Geothermal Power

geothermal heat exchangersOne green energy source that seems to have few detractors can be found in southeastern Idaho, near Raft River.

This old Department of Energy site is now the home of a geothermal plant, the first commercial power producing plant in the northwest.

"We're very proud of that," says plant manager Chris Harriman. "Certainly we're involved in a lot of different disciplines here. We've got transmission, electrical, the power generation component, the binary cycle piece. We've got drilling. There's a lot of things going on in this little place just short of nowhere!"

The plant converts the earth's natural hot water into electricity. Sounds simple, but first you have to find the hot water.

The U.S. Department of Energy did initial drilling in the 1970's and '80's, and found 300 degree water more than a mile underground. At that temperature, geothermal energy becomes a viable operation.

geothermal water source

The 300 degree water flows through pipes, from the source to the site, where it heats isopentane, turning it from liquid to gas. Scientists discovered that isopentane, which is similar to butane in cigarette lighters, flashes to a gas at much lower temperatures than does water.

"We're able to superheat that gas and run it through a turbine at much lower temperatures than you would with steam, and so then we run the turbine, it drives the generator, that produces electricity," says Harriman.

Another way to look at it: "the water comes in at 300 degrees, goes out at 145 degrees, and that 155 degrees is the heat that we've extracted from the water, that we're converting into electricity," explains Harriman.

The only byproduct of this kind of energy is water, or steam. "It's a non consumptive, environmentally safe method of generating power," says Harriman. "Of all the different types of energy that are available to us, geothermal provides the least environmental risk."

a steamy geothermal pond in winter

But to guarantee the longevity of this green energy source, the company has to pump the cooled water back into the ground, just not too close to the primary source. Otherwise, you could kill the temperature of the resource.

If handled properly, this source of green energy could eventually generate forty, maybe even 100 megawatts of steady power, the kind engineers call base load power. That's power available 24 hours a day, regardless of whether the sun is shining or the wind is blowing.

The company, U.S. Geothermal, has been selling the electricity to Idaho Power Company, transferring it onto the nearby power grid.

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