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With funding from Google, Potter hot water drill could reduce cost of geothermal energy

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A new drill that uses super-hot water to cut through rock could help make geothermal energy a viable alternative to fossil fuels.

A new drill that uses super-hot water to cut through rock could help make geothermal energy a viable alternative to fossil fuels.

Made by Redwood City, Calif.-based Potter Drilling with funding by, the drill aims to make geothermal power more economical because it can drill holes more simply and cheaply.

To understand the new drill, you must first understand how geothermal energy is currently produced.

Here's how it works: Technicians drill deep into the Earth, where rock temperatures can reach more than 400 degrees Fahrenheit, and pump water into the hole. The water fractures the underground rock, allowing it to circulate, heat up and return to the surface. That hot water is then used to drive turbines and produce electricity.

Potter's drill uses the rapid application of heat -- instead of mechanical abrasion -- to break rock apart. Because certain types of hard rock, such as quartz, do not expand uniformly when they get hot, the heat causes them stress that breaks them apart. In a unique twist on what is called "hydrothermal spallation," the Potter drill uses water, not air.

Geothermal energy is seen as clean and plentiful, but tapping it efficiently has been a concern.

According to research (.pdf) by the Massachusetts Institute of Technology, tapping 2 percent of potential "enhanced geothermal systems" between three and 10 kilometers below the surface of the continental United States could supply more than 2,500 times the country's total annual energy use.

Several nations, including Germany and Australia, generate power through geothermal projects. Geothermal power plants are more productive than plants using fossil fuels, and are attractive as "baseload," 'round-the-clock energy sources that help smooth a portfolio full of inconsistent wind and solar sources.

One downside to Potter's drill? It requires some fossil fuels to initially heat the water.

One upside? There's no drill bit to replace, allowing for much faster progress.

Potter plans to conduct preliminary tests with the drill in the field in August, attempting a four-inch-diameter hole at a depth of 1,000 feet. The trial run will be funded by the U.S. Department of Energy.

Eventually, the company wants to drill some six miles into the Earth.

Google's interest, by the way? Its philanthropic arm named EGS as a promising alternative energy source.

Here's a brief video by on the subject:

[via The Guardian]

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Andrew Nusca

Editor Emeritus

Andrew Nusca is editor of SmartPlanet and an associate editor for ZDNet. Previously, he worked at Money, Men's Vogue and Popular Mechanics magazines. He holds degrees from the Columbia University Graduate School of Journalism and New York University. He is based in New York but resides in Philadelphia. Follow him on Twitter. Disclosure