Energy efficient cold start of a Polymer Electrolyte Membrane Fuel Cell coupled to a thermochemical metal hydride preheater

Abstract

Cold start is still a major factor for proton exchange membrane (PEM) fuel cell degradation. Using a metal hydride-based preheater can significantly reduce the time to reach temperatures above 0 °C without consuming any extra energy due to two specific features of the fundamental thermochemical reaction: First, thermal energy provided during fuel cell operation as waste energy can be stored long-time and loss-free for the next cold start event. Second, providing a hydrogen pressure of 8 bar immediately triggers the exothermal absorption reaction to heat up a system from temperatures as low as −20 °C. The manuscript presents the first in time results of a system with a 1 kW PEM fuel cell starting from temperatures of −5 °C with and without an active preheating module at a hydrogen pressure of 6 bar. The experiments indicate that the single-cell voltage behavior is improved when the preheating module is active as the lowest values measured are in the range of 0.6 V in contrast to 0.45 V without a preheater. These findings are supported by simulation data of the modeled system, which indicates severe ice formation of up to 87 % in case of the cold start without a preheater in comparison to <1 % ice formation with a preheating module.