Geological conditions deep in the earth under Rüdersdorf are optimal for building caverns because 150 million years ago, there was a sea here. Today, what remains of it is a layer of salt rock that begins at 600 metres below the surface and continues down to 2,500 metres.
A hole that leads down to the salt rock has already been bored. A pipe will be pushed into this hole and cemented in place. This is slightly wider than a ring binder and extends down to where the test cavern will be built, at a depth of 1,000 metres.
Water is pumped into the hole through the pipe. The water dissolves the salt and a dome 500 cubic metres in size and filled with salt water – “sole” – is formed. This is the size of a swimming pool that is 25 metres long, 10 metres wide and 2 metres deep. This makes the test cavern only around one thousandth of the size of the natural gas cavern most recently built on the Rüdersdorf site.
When the cavern is later filled with hydrogen, the salt water is removed and disposed of in a climate-friendly manner. A pipeline transports the sole to a brine operating station in Heckelberg. There, it is piped into a natural underground salt water reservoir.
EWE built this station in the late 1990s when the first cavern was built in Rüdersdorf. It will continue to operate – for example, for expansion measures such as this.