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Energy resources: Hydropower


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Energy from sources other than fossil or nuclear fuels is to a large extent free of the concerns about environmental effects and renewability that characterise those two sources. Each alternative source supplies energy continually, whether or not we use it. Many alternative sources of energy have been used in simple ways for millennia, e.g. wind and water mills, sails, wood burning – but only in the last two centuries has their potential begun to be exploited on an industrial scale. Except for geothermal energy, all have their origins in energy generated outside the Earth, yet the potential of each is limited by its total supply set against its rate of use. Each is likely to be renewable in the sense that the available rates of supply of each exceed those at which they are used. The main concern is whether or not such alternatives can supplant fossil- and nuclear-fuel use to power social needs fast enough to avoid the likelihood of future global warming and other kinds of pollution.

One of the alternative sources to consider is hydropower.

Hydroelectric energy is ultimately solar energy converted through evaporation of water, movement of air masses and precipitation to gravitational potential energy and then to the kinetic energy of water flowing down a slope. That energy was harnessed for centuries through the use of water wheels to drive mills, forges and textile works, before being supplanted by coal-fired steam energy.

The principle of hydroelectric power generation is simple; water flowing down steep gradients or from dams is channelled through pipes and transfers its kinetic energy to rotating turbines that drive electricity generators. Steep gradients ensure high flow speeds, and piping is necessary to maintain the pressure head. Some energy is lost to friction and turbulent flow in the pipes, in turbine rotation, and in the conversion of mechanical energy to electricity in the generator. However, most of the potential energy of water stored in a reservoir can be converted into electricity.

This unit considers hydropower as a potential source of useable energy.

This unit is from our archive and is an adapted extract from Earth's physical resources: origin, use and environmental impact (S278) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore other courses we offer in this subject area [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .

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