Energy from earth’s depths

Soultz-sous-Forêts / DPA

France and Germany could hardly be more different in their attitudes to tapping the free heat from deep under the earth. The French have enthusiastically sunk bores and exploited the heat, which is invitingly close to the surface at a hot spot which straddles the two countries’ border, whereas residents on the German side are squabbling about whether geothermal extraction might trigger an earthquake.
At Soultz-sous-Forêts in its Alsace region, a joint Franco-German power station begun 30 years ago as a test site has just begun producing electricity on a full commercial basis. Silver pipes, a couple of red pumps and a small hall painted in camouflage over a site half the size of a football field are all that can be seen amid the hills and maize-fields of this thinly populated region.
The French are operating another deep geothermal power plant of their own at Rittershoffen to generate industrial heat, and a further two are under construction in the region, where geological conditions are ideal for extracting the earth’s heat. On the German side, progress has been sluggish because people are averse to risk and fearful that their beloved environment will be harmed. One plant, at Insheim, is producing heat. A second at Bruchsal has an uncertain future, with commercial usage still under trial. German activists have put a stop to plans for a plant at Neuried.
“This is a technology that gets everyone excited, pro and contra,” says Wolfram Muench, who heads research at German electricity utility EnBW, which is one of the parties operating the Soultz plant. “It is wonderful when you see a few pipes that provide heat and electricity the whole year round,” Muench adds, but he cautions that operating a power station of this kind is not that simple either.
Germany has moved away from nuclear power since March 2011, when an earthquake and tsunami in Japan triggered meltdowns, explosions and contamination at Fukushima Daiichi Nuclear Plant. German public opinion swung against nuclear power after the disaster, leading Chancellor Angela Merkel’s government to order the shutdown of the country’s nuclear plants by 2022.
At the time Germany had 17 operational or idled reactors. At first, the country turned to power plants burning lignite, the cheapest and dirtiest form of coal, as a prelude to a major shift to renewable sources like geothermal.
Visitors to the Soultz plant have to wear safety helmets, and a yellow line demarcates danger areas. Gases are used that could explode. But the real danger is accidentally setting off earth tremors with the bores. The boreholes at Soultz go down 5,000 metres, where water temperatures rise up to 200 degrees Celsius. This water is pumped up for heating industrial plants and households, but can also be used to drive turbines to generate electricity. The water is returned underground once more after the energy in it has been extracted.
Re-injecting the water at high pressure can cause rock layers under the surface to shift, with resulting tremors. In 2009 in the German town of Landau, an earth movement left cracks in the home of Werner Mueller. Across the border a road in the French village of Lochwiller was also so badly cracked that it has been permanently closed to traffic. However the cause of that quake was not a deep geothermal bore, but householders tapping mild warmth from the soil with a borehole just 140 metres in depth to heat a home. Something similar happened in Staufen, a town south of the German city of Freiburg. The cause was cold water being pressed down into underground rock layers that swell when they become wet.
“In most cases nothing happens, but when something does, it really does,” Muench says. Although the depths of the bores used by householders and by power companies are vastly different, the distinction is lost on the non-scientific public. When media reports then suggest that historic buildings are at risk, the hype only increases. There have been protests on the German side, and on the French side in Lochwiller, which lies to the north-west of Strasbourg. On one half-timbered house in the village there is a banner reading: “Built in 1617, wrecked in 201…?”
In Soultz by contrast there was little excitement over a minor tremor in 2003. Muench suspects that the reason lies in the fact that “people were drilling for oil in Alsace as early as the 18th century,” and so the locals are used to a certain amount of ground movement. The remains of the wells can still be seen in the shape of silver pyramids the height of a man scattered between the maize fields and housing the old pumps. Poor communication with the locals is also being blamed on the German side, as Erwin Knapek, the head of an association for promoting geothermal energy, explains.
“They didn’t explain things well to the local population and they constantly denied blame,” he says in criticism of the investors at Landau. He thinks householder Mueller should be compensated for the cracks in his home so that everyone can now move on. He is now hoping that the French projects will demonstrate that geothermal projects can be successful without creating hazards. The rock is the same on both sides of the border, so no one can claim conditions in Germany are any different.
Muench believes there is another reason for the slow progress in Germany. There is simply too little public understanding “of what goes on down there,” he says. Knapek adds: We’ve researched outer space much better than the subterranean world beneath us.”