THE FEW engineers who recently saw super heated water explode into a geyser of steam out of the red dirt of South Australia's remote Cooper Basin said it screamed so loudly their ears hurt.

But the weird sight, a plume of steam shooting briefly into the sky in the vastness of an empty desert, accompanied by maybe the loudest sound ever heard across its mirage-rippled wastelands, may have announced breakthrough in clean, renewable energy.

A big step closer

It represented a big step closer to the goal of Australian firm Geodynamics Limited, to tap into the natural heat stored in vast beds of underground granite and use it to generate electricity.

The company says there is enough usable heat energy in a 1000 square kilometre section of the rocks to replace 50 billion barrels of crude oil — or around 12 times as much oil as there is in the country's largest proven oil reserves, in the north west shelf off the tip of Western Australia.

The hope is the project can help solve the dual crises of shrinking oil supplies and greenhouse gas emissions. Dr Bertus de Graaf, Geodynamics managing director, says the lode of hot rocks under the Cooper Basin is the largest resource of its type known in the world, other than beneath volcanoes.

"(These rocks) are a reef of granite trapped in the upper crust that makes up the continental plate in which small amounts of radioactive elements including thorium and potassium have been releasing heat as they decay over millions of years," he said.

Wet geothermal energy has been used in Iceland and New Zealand where steam from hot springs are used to drive the turbines in power stations. But hot dry rock or HDR geothermal energy has proven far harder to tame, even though the principle is simple and has been the subject of research in dozens of countries for many years.

After two years of drilling holes up to 4.4 kilometres deep Geodynamics is now able to pump cold water down into the granite reef where it becomes superheated and blasts its way back to the surface through a return shaft.

According to the engineers, about 75 per cent of the heat in the hot water was lost as predicted when it exploded into steam out of the exit valve.

However enough energy was captured by a heat exchanger to satisfy the needs of a future power station.

Pilot power station

Geodynamics' next step is to hook up a pilot power station and prove that part of power generated can be used to drive the water back into the subterranean heat source.

Dr de Graaf believes it will cost only four Australian cents per kilowatt per hour to produce electricity from the Cooper Basin site, or about the same as the cost in Australia for getting the energy from coal and natural gas.

If the pilot plant works as planned in the next year or so the company will sink 16 injection and 21 extraction holes into a seven square kilometre section of the lode to build a non-polluting power station generating 275 megawatts.

To put this in perspective, the state of South Australia consumes 1500 Megawatts in the cool months and tries to draw 3000 Megawatts each scorching summer, when the only large city, Adelaide, turns its air-conditioning up to maximum.

This causes widespread `brown outs' because the state's generating capacity is about 2700 Megawatts.

Geodynamics has already identified other comparatively easy-to-tap hot rock reefs in New South Wales, ironically beneath the richest coal fields in Australia, and in parts of Queensland and believes many more lodes await discovery in Australia and other parts of the world.

Dr de Graaf says HDR is the only form of non polluting renewable energy capable of providing the power required by heavy industry and major cities, as it doesn't suffer from the variability and minuscule efficiency of solar and wind power.

If the screaming geyser of the Cooper Basin gives up its energy as cost effectively as its backers believe, they stand to become very rich as well as very green power brokers. —

© Guardian Newspapers Limited 2004

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