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29.06.2008 
Acting as part of a consortium, Siemens has built a coal-fired power plant in the
Australian outback that operates with almost no cooling water. By means of a special
air-cooled condenser, the plant uses air instead of water to cool the hot steam from
the plant turbine. As reported in the latest issue of the research magazine Pictures
of the Future, the Kogan Creek power plant uses 90 percent less water than conventional
plants, an ideal solution for coal-based power generation in arid regions.
Kogan Creek, which is about 300 kilometers from Brisbane, is the largest power plant
in Australia, with an output of 750 megawatts. Moreover, with its 45-percent efficiency,
it is also one of the most efficient power plants in the country. While similar power
plants have enormous cooling towers, here there is a roof the size of a football field
instead, supported on 15-metre-high stilts. Beneath this roof of corrugated steel
sheets, two low-pressure turbines emit hot steam at 60 to 80 degrees Celsius, which
flows through large heat exchangers. Fans nine meters in diameter blow air against
the metal sheets from below and cool the steam, which in turn condenses. Five hundred
liters of water per second flow into a collector at the lower end of the heat exchanger
and then into a tank, from where pumps feed it back into the power plant to generate steam.
The power plant cannot operate entirely without fresh water, however. Water drawn from
deep bores replenishes losses in the steam cycle of the turbines and serves as cooling
water for the electrical equipment, which cannot be cooled with air alone. Nevertheless,
with its water savings rate of 90 percent, Kogan Creek far outperforms comparable
power plants when it comes to economy of water use. That offers extra reserves in
extremely dry periods, when water-cooled power plants are forced to scale back their
output. At Kogan Creek, water can be sprayed beneath the condenser surfaces for
additional cooling. This enables the plant’s operators to run it at its full capacity
of 750 megawatts even at temperatures well over 40 degrees Celsius, or tease out
a few more megawatts when there are bottlenecks in the grid.
Since it was commissioned in late 2007, Kogan Creek has been feeding its electricity
into the high-voltage transmission line between the federal states of Queensland
and New South Wales in the south. The high-voltage transmission line supplies
communities including major cities on the east coast, such as Brisbane and Sydney,
and thus provides approximately half of Australia’s population with electricity.
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