Fracking for heat could expand role of geothermal energy

Hydraulic fracturing or fracking for gas has been around for a few years, but the same technique could open up new vistas for tapping an abundant, clean energy source - geothermal energy.

The technology, which is under development could potentially turn a marginal power source into a major source of carbon-free electricity and heat in the US.

The key part of the technology, which is being developed US-based geothermal energy firm Alta Rock was demonstrated, earlier this year near the Newberry Volcano in Oregon.

The new technology is aimed at releasing heat trapped in underground shale formations by pumping high pressure liquids. Heat from the hot rocks turns water into steam, which is then pumped up to the surface, to drive a turbine generating electricity.

The energy would be available at all times, and in all weather conditions, unlike energy from solar and wind power plants.

Geothermal power meets only a small fraction of the global energy needs with the US, which is one of the biggest producers having total geothermal capacity is about 1 per cent of the country's coal power capacity.

The problem with conventional geothermal plants is their operation is dependent on a rare combination of geological features.

They need hot rock along with large amounts of hot water or steam which could easily be pumped to the surface, where it would drive steam turbines generating electricity. Further the rock formation has to be porous enough to keep the water recirculating and reheating continuously to keep a power plant running.

In April Ormat Technologies, the first such project - known in the parlance as enhanced geothermal system (EGS) was connected to the US electric grid near Reno.

Scientific American quoted Douglas Holett, director of the Geothermal Technologies Office at the US Department of Energy (DoE) as saying that EGS was the big prize. He added, the key was learning how to do it in a reliable way in a responsible way.

According to some estimates, the US could tap around 2,000 times its current annual energy use of roughly 100 exajoules via enhanced geothermal technologies.

According to the DoE at least 500 gigawatts of electric capacity could be harvested from such EGS systems.

The technology is proven with people having used naturally produced steam from hot springs to produce electricity.

A geothermal power plant in Larderello, Italy, has produced electricity this way in Tuscany for over a century.