Metal hydride reactor for output temperature control

Abstract

Precise temperature control of fuel cell stacks is crucial to avoid degradation mechanisms and thus to extend lifetime. The present study demonstrates that metal hydride based modules can assist in controlling this temperature by serving as active thermal energy storage. The reversible reaction of metals with hydrogen is characterized by a temperature pressure correlation. Therefore, the temperature as well as the thermal power at which the thermal energy is released can be defined by the gas pressure. This enables the design of temperature controllers using the pressure as actuating variable on the metal hydride device. In this study, an existing metal hydride reactor based on LaNi4.85Al0.15 is integrated into a hydrogen and cooling fluid testing infrastructure. Based on experiments indicating the step response behaviour, the parameters for a 0D model have been identified. A PI controller was designed based on simulations and implemented on the test rig hardware. First experimental results show that it is possible to stabilize the temperature of the cooling fluid circuit to 70°C ± 1.5 K while a thermal power of +755 W/kgMH and 140 W/kgMH is provided for absorption and desorption, respectively.