How Wind Turbines Work
Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetation. Humans use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity.

The terms wind energy or wind power describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity.

So how do wind turbines make electricity? Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. Take a look inside a wind turbine to see the various parts. View the wind turbine animation to see how a wind turbine works.

Types of Wind Turbines
Modern wind turbines fall into two basic groups: the horizontal-axis variety, as shown in the photo, and the vertical-axis design, like the eggbeater-style Darrieus model, named after its French inventor.

Horizontal-axis wind turbines typically either have two or three blades. These three-bladed wind turbines are operated "upwind," with the blades facing into the wind. The other common wind turbine type is the two-bladed, downwind turbine. Horizontal axis turbines are the most common type used today. DOE research focuses on development of horizontal axis turbines.

Sizes of Wind Turbines
Utility-scale turbines range in size from 50 kilowatts to as large as several megawatts. Larger turbines are grouped together into wind farms, which provide bulk power to the electrical grid.

Single small turbines, below 50 kilowatts, are used for homes, telecommunications dishes, or water pumping. Small turbines are sometimes used in connection with diesel generators, batteries, and photovoltaic systems. These systems are called hybrid wind systems and are typically used in remote, off-grid locations, where a connection to the utility grid is not available

Advantages
Wind energy is fueled by the wind, so it's a clean fuel source. Wind energy doesn't pollute the air like power plants that rely on combustion of fossil fuels, such as coal or natural gas. Wind turbines don't produce atmospheric emissions that cause acid rain or greenhouse gasses.

Wind energy is a domestic source of energy, produced in the United States. The nation's wind supply is abundant.

Wind energy relies on the renewable power of the wind, which can't be used up. Wind is actually a form of solar energy; winds are caused by the heating of the atmosphere by the sun, the rotation of the earth, and the earth's surface irregularities.

Wind energy is one of the lowest-priced renewable energy technologies available today, costing between 4 and 6 cents per kilowatt-hour, depending upon the wind resource and project financing of the particular project.

Wind turbines can be built on farms or ranches, thus benefiting the economy in rural areas, where most of the best wind sites are found. Farmers and ranchers can continue to work the land because the wind turbines use only a fraction of the land. Wind power plant owners make rent payments to the farmer or rancher for the use of the land.

Disadvantages
Wind power must compete with conventional generation sources on a cost basis. Depending on how energetic a wind site is, the wind farm may or may not be cost competitive. Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators.

The major challenge to using wind as a source of power is that the wind is intermittent and it does not always blow when electricity is needed. Wind energy cannot be stored (unless batteries are used); and not all winds can be harnessed to meet the timing of electricity demands.

Good wind sites are often located in remote locations, far from cities where the electricity is needed.

Wind resource development may compete with other uses for the land and those alternative uses may be more highly valued than electricity generation.

Although wind power plants have relatively little impact on the environment compared to other conventional power plants, there is some concern over the noise produced by the rotor blades, aesthetic (visual) impacts, and sometimes birds have been killed by flying into the rotors. Most of these problems have been resolved or greatly reduced through technological development or by properly siting wind plants.

What You Need to Make Wind Work

First, and most importantly, you'll need a place to put the wind turbine. The site should be well exposed to the wind and free of any obstructions within 200 feet. If there are any nearby trees, the turbine must be mounted on a tower at least 20 feet above the tallest tree. And keep in mind that trees often grow taller, particularly softwoods.

Next, determine if you have enough wind. Hybrid power systems for living off-the-grid require less wind than those that have to compete directly with utility power. If possible, measure the wind at your site with a recording anemometer over several seasons. We offer the very moderately priced (for a recording anemometer) Totalizer 2100 in the following Product Section.

Next you'll need a reliable wind turbine. There are several on the market but we offer only ones that we've found to be the most reliable. The appendix of Wind Power for Home & Business (item #80-192, $35) contains an extensive and up-to-date list of wind turbine manufacturers worldwide. The appendix lists most available wind turbines, including micro turbines, small wind turbines, and medium-sized wind turbines like those used in California wind farms.

After these first three steps have been completed, you'll need to determine the height of your tower. The "taller the tower the greater the power" is an adage that has been proven time and again. For micro turbines towers of 20-50 feet tall are sufficient. Small wind turbines typically justify towers 100 feet tall or more, depending upon the terrain.

And don't forget the paperwork. Check if there are any regulations governing wind turbines in your area and apply for the necessary permits.

Typical Costs

The cost of a wind power system includes the cost of the wind turbine itself, the tower, and its installation. The total cost of micro turbines can be as little as $500-$1,500 depending upon the tower used and its height. Bigger machines are more costly, but can be more cost-effective. Whether wind energy is a good investment at your site depends on a host of factors, including the average wind speed, the installed cost, inflation, utility buy back rates, taxes, and so on. (For more on how to determine cost-effectiveness see Wind Power for Home & Business, especially the chapter "Economics: Does Wind Pay?") If the wind turbine will be part of an off-the-grid power system and there is at least an 8 mph average wind speed, a wind turbine will nearly always make economic sense.