Effect of the Metal Hydride Tank Structure on the Reaction Heat Recovery for the Totalized Hydrogen Energy Utilization System

Abstract

A Totalized Hydrogen Energy Utilization System (THEUS) is proposed for load leveling and stabilizing the grid. The THEUS is a novel unitized regenerative fuel cell system that achieves high overall efficiency through optimized heat utilization. In this paper, a metal hydride tank (MHT) is chosen as hydrogen storage. In the MHT, the heating and cooling from adsorption/desorption processes is used to produced heated and chilled water for building ventilation systems. A new horizontal type MHT was developed to enhance the recovery rate of the reaction heat. This tank has a double coil heat exchanger and contained 50kg of AB5 metal hydride. The experimental results were compared with the results which were developed previously at AIST. The new tank results showed an improvement for the heat recovery rate which is the ratio of recovered energy to the entire reaction heat of the metal hydride. The reaction heat recovery was improved due to the decrease of the thermal capacity of the tank.

Research and development for a metal hydride tank with double coil type heat exchanger below 1.0 MPa (G) operation

“…After the first absorption process, the reaction heat recovery rates decreased as compared with the results in the individual absorption-desorption test because a part of the reaction heat was consumed in the heating or cooling of the metal hydride material and the stainless-steel tank. Even if the operating pressure range was different, it could be confirmed that the heat recovery ability was almost the same as that of the metal hydride tank at SRNL [16].…”