All technologies have variations in design and capability, and wind power technology is no exception. There has been much heated discussion amongst home built wind power devotees concerning the relative merits of the Swift small wind turbine and conventional home-built turbines. This article is a pointed entry into the fray, with a definite bias based upon experience and investigation, and supported by a little simple mathematics.
Modern roof top wind generators, sometimes called micro-wind generators, have been the object of a lot of bad public relations recently, and I must say right up front that I am in agreement with just about all of it. Buying and installing one of these roof top systems, Swift small wind turbines being the most prominent, is a very poor investment. Home Built Wind Power generators are far superior. Let me elaborate.
First, a poignant point about wind power generators; the best measure of a wind power generator’s capability is the diameter of the propeller. This is known to professionals as the swept area, and it is equivalent to the solar panel’s collector area. The following comparisons are between the cost per kilowatt hour for energy produced by a Swift small wind turbine and a home built wind power generator with about one half the swept area of the Swift generator.
To calculate the approximate production of electric power in kilowatt-hours, you need to know only the average wind speed at the generator’s location and its swept area. Multiply that number times the life expectancy of the generator in months, and divide the cost of the generator by the resulting number. The result is the cost, per kilowatt hour, of the wind power turbine over its estimated useful life.
Wind Speed Calculation
Assume that the height of a typical single-story home is 15 feet. Determine the average wind speed at the location of the home (this can be found in the Wind Energy Resource Atlas of the United States). For purposes of my example, I calculated an average wind speed of 8.2 miles per hour.
Calculating Monthly Kilowatt-Hour Output for the Swift Turbine
With an average wind speed of 8.2 miles per hour coupled with the Swift turbine’s 7-foot swept area, the monthly output is estimated to be 32 kilowatt-hours. This extrapolates to a lifetime output of approximately 7,700 kilowatt-hours. This figure is confirmed by the manufacturer’s own published figures.
Calculating Monthly Kilowatt-Hour Output for the Home-Built Wind Power Turbine
With an average wind speed of 8.2 miles per hour coupled with the home-built wind power turbine’s 4-foot swept area, the monthly output is estimated to be 10.6 kilowatt-hours. This extrapolates to a lifetime output of approximately 2,500 kilowatt-hours over 20 years.
The average cost of the Swift turbine is $11,000. If you consider the 30% energy tax credit, the cost is lowered to $7,700. The total cost of the home-built wind power turbine, considering that it would require replacement every six years is about $350.
After doing some simple mathematical manipulation, it turns out that the Swift turbine averages about $1.00 per kilowatt-hour, while the home-built wind power turbine averages about $0.14 per $0.09 per kilowatt-hour. Quite a difference!