Rock-solid energy

Sunday Tasmanian
13/01/2008 Page: 67

POWER stations conjure up images of great hulking buildings belching out smoke and noise. But what if a power station could be the size of a shed, sitting alongside residential houses and releasing no emissions? The power it draws is at the mercy of neither sun nor wind and, unlike hydro electricity, it is drought-proof.

Experts say it could one day compete with coal-fired power stations and eliminate the need for nuclear reactors. It is not hard to see why geothermal or "hot rock" energy was for years considered the product of overactive imaginations. Technical director of Victorian-based consultancy Hot Dry Rocks Graeme Beardsmore first tried to rouse interest in Tasmania's promising geothermal resource four years ago.

"I am a bit of a fan for geothermal in Tasmania - the geology is good, the infrastructure is good and you have got Basslink across to the mainland so you can sell the power for a reasonable price," Mr Beardsmore said. "The government and industry people smiled and nodded, but at that stage they thought geothermal was pie in the sky and not serious at all." But late last year residents of the German city of Landau proved the elaborate promises of the technology were more than hot air when they became the first commercial users of hot rock energy.

In theory the concept is simple. Two holes are drilled up to 5km into rocks (usually granite) that hold heat from the earth's core. Water is injected down the first hole and becomes superheated to temperatures between 150 to 250 degrees as it passes through fractures in the hot rock before rising from the second hole as steam. The steam either drives a turbine directly or is used to boil a secondary liquid before being condensed and injected back underground to form a closed loop.

In a perfect system the water used can be recirculated indefinitely. Without careful management the heat reserves in the rocks can be temporarily exhausted. "But there is no risk of cooling the earth's core, which you hear from panic merchants occasionally," Mr Beardsmore said.

After a slow start, Australia isn't far behind Landau in proving hot rock energy is viable. Industry leader Geodynamics plans to start producing demonstration power in the Cooper Basin in outback South Australia by the middle of this year. In the past five years 32 companies (including three in Tasmania) have started looking for suitable geothermal resources. The Energy Supply Association of Australia estimates that by 2030 almost 7 per cent of Australia's electricity will be sourced from hot rocks.

But with massive resources available underground, experts have their sights set on the energy industry's big guns. "We don't see ourselves as competing with solar, wind or biofuels. Our competitors are clean coal and nuclear and natural gas - the other potential base load providers of clean energy," Mr Beardsmore said. geothermal is the only renewable energy source capable of supplying constant baseload power to keep cities and towns running 24 hours a day.

For Tasmanian-based KUTh Energy, the granite boulders at Bicheno and the iconic Hazards at Freycinet are monuments of promise to geothermal energy. It is that granite, buried deep underground in their nearby tenements, from which they hope to produce up to 200 megawatts of energy. KUTh general manager Malcolm Ward estimates it will take five years and cost at least $35 million to build a five megawatt pilot power station in Tasmania.

"Geothermal is more expensive than existing dirty coal and gas, but if a carbon tax is put on them, their costs will go up, and geothermal, over the long run, will be at least competitive and maybe even cheaper than fossil fuels." Tasmania's major advantage is that its high-voltage power network is easily accessible from anywhere in the state.

As the technology matures, state and federal governments are starting to take notice of the hot rock industry. But it is the enthusiastic stock market and environmentally conscious mum and dad investors that has secured the future for hot rock energy with $800 million in private investment. Hot Dry Rocks geologist Ben Waining said: "A lot of it is being driven by people's awareness of climate change and they are really willing to put their money where their beliefs are. You can see that in Tasmania."