Geothermal - how it works

Geothermal energy is an energy source generated from naturally occurring heat within the Earth.

In hydrothermal geothermal systems, deep groundwater, which has been naturally heated to steam temperatures, is brought to the surface and used to turn turbines. In dry rock systems, water is injected into hot rocks and returned to the surface once heated.

Geothermal energy’s immense potential has been hailed by government ministers and industry representatives. With the Federal Government’s 20 per cent by 2020 renewable energy target, and the states and territories working towards their own goals, geothermal energy is a viable, if as yet, underdeveloped renewable energy source. Australia’s potential resources are great, and hot rock energy generates no greenhouse gas emissions and leaves no waste. Moreover, in the last two years the number of companies exploring for geothermal energy sources in Australia has doubled.

With so much potential, state and federal governments are racing to open up tenements and capitalise on an industry that could greatly contribute to diversifying Australia’s power supplies and lowering its carbon footprint.

Around Australia

Victoria

Late last year, the Victorian Minister for Energy and Resources Peter Batchelor said the geothermal industry in Victoria had plenty of potential and was entering an exciting period of growth.

“The huge potential of the geothermal industry in Victoria offers the opportunity to create jobs and investment and to develop an environmentally sustainable energy industry, which can help tackle climate change,” he said.

“The geothermal industry is still in the early stages of development in Victoria. However, the Brumby Government is keen to encourage its development in the renewable energy sector.”

The State Government awarded 12 geothermal exploration permits to five companies in 2007, and 19 further permits will be offered in April this year, allowing companies to search across more than 154,000 km² of previously unexplored areas.

Western Australia

In Western Australia, the race is on to develop the state’s geothermal energy potential, following the first release of acreage for geothermal exploration in January.

The acreage stretches from south of Kalbarri down to Dunsborough and has been divided into 495 lots. Going about 250 km inland, it finishes slightly east of Cunderdin, Narrogin and Wagin and west of Mount Magnet.

Bids for the exploration permits close on April 24. A second acreage area, to be situated in the Carnarvon basin region, will be released later this year.

WA Resources and Energy Minister Francis Logan said the opening of geothermal acreage would signal the beginning of a dynamic clean energy industry in WA.

“We are fortunate in WA to have an abundance of natural energy resources that are in demand across the world,” Mr Logan said. “But we need to diversify our energy supply to keep up with the demand for domestic power, as well as to make a positive contribution to the environment.

“Geothermal power systems are basically closed systems without emissions. It is one of the cleanest forms of energy possible.”

Queensland

According to Queensland Mines and Energy Minister Geoff Wilson, geothermal energy has the potential to generate one fifth of Australia’s total electricity needs over the next 25 years without producing any carbon dioxide emissions.

Mr Wilson said “Queensland is best placed to capitalise on geothermal energy – we are home to most of Australia’s hot rocks.

“Indeed, initial estimates indicate that the hot dry rocks beneath the Eromanga and Cooper basins could meet all of Australia’s energy needs for many years into the future.”

He called Queensland’s geothermal industry a sunrise industry which has State Government support – in September 2007, Premier Anna Bligh announced that the government would provide $15 million over the next five years to establish a Queensland Geothermal Energy Centre of Excellence.

“It faces a bright future because it has the potential to produce more base load energy than any other renewable energy source,” said Mr Wilson.

Thirteen new areas were opened for tender for geothermal exploration across Queensland in late December 2007, totalling more than 7,000 km².

Six of these areas are located in north Queensland, including Skardon River north of Weipa on Cape York and three areas southeast of Karumba in the Carpentaria Gulf country. Of the remaining areas, one is located southwest of Longreach, three are northeast of Birdsville and three are southwest of Eromanga.

South Australia

South Australia has major geothermal potential and will likely see Australia’s first geothermal energy generation. The State Government has received applications from over 20 companies for more than 200 geothermal exploration licences. Nearly 40,000 km² of onshore exploration licences are currently under application with the Department of Primary Industries and Resources SA (PIRSA).

Torrens Energy has announced that its hot rock exploration drilling, underway at the Torrens Project Area, north of Port Augusta in South Australia, has returned outstanding early temperature results. The company has announced that temperature gradients measured from two wells have yielded very high values – above the averages recorded in the Cooper Basin. Torrens Energy’s standard temperature modelling shows that temperatures of 240°C are achievable at approximately 5,000 metres depth. The company has completed drilling four and commenced a further three planned exploration drillholes at the Torrens Project Area.

Geodynamics is gearing up to produce Australia’s first megawatts of geothermal power from its Cooper Basin joint venture project with Origin Energy, as well as finalising the design of a 50 MW power plant. Origin has invested in 30 per cent of Geodynamics’ South Australian tenements as part of a $105.6 million deal.

Geodynamics’ pilot project will result in the installation of the first hot fractured rock power plant in Australia, using the circulation loop between the Habanero-1 and Habanero-3 wells. The 1 MW power station will enable Geodynamics to use geothermal energy to power the company’s field operations.

Geodynamics also plans to finalise its preferred design for a 50 MW power plant this year, with operations planned to commence in 2012. The power plant, which will produce zero emissions with zero water requirements, will produce enough electricity to power approximately 50,000 households on a continuous basis. Geodynamics aims to achieve production output of 500 MW by 2016, based on ten 50 MW power plant modules to be constructed progressively from 2010.

Petratherm, together with its joint venture partner Beach Petroleum, is also exploring geothermal energy potential in South Australia. The Paralana Geothermal Energy Project covers over 500 km² of known hot rock granite resources adjacent to the Mt Painter region of South Australia’s northern Flinders Ranges. The project is now in its third stage and is likely to be one of Australia’s first commercial geothermal energy supplies. In February, PIRSA granted a $100,000 grant to the joint venture for the Paralana project.

Petratherm has drilled one well to just over 1,800 metres, with results suggesting that a temperature of 200°C could be attained at a depth of approximately 3.6 km. In 2008, Petratherm and Beach Petroleum plan to drill two new deep wells to confirm the expected thermal resource, undertake circulation tests and establish an underground heat exchanger at Paralana. Petratherm’s initial commercialisation phase involves the deployment of a 7.5 MW power station at Paralana, at a nominal cost of approximately $50 million.

Tasmania

Major geothermal exploration in Tasmania is being carried out by KUTh Energy – see EcoGeneration’s interview with KUTh Chief Operating Officer Malcolm Ward on p33.

In November last year, Geothermal Energy Tasmania Holdings Ltd was also granted its first geothermal exploration licence. Covering 2,205 km² in western Tasmania, the licence is the first of three applications to be granted to the company.