Beneath the Earth’s surface there is a massive amount of heat contained in certain granite rocks. These special granite rocks are often referred to as Hot Dry Rocks. The method used to harness energy from these rocks involves drilling 3-5 kilometres beneath the earth’s surface. The drilling aspect of Geothermal Energy uses techniques established by the oil and gas industry.
The technology that converts heat to electricity is quite simple. Water is pumped down the drilled hole and is then heated and returned to the earth’s surface as steam. This steam then drives a turbine to generate electricity. This means the by product of Geothermal Power is water, making it a 0 emission energy source.
One of the advantages of geothermal energy is the small amount of land area that is needed. When compared to other alternatives. It is estimated that 3.5 square kilometres of area is required per gigawatt of electricity produced by a geothermal power station.
The Bottle Rock Power Plant is located north of San Francisco, USA and successfully provides electricity to homes in northern California.
Geothermal Energy in Australia
Geothermal energy is in its early stages in Australia. There is a vast resource of hot granite rocks to tap into but the biggest predicted issue is going to be connecting the power generated to the network.The only geothermal power station currently in operation in Australia is located in Birdsville, QLD. The Birdsville Geothermal Power Station is one of the few geothermal power stations in the world and is currently providing Birdsville with power. The Birdsville power station uses Geothermal energy to take the demand off the town’s diesel generated power. Geothermal Power provides enough electricity for Birsville at night and during winter periods but during peak times the diesel generated power comes online. The integration of the geothermal power in Birdsville’s power generation has reduced the amount of diesel required by their generators by 160 000 litres per year. For more detailed information on Birdsville’s Geothermal Power Station download this fact sheet.