Wind Power

Wind power is one of the oldest renewable energy technologies. Wind has been used for centuries to pump water and grind grain. Modern wind turbines convert wind energy into electricity. This can be one of the most cost-effective of all renewable energy technologies. However, wind generators are not for everyone. They require a suitable windy site location and some maintenance for upkeep. If there is any question about wind velocity and consistency at a site, we suggest first installing a recording anemometer system to record daily wind speeds for at least a year. We also recommend that anyone interested in installing a wind system first review the articles and books cited below under "More Information".

Key Benefits

	Low cost renewable energy (given a suitable site)
	Unlike photovoltaics, generates electricity at night
	Can be integrated with a photovolatic system to supplement electrical production during winter low light conditions

How Does it Work?

Wind generators convert the winds pressure against the blades into rotational energy which drives a small electric turbine and generates electricity.

The power in the wind is proportional to:

	the total area being swept (determined by blade diameter)
	the cube of the wind speed
	the air density - which varies with altitude

Different wind speeds to consider are:

	Start-up wind speed - the wind speed that will turn an unloaded rotor
	Cut-in wind speed – the wind speed at which the rotor can be loaded
	Rated wind speed – the wind speed at which the machine is designed to run (this is at optimum tip-speed ratio)
	Furling wind speed – the wind speed at which the machine will be turned out of the wind to prevent damage
	Maximum design wind speed – the wind speed above which damage could occur to the machine

There are three general types of towers: guyed tilt-up (left), free standing lattice (center) and cantilevered tubular (right). Guyed towers are usually the most economical for small wind turbines, but do require occupy considerable ground area for the anchored wires.

What Does it Cost?

As a rule of thumb, wind turbine systems will cost about $4000 per installed kilowatt. This is about half the price of an equivalent photovoltaic system. Thus, a typical 3 to 10 kilowatt residential wind system with 80 foot tower, batteries, and inverter would cost between $12,000 and $40,000. Larger systems are generally more cost effective.

How Much Wind Do You Have?

We can provide a free estimate of the feasibility of using wind power at your particular site based on average annual wind speed. However, before installing a system we recommend a detailed wind analysis and report, which we can provide for about $1200.

More Information

Wind Electric Systems Simplified by Ian Woofenden (Home Power Magazine Vol 110).

Small Wind Electric Systems: A Washington Consumers Guide (U.S. Department of Energy)

Gipe, Paul. 2004. Wind Power. Chelsea Green Publishing Company. 496 pp. ISBN 1-931498-14-8