What is geothermal energy?
Geothermal energy is the energy stored as heat in the earth. In Australia, this energy is abundant.
There is a steady flow of heat from the centre of the Earth (where temperatures are above 5000°C) through the surface of the Earth (-30 to +40°C) into space (-273°C)—heat flows from hot to cold. The heat is generated by the natural decay over millions of years of radiogenic elements including uranium, thorium and potassium.
Energy is brought to the surface by extracting hot water that is circulating amongst the sub surface rocks, or by pumping cold water into the hot rocks and returning the heated water to the surface, to drive steam turbines to produce electricity.
Geothermal energy holds the promise of being a renewable energy source that can operate 24 hours a day, providing critical large scale baseload power for Australian homes and industries. In addition, geothermal energy can be used for heating and cooling purposes. There are a number of buildings, residential homes and swimming pools that currently use geothermal for these purposes.
It has only become evident in the last decade that Australia has considerable geothermal energy potential. This is partly because of a perception that geothermal resources are found only in regions of active volcanism, which excludes Australia. Although there are no active volcanoes on the continent, Australia does have substantial potential for hot rock and hot sedimentary aquifer resources.
How is geothermal energy used in Australia?
In Australia, two types of projects are under development. They are:
- enhanced geothermal systems (EGS or hot rocks)
- hot sedimentary aquifers (HSA).
Most current geothermal projects in Australia are still at proof-of-concept or early demonstration stage.
Direct use technologies are at a more advanced stage of innovation and the challenges lie in improving project economics and reducing upfront costs.
ARENA International Geothermal Expert Group
The ARENA International Geothermal Expert Group was established to investigate and report on the prospects for the commercial development of geothermal energy in Australia. The Expert Group reported its findings to the ARENA Board in July 2014.
The Expert Group has critically evaluated the prospects for either Enhanced Geothermal Systems or Hot Sedimentary Aquifer geothermal energy to deliver cost competitive energy to Australia without long-term subsidy.
The report provides options to the ARENA Board on how it may wish to allocate and prioritise its funding for geothermal energy as part of its portfolio approach to supporting renewable energy in Australia.