Getting the energy from the hot rocks relies on techniques established by the oil and gas industry. Wells are drilled to a depth of 3 - 5 kilometres below the surface to find the heat–producing granites. Water is then pumped down in the wells and through the cracks in the rocks. The water is heated to a temperature of up to 300°C and pushed back to the surface where the heat is used to drive a turbine and produce electricity. The water used is recycled.
Greenhouse gas savings
Geothermal power is a zero-emission electricity source. One megawatt hour of geothermal-derived
electricity avoids approximately one tonne of CO2.
While some of the world’s best sites for hot rocks are in Australia, at this stage the only working
geothermal power station in Australia is in Birdsville, Queensland. It uses hot water from the Great
Artesian Basin and is rated at 120 kilowatts.
Currently over 50 companies are working on geothermal exploration in
Australia and several of these expect to have working hot rocks geothermal generators working within the next 2 - 5 years. Around $1.5 billion worth of exploration work is in progress. The major areas of exploration in Australia are:
- the Cooper/Eromanga Basin in South Australia;
- the Hunter Valley near Newcastle;
- Otway Basin in Victoria; and
24 countries are currently generating geothermal energy. Significant producers are the USA, Iceland, Italy, New Zealand and Japan. The majority of this generation comes from hot springs associated with volcanic activity. As many as 46 countries could be generating geothermal power by 2010.
A total of around 9,700 megawatts of generation is installed worldwide producing approximately 56,800 gigawatt hours a year.
Geothermal energy in Australia is still in its early stages. It requires more government funding for research and development. Once pilot plants have been proven and the technology moves towards deployment, the biggest issue is likely to be network connection.