Energy its a hot topic Centrepiece Energy feature

Saturday, 01 June 2002


    The world is running out of oil and coal and finding new energy sources is paramount if we are to avoid fighting over dwindling supplies.

     Australia is about to tap the geothermal energy beneath the earth that holds the promise of providing base load supplies. John Arbouw reports.

    "The fifth revolution will come when we have spent the stores of coal and oil that have been accumulating in the earth during hundreds of millions of years ... It is hoped that before then other sources of energy will have been developed ... but without considering the detail it will be obvious that there will be a very great difference in the ways of life ... Whether a convenient substitute for the present fuels is found or not, there can be no doubt that there will have to be a great change in the ways of life. This may justly be called a revolution, but it differs from all preceding ones in that there is no likelihood of its leading to increases of population, but even perhaps to the reverse." - Sir Charles Darwin, 1953

    There are those that still believe that the US Civil War (1860-64) was a fight to free the slaves rather than a struggle between the agricultural South to have tariff-free markets for its cotton against an increasingly industrialising North that wanted protection against imports.

    The efforts to disguise armed conflict in terms of a noble justification rather than a means to gain economic ends continue today.

    The current economic battle is oil and the noble justification is the war on terrorism.

    The reason is simple. Sometime within the next 20 years, global demand for cheap oil will exceed supply as the world's proven oil reserves reach their midpoint of depletion, to be followed by steadily declining petroleum production.

    Since 1979 oil production per capita has declined an average 0.33 percent a year because producers can't keep up with the booming world population growth and the world's demand for energy.

    While there has been a significant switch to natural gas for power generation and transport, gas is still a non-renewable energy resource and Australia will need a lot of North-West Shelf and Cooper Basin type projects to maintain its supplies over the long-term.

    The use of coal to generate electricity is big business for Australia which has some of the best coal reserves on the planet. But coal reserves are also dwindling and electricity demand continues to expand worldwide, with consumption projected to grow by nearly 100 percent by 2020 (International Energy Outlook 2001).

    By 2010 an additional 9500 gigawatt-hours of renewable electricity will be required in the Australian market. This is equivalent to more than 1000MW of new generation capacity.

    In addition the green power market, where individual consumers elect to purchase renewable energy, will add at least another 2000 gigawatt hours onto the renewable energy market by 2010, adding a further 200MW of capacity for which RECs will be required.

    So where will the world gets its new energy source, even if the West can secure new supplies from the new Soviet Republics or install US-friendly governments in Iraq or Iran?

    The answer is no one knows. Alternative energy has had a chequered history. The Snowy River and Tasmania's lakes produce hydro energy, but this only supplements not replaces base load requirements.

    Biomass, solar, wind, tidal power, hydrogen, fuel cell are all used in one form or another but they are insufficient to replace non-renewables such as coal, oil or gas. Development of new sources such as cold fusion (the use of nuclear energy without generating excessive heat), zero point energy (extracting energy from the vacuum flux of space) or tapping the immense forces inherent in magnetism and gravity are still well down track.

    So what about geothermal energy?

    What could be more natural or plentiful? The source of geothermal power is the heat contained inside the earth. This heat is so intense that it creates molten magma. Some geothermal systems are formed when hot magma near the surface (1500 to 10,000 meters deep) directly heats groundwater. The heat generated from these hot spots flows outward toward the surface, manifesting as volcanoes, geysers, and hot springs.

    Naturally-occurring hot water and steam can be tapped by energy-conversion technology to generate electricity or to produce hot water for direct use. Other geothermal systems are formed even when no magma is nearby as magma heats rocks which in turn heat deeply-circulating groundwater.

    In order to maximize the energy gleaned from these so-called "hot dry rocks", geothermal facilities will often fracture the hot rocks (250C) and pump water into them, using the heated water to generate electricity.

    Generating electricity from the earth's heat isn't new. There are facilities of one kind or another in France, Italy, Japan and new Zealand. The interesting dimension is that, unlike other presently available alternative energies, electricity generated from geothermal sources has the potential to carry base-loads.

    The potential is enormous with one cubic kilometre of hot granite at 250C potentially generating the energy equivalent of 40 million barrels of oil. A four cubic kilometre of hot granite can sustain a 312MW power station for 30 years.

    Oh, and Australia is believed to have 10,000 cubic kilometres of hot granites with prospects already identified in the Cooper Basin in SA, the Eromanga Basin in Qld and at Muswellbrook in the Hunter Valley.

    Sometime this month, Queensland company, Geodynamics will go to the market looking for $20 million to prove that it is not only possible to use the heat generated 3km below the surface to generate electricity but that this can be done at comparative costs to other energy sources.

    Hot dry rock (HDR) geothermal energy uses well-established deep-sea oil drilling technology to reach the required depths.

    The HDR process itself is a closed system, with two loops.

    The first loop uses water to extract heat from the buried hot rocks. The simplest hot dry rock power plant comprises one injection well and two production wells. Cold water is pumped under pressure down an injection well where it flows through an underground heat exchanger in the hot granite. It is then returned to the surface through production wells.

    Because this loop operates under pressure, the super heated water remains a liquid, with no steam generated.

    The heated water (200C) returns to the surface under pressure. The high temperatures of the hot water are transferred to the geothermal power station loop via a heat exchanger. This second closed loop uses liquids with a low boiling point (similar to those in fridges and air conditioners) and this drives a turbine system.

    The cooled geothermal water returns to the underground heat exchanger where it is reheated, the twin loop system being known as a binary geothermal power plant.

    Geothermal energy is an accepted energy source. The process is technologically easy. What is required now is not simply proving that the resource is there or capable of generating electricity but that costs of scaling this up to base load levels is competitive with existing sources.

    Considering the alternatives it is worth having a go.


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