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Green power

Wind farms

Wind farms - a form of green power.

Credit: iStockphoto

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The third popular form of green electricity is hydroelectric, which is used as a major form of electricity generation around the world. Hydro can be in the form of dams, from the mighty 3,756 MW Snowy Mountains Hydro plant to the 4.5 MW Wivenhoe dam in Queensland, which nevertheless displaces around 20,000 tonnes of greenhouse gas emissions each year, or in micro-hydro plants based in rivers and other fast-running waterways.

Hydro has the advantage that it releases no greenhouse gases during operation, and it’s often very reliable and flexible: power can be generated at a moment’s notice by simply opening a valve. However, there’s not much more capacity for large hydro plants here in Australia or around the world, as most of the suitable locations are already being used. And in Australia, global warming is making water a bit scarcer every year.

Another very popular form of green energy is derived from biomass, which is basically any organic material. There are two common forms of biomass power: thermal and biochemical. Thermal sources include burning sugarcane bagasse, or tapping landfill and extracting the methane formed from the decomposing garbage, which is then run through a gas turbine. Biochemical processes convert organic matter into fuels, such as ethanol or biodiesel, which can then be burnt or used as fuel in vehicles.

Biomass is currently being exploited in many regions of Australia, with over 650 MW coming from a variety of sources, according to an Australian Business Council for Sustainable Energy report in 2005. Not surprisingly, bagasse is most popular in Queensland, where the majority of sugarcane production takes place. Much of the power generated from bagasse doesn’t go back into the grid: it’s usually used to power the sugarcane mills themselves. Burning methane from landfill gas is another popular source of green electricity, although ironically, as our waste practices improve and we recycle more, landfill gas could actually play a smaller role in the future.

Solar, hydroelectric, wind and biomass are the four most common forms of green energy in use around Australia, although there are other technologies that may be used in the future.

One of these is geothermal, which taps into the natural heat below the Earth’s surface and uses it to run steam turbines. Deep below South and Central Australia lies the equivalent of billions of oil barrels of geothermal energy waiting to be accessed. The heat is trapped in massive slabs of rock, which may one day provide large quantities of renewable, emission-free electricity. Like many wind farms, they are located far from the cities (where the energy is most needed); but efforts are underway to extract the energy and deliver it afar at low cost.

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