. The proposed annular MH reactor with radial fins yielded a system-level gravimetric storage density of 560 kJ/kg, much higher than the present sensible and latent heat storage systems.