German town digs deep for hot rock geothermal energy to replace gas networks

Residents in the German town of Geretsried have long wanted to run their buildings with clean heat and electricity from geothermal energy instead of fossil fuels.

Their hopes were dashed about 15 years ago when a drilling company couldn’t find enough hot water close to the surface to be profitable using traditional geothermal technology. That basically left them with fossil gas. 

“We gave up. We had big hopes,” recalled First Mayor of Geretsried Michael Müller.

Today the next generation of geothermal companies is trying to succeed where previous efforts failed. 

They don’t rely on hot water close to the surface, but instead use techniques developed in the oil and gas industry to drill deep and extract heat from dry, hot rock. 

One of them, Eavor, is starting up its first commercial power plant in Geretsried — turning the tiny town of about 26,000 people, south of Munich, into a proving ground for the future of geothermal energy.

Can technology like this be scaled and really make a difference for the future of the planet? 

The International Energy Agency thinks so. 

In a recent report, it said technology breakthroughs are unlocking huge potential for geothermal energy. 

Now that companies are drilling deeper than three kilometres nearly every country has the potential to make heat and electricity this way, the IEA said.

“It has been a niche energy and concentrated in a few countries,” IEA Executive Director Fatih Birol said in an interview. 

But soon, Birol said: “geothermal can contribute to the global energy picture in an accelerated manner”.

Eavor was drawn to Geretsried because the traditional technique failed there.

No one would’ve been impressed if the Canadian company demonstrated its technology in Iceland, a place with abundant, easily accessible hot water, Eavor CEO John Redfern said.

“Our whole point is that we want to have geothermal anywhere, everywhere,” Redfern said. 

“What better way to prove that than to put our first well where they tried and failed with traditional geothermal systems.” 

Eavor says Geretsried geothermal will power up this year. 

This project will start by generating electricity in Geretsried, then add heat as the town fully builds out a district heating system.

With district heating, heat is generated in a central location and distributed to homes and businesses. 

The way it works is that Eavor drills two wells about four kilometres deep, then branches out and drills a dozen lateral wells, to maximize contact with the hot rock. 

The wells intersect to create a closed loop where water can flow, the “Eavor loop.” 

The Geretsried project will have four loops, each with two vertical wells and about 12 lateral ones.

Eavor does not frack, or hydraulically fracture, to create cracks and increase the permeability of rock.

Instead in Geretsried, it will pump water down to flow through the hot rock, heating up on contact. 

It will rise naturally to the surface through an outlet well.

That hot water can be used to heat the utility’s water so it can be sent through pipes to heat the equivalent of about 36,000 homes. 

The hot water also can be routed to a power plant to make steam and then recirculate. 

When used to spin a turbine, that steam can generate electricity without any planet-warming greenhouse gas emissions.

Müller, the mayor, said it’s better to start changing the approach to energy today than push it off to tomorrow. 

“We want to remain future-proof,” he said. “So let’s start the future.”

Source: AP