Hot rocks produce tremors, and hope

A Swiss company wants to be the first to produce energy by boiling water - 3 miles underground.

Published August 5, 2007

BASEL, Switzerland - When tremors started cracking walls and bathroom tiles in this Swiss city on the Rhine, the engineers knew they had a problem.

"The glass vases on the shelf rattled, and there was a loud bang," said Catherine Wueest, who owns a tea shop. "I thought a truck had crashed into the building."

But the 3.4-magnitude tremor on the evening of Dec. 8 was no ordinary act of nature: It had been accidentally triggered by engineers drilling deep into the Earth's crust to tap its inner heat and thus break new ground - literally - in the world's search for new sources of energy.

After more, slightly smaller tremors followed, Basel authorities told Geopower Basel to put its project on hold.

But the power company hasn't given up. It's in a race with a firm in Australia to be the first to generate power commercially by boiling water on the rocks 3 miles underground.

On paper, the Basel project looks 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.

Scientists say this geothermal energy - clean, quiet and virtually inexhaustible - could fill the world's annual needs 250,000 times over with nearly zero impact on the climate or the environment.

A study released this year by the Massachusetts Institute of Technology said if 40 percent of the heat under the United States could be tapped, it would meet demand 56,000 times over. The study said an investment of $800-million to $1-billion could produce more than 100 gigawatts of electricity by 2050, equaling the combined output of all 104 nuclear power plants in the United States.

"The resource base for geothermal is enormous," Professor Jefferson Tester, the study's lead author, told the Associated Press.

But there are drawbacks. A so-called hot-rock well 3 miles deep in the United States would cost $7-million to $8-million, according to the MIT study. The average cost of drilling an oil well in the United States in 2004 was $1.44-million, according to the U.S. Energy Information Administration.

And rocks tapped by drilling would lose their heat after a few decades, so new wells would have to be drilled elsewhere.

A lack of investment

Humans have used heat from the earth for thousands of years. The ancient Romans drew on hot springs for bathing and heating their homes. Geothermal energy is in use in 24 countries, including the United States.

But those sources - geysers and hot springs - are close to the surface. Hot dry rock technology, also called enhanced geothermal systems, or EGS, drills down to where the layers of granite are close to 400 degrees Fahrenheit. The equipment is similar to that used for oil, but it needs to go much deeper and wider to accommodate the water cycle, while staying well away from the 99 percent of the Earth's interior that is over 1,000 degrees.

Backers in the United States hope government funding will increase as oil and gas prices rise. But Steve Chalk, deputy assistant secretary for renewable energy, said the Department of Energy won't spend more money beyond the $2-million it has already allocated to hot rock technology.

Major energy companies, including ExxonMobil, Chevron and American Electric Power, say they are following the research but not investing in it.

Still decades away

In Basel, the first shaft was bored last year by a drilling rig towering above nearby apartment buildings. Water was pumped down the injection well in the test phase in December, and as expected, it heated to above 390 F as it seeped through the layers of rock below.

But that's where the water remains, for now; it caused the rock layers to slip, causing the tremors and rumbles.

Geopower Basel had forecast some slippage but 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 surface.

But with $51-million already spent, drilling stopped and the official launch date was moved back from 2009 to 2012.

Still to be drilled are the two wells that would suck the pressurized, superheated water out of the cracks and up to the surface to create steam for driving a turbine and generating electricity. The water, having cooled to around 340 degrees, would heat public buildings and homes before being pumped back into the ground for another cycle.

The rival project near the southern Australian town of Innamincka faces more benign geological conditions. Its target date for operations is now two years ahead of Basel's, aiming to produce 40 megawatts of electricity by the end of 2010, enough for over 30,000 households.

Experts say hot rock geothermal energy can operate 24 hours a day and doesn't depend on sun or wind, but that it's decades away from serious rivalry with existing energy sources.

Fast Facts:

More online

To learn more about the latest in alternative energy, go to blogs.tampabay.com/energy.

What's it cost?

How existing geothermal energy compares with other renewable energies, in U.S. cents per kilowatt hour:

Geothermal: 2 to 12

Biomass: 2 to 16

Wind: 3 to 12

Solar: 18 to 50

Hydro: 2 to 16

Source: International Energy Agency


To learn more about the latest in alternative energy, to to blogs.tampabay.com/energy.

What's it cost?

How existing geothermal energy compares with other renewable energies, in U.S. cents per kilowatt hour:

Geothermal: 2 to 12

Biomass: 2 to 16

Wind: 3 to 12

Solar: 18 to 50

Hydro: 2 to 16

International Energy Agency