Tim Treadgold’s article on hot fractured rock geothermal power (WA Business News, July 15) is not only cynical and highly factually incorrect, but is without a clear understanding of what HFR geothermal developments are based on.
The evolution of the geothermal industry has followed a natural path. It started with utilising existing hot springs, followed by drilling wells in volcanic centres to locate new resources, initially for steam only and now for steam and hot water.
Modern conventional geothermal power stations only use the heat, reinjecting the water in the aquifer where it came from. The pursuit of HFR geothermal is part of this natural evolutionary development. The first HFR geothermal power station is expected to come on stream in 2005 in France.
Australia happens to be well endowed with HFR geothermal resources and prospects. The heat is there, it is now a question of harnessing it. The scope is enormous and serious efforts to demonstrate the economic viability can be fully justified.
The factual errors in Tim Treadgold’s article are as follows.
- The target hot granites are not being fractured by high water pressure. These crystalline rocks are opened along existing natural joints and fractures by hydraulic pressure. Geodynamics has successfully completed the first phase of this in its target hot granites, with results exceeding expectations.
- The super heated water (240°C) is not converted into steam but the heat is taken out by a surface heat exchanger and transferred to a binary geothermal power plant, after which it is reinjected.
- Geodynamics has the support of Woodside Petroleum, Australian National University, Origin Energy, the CSIRO, University of Queensland and from international agencies such as Los Alamos, Tohoku University, and Shell International.
- There is no secret that the heat in the target granites is the result of decay of natural radioactive minerals. It is well known that these are present in all granites and it is part of the environment. As a consequence, some radon gas will be present in the hot water returning to the surface. Radon has a half-life of 3.7 days, i.e. it decays (disappears) in a short period of time. Modelling studies have shown that radon concentration in water in an open HFR geothermal system is less than one third of the maximum permissible limits for drinking water (Australian Code of Practice) and is not an issue.
- These are objective facts supported by independent scientific data.
- HFR geothermal development is currently in a pioneering phase. We do not shy away from the fact that there are still challenges and risks. HFR geothermal power generation is classified as renewable energy by the International Energy Agency.
Bertus de Graaf