Ever attempted a Jules Verne type, ‘Journey to the Centre of the Earth?’ No? Well neither have we. But we have heard it’s a hot place to be. It has always bothered though, us why the characters in the movie, barely raised a sweat.
You don’t really need to go to the centre of the Earth to get hot. In some places on the planet the heat is fairly close to the surface of the Earth. Think volcanoes and the hot water geysers in New Zealand, Russia, Iceland and North and South America.
So what do these hot spots have to do with us apart from photo opportunities and the odd scalded foot? Some clever people have recognised that the energy created by the Earths hot spots can be harnessed and turned into clean energy.
This is not a new idea: this energy has been used for thousands of years in some countries for hot water, cooking and heating. Technology is getting more and more advanced. It’s getting to a point where we can think about powering towns and even cities with this little known energy source.
The beaut thing about geothermal energy is that it is entirely renewable and clean. Like the sun, the wind and the tides, it will never run out. But unlike energy from the wind and the sun, geothermal energy can provide steady power that can be accessed 24 hours a day. Energy from the wind and sun is less steady.
Emissions produced from geothermal are tiny compared to coal. Geothermal energy has almost no impact on the landscape, while coal requires the removal of mountaintops, re-routing of rivers and the digging of massive holes in the ground.
So how exactly does it work, we hear you ask? Here comes the short version.
The Earth has a very, very hot molten core (melted rock). But the core of the Earth doesn’t have a monopoly on heat: in some places, at only about 3-6km below the surface of the Earth there are layers of super hot granite. These can be as hot as 250 degrees centigrade, and just one cubic kilometre of this hot granite is thought to have as much energy in it as 40 million barrels of oil.
There are a couple of ways that we can get this heat out of the ground and turn it into energy.
Wet Geothermal Power
Wet geothermal power is currently the only way to generate enough energy to sell. It works by drilling into the hot water and steam trapped in the hot granite under the Earths surface.
In places like New Zealand and Iceland, the naturally rising magma (underground lava) beneath volcanoes brings high heat to very shallow depths below the surface.
Water trapped close to this heat is then pushed to the surface where the pressure created from the steam of the hot water is used to power generators to create electricity. In Iceland, 20% of its electricity and almost all its heating comes from this form of geothermal energy.
In Australia we don’t have any molten lava just beneath us. What we do have is heaps of hot granite. Because of this, we need to develop a different way to harness geothermal energy. And we have!
Dry Geothermal Power
Dry geothermal power – or Hot Rocks – works by drilling holes into the hot rocks that are below the Earth’s surface. Water is then forced into the drilled hole and great pressure is applied to it to naturally fracture the rock. This image shows how a hot rocks power station might work (from Australian National University). Click image to enlarge.
This generates very small earthquakes and which create pathways that the water then moves through. In moving through these cracks, the water is heated by the hot rocks and then drawn out of the holes. This hot water is then used to power a turbine on the surface that spins out electricity.
So how can you get your hands on some of this electricity? Well, at the moment, production of geothermal energy is still in the early phase. Companies are setting up camp in outback South Australia. This area is called the Cooper Basin and has been described as “Australia’s hot rock haven”. It is estimated that the geothermal energy in South Australia could provide 10% of Australia’s energy needs by 2030.
What is Australia doing about geothermal?
Why aren’t we making the most of the Earths’ natural internal heat?
Well, geothermal energy production in Australia is not without its challenges. While the actual drilling of holes is in fact a significant expense, building the infrastructure to cart the newly generated electricity from the desert to the cities will also be very costly. Geothermal power won’t be much use if no one can use it.
The federal Government is thinking about geothermal. They have committed, “$50 million to the geothermal industry to help it begin making the technology viable for baseload energy production”. Stay tuned for more information.
