A metal hydride system for a forklift: Feasibility study on on-board chemical storage of hydrogen using numerical simulation

This paper describes a technical feasibility study of on-board metal hydride storage systems. The main advantages of these systems would be that of being able to replace counterweights with the weight of the storage system and using the heat emissions of fuel cells for energy, making forklifts a perfect use case. The main challenge is designing a system that supplies the required energy for a sufficiently long period. A first draft was set up and analyzed to provide a forklift based on a fuel cell with hydrogen from HydralloyC5 or FeTiMn. The primary design parameter was the required amount of stored hydrogen, which should provide energy equal to the energy capacity of a battery in an electric vehicle. To account for highly dynamic system requirements, the reactor design was optimized such that the storage was charged in a short time. Additionally, we investigated a system in which a fixed amount of hydrogen energy was required. For this purpose, we used a validated simulation model for the design concepts of metal hydride storage systems. The model includes all relevant terms and parameters to describe processes inside the system's particular reactions and the thermal conduction due to heat exchangers. We introduce an embedded fuel cell model to calculate the demand for hydrogen for a given power level. The resulting calculations provide the required time for charging or a full charge depending on the tank's diameter and, therefore, the necessary number of tanks. We conclude that the desired hydrogen supply times are given for some of the use cases. Accordingly, the simulated results suggest that using a metal hydride system could be highly practical in forklifts.