JOIN USDepending on your point of view, hydraulic fracturing or “fracking” is either the future of clean, natural gas or an environmental apocalypse.
Fracking liberates gas trapped underground by drilling sideways from vertical well-shafts into horizontal layers of shale rock. Millions of gallons of a cocktail of water, sand and chemicals are injected into the horizontal wells at high pressure, fracturing the shale, releasing the gas and causing violent protests in Europe and parts of the United States.
Geothermal energy, by contrast, has yet to stir much controversy. Most geothermal plants are located where water has seeped down into the Earth’s crust, been heated and forced back up through permeable rock. Drill a well to between 3,000 and 12,000 feet, and the searing water and steam can be released to drive generators.
Geothermal is a minnow among power sources. America has the world’s highest installed capacity of geothermal generating plants – 3.4 gigawatts’ worth at last count, but they generate only 0.4 per cent of its electricity. New “enhanced geothermal systems” (EGS), however, look set to make geothermal a bigger contributor and potentially as controversial as shale.
The industry may dislike the comparison, but EGS is geothermal fracking. Millions of gallons of water and chemicals are injected into mostly vertical wells at relatively high pressure, and the combination of cold-meets-hot, pressure and chemistry shears the deep, hot rock. This creates new “fracture networks” through which water can be pumped, heated and sent back to the surface to generate power.
The new technique can reduce the failure rate and extend the size and life of existing geothermal fields. In time, think EGS fans, it will allow geothermal fields to be established wherever there is suitable hot rock.
Investors are intrigued but wary. AltaRock Energy, a Seattle-based company partly financed by Khosla Ventures, has built a demonstration project in Oregon that it claims can extract six to ten times as much power from a field as older EGS techniques.
The sticking-point, said Susan Petty, AltaRock’s founder, is commercialisation. Geothermal is a steady source of energy, has very high capacity-utilisation rates, zero fuel costs and near-zero greenhouse-gas emissions. The trouble is that successful existing geothermal plants do not need EGS, and for many failed wells it is uneconomic to introduce it.
AltaRock plans to buy up existing fields that it thinks it could make profitable using its version of EGS. That way it will avoid the costs of new infrastructure while demonstrating its technology’s viability.
The energy department reckons that EGS techniques could be commercially viable as soon as next year, at which point more private investors and perhaps utilities might pile in. It is not alone in its optimism: Germany, France and Britain have state research programmes for EGS.
All this has environmentalists gearing up for another fight. EGS can trigger earthquakes. Most are minuscule but an early project on a seismic fault in Basel, Switzerland, was scrapped after several not-so-small quakes. It is also possible that water used for EGS may leak, contaminating surface water or soil. Whether this will prevent protests or prohibitions is open to hot debate.