Earth's interior heat could provide much of the world's energy, according to a new study. U.S. experts say geothermal energy is a largely untapped and inexhaustible clean resource that could reduce reliance on fossil fuels like oil and coal. As VOA's David McAlary reports from Washington, the researchers call for a 15-year U.S. government-led program to develop geothermal energy into an economically competitive source of electricity for Americans.

Is the answer to our energy needs under our feet?

World's largest geyser, called Steamboat, erupts at Yellowstone National Park in US state of Wyoming (file photo)

Earth's molten interior heats up the rocks deep in the surface crust, which in turn heats underground water reservoirs. Steam from this process now creates 10,000 megawatts of power around the world. Nearly one-third of that amount is generated in the United States, the world's biggest producer of geothermal energy.

A panel of experts led by Massachusetts Institute of Technology chemical engineer Jefferson Tester says this is only a tiny fraction of the country's geothermal potential. He thinks America can do much better.

"There is still some technology required to actually achieve it in commercially competitive markets, but the resource itself is very large, has a lot of positive environmental attributes, and could provide a significant amount of electricity for the long term," he said.

Current projects take advantage of the most easily obtainable geothermal energy - locations where natural factors bring hot water and steam near the surface, such as Iceland and California. But the researchers say new technology developed for oil fields can be used to drill kilometers underground and create artificial geothermal reservoirs. Hot rocks could be split and water from nearby wells pumped through them to create the steam to run surface generators.

"We're trying to emulate not only the structure of a natural system, but the performance of a natural system in terms of how much fluid we could push through the rock and how much energy we could mine out of the thermal energy that is stored in that rock mass," he said.

Tester says geothermal energy is clean, producing none of the carbon emissions or other pollutants blamed for global warming. It would offer a continuous domestic supply of energy not relying on changes in wind or sunlight. Moreover, a geothermal generating plant would be small compared to nuclear power and coal plants.

But such systems would use huge amounts of water, which is in short supply in some regions. Furthermore, scientists say, fracturing underground rocks and forcing water through them might create minor earthquakes.

U.S. government support for geothermal and other forms of alternative energy has dropped sharply since the 1980s.

The MIT group calls for a 15-year program of government and private investment to fund research into new geothermal technologies to lessen the risks and make rock drilling more efficient, to choose the best drilling sites, and to conduct field trials. They estimate the cost at about $1 billion, the price of one clean coal-burning power plant.

"If you can do it anywhere in the United States, most likely you can do it anywhere in the world. There would be a lot of benefit from a very serious and much more aggressive international collaboration," he said.

Tester says the ultimate goal for the United States should be to generate 100,000 megawatts of geothermal power by 2050, about one-tenth of all the power generated in the country today.