Storage in salt caverns

There are various ways of storing hydrogen, both underground and above-ground. For the Netherlands, salt caverns appear to be the most practical and affordable solution. We have been using these caverns for a long time for the safe storage of natural gas. New caverns can be developed relatively quickly, within seven years or so. Moreover, the storage of hydrogen in salt caverns is already being used safely in other countries, such as the United States and the United Kingdom.

In the subsurface near Zuidwending in Groningen a salt layer has been pushed up to a mountain of salt as big as Mont Blanc. Salt is extracted from the salt mountain by drilling holes and leaching them with water. This makes the Netherlands one of the few countries in Europe with salt caverns that have a large storage capacity. This makes storage in salt caverns the most efficient for the Netherlands. Large quantities of hydrogen can be stored at relatively low cost with an efficiency of approximately 98 percent.

Pre-designated holes must be flushed out in such a way that they become suitable for gas storage. They are cigar-shaped, somewhat further apart from each other and four to six times smaller than caverns that are only used for salt production. Ten locations have been licensed for gas storage by the Ministry of Economic Affairs. Six are already in use as natural gas storage. The remaining four can be used for hydrogen storage, provided licences for this are granted by the Ministry of Economic Affairs. From the granting of permits through drilling and leaching to the conversion of the cavern, the entire process takes about seven years.

When the salt cavern is clean enough, we can connect an installation to it. Pipes and valves connect the ground level to the cavern, which starts at a depth of 1,200 metres. Each cavern will have room for at least 6 kilotonnes of hydrogen. One central installation regulates the pressure, production and injection of all hydrogen caverns. With this volume and power, an underground hydrogen storage facility becomes a huge battery under the ground that can store energy for a long time.