Small wind turbine works at low wind speeds

Homeowners this fall will be able to buy a wind turbine at hardware stores that tackles the small wind industry's bete noire: slow wind.

WindTronics, based in Muskegon, Mich., has developed a wind turbine sized for individual homes that it says can operate at speeds as low as 2 miles an hour.

It will be sold for $4,500 as the Honeywell Wind Turbine and distributed through Ace Hardware stores in the U.S. starting in October. WindTronics developed the turbine and licensed the technology to buildings systems giant Honeywell.

The fan-like turbine will generate 2,000 kilowatt-hours in a year for a home with a very good--called Class 4--wind resource, according to the company. That's between 15 and 20 percent of the annual electricity consumption for the average U.S. home.

Turning a turbine inside out: rather than having power generation occur at a gear box in the shaft, WindTronic's turbine has magnets at the edges of the fan to generate a current.

(Credit: WindTronics)

The turbine is rated at 2 kilowatts, but WindTronics executives say that most turbines' rated capacities--the amount of power they can produce at a given moment--are misleading.

"We say if a turbine only works between 8 and 25 miles per hour, you have a very limited range of operation," said Brian Levine, the vice president of business development at WindTronics, a division of EarthTronics. "Our device is rated to address a wider range at the low and high end."

The 95-pound turbine, which is 6 feet in diameter, can be mounted on rooftops, attached to chimneys, or put on a pole. The company hopes to sell the turbines through Ace Hardware stores or through contractors--who are needed for the installation--to homeowners or businesses.

Spinning magnets
With people seeking out alternative forms of power generation, there's been a surge in interest--and sales--in small wind turbines in the past year. But it's still not clear that these small wind turbines are cost-effective enough to be used beyond a niche of green-minded buyers.

Two studies--one in Massachusetts and one in the U.K.--discovered that many small wind turbines far underperformed manufacturers' specifications.

The tests found that people often chose locations that didn't have sufficient wind or obstructions that blocked wind. In most cases, turbine makers rate products assuming a very good wind resource--anywhere from 12 to 25 miles per hour.

By using a novel design, WindTronics' turbine can generate electricity between 2 miles per hour and 45 miles per hour, the company says.

Photos: Small wind turbines take shape

Typically, turbines convert the mechanical energy of spinning blades to electricity with a gearbox and generator in the turbine's nacelle, the enclosure where the rotor's shaft is mounted.

WindTronic's turbine has small magnets at the tips of its fan blades. When they spin from the wind, equipment in the fan's housing captures the current produced.

The installation kit also comes with an inverter to convert the direct current to household alternating current and a "smart box," which regulates the flow of electricity and monitors wind speed. At 45 miles per hour, the unit turns itself sideways to avoid damage.

Levine, who said the turbine was originally developed for developing countries, said WindTronics expects it can produce 50,000 units in its first year. A number of utilities, including Duke Energy, are testing the turbine, he added.

He said that mounting the turbine on a house should not cause vibration because the unit is lighter than most turbines. The sound is rated at between 35 and 45 decibels, which is quieter than normal conversation, Levine said.

Right problem
There is a growing number of companies designing turbines to operate in less-than-ideal wind conditions. A wind map from the Department of Energy shows that most of the fair and good wind--class 3 and class 4--is in the plains states and on the coasts of the continental U.S.

One technique to squeeze more power from available wind is to concentrate the wind to increase the speed of the air going past rotor blades. OptiWind, FloDesign Wind Turbine, and Green Energy Tech are among the companies exploring that approach in small or mid-size turbines.

Other turbine manufacturers, like WindTronics, use permanent magnets in a direct drive design rather than gearboxes to generate electricity.

WindTronics has only built prototype systems, which it first showed at a hardware show last month. But if its turbines can operate in low wind with little vibration and sound, the company could make small wind turbines economically attractive to a much larger audience.