Electricity Education - Wind
Wind Energy Generation
Historically, wind energy has been used for thousands of years. Sails have been used to move boats for more than 5,000 years. Windmills have been used to grind grain, pump water and saw wood. As power lines were built in the 1930s that could transmit electricity over long distances, the use of windmills died out, although a few windmills can still be found in isolated areas such as western ranches. Today, wind energy can also be used to generate electricity and charge batteries. Availability of wind energy varies noticeably from place to place. Using wind energy is most feasible, economically, in locations where steady breezes are available.
According to the U.S. Department of Energy, at one time the U.S. led the world in wind energy generation, producing 90% of the world's wind-generated electricity. By 1996, however, the U.S. share had fallen to 30% due to other countries' increased investiture in wind generation, in which trend the U.S. did not participate.
Wind Energy Technologies
The principal behind a wind-energy generating device is very simple: the force of the wind pushes against the blades of a turbine, which turns the turbine. Today, there are two kinds of windmills. Horizontal-axis windmills look like airplane propellers and are the most common. Vertical-axis windmills look like egg-beaters and are only used about 5% of the time. Horizontal-axis machines must face into the wind, so they are built with tails like weather vanes, and swivel when the wind changes directions. Vertical-axis machines turn whichever way the wind is blowing. The turbine is connected to a drive shaft that turns an electric generator. Wind turbines can be used alone, can be connected to a utility power grid or can even be combined with a photovoltaic (solar cell) system.
People are still working on the problem of what to do when the wind isn't blowing. Turbines that are connected to the utility power network and some other kind of generator does the work when the wind isn't blowing. Stand-alone turbines sometimes are used to charge a battery, which then provides power when the turbine isn't turning. Other windmills are used together with small gas or diesel generators that burn fuel and serve as a backup when the wind's not blowing.
For utility-scale generation, a large number of turbines are usually built close together to form a wind farm. Several electricity providers today use wind farms to supply power to their customers.
Small turbines are used by homeowners and at remote locations to help meet energy needs. Stand-alone turbines are typically used for water pumping or communications. However, homeowners and farmers in windy areas can also use turbines to generate electricity.
As with all inventions, people are continually improving wind turbines. The largest wind turbine in the world, with adjustable blade tips so that it can capture more energy, is in operation in Traverse City, Michigan. Another, much smaller system has been designed that uses small turbines with wind amplifiers that funnel more wind to the turbines. In the future, turbines may be placed on top of tall buildings, offshore oil platforms and on wireless communications towers to provide electricity for them.
Issues in Wind Energy
Wind Resources: The wind is the fuel source for wind energy. The U.S. has areas with abundant winds, for example, in the Midwest, Great Plains, and mountainous regions, but wind speed varies from day to day and from season to season. Detailed knowledge of the wind at a site is needed to estimate the performance of a wind energy project.
Environment: Wind energy is considered a green power technology because it has only minor impacts on the environment. However, all types of energy production impact the environment, including wind.
In order to be efficient, wind turbines must be large and in order to generate significant amounts of electricity, there must be groups of them. Wind farms usually have dozens of turbines spread over a large area. One turbine needs about two acres of land, but the land beneath it can be used to grow crops or for grazing. Horizontal wind machines are typically about the height of a 20-story building, with blades that stretch 200 feet wide. According to the U.S. Dept. of Energy, "The largest wind machines in the world have blades longer than a football field!" Wind machines must be placed where the wind will not be obstructed: in the waters offshore, on the tops of mountain ridges or in the middle of plains. Another good location is in mountain gaps, where the wind is funneled through a small opening, giving it more power.
Their large size and placement in open or wilderness areas make wind turbines impossible to ignore. Many people do not want their views disrupted by their installation. Power lines are also necessary to transport the power generated by wind turbines, and they have their own environmental impact.
Economics: The cost of energy from the wind has dropped by 85% during the last 20 years. Incentives like the federal production tax credit promote wind energy usage. California produces more energy using wind than any other state in the U.S., because California's state policies encourage the development of renewable energy sources.