GeoDynamics Update  

The SMH has a enthusiastic report on the growing interest in geothermal energy - Renewable energy just got hotter.

The world is watching a hot rocks plant with massive potential in South Australia. It is clean, renewable and quiet, writes Phil Cornford. By the end of the year, the diesel-fuelled generators in Innamincka will fall silent when Australia's first power plant fuelled by hot rocks, four kilometres below the Earth's surface, supplies electricity to the sun-scorched Cooper Basin outpost 1100 kilometres north-west of Adelaide.

"It'll be a lot quieter without the generators running 24 hours a day," says Kym Ford, owner of the Innamincka Hotel, one of only a half dozen buildings in the hamlet, which was not there when explorer Charles Sturt rode past in 1845. It will also save the hotel an annual diesel bill of $150,000.

Innamincka, which has a population of 12, is a long way from everywhere, and the power plant will generate only 1 kilowatt of electricity, a modest beginning. But it will be the first exploitation of deep-earth geothermal energy in what is known as the South Australian Heat Flow Anomaly, a vast area of subterranean fractured granite with estimated potential to produce 60 times more electricity than the Snowy Mountains hydro-electric scheme.

In these times of climate change, it is significant that geothermal power replenishes itself and is clean, producing none of the carbon dioxide gases that contribute to global warming. Geothermal power figures as a major contributor in Federal Government plans to drastically reduce greenhouse emissions, with predictions that hot rocks will supply 6.8 per cent of Australia's total energy by 2030.

The Innamincka power plant is being developed by Geodynamics Limited, which plans to expand it to 50megawatts in 2012. That is enough capacity to supply up to 50,000 households, but it will send electricity 110 kilometres to the Moomba oil and gas field. The company plans a 500 megawatt plant by 2016, when it expects to supply power down a 500-kilometre, high-power transmission line to the national electricity grid in Port Augusta, and another transmission line to BHP Billiton's Olympic Dam mine, 490 kilometres away. The estimated cost is $2 billion.

Petratherm Limited will drill two four-kilometre wells later this year and early next year at its Paralana site, 320 kilometres north-east of Port Augusta and 180 kilometres south of the Geodynamics tenements. Petratherm plans a 7.5 megawatt power plant by 2010, supplying electricity to the nearby Beverley uranium mine, expanding to 30 megawatts in 2012 and 260 megawatts in 2020, with transmission lines to Port Augusta, and 300 kilometres east to Olympic Dam. The estimated cost is $2 billion.

One of the advantages of hot rocks energy is that, unlike coal and gas which are consumed in generation, the heat and water resources are recirculated, giving them life expectancies of 50 years and more.

To produce 50 megawatts, the explorer Geodynamics will drill nine wells four kilometres down into fractured granite, heated to more than 250degrees by the radioactive decay of uranium, thorium and potassium.

Broken by horizontal fractures, the granite becomes a conduit for a reservoir of superheated water which is thrust up five wells at great pressure, surfacing at 210 degrees as steam to drive electricity turbines. When it is used and cooled, it is pumped down four wells to be used again.

Each well costs $10 million and takes about 110 days to build, although Geodynamics expects to reduce this to 70 days after spending $32 million buying the biggest drilling rig in Australia, capable of drilling down to six kilometres. But to expand its power plant to a 500 megawatts capacity, it will have to drill 81wells in four years, a task needing at least six drilling rigs.

But there is a worldwide shortage of deep drilling rigs, and Geodynamics, Petratherm and other explorers will all want them at the same time. Where to get them? "It's a problem we're working on," a spokeswoman from Geodynamics says.

By the end of last year, four other geothermal companies had drilled in the Cooper Basin - Green Rock Energy Limited, Geothermal Resources Limited, Torrens Energy Limited and Scopenergy-Panax. Thirty-three companies have taken exploration licences in the Cooper Basin, where the Heat Flow Anomaly has the world's greatest and hottest reservoir of hot fractured rocks within a depth of five kilometres.

Geodynamics estimates the potential of its 2500 square-kilometre exploration area to be 11,000 megawatts. Petratherm estimates its resources will provide 13,000 megawatts. The potential of the entire Cooper Hot Rocks Flow Anomaly is estimated to be 100,000 megawatts. These are enormous resources when compared to Australia's 2006 production of 44,000 megawatts from mostly coal-fired power plants.

Geodynamics also has exploration tenements south of Muswellbrook where seismic tests suggest there are hot rocks granite deposits, not yet confirmed by deep drilling. If there is potential for geothermal energy, it has the enormous advantage of being close to big markets, unlike the isolated South Australian tenements.

Petratherm has geothermal projects in Spain, the Canary Islands and China. Geothermal developments are under way in France, Germany, Switzerland and California, where hot rocks generate 1.6 per cent of total United States energy, the most in the world. But it is the Cooper Basin which has the greatest prospects, with geothermal potential estimated to be sufficient to meet Australia's total electricity demand for 450 years.

A company proposing to tap into a geothermal energy source in the upper Hunter Valley will drill deeper, with tests showing temperatures are hot enough for the project to be viable. GeoDynamics' Hot Rocks project involves pumping water down boreholes onto hot underground granite and using the steam that is generated to drive power station turbines. The company has been conducting shallow test drills near Singleton for eight years.

The latest results show temperature gradients of up to 58 degrees Celcius per kilometre, which are comparable to those in the company's larger Cooper Basin project in South Australia. Executive director Doone Wyborn says the next step is deeper drilling to between four and five kilometres underground.

Mr Wyborn believes temperature gradients at that depth would exceed 100 degrees Celcius per kilometre. "We've got pretty reasonable temperature gradients, not as good as in South Australia," he said. "But they're pretty reasonable considering we're right in the middle of the energy capital of Australia, if you like, with all the coal fired power stations. There's powerlines virtually running overhead from our site so we are keen to start looking a bit deeper down."