Geothermal heats up: developing Alaska's steamy resources.

• Author: Kalytiak, Tracy
• Position: SPECIAL SECTION: ALTERNATIVE ENERGY

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Millions of years ago, near the place now called Chena Hot Springs, magma bubbled its way upward from deep inside the earth, solidifying into underground formations of granite rich in uranium and thorium. Those elements decayed, generating heat.

"Granite rock isn't sedimentary rock; it cracks really nicely in all different directions depending on where the stresses are," said Gwen Holdmann, director of the Alaska Center for Energy and Power. "The rock itself is hot and that heat can be transported to the surface through circulating ground water. It's very site-specific--you might be able to drill two miles deep and hit hot rock, but getting that heat to the surface is another matter entirely. You would need to have pathways for water to circulate through that rock, and then come to the surface either naturally, like at a hot springs, or artificially, by using a pump."

CLEAN RENEWABLE ENERGY

That heat generated by the earth itself is geothermal energy--a clean, renewable resource that puts water as hot as 700 degrees Fahrenheit to work producing power in the U.S. and around the world in myriad ways. Geothermal energy--like that eventually harnessed five years ago at Chena Hot Springs--can produce electricity and heat, or cool homes and businesses and industrial complexes.

"Although areas with telltale signs like hot springs are more obvious and are often the first places geothermal resources are used, the heat of the earth is available everywhere, and we are learning to use it in a broader diversity of circumstances," according to the Geothermal Energy Association.

Geothermal energy is considered renewable because the heat emanating from Earth's interior is essentially limitless. It is estimated to carry the potential for 42 million megawatts of power and is expected to remain so for billions of years, ensuring an inexhaustible supply of energy.

Hot geothermal water can appear on the surface as hot springs or geysers. Most geothermal water--known as geothermal geysers--stays deep underground.

The use of geothermal resources has a long history. Romans used geothermal water to treat eye and skin disease and, at Pompeii, to heat buildings, according to the Geothermal Energy Association, and medieval wars were even fought over lands with hot springs. The first known "health spa" was established in 1326 in Belgium at natural hot springs. And for hundreds of years, Tuscany in central Italy produced vegetables in the winter...