Several parts of Australia show great potential for developing geothermal energy, according to a newly released map in the Global Atlas for Renewable Energy, provided by the International Renewable Energy Agency (IRENA).
Enhanced Geothermal Systems (EGS) is an emerging source of geothermal energy based on a heat source (hot rock) containing only small amounts of natural water in small cracks, as opposed to mainstream geothermal sources with naturally occurring heat, water and extensive fractures.
Layers in the map indicate the average predicted temperature of basement rocks at one kilometer intervals, at depths of 3-10 kilometers (km). Vast areas of Queensland, New South Wales and South Australia boast temperatures exceeding 2400C at 4.5 km depth. Higher temperatures – between 2800C and 3500C – appear obtainable at depths below 7 km.
“This latest map suggests the clear potential for enhanced geothermal in Australia,” said Nicolas Fichaux, program officer for resource assessment at IRENA. “Ehanced geothermal resources can provide significant heat energy in parts of the world not normally known as geothermal hotspots. And while the technology is still relatively nascent, the potential is huge.”
EGS development usually requires hydraulic stimulations, such as the relatively novel hydro-shearing process, where small existing cracks are enhanced after drilling into a resource field. Water is then poured into the vertically drilled well in order to permeate the cracks, absorb the heat and be transported back to the surface through a second well as superheated water. The energy in the superheated water is used to produce steam for electricity generation. As EGS is usually a closed-loop system, the water is then re-injected into the well to start the process all over again.
Unlike the hydraulic fracturing – or “fracking“ – process used in the oil and gas industry, hydro-shearing does not inject harmful chemicals into the ground, nor does it blast through rock, rather, it creates a network of very small cracks (about 1.2mm) to facilitate easy fluid movement.