P. Godart, J. Fischman, D.P. Hart
Keywords: aluminum, hydrogen, activation, fuel cell, hydrogen vehicle, emergency power, desalination
Summary:Aluminum has an energy density of 83.8 MJ/L (40x Li-ion, 8x liquid hydrogen), and in recent years, we have seen the development of promising aluminum-based fuels that can be used as alternative, highly energy-dense sources of hydrogen. By using various methods including ball milling, alloying, or surface treating with other metals, bulk aluminum can be made reactive with water, enabling the release of its internal energy as hydrogen gas and heat. These processes allow for a system where aluminum fuel is stored, shipped, and used to produce hydrogen later on site, overcoming current logistical challenges with hydrogen storage. We present here a review of these aluminum fuel technologies, as well as an in depth look at a novel process developed in our group at MIT in which aluminum is activated by infusing a gallium-indium eutectic into the grain boundaries via a simple surface treatment. This process, which only alters the composition of the original aluminum by 3% by mass, allows the treated aluminum to remain mostly inert to oxygen but highly reactive with water. The eutectic itself is non-reactive and can therefore be recovered and recycled to make new fuel. Research at MIT has proven the efficacy of the fuel production process and the fuel’s ability to react completely with water to produce hydrogen and heat. We also present here our recent power applications of this fuel, including a 3-kW emergency generator, a 10-kW fuel cell power system integrated into a BWM i3, and a process for utilizing the thermal energy released in the aluminum-water reaction for directly powering seawater desalination.