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  • Eveready Group

New and Improved Wind Power

Date: 15 July 2007

For many, home energy costs recently have increased by 50 percent (or more), motivating a growing number of people to look for alternatives. The proliferation of net metering laws, in about 40 states, as well as a growing number of state residential wind incentive programs, has given a strong boost to the small-scale wind turbine industry.

Whatís more, recent technical developments have reduced blade noise and improved both turbine efficiency and longevity. There now are a number of new home-scale wind turbines with advanced technology, and thereís the promise of more to come in the near future.

For many years, residential wind turbines have been most popular in rural locations where zoning laws tend to be less restrictive and neighbors less likely to object to them (mainly on aesthetic grounds). That may be about to change. Many in the small-scale wind turbine industry think residential wind power is about to enter suburbia with simpler, less expensive systems that perform more like household appliances than complicated renewable energy systems. And the potential is enormous; itís estimated there are at least 15 million homes with the resources necessary to make a wind installation cost effective.

But does it really make sense to install a wind turbine in your back yard? Maybe, maybe not. A wind power system that works well in one location may not work in another. There are many variables to consider: the size of your lot, zoning restrictions, wind speeds in your area, the cost and amount of electricity you use, whether your utility offers net metering, and the availability of state rebates and incentives.

WIND POWER PICKS UP SPEED

Harvesting the wind to generate electricity is not a new idea. In 1888, Charles F. Brush of Cleveland created a wind turbine for this purpose. Early turbines could supply enough energy for a house or two. Today, large commercial-scale turbines can produce about 3 megawatts or more, enough to power about 750 U.S. homes. The recent growth of this industry in the United States has been dramatic. Wind power capacity increased by 27 percent in 2006 and is expected to increase an additional 26 percent this year, according to the American Wind Energy Association. Enthusiasm for small-scale wind also is on the rise, with sales for residential systems at $17 million in 2005, up 62 percent from 2004, according to the association.

Residential wind turbines were first commercialised in the United States in the 1920s and were fairly popular until the Rural Electrification Administration extended electric lines to many remote areas in the 1930s and í40s. The oil crises of the 1970s spurred a flurry of renewed interest in residential wind power until the tax credits and other government incentives that supported the industry ended in the 1980s.

But now, interest in residential wind power is on the rebound, some attribute the recent growth to robust state and utility rebate programs and growing interest in clean energy technology. (Visit the Database of State Incentives for Renewables & Efficiency to see if incentives are available in your state.)

Net metering laws, which simplify the connection of residential renewable energy systems to the electric grid, also have made wind more attractive to those looking for a way to reduce their energy bills. An example of this is the grid interconnection on the solar-electric market as instructive. In the past, the vast majority of solar was battery-connected off-grid; now itís the opposite. Grid-interconnection allows the homeowner to reduce their grid-based energy use, while not requiring them to rely solely on wind for their needs.

Others point to the increasing number of financial incentive programs that help reduce the high initial cost of wind systems. People also are choosing wind simply because itís the right thing to do. Another key factor is unquestionably the environment as people are looking for ways to make a difference.

These days there are high hopes in the residential wind industry for the passing of legislation that would establish a federal tax credit for those who purchase wind turbines. A federal credit would not only be an immediate benefit to taxpayers, but would also drive turbine prices down through increased manufacturing. (For help contacting Congress to voice your support, click here.)

THE BASIC TECHNOLOGY

Residential wind power has come a long way from the 1920s, but in some respects the basic technology hasnít changed much. Turbine subsystems include a rotor (the blades) that converts the windís energy into rotational shaft energy; a nacelle (enclosure) containing a drive train and a generator; the tower to support the turbine; and electronic controls, electrical cables and grid interconnection equipment. Off-grid turbines do not have interconnection equipment, but normally have banks of batteries to store electricity for use during windless periods. Grid-connected turbines, on the other hand, essentially use the grid as their storage battery.

Because the rotor is what actually captures the wind, its size is extremely important. In general, the larger the rotor the better, as long as itís matched to an appropriately sized generator.

Improved aerofoil designs have boosted efficiency by as much as 35 percent at the average wind speeds typical of many residential locations. Wooden blades have been replaced by reinforced fiberglass, which reduces blade maintenance (although routine turbine and tower upkeep is still extremely important). The blades also have been redesigned to reduce the amount of noise they produce. The Kestrel range, for example, uses advanced aerofoil design to improve efficiency in wind speeds as low as 9 miles per hour. In addition, new direct-drive axial flux alternators have been paired with sophisticated pitch control, charge controllers and inverters designed specifically for small wind turbines.

REAL-WORLD PERFORMANCE

So, how do residential wind turbines actually perform? If they are properly installed and maintained, the record is good.

In some cases a 33-foot tower is not a good match for site installations, especially where part of the property is heavily wooded. ďI put the turbine on a clear hill near the street in a corridor that I thought would have pretty good winds, but I have been stunned by how much reduction in wind has resulted from turbulence caused by the trees. Consequently, my power output is running at about one-eighth what it should be.Ē Westbrook plans to install a taller tower to get the turbine well above the trees.

Westbrook had another problem ó getting his system connected to the grid. Heís served by an electric cooperative that had no net metering provisions and no interest in establishing any. It took five months of persistent negotiation to get the connection. Installation experiences like these highlight how crucial it is to study all the issues involved with a site before you proceed. With proper siting, residential wind may be a great way to reduce your energy costs and make a positive difference for the environment.

With growing consumer interest, thereís a good deal of optimism in the small wind sector. Weíre in a very dynamic, emerging market right now with all these state incentives in place, but a lot still depends on the future of energy prices. Provided that the cost of utility energy keeps on going up, and we keep the cost of renewable energy down with innovative technologies, itís going to be very exciting.

By Greg Pahl

*Edited by Kestrel Marketing

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