Google-funded hot rock ‘water’ drill could reduce cost of geothermal energy

Enhanced geothermal systems ‘could be the killer app of energy world’ says Dan Reicher, Google’s climate and energy chief

A novel drill that is inspired by a jet engine and uses super-heated water to carve through rock could help make clean energy from underground rocks more economically viable, according to its backers at Google.

Potter Drilling is part-funded by Google.org – the internet search giant’s philanthropic arm – and wants to use its technology to develop geothermal energy, which involves tapping the energy from hot rocks deep in the Earth.

Geothermal energy is seen by environmentalists as a vast potential source of clean, carbon-free energy if it can be tapped efficiently. Traditional methods drill into the Earth and use naturally occurring underground pockets of steam or hot water in order to make clean electricity.

A report (pdf) by the Massachusetts Institute of Technology estimated that tapping just 2% of the potential resource from so-called enhanced geothermal systems between 3km and 10km below the surface of continental USA could supply more than 2,500 times the country’s total annual energy use.

Geothermal projects in countries from Australia to Iceland and Germany already generate thousands of megawatts of electricity. Geothermal power plants can be used as baseload electricity because they are usually productive for more than 90% of the time, compared with 65%-75% for fossil-fuel power plants. They also produce virtually no greenhouse gas emissions.

Enhanced geothermal systems (EGS) allow the traditional techniques to be applied almost anywhere. By drilling deep into the Earth (where rock temperatures can reach more than 200C) and pumping water into the hole, the underground hot rocks fracture, thus allowing the water to circulate and heat up. The hot water comes back to the surface and is then used to drive turbines and produce electricity.

“EGS could be the killer app of the energy world,” said Dan Reicher, director of climate and energy initiatives for Google.org, when its funding was first announced for Potter Drilling. “One of the attractive aspects is that it’s baseload, it’s 24-hour power and that’s a nice complement to solar and wind, which are intermittent sources. If you can put all three of these technologies together, we’re going to have a much more attractive green electricity mix.”

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