There is the potential to access high levels of heat from hot rocks at depth where there is not already water present and to harness that heat to produce power on an even larger scale. This approach involves injecting water into the rock at depth to create a heat exchanger and drilling additional wells to recover the injected water. This process is sustainable, virtually emissions free and the power is controllable - it can be generated on request. It is not dependent on whether the sun is shining or the wind blowing……
Engineered Geothermal Systems (EGS) also sometimes called enhanced geothermal systems, extract heat by creating a subsurface fracture system to which water can be added through injection wells.
Natural fractures in the rock may provide adequate flow rates and the creation of a heat exchange area large enough to sustain power generation. However, EGS allows for enhancing natural fracture networks or creation of a geothermal system by hydraulic stimulation when the in situ fracture network will not support economic flow rates. This enhancement of permeability is achieved by pumping water into the rock.
Despite over 30 years of development of engineered geothermal systems within various academic environments, only in recent years has there been a focus on geothermal as a viable renewable energy source.
A lead was taken in Australia in the early 2000s and a publicly funded programme has emerged, with commercial lead being taken by Geodynamics Limited. At the same time, there has been mounting interest in hydrothermal power generally in countries such as Germany, Hungary and Turkey.
As regards pure engineered geothermal systems, where water is circulated through the rock to extract the heat, AltaRock Energy, Inc. in the US is far advanced in its creation of such a heat reservoir.
There are EGS systems currently being developed in Europe, Australia, Japan, Germany, the US and Switzerland. The largest EGS project in the world is currently being developed in the Cooper Basin, Australia - with the potential to generate 5,000-10,000 MW.