The stainless steel tank which was part of The Hydrogen Office Project (2008-2014) weighed 7500kg but only stored 11kg of hydrogen at 12bar pressure. These types of tank will have a low hydrogen to tank weight ratio. At higher pressure, like those needed for transport refuelling, the tanks can hold hydrogen at 350bar or 700bar. These tanks are made from carbon fibre composites with a metal lining in order to reinforce the structure of the tank.

Since undertaking the Levenmouth Community Energy Project, BGH now houses 2 tanks, which combined store 50kg at 30bar. These are used not only for our energy storage, but for hydrogen transport too.

There are several other interesting ways to store hydrogen that are currently in the research and development phase. The nearest to deployment is metal hydride storage. Metal hydride storage, where hydrogen is bonded with a metal, can offer a better ratio of hydrogen to tank weight. However, there remain issues with efficiency and the reaction speeds. The small tanks used in Bright Green Hydrogen and Arcola Energy’s UK schools challenge are metal hydride storage tanks.

Another interesting proposal for hydrogen energy storage is chemical synthesis, using hydrogen to produce more commonly used fuels/chemicals. Two interesting prospects for this are synthetic methane and ammonia. In order to produce methane using hydrogen you would require a source of CO₂. It is therefore of interest in the Carbon Capture and Storage industry. This synthetic methane could then be injected into the gas grid to decarbonise the countries gas network. Ammonia is of interest because it is the chemical feedstock used to produce fertiliser. To produce ammonia you only require nitrogen, which is abundant in the air, and hydrogen. This kind of energy storage could allow farmers in remote areas to produce their own fertiliser from local renewable energy.