The world has never been short of wind. For thousands of years it has turned windmills, flown kites, cooled houses and filled sails (Box 1: What causes the wind?). Now, technological advances are breathing new life into our use of wind power as a clean, renewable, cost-effective means of generating electricity. Wind has its turn The first electricity-generating wind turbines were invented in the United States and Europe in the late 1800s. In the early 1900s, as electricity became more widely available in towns and cities, many rural communities and homesteads turned to small-scale wind turbines for their electricity supply. Many were built on-site, using old car generators and hand-carved rotor blades or old biplane propellers. Wind power is increasing in popularity as an energy source. In 2008, the installed capacity of wind turbines worldwide was about 120 gigawatts and was increasing at approximately 30 per cent every year. Much of the growth is in the USA and European countries such as Spain, the United Kingdom and Germany. Denmark currently obtains about 20 per cent of its electricity from wind turbines and aims to increase this to 35 per cent by 2015. Interest in wind power is also growing in countries such as India and China, and Australia is paying increasing attention to the concept. Why the recent interest? There are probably two main reasons for the increasing interest in wind power. First, most electricity generated today uses non-renewable fuels such as coal, oil and gas. These contribute vast quantities of carbon dioxide to the atmosphere, causing the enhanced greenhouse effect warming Earth's atmosphere. The second reason is that advances in wind power science and technology are reducing the cost of wind power to a point at which it is becoming competitive with many other energy sources (at about 7 cents per kilowatt hour). The world has long been searching for a non-polluting, renewable source of energy that is as cheap as coal and oil (Box 2: The environmental credentials of wind power). The science of wind generation In a coal-fired power station, chemical energy stored in coal is converted first to heat energy by burning and then into kinetic energy (energy of motion) by heating water to produce steam. A high pressure jet of steam is used to turn a turbine (mechanical energy), which is then used to turn a generator to produce electrical energy. (See Box 3: Energy basics for a simple introduction to energy.) In generating electricity from wind, the chemical and heat energy steps are not needed: the kinetic energy of the wind turns the turbine (or blades), which then turns a generator to produce electricity. The potential power of wind turbines The power available from a wind turbine increases very rapidly with wind speed: a doubling of wind speed results in as much as an eight-fold increase in power. Therefore it is important to site wind generators in a place where the wind speed is high, as well as reasonably constant. The length of the rotor blades is also important – doubling the diameter of the circle made by the blades produces a four-fold increase in power (Box 4: The power of the winds). Whipping up the wind A drawback to wind power is that the wind can be erratic, changing direction by the hour. There may be no wind at all one day and a howling gale the next. It may blow hard at times when electricity demand is low, and be a mere gentle breeze when demand is high. But many of the problems of wind power are now being solved. For example, locating wind turbines in areas where the wind blows regularly and at optimum speeds would be a good way to start. In Australia, important advances have been made in this regard: CSIRO researchers have used computer models of wind-flow over complex terrain, together with extensive wind measurements, to calculate potential wind energy yield at different locations. There are other relatively simple tricks to catching the wind. For example, the wind is slowed by friction with the land surface. Modern wind turbines are therefore mounted on towers 40-60 metres high to expose the blades to a higher wind speed. Rotor length Rotor blades need to be strong, light and durable. These qualities become more elusive as blade length increases. Recent advances in fibreglass and carbon-fibre technology have enabled the production of lightweight rotor blades (usually two or three per turbine) between 20 and 30 metres long. These blades are capable of performing for years in the rugged conditions of some of the world's windiest locations. Turbines with blades of this length can generate up to 1 megawatt of power. Plugging into the power supply The large-scale production of wind-powered electricity involves the use of windfarms. These are concentrations of wind turbines – from just a few to hundreds that feed electricity directly into the supply network. Electrical engineers know that the wind doesn't blow all the time and have devised a number of strategies to ensure that electricity supply meets electricity demand. A network of windfarms feeding into a common grid, for example, may help provide a steady supply: when one windfarm is becalmed, others elsewhere in the region and the continent may continue to operate. Alternative energy sources (such as solar, coal, hydroelectricity or gas) may also help smooth the load. And new technologies are available to store surplus energy generated during windy periods for use at a calmer time. The winds of change How far can wind power take us? The Australian government wants 20 per cent of the nation's electricity to be obtained from renewable sources such as wind power. Wind power technology has the potential to supply a significant proportion of the nation's electricity needs – just as long as the wind keeps blowing. Boxes 2. The environmental credentials of wind power Related Nova topics: Harnessing direct solar energy – a progress report Generating new ideas for meeting future energy needs Which way ahead for hydrogen cars?
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Page updated January 2010.
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This topic is sponsored by Pacific Power and the Australian Government's National Innovation Awareness Strategy.
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