Wind Turbines for the Home

Wind turbines are devices that convert energy into electricity. Local wind conditions determine placement, while aerodynamic modeling determines the shape of the blade, the orientation of the axis and the number of blades or other wind-catching forms. All these devices are made up of three components:
- Rotor and blades
- Generator and control systems
- Structural support

About two-thirds of the total cost is allocated toward the generator and control systems, with the other two components splitting the remainder of the cost. In large turbines, a gearbox is responsible for converting the low-speed rotor rotation to a higher speed that will enable the generator to create electricity; in smaller ones, the generator is run by a direct-drive gearing.

The axis of rotation can be either vertical or horizontal. Horizontal-axis wind turbines are often placed on the top of tall towers, and must be allowed to move about in order to point into the prevailing air current. Large ones use wind sensors and servo motors to do so. However, the location of these large devices are therefore largely determined by the prevailing wind direction. Gear trains are used to convert the rotation to a speed suitable for generating Alternating Current (AC) power.

Vertical-axis wind turbines are smaller and have the rotor shaft oriented vertically. The chief advantage of a vertical orientation is that the device does not need to be pointed this way or that with respect to the direction of the air currents. No tower is necessary, and the generator and gearbox can be placed closer to the ground, which makes maintenance easier. One drawback, though, is that wind speeds are generally less at a lower height and therefore provide less energy for conversion to electricity. Also, these units generally produce only Direct Current (DC) power. DC power must be converted to AC power for most household appliances and other electrical devices.

No matter the type, placement must be carefully chosen to avoid blockage of the wind by obstacles. In general, the device should be 30 feet higher than any tall obstacle within 500 feet. If the device is to be installed on a roof, extra care must be taken to fasten the device firmly due to the related vibration and possible turbulence.

In the US, a residential wind turbine that will provide an electrical output of 2 kilowatts will cost about $12,000. A 10 kilowatt output will cost $55,000. That works out to about $6 per watt. Many states do provide rebates and incentives to homeowners that will reduce the cost by 50 percent.

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