A good example of a site where wind power has been put to good effect is Fair Isle, an isolated island in the North Sea north of the Scottish mainland.48 Until recently, the population of 70 people depended on coal and oil for heat, petrol for vehicles and diesel for electricity generation. A 50-kW wind generator was installed in 1982 to generate electricity from the persistent strong winds of average speed over 8 m s-1 (29 km h-1 or 18 mph). The electricity is available for a wide variety of purposes; at a relatively high price for lighting and electronic devices and at a lower price controlled amounts are available (wind permitting) for comfort heat and water heating. At the frequent periods of excessive wind further heat is available for heating glasshouses and a small swimming pool. Electronic control coupled with rapid switching enables loads to be matched to the available supply. An electric vehicle has been charged from the system to illustrate a further use for the energy.
With the installation of the wind generator, which now supplies over 90% of the island's electricity, electricity consumption has risen about fourfold and the average electricity costs have fallen from 13p per kWh to 4p per kWh. A second wind turbine of 100 kW capacity was installed in 1996/7 to meet increasing demand and to improve wind capture.
of installed capacity ranks as fourth in the world in wind generation. By 2050 under the IEA BLUE Map scenario, 12% of global electricity is projected to be provided from wind energy.
Wind energy is also particularly suitable for the generation of electricity at isolated sites to which the transmission costs of electricity from other sources would be unacceptable. Because of the wind's intermittency, some storage of electricity or some back-up means of generation has to be provided as well. The installation on Fair Isle (see box) is a good example of an efficient and versatile system. Small wind turbines also provide an ideal means for charging batteries in isolated locations; for instance, about 100 000 are in use by Mongolian herdsmen. Wind energy is often also an ideal source for water pumps - over 1 million small wind machines are used for this purpose worldwide.47
In the longer term it can be envisaged that wind generation could expand into areas remote from direct electrical connection providing an effective means for energy storage can be developed (for instance, using hydrogen; more of that possibility later in the chapter).
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.