Tuesday 13 February 2007

Saving precious water at the flick of a switch

Age
February 12, 2007
By Tim Flannery

What is the best way to save water? You might be surprised to learn that turning off the light can help. It takes enormous quantities of water to generate Australia's electricity.

That's because we're so dependent on old-fashioned coal-fired power stations. For every megawatt of power they generate, they take two tonnes of water (and produce one to 11/2 tonnes of carbon dioxide and lesser amounts of greenhouse gases such as methane and nitrous oxide).

For a city such as Sydney, so great is the power demand that a fifth of the city's water needs is consumed by electricity generation. That water is used in steam generation and cooling. Nuclear power uses lots of water too. Those ominous, steaming towers that most of us associate with nuclear power plants are in fact cooling towers, and it is water vapour, not radiation, that they emit.

Coal-fired power stations often have a lake of warm water nearby. That's the residue of water left from cooling the plant. In cold regions such as Gippsland they steam in winter, and as legends of the bunyip abound in the same regions, the warm ponds have an eerie feel about them

There are, of course, technologies that can generate electricity using less water than conventional coal, or no water at all. The newest two of Queensland's coal-fired power plants are air-cooled, so while they still generate greenhouse gases, they don't use precious water. Modern gas-fired power plants use just one tonne of water for each megawatt of electricity generated, and far less carbon dioxide than coal, so switching to them is a great step forward.

But wind, solar and hydro power don't use any water at all, and none of these technologies generates greenhouse gases in producing electricity. Some kinds of geothermal energy (such as that found in central Australia) also use no water, and none generates greenhouse gases. Hastening the uptake of any of these technologies can thus help ease the water crisis.

There's no need to install solar panels to help save water (though that helps significantly). Buying a green energy option can do a great deal, and it is cheaper. Given that it takes around a megawatt of power to provide electricity to 600 homes, by either switching to green power, or by saving electricity, you can do a great deal to save water.

All around Australia our water crisis is growing so desperate that the managers of the old-fashioned, coal-fired clunkers face enormous problems in sourcing water. In NSW, dam levels have fallen so low that the remaining water has become too salty to be used to cool the power plants, so managers are having to invest in a type of desalination.

And everywhere coal-fired power plants are trying to source recycled water for cooling. On the face of it, this sounds like a great idea, but recycled water is valuable stuff, and will become increasingly valuable in future. Should we really allow it to be used in such prodigious quantity to keep the old clunkers going?

In future, the rising price of water, and the need to resort to technologies such as desalination, must drive up the price of the electricity generated using this technology, which will make the renewables more competitive. This means that the old-fashioned, coal-fired power plants are being caught in a pincer movement that must inevitably hasten their decommissioning.

Given the enormous problems we face in managing water, and in combating climate change, it may be best to face the issue of their decommissioning now, rather than wait until the ever-drier heavens forces the issue.

Tim Flannery is the 2007 Australian of the Year.

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