Australia's vast geothermal energy resources represent thousands of years worth of untapped power

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Temperature readings taken in existing oil and gas bore holes indicate a huge amount of geothermal energy below the surface of Australia.(Credit: Australian Geothermal Energy Association)

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Australia is sitting on top of some of the world's most potent geothermal energy sources, according to government estimates. Just one percent of the hot rock energy less than 5 km under the surface would be enough to meet the whole country's entire power needs for 26,000 years if it was tapped. So why aren't we seeing more movement on it?

Geothermal energy is a very handy, virtually inexhaustible clean energy source for those areas lucky enough to find themselves on top of it. Massive amounts of hot rock just below the Earth's surface can be used to heat water and drive steam turbines for reliable electricity generation with virtually no emissions or environmental impact.

Where wind and solar tend to generate power at inconvenient or uncontrollable times, geothermal can be easily regulated and is ready to go 24/7. Surveys testing the available heat in existing bore holes down to a depth of 5 km (3 miles) below the surface indicate that Australia is sitting on some seriously large hot rock resources, as shown in our lead image.

So why is this enormous resource apparently so underdeveloped?

Part of the answer is geographic. Much of Australia's hot rock is simply not conveniently located close to major cities. The big red splotch of prime red geothermal activity to the centre right of the map is more or less on top of a large, barren desert area several hundred kilometres from Sydney or Adelaide, and large scale power transmission can be an expensive proposition.

Another part is geological. Australia has a ton of hot rock, but not a lot of the highly porous rock that makes for easy power extraction. To generate power, you need to be able to pump large amounts of water into a deep rock hole and let the water filter through pores and cracks in the rock, picking up heat as it goes, and then pump the heated water back to the surface on the other side.

Much of Australia's hot rock isn't porous enough to let a good flow of water through, which means in order to set up a geothermal power plant, engineers need to forcibly crack the rock, slowly pumping water into an underground rock reservoir at high pressure, to create the appropriate kinds of cracks and channels. It's a costly process, and it's a bit hit and miss.

A final problem facing all renewable energy sources may be political. While the fossil fuel energy industries enjoy some AU$4 billion in direct subsidies and tax breaks, the Australian government has allocated just AU$50 million to geothermal development.

On top of that, the current conservative government has succeeded in slashing Australia's 2020 renewable energy target from 41,000 gigawatt hours by about 20 percent down to 33,000 – and managed to include the burning of scrap wood in the "renewable" target at the same time.

Australian Prime Minister Tony Abbott has made his beliefs on renewable energy clear, saying "Coal is good for humanity… Essential to the prosperity of the world," while describing wind farms as "ugly… noisy and they may have all sorts of other impacts… It's right and proper that we're having an enquiry into the health impacts of these things." Abbott's treasurer Joe Hockey has also described wind generators as "utterly offensive."

Still, the Australian Geothermal Energy Association views both State and Federal governments as "very supportive" to the handful of operators currently working on developing geothermal projects. So perhaps there's a cleaner future in store for a country that currently ranks as the 10th highest carbon polluter per capita in the world.

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