Energy: MATERIALS ENCYCLOPEDIA
Balance of system as required
How the system works
Airfoil blades are attached to the shaft of a generator. The force of moving air causes the blades to spin and the generator to produce current.
The blades and generator are mounted on a pivot at the top of a tower that places the unit in clean air flow, undisturbed by obstructions that cause turbulence in the wind.
Most residential units produce “wild” power, with output levels that vary based on wind speed. Controllers even out the power delivery. Power may be produced in either AC or DC current, depending on the design of the unit.
Some form of wind speed limiter will be used for every turbine, as extreme wind conditions can severely damage the unit.
Wind generators are rated according to their output at a particular wind speed. The wattage advertised is not a static output, and manufacturers do not all use the same wind speed for their ratings. This makes direct comparisons difficult.
More important than any advertised rating is the power curve for the unit, which shows how much power is produced at any given wind speed. Choose a unit that has the best possible output at the average wind speed at the installation site.
Environmental impacts: low
Wind power emits no carbon or other pollutants to produce power. The units will produce many times more power than was used in their creation.
Environmental issues that are sometimes raised for large-scale turbine installations do not typically apply to small residential units.
Material costs: Moderate to high
Labor input: high
Raising a tall tower can be a labor-intensive process, and typically represents the majority of the labor time for a wind installation.
Skill level required for the homeowner
Installation — Moderate to Difficult. Raising a tall tower can require experience and special equipment.
Use — Easy.
Maintenance — Moderate to Difficult. The turbine will need to be inspected on an annual basis, which can require bringing down or climbing the tower.
Sourcing/availability: moderate to difficult
Numerous companies manufacture residential wind turbines, and experienced installers can be found in most regions with viable wind resources.
All electrical codes address the wiring of residential wind turbines. Building codes and/or municipal bylaws may govern the construction of towers.
Durability: low to moderate
Wind turbines are often subjected to extreme conditions, and can experience durability issues. High wind speeds and buffeting, freezing rain and lightning strikes can all cause failure. In reasonable conditions, key components like blades, bearings and generator should last five to ten years and can be replaced to keep the unit functional for much longer.
Wind power is limited by two key factors that cannot be overcome by technological advancements: average wind speed and height above obstructions.
There is no magic way to make more power than the average wind speed can produce. Refinements in blade design and innovations in vertical shaft technology have raised outputs minimally, but most turbines do not produce useful power in wind speeds lower than 13–16 km/h (8–10mph).
Turbines must be placed in clear air flow, at least twice as high as the tallest obstruction within ten times the tower height.
If wind speed and height conditions exist to make an installation feasible, wind power is a feasible option and improvements in controls, aerodynamics and durability will be appreciated.
It is possible to build and install a wind turbine in a low- or no-energy scenario.
Tips for a successful wind turbine
1. Lack of obstruction is critical for residential-scale wind turbines. In general, the turbine must be twice as tall as any obstruction within ten times its height. Otherwise it will be in turbulent air and produce much less power.
2. Follow the manufacturer’s instructions for tower assembly and turbine installation.