Overview
The earliest conventional method for generating electricity was by burning lump coal on a grate in boilers to raise steam. In modern, highly efficient, versions of this system, the coal is first milled to a fine powder in a pulveriser. This increases the surface area of the coal and hence the rate of combustion. The powdered coal is blown into the combustion chamber of a boiler where it is burnt at around 1400°C. The hot gases and radiant heat energy produced convert water in tubes lining the boiler into steam.
The high-pressure steam is passed into a turbine containing thousands of propeller-like blades. The expanding steam hits these blades causing the turbine shaft to rotate at high speed. Mounted at the end of the turbine shaft is the generator, consisting of carefully wound wire coils. Electricity is generated when these are rapidly rotated in a strong magnetic field.
After passing through the turbine chamber, the steam is condensed and returned to the boiler to be heated once again.
The electricity is transformed into the higher voltages used for economic transmission via power line grids (400,000 volts and above). Near the point of consumption, the electricity is transformed down to the safer 100-250 voltage systems used in the domestic market.
To see an animation of how electricity is produced at a coal-fired power station, click on 'Further Reading' at right. Animation from the Oresome Resources site, courtesy of the Queensland Resources Council.
Coal and Electricity Generation in Australia
Combined, black and brown coal currently account for over 80 per cent of Australia’s electric power, with black coal accounting for around 57 per cent.
Large base-load black coal-fired power stations are located in relatively close proximity to the extensive black coalfields in both New South Wales and Queensland as well as in Western Australia.
Note that the emissions from the 'smokestacks' shown here are mainly water vapour.
Bayswater Power Station, New South Wales, Australia
Brown coal-fired base-load power stations are located in the Victoria’s Latrobe Valley. South Australia also relies heavily on sub-bituminous coal mined at Leigh Creek in the north of the state.