One of the key challenges of Hydrogen going forward will be the development of compact, reliable, safe, and cost-effective storage.
Hydrogen fuel is one of the most energy-dense materials in terms of weight. However, in terms of volume, it is significantly less dense than diesel fuel. Hydrogen is typically stored at 700 times atmospheric pressure or 700 BAR. At this pressure, Hydrogen fuel is still around 3-4 times less energy-dense than diesel. As such, finding more compact ways to store Hydrogen fuel is essential to Hydrogen Fuel.
One simple way of Hydrogen Storage, and the method used by modern first-gen fuel cell vehicles, is simply to place Hydrogen in a specialized tank. Specifically, 700 BAR Type IV pressure vessels, which have a plastic liner overwrapped by expensive carbon-fiber composite material to provide strength. However, Carbon Fiber is expensive, running at more than 10X times the cost of steel per kg. Currently, researchers are looking at ways to either reduce the cost of Carbon Fiber or come up with an entirely new material that is cheaper but fits Carbon Fiber’s purpose.
New Hydrogen storage methods are also being developed. Of all the potential ways of storing Hydrogen, most fall into 2 categories: sub-ambient temperatures based, or materials based.
Sub ambient storage takes advantage of the fact that gasses are denser at lower temperatures, even if the pressure is unchanged. Currently, researchers are looking at ways to design better insulation systems, as well as researching how different materials react to super-low temperatures.
Materials based storage means chemically binding Hydrogen to anther material that allows Hydrogen to exist densely at lower pressures. One method takes advantage of Avogadro’s Hypothesis, which states that all gasses at the same pressure, temperature, and volume contain the same number of molecules. A hydrogen molecule, H2, contains 2 Hydrogen atoms. Therefore, any material that contains more 3 or more Hydrogen atoms will be more compact (eg, ammonia, or NH3). Other forms of materials-based storage see Hydrogen bonding with other elements to form solids. For all materials-based storage, cost is a major obstacle. However, developing materials that can rapidly discharge Hydrogen when needed is also crucial to material based storage.
Production and consumption of Hydrogen are only parts of the puzzle. Developing better storage methods is another crucial step.