Imagine that in order to play computer games, listen to music, or talk on the phone, you first had to find a way to generate the electricity to power your electronic devices. Most people in the United States access electricity simply by plugging into a wall outlet or flipping a switch. Their homes are connected to power plants through the electrical grid, an extensive network of cables and wires that carry electrical current. However, whether by choice or by circumstance, some people are detached from this grid. This interactive activity produced for Teachers' Domain presents three such scenarios and challenges users to design systems that will generate electricity by harnessing the wind.
In recent decades, it hasbecome increasingly clear that fossil fuels will one day be inshort supply. In addition, burning fossil fuels has hidden costsin the form of environmental degradation. To combat rising energyprices and to ease environmental threats such as global warming,some countries and individuals have begun turning to renewableforms of energy, such as the wind. Unlike fossil fuels, wind isinexhaustible. As long as the Sun continues to shine, the wind willcontinue to blow, and where the wind blows reliably it offers anendless supply of clean energy. Harnessing that energy to generateelectricity on a large scale, however, requires careful planning anda high degree of technological innovation.
For centuries,people have used windmills to transform wind energy into moreusable forms of energy. The principle is fairly simple. As windpasses over the blades of a windmill, it causes the blades —and the entire rotor assembly to which they are attached — toturn. In this way, traditional windmills convert wind energy intomechanical energy, which has generally been used to grind grainor pump water. Modern windmills, called wind turbines, are basedon the same principles as these traditional windmills, but theyuse the wind energy they capture to turn electrical generators andproduce electrical current.
Although wind is free, generatingelectricity from the wind is not. Modern wind turbines, as wellas the towers on which the turbines are mounted and the electricalcomponents that make up a wind power system, are expensive. Engineerswho develop these systems — from a single, small wind turbinefor one family to hundreds of turbines for a large community —must consider a variety of factors to determine if such a systemis economically feasible in a particular area.
The mostimportant considerations for an engineer developing a wind powersystem are the reliability of the wind in the area, the poweroutput of various sizes of wind turbines, and the power needs ofthe household or community being served. A small difference in windspeed or windmill size translates into a large difference in both theproductivity and the cost-effectiveness of a system. Because of this,engineers carefully consider the benefits and costs of various sizesof windmills. They also weigh the wind speed benefits of placingwind turbines high above the ground against the financial cost of thetall towers on which the turbines are placed.
In addition tothese economic considerations, engineers must also consider factorssuch as zoning restrictions, the effect of wind turbines on hawks,eagles, and other birds, the noise created by wind-driven generators,and the potential for wind turbines to obstruct the flight paths oflocal air traffic. People who develop large-scale wind farms mustalso consider whether consumers are willing to pay for wind-generatedpower even if it costs more — at least to start — thanelectricity generated by fossil fuel-burning power plants. Onlythen will wind begin to take its place as a legitimate alternativeto fossil fuels.
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