What are Hot Fractured Rocks or Enhanced Geothermal Systems?  
Hot Fractured Rocks (HFR) or Enhanced Geothermal Systems are both terms that refer to granite bodies, generally located between 3 and 5km of the surface, although they can be found closer to the surface than that.

Granites form as a result of a magmatic melt, and they are solid and do not transmit water.

How hot are they?
The bodies currently under investigation by Geodynamics range form 200 - 250^oC, between 3 and 5km from the surface.

The tenement held by Geodynamics in the Cooper Basin covers an area regarded as the hottest spot on earth outside volcanic centres.

Why are they so hot? 
Two factors are involved: the nature of the granites themselves, and the sedimentary rock layers above the granites.

High Heat Producing Granites have naturally occurring radiogenic minerals which produce their own heat.

The heat is trapped inside these granites by an overlying blanket of insulating rocks. Such a blanket has to be about 3km thick for the required >200^oC temperatures to be generated.

What is the link between EGS power generation and radiation?
There are no environmental radioactive issues associated with EGS geothermal power generation.

How much energy is down there?
One cubic kilometre of hot granite at 250^oC has the stored energy equivalent of 40 million barrels of oil when the heat is extracted to a temperature of 150^oC.

Australia is known to have several thousand cubic kilometres of identified high heat producing granites and these have the potential to meet the total electricity demand of the country for hundreds of years.

How do you generate the electricity?
Heat is extracted from the granites by circulating waters through them in an engineered, artificial reservoir.

The heated water returns to the surface under pressure, and is converted into electricity via a heat exchanger and conventional geothermal power plant technology.
Click here to find a more detailed explanation.

Why are Australian conditions so favourable?
Firstly, we have extremely large quantities of hot rocks within 3 - 5km of the surface, in favourable locations throughout Australia.

The data so far indicates that these bodies are favourably shaped and stressed. The ideal shape for developing EGS geothermal power plant is a horizontal lens shaped body, with relatively uniform temperatures, and strong horizontal stresses (pushing in on the body, rather than pushing down on it).

These conditions allow for multiple reservoirs to be produced at one site, both stacked on top of each other, and side by side over a wide area. These conditions all suggest that the economic viability of EGS geothermal energy in Australia is very strong.

Why hasn't anyone done this before?
The technology required to develop an efficient EGS geothermal power plant has come about as the result of over US$500 million in research & development worldwide. Several projects around the world have contributed to this process. Their combined efforts make it possible to attempt this project in Australia.

However, the main reason why this hasn't been done before is because social and political conditions have not allowed for it. Developing a power source such as EGS Geothermal energy requires a strong commitment from both government and consumers, and this has been building steadily over the past few years.