Switzerland has ended a pioneering geothermal project, authorities said Thursday, three years after the deep drilling into the ground caused a series of earthquakes, scaring residents of the northwestern city of Basel.
The project, led by Geopower Basel, aimed to be the world's first to generate power commercially by boiling water on naturally-ocurring rocks buried three miles (five kilometers) underground. But when the site in the middle of the city accidentally triggered tremors, including a 3.4 magnitude quake three years ago, the project was put on hold and a risk analysis was conducted.
On paper, the Basel project looked fairly straightforward: Drill down, shoot cold water into the shaft and bring it up again superheated and capable of generating enough power through a steam turbine to meet the electricity needs of 10,000 households and heat 2,700 homes.
The head of Basel's environmental and economic department, Christoph Brutschin, said Thursday an assessment clearly showed that the risk of further earthquakes would be too high to continue drilling up to 5,000 meters (16,400 feet) into the ground _ the depth necessary to heat the water from the rocks.
Continuing the project in Basel is impossible because it would trigger up to 30 earthquakes in the first phase of drilling alone, Brutschin said.
Ahead of the project, Geopower Basel had forecast some rock slippage. In fact, it said the location on top of a fault line _ the upper Rhine trench _ was an advantage because it meant the heat was closer to the Earth's surface. But it did not expect such tremors.
The project designer and geologist, Markus Haering, has been charged with property damage and will have to stand trial in a Basel court next week. He could be sentenced to up to five years in prison. Geopower has paid around 9 million Swiss francs ($9 million) in compensation for cracked walls and similar damage on nearby houses and other buildings.
Other attempts in Switzerland to tap the heat of the Earth's crust to produce clean energy continue in zones that are less earthquake-prone. Engineers in Zurich started preliminary drilling last month to see if the area was suitable for such a geothermal project.
Another Swiss city, St. Gallen in the east of the country, plans to start drilling on its own project next year.