The European HyPSTER Project is coordinated by Storengy and brings together seven partners from France, England and Germany. It aims to design and operate an industrial demonstrator for the production, underground storage, and use of green hydrogen. This project is located at the underground natural gas storage site at Etrez (Ain Department). This site is the ideal candidate for a project of this kind with, on one hand, operational salt cavities in the subsoil which can be converted in future to store hydrogen and, on the other hand, the river Rhône is nearby, being an industrial corridor with multiple potential users and uses.
The principle involves using electricity from renewable energy sources to produce hydrogen by electrolysis. This is then compressed and stored in an underground reservoir, in a salt cavity. The hydrogen is then tapped on demand. There are various potential uses for hydrogen, such as direct use by injection into the gas network, as a base substance in a wide range of industries, or after being converted into electricity to power vehicles.
Storing natural gas in salt cavities has been done for over 50 years, both in France and elsewhere in the world. So, from a technical and financial point of view, as well as in terms of safety, this technology is mature. Conversely, there is much less past experience of storing hydrogen in salt cavities, as there are only 4 such cavities in the world; in the United Kingdom and the United States.
Even though these cavities have been operated for decades without notable incident, hydrogen storage that aims to regulate variations in the production of renewable energies - which are by their very nature intermittent - will lead to far greater stress on the salt cavities, with more frequent cycles of injection and withdrawal, perhaps even on a daily basis. The safety aspect of using cavities in this way is still to be demonstrated.
The main risks associated with hydrogen storage in salt cavities are the same as those for the storage of natural gas. That is, a risk of leakage that could lead to ignition or an explosion. Even so, hydrogen’s physico-chemical nature, being a light, mobile, highly flammable substance which can react with the surrounding environment, needs to be considered when analysing and controlling risks. The cavity’s long-term mechanical stability, which is subject to strong, rapid demands, must also be carefully evaluated. These points are what Ineris will be studying in this project.
The HyPSTER Project has just entered it’s initial phase with the underground engineering and surface study. This stage will be carried out by constructing the facilities needed to produce hydrogen upstream (1 MW electrolyser attached to a compressor), and downstream, to treat and store it before it is supplied to users (dehumidifier, buffer storage). In terms of its production, what is called “green” hydrogen will be produced from electricity coming from renewable sources (solar panels, wind farms and hydraulic power). The 1 MW electrolyser will produce 400 kg of hydrogen per day. This represents the consumption of 16 hydrogen-fuelled buses. During the trial phase only a small section of the experimental cavity will be filled with hydrogen, so 2 to 3 tons of hydrogen. In a later commercial phase, this cavity could eventually reach a final capacity of 44 tonnes, equivalent to the consumption of 1,760 hydrogen-fuelled buses. The energy benefits are what make this project so strategic. However, it is important to make sure it is done in complete safety.
