Wind Power Basics

“Do I have a good site for wind power?”

Wind-powered battery-charging systems can be cost-effective if the average wind speed is nine miles per hour or more at the location of the wind generator. If you are using wind in combination with photovoltaic power, it may be cost-effective if good wind is available only during part of the year. When the wind speed doubles, the power delivered is eight times as great. Most wind generators are designed to deliver maximum power at a wind speed of 30 mph. At 15 mph, they will deliver about 1/8 their rated power. The power output of a wind generator will decrease roughly 3% for every 1000 feet of elevation.

A wind generator should be mounted at least 20 feet higher than any obstruction within 300 feet to avoid turbulence. If you measure wind speed at ground level, you can expect about 1.5 times the wind speed 30 feet up, which equates to about three times the power. At 120 feet above the ground, wind speed will be twice what is measured at ground level and power output will be more than twice the output at 30 feet, and about 6 times the output at ground level.

Measuring Wind Speed

Before installing a wind-power generator, make a measurement for the wind-power resource at the site. Local weather data will be helpful, but wind is very site-specific based on local terrain, site elevation, wind direction, and any obstructions such as trees or buildings. Average wind speeds should be calculated, along with peak speeds during storm events.

Towers

Wind generators can be mounted on freestanding towers designed for antennas. They require a large, engineered concrete base for support, but since they do not require guy wires, they can be installed in a smaller space. Guyed steel truss towers, also designed for antenna mounting, are less costly and require a large area for guy wire placement. A tilt-up pole tower is the most economical and the easiest to install. Wiring and mounting of the wind generator are done before the tower is erected. No climbing is necessary. Steel tubing can be purchased locally to save freight.