In Groningen village, heat must come from underground salt

Underneath the Groningen village of Onstwedde is a large salt dome, rock salt pressed upwards that forms an underground layer. But the salt has never been extracted from it. In addition to salt production, countless other destinations have been reviewed.

TNO already examined whether the location is suitable for the storage of natural gas, oil, hydrogen, nitrogen, compressed air and CO2. And there is a plan to use the Onstwedde salt dome, like other salt domes in the Northern Netherlands, as a permanent storage place for nuclear waste.

Mountain landscape of salt

Since this week there is a new plan: heat recovery. The salt dome under the village has the advantage that it is like a kind of underground mountain with a high peak that lies just below the surface.

If you start drilling in the right place, you will come across the top tip of the salt dome after 250-300 meters, which is further down to a few kilometers below the village.

You then apply the technology that is already widely used in the Netherlands for geothermal energy. You get heat up by bringing cold water down through pipes, letting it heat up there and then bringing it up hot to use for heating or as hot tap water.

Theory is also practice?

Henk Groenewold founded the company LTA Energy last year, received a subsidy of 50,000 euros from the province of Groningen and the municipality of Stadskanaal and is now going to test whether the idea – which sounds good in theory – will also work in practice.

“We are installing a geothermal heat exchanger at the top of the salt pier,” he explains. “Then we spray water through it. When it comes to the top, that water is expected to be 35 degrees. It is a way of extracting heat that is already widely used, just not yet in salt pillars. It is a closed system and there is So no pollution of the ground.”

Not so deep

The big advantage of using those salt pillars is that you only have to drill a few hundred meters deep. The job was done in one day. Most geothermal projects require you to be miles underground for a high temperature.

According to Groenewold, salt conducts heat well so that much of the heat at the bottom of the underground salt dome goes to the top of the salt ‘mountain’, just below the village. Another big advantage is that that temperature is high enough to heat the house without an expensive heat pump.

Swimming pool

A test drilling will be started within a few weeks to heat the local swimming pool.

“The swimming pool needs a lot of gas for heating,” says Groenewold. “Fortunately, they still have a good contract.”

Before that ends, Groenewold hopes to show here that heat from salt is a good alternative. “After that we can do the rest of the village.” The idea is that 1200 households will then use the heat from the salt to heat their homes. That’s still a job though. “A drilling is done separately for each house.”

undisputed ideal

The technology can turn out well for Onstwedde, but it only works if there is a salt dome close to the location where you need the heat.

“That is the case in several places here in the north. But Onstwedde is unique, because here the entire village is located exactly above the salt dome.”

The sector association Geothermie Nederland tells RTLZ that it is looking forward to the results of the project. “It is also something new for us,” said a spokesperson. “We are curious about the results of the test drilling.”