Hydrogen storage is moving forward in Europe as the European Union has just provided €5 million to the HyPSTER underground storage project. Led by StorengyThis project consists of the creation of a site for the production and storage of hydrogen in salt caverns. The objective is to test the viability of this type of production and storage on a large scale. Commissioning is scheduled for 2023.
In parallel, other types of hydrogen storage are being developed. When the energy transformed into hydrogen comes from renewable sources, storage reduces the impact of their intermittency and lowers their cost.
Focus on the HyPSTER project and existing storage techniques.
Hydrogen storage in saline cavities in France
The new large-scale HyPSTER project
The hydrogen storage of the new HyPSTER project will consist in testing the viability of underground storage on a large scale.
Led by Storengy, the salt cavern storage project will be accompanied, from 2022, by the construction of a 1MW electrolyser. This will enable the production of green hydrogen on site, based on local renewable energies. Thanks to a fuel cell, the hydrogen can then be converted into electricity.
It will be 2023 before the first tons of converted hydrogen are stored on site in Etrez, France. Eventually, the goal is to produce 400 kg of hydrogen per day and to store up to 44 tons. Moreover, this underground storage technique is already well proven.
A proven method
Indeed, four hydrogen storage sites in saline hydrogen caverns already exist. Three in the United States and one in the United Kingdom. But the HyPSTER project is the first one supported and subsidized by the European Union (5 million euros) via the FCH2JU joint undertaking.
According to Ineris calculations, a 500,000m3 saline cavity under 200 bar pressure could store 150GWh of hydrogen. The salt would also have good sealing ability, low flow losses, and a low degree of hydrogen perversion by microorganisms. Nevertheless, these properties are still to be proven.
Also, other types of storage are currently being developed.
An update on existing storage techniques
In gaseous form at very high pressure
At atmospheric pressure (1 bar) and “room” temperature, hydrogen is a gas. On the other hand, it is so sparse that a m3 can only contain 90mg. This means that it takes 11m3 to store 1kg of hydrogen, the amount needed to travel about 100km.
In fact, to be usable in gaseous form, hydrogen must be maintained at high pressure as a compressed gas at least 700 bars.
Therefore, the materials used in the cylinders and tanks must be waterproof and extremely resistant to pressure. This is why Air Liquide is working in particular on improving the mechanical strength of the materials currently used.
In liquid form at very low temperature
Hydrogen can also be stored in liquid form. However, it is necessary to maintain it below -252.87°C.
Even at low pressure, the density of liquid hydrogen is much higher than when it is gaseous. It thus allows very good storage performance. On the other hand, the conditions for maintaining the liquefaction temperature are extremely restrictive.
In fact, this type of storage is not developed for current mobility applications such as the supply of hydrogen service stations for example. It is rather the high technologies very greedy in energy like the aerospace which make use of it.
In solid form by hydriding
Storage in solid form is also in full development. This consists in the absorption of hydrogen by another material, forming together a hydride. With metals such as magnesium or silicon, the “mixture” thus gives metal hydrides.
This type of storage has the advantage of not being constrained by pressure or temperature. Better still, when hydrogen atoms occupy the “gaps” left by matter, they are paradoxically closer than when they form a molecule together. Hydrogen in a solid container is therefore even more dense than in liquid form.
Thus, the hydride offers a wide range of applications, including nomadic applications and light mobility. Also, its production costs are relatively low.
To solve technical and geopolitical problems
Problems inherent to each type of storage
On the other hand, just like gaseous or liquid storage, solid storage has some disadvantages. In this sense, the extraction of hydrogen from the hydride requires a lot of heat. Its calorific value is thus largely reduced before use.
Same thing but to a lesser extent for high pressure gas. The very small size of the hydrogen atom also requires very high sealing capabilities. Concerning liquid hydrogen, its maintenance at -252.87°C requires great insulation capacities and losses are almost inevitable.
Finally, the price, since hydrogen production is currently less competitive than fossil fuels or renewable energies. On the other hand, storage could help to drive prices down. Also, to reduce losses due to the intermittency of renewable energies.
Storage and transport in gas pipelines ?
The HyPSTER project will thus make it possible to test underground storage on a large scale. On the other hand, salt cavern storage still requires the study of the molecular behavior of hydrogen in a saline environment. This does not address the issue of decentralized production and storage.
This inevitably raises the question of hydrogen transport, especially in a “smart grid” system combining storage and transport. For this, gas pipelines could be a solution. Theoretically, their use is already possible.
Thus, while participating in energy transition efforts, hydrogen storage could also upset the geopolitical balance of power.