Geothermal energy is harnessed from kilometres below the earth's surface through large pipes pumping water into the ground. Although probably the least known about renewable option for Australia, there are some major projects in operation especially in South Australia which is home to some of the hottest underground rocks in the country. I have found these videos which give a really good introduction to the concept, and also describe a bit about the process.
So how does geothermal energy work? Essentially energy is produced from the hot rocks deep below our Earth's crust. Water is sent down into shattered rock where it is heated to several hundred degrees before it returns to the surface turning steam turbines. Water is recaptured in condensers and sent back down into the ground to be reheated. This process is virtually unlimited in terms of availability and as the video below describes, hot rock resources are fairly evenly distributed around the country.
In Australia one of the largest discovered hot spots is the cooper basin in South Australia where a 50MW facility is currently in production. With current oil prices set to sky rocket, the phasing out of coal and the necessity to hang onto our non renewable natural gas supplies, geothermal energy is one of the most exciting future energy sources. It can provide base load energy as well unlike wind and un-stored solar energy (base load solar thermal can be provided by storing excess energy in the form of heat in molten salts).
Geothermal Heat Pumps
Geothermal power stations use super heated steam from some 5km below the earth's crust. There is however a large untapped source of heat closer to the surface which can be used to heat buildings, water for showers and other heating needs. This is usually done in small heat pump systems for large buildings to offset electricity needs. Naturally occurring springs also occur where hot water forms towards the earth's surface, and there are a number of places in the world where you can go to experience these naturally heated pools.
Geothermal Resources in Australia
Estimated Crustal Temperature at 5km Depth
Source: Geoscience Australia
Note: this data is out of date and only a vague indication of regions with hot rock resources. Areas which appear blue may not have had any geothermal exploration at the time this image was created. Ironically much of our knowledge about deep crust temperatures has come from mining explorative drilling, however with geothermal explorative drilling now allowed, deep bore data is starting to fill in the gaps and expose other potential geothermal hotspots not shown on this map.
If anyone has access to or can tell me where I can source a more comprehensive image for this site, please let me know.