Hot rocks bring clean energy to Britain

Researchers break more ground for geothermal in England. Will this be the country's next leading renewable energy source?

Britain is tapping into a new geothermal energy source, the first of its kind in the English countryside.

At a former cement site last Wednesday, hot and salty water sprang from almost 1,400 feet below into a heat exchanger to produce clean energy. Heated via radiation emanating from the area's underlying granite, the water will issue subterranean power to the "eco-village" of Eastgate. (To boot, the water may even bring steamy relaxation to the proposed community's spas. No such wells have been drilled for this purpose since the Romans drew their natural baths in Bath.)

Granite aquifers are salty. According to the researchers, the 104-degree-Fahrenheit water emerging from the well is saltier than seawater, about twice as much. This can be problematic for corroding pipes and for releasing the water back into the environment. Treating this water can also be costly. After six years of research and a £460,000-grant (almost $700,000) from the UK's Department of Energy and Climate Change, a team of scientists have seemingly found a way around the predicament, by boring two holes into the Earth.

One for going up, one for going down.

The first one, completed three years ago, brings the steamy water from about 3,260 feet below. The second, drilled this year, returns the water to the granite at a depth of almost 1,380 feet. Here, the water absorbs heat as it seeps down through the rock's cracks and crevasses. Then, the liquid is sucked back up. And repeat.

Engineer Paul Younger of Newcastle University says in a statement:

In this system we are re-injecting the water using a second borehole. This means we are able to maintain the natural water pressures in the rocks and allow pumping to continue for many decades to come.

So, by recycling the hot water through what is essentially a huge central heating system deep underground, we can produce an almost carbon-neutral source of energy.

The granite located beneath Weardale in northeastern England is special in its natural permeability. This porous rock heats groundwater very well and does so close to the land's surface. Going deeper, Younger speculates that they may find naturally boiling water, which might be used to generate electricity.

Currently, the only other British geothermal plant (with a single borehole) exists in Southampton.

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Images: Newcastle University
: The Guardian

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