PDF《Small Wind Electric Systems》

s utility- supplied electricity. World Power Technology/PIX07168 Small Wind Electric Systems What Size Wind Turbine Do I Need? The size of the wind turbine you need depends on your application. Small turbines range in size from

20 watts to

100 kilowatts (kW). The smaller or micro (20- to 500-watt) turbines are used in a variety of applications such as charging batteries for recreational vehicles and sailboats. One- to 10-kW turbines can be used in applications such as pumping water. Wind energy has been used for centu- ries to pump water and grind grain. Although mechanical windmills still provide a sensible, low-cost option for pumping water in low-wind areas, farmers and ranchers are finding that wind-electric pumping is a little more versatile and they can pump twice the volume for the same initial investment. In addition, mechanical windmills must be placed directly above the well, which may not take the best advantage of available wind resources. Wind-electric pumping systems can be placed where the wind resource is the best and connected to the pump motor with an electric cable. Turbines used in residential applica- tions can range in size from

400 watts to

100 kW (100 kW for very large loads), depending on the amount of electricity you want to generate. For residential applications, you should establish an energy budget to help define the turbine size you will need. Because energy efficiency is usually less expensive than energy produc- tion, making your house more energy efficient first will probably be more cost effective and will reduce the size of the wind turbine you need (see How Can I Make My Home More Energy Efficient?). Wind turbine manufacturers can help you size your system based on your electricity needs and the specifics of local wind patterns. A typical home uses approximately 10,000 kilowatt-hours (kWh) of elec- tricity per year (about

830 kWh per month). Depending on the average wind speed in the area, a wind tur- bine rated in the range of

5 to 15?kW would be required to make a signifi- cant contribution to this demand. A 1.5- kW wind turbine will meet the needs of a home requiring

300 kWh per month in a location with a 14- mile-per-hour (6.26-meters-per-sec- ond) annual average wind speed. The manufacturer can provide you with the expected annual energy output of the turbine as a function of annual average wind speed. The manufac- turer will also provide information on the maximum wind speed at which the turbine is designed to operate safely. Most turbines have automatic overspeed-governing systems to keep the rotor from spinning out of control in very high winds. This information, along with your local wind speed and your energy budget, will help you decide which size turbine will best meet your electricity needs. This 1-kW Whisper turbine provides direct AC power for the water pump for stock tanks on a ranch in Wheeler, Texas. Elliott Bayly/PIX09681 Small Wind Electric Systems What are the Basic Parts of a Small Wind Electric System? Home wind energy systems gener- ally comprise a rotor, a generator or alternator mounted on a frame, a tail (usually), a tower, wiring, and the balance of system components: controllers, inverters, and/or batter- ies. Through the spinning blades, the rotor captures the kinetic energy of the wind and converts it into rotary motion to drive the generator. Wind Turbine Most turbines manufactured today are horizontal axis upwind machines with two or three blades, which are usually made of a composite material such as fiberglass. The amount of power a turbine will produce is determined primarily by the diameter of its rotor. The diameter of the rotor defines its swept area, or the quantity of wind intercepted by the turbine. The turbine'