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Hydroelectric power is created by the flow of water. It can come from rivers, or from man-made installations where water flows from a high reservoir through a tunnel and away from the reservoir’s dam. Water power has been used to power machinery for centuries. For example, it was used to grind corn or in mills and factories, but in the Industrial Revolution steam power largely replaced it. Water-power is now mainly used to generate electrical energy.
Turbines are placed in flowing water. The water’s kinetic energy drives the turbines, which, in turn, drive a generator that converts the mechanical energy into electrical energy. Hydroelectric systems can be connected to the main electricity grid, or as part of a separate power system.
Water power has driven machinery for centuries. Using water to generate electricity is also well established – Scottish Power’s oldest hydro power station in Lanarkshire dates back to 1927.
Hydroelectric power currently provides around 0.8 per cent of total UK electricity supply, mostly from large-scale hydroelectric schemes in the Scottish Highlands.
Opportunities to increase large-scale hydroelectric power in the UK are limited, as most commercially attractive and environmentally acceptable sites have now been used. A large 50 to100-megawatt scheme at Glendoe has been approved and is due to begin construction in spring 2005. There are several new small-scale hydroelectric schemes in planning or development. A number of other smaller schemes have also been approved in Scotland, such as the 3.5-megawatt development at Kingairloch in Lochaber and the 2.2-megawatt scheme at Braevallich in Argyll. These were approved in 2003 and will provide enough electricity for over 5,000 households.
Some old watermills are being refurbished and bought back into the energy supply network. If small-scale hydroelectric power from all of the streams and rivers in the UK could be tapped, it would be possible to produce 10,000 gigawatt hours (1 gigawatt hours = 1,000,000 kilowatt hours) per year – enough to meet just over 3 per cent of our total electricity needs and making a significant contribution to the Government’s renewables target of 10 per cent by 2010.
Noise and emissions are very low. Large-scale schemes can cause disruption while they are being built, and, if flooding is involved, some carbon dioxide emissions may arise from rotting vegetation in the short term. River ecology is protected through the Environment Agency, which requires all schemes to have an abstraction licence. Eroded shorelines and dams can be seen as unattractive, but many schemes also attract visitors and offer leisure opportunities.