Australian news, and some related international items

Geothermal energy – not necessarily renewable, nor environmentally benign.

Dennis Matthews, 3 Sept 16 It’s important to understand that what companies such as Geodynamics, and organisations like the SA Centre for Geothermal Energy Research at Adelaide Uni have been trying to do is a special sort of geothermal energy, commonly known as “Hot Rocks”. This type of geothermal energy is not renewable in the normal sense of the word, and it is not environmentally benign.

Hot Rocks geothermal requires the expenditure of large amounts of energy to drill 5km underground and to pump liquid under pressure in order to fracture rocks (fracking) 5 km underground. for which it uses a large amount of water to do this.

geothermal energy hot rocks

In SA, where most of the hot rocks projects were being pursued, the eventual market for the electricity would have been mining companies especially uranium mines such as Roxby Downs and Beverley. This is no coincidence. The rocks are hot, not because of heat from the earths interior, but because they are radioactive.

By fracking the radioactive rocks and pumping water through them, radioactive radon gas is released and the water becomes radioactive through a host of radioactive isotopes that have built up over millions of years. In principle, during operation the water is not released to the environment but this is the ideal scenario. Accidents and maintenance work is highly likely to rel;lease radioactive water. The water used in fracking is not recycled. I assume it is put into tailings dams and allowed to evaporate leaving behind a concentrated radioactive waste. Often this occurs in areas, such as near the Cooper, which are subject to flash flooding.

Each hot rocks site has a very limited life (approx 20 years), because the rate of heat replacement is much less than the rate of extraction. This means that the project has to constantly move from one set of 5km holes and the exhausted holes will not be viable for “many hundreds of years”. This is not renewable energy. Growing trees for biomass is quicker. Solar is instantaneous in the sense that the sun is essentially an infinite source of energy; using solar energy in no way diminishes the amount available.

Despite several attempts, I was never able to get an answer on the energy payback time, or on greenhouse gas emissions and payback time, or water consumption. For the last 20 years these projects have been powered by govt subsidised diesel and have received very generous Govt funding, both State and Federal, including for the Centre for Geothermal Energy Research. Up to April 2010, public funding totalled approx $300 million.

When these projects were first proposed with backing from the SA mines and energy dept I publicly stated that they were economically and environmentally risky. I see no reason to now change that position.

September 3, 2016 - Posted by | energy, South Australia

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