Enhanced or engineered geothermal systems aim at using the heat of the Earth where no or insufficient steam or hot water exists and where permeability is low. EGS technology is centred on engineering and creating large heat exchange areas in hot rock. The process involves enhancing permeability by opening pre-existing fractures and/or creating new fractures. Heat is extracted by pumping a transfer medium, typically water, down a borehole into the hot fractured rock and then pumping the heated fluid up another borehole to a power plant, from where it is pumped back down (recirculated) to repeat the cycle.
EGS can encompass everything from stimulation of already existing sites with insufficient permeability to developing new geothermal power plants in locations without geothermal fluids. EGS has been under development since the first experiments in the 1970s on very low permeability rocks, and is also known as hot dry rock technology. On the surface, the heat transfer medium (usually hot water) is used in a binary or flash plant to generate electricity and/or used for heating purposes.
Among current EGS projects worldwide, the European scientific pilot site at Soultz-sous-Forêts, France, is in the most advanced stage and has recently commissioned the first power plant (1.5 MWe), thereby providing an invaluable database of information. In 2011, 20 EGS projects are under development or under discussion in several EU countries.
EGS research, testing and demonstration is also under way in the United States and Australia. The United States has included large EGS RD&D components in its recent clean energy initiatives as part of a revived national geothermal programme.
In Australia, 50 companies held about 400 geothermal exploration licenses in 2010. The government has awarded grants of approximately USD 205 million to support deep drilling and demonstration
geothermal projects. The largest EGS project in the world, a 25 MWe demonstration plant, is under development in Australia’s Cooper Basin. The Cooper Basin is estimated by Geodynamics Ltd to have
the potential to generate 5 GWe to 10 GWe.
In China, there are plans to test EGS in three regions where the geothermal gradient is high: in the northeast (volcanic rocks), the southwest (volcanic rocks) and the southeast (granite).
In India, hot rock resources have been estimated to be abundantly available, because of a large volume of heat-generating granites throughout the country, but geothermal energy exploitation has yet to be initiated (Chandrasekharam and Chandrasekhar, 2010).

1. Enhanced Geothermal System Visualized

   1. Injection well An injection well is drilled into hot basement rock that has limited permeability and fluid content. All...

2. Geothermal – How It Works

   Geothermal energy involves the exploitation of different grades of thermal energy stored within the earth. In certain geological areas, heat...

3. New Zealand To Research The Country’s Geothermal Energy Potential

   Reported last week, “A large research and development effort is under way in New Zealand, aimed at harnessing a natural...

4. Types Of Geothermal Power Plants

   There are three types of geothermal steam plants depending on the way the energy is generated: 1.The first one is...