Tiny turbines on short towers may make people feel good about generating "green energy," but they make no sense economically. The fact that the real cost may be hidden or spread out over millions of payers does not change the basic economics.

The article on the proposed Westport wind turbine (Standard-Times, Aug. 2) reveals just how uneconomic small wind turbines can be. The turbine has a power rating of 10 kilowatts (not 110 megawatts as stated in the article) and will cost $63,400. It matters not whether the residents of Westport are actually the ones paying for it or if the Massachusetts Technology Collaborative (MTC) funds it; someone will have to pay for it. If the MTC funds it, that means all of us in Massachusetts who contribute to the Renewable Energy Fund on our electric bills will be paying for it.

Is it a good investment? How soon will we get our money back in terms of savings on Westport's electric bill? From our experience with measuring wind in Dartmouth, it can be estimated that the Westport turbine will operate at 10-20 percent of its rated power on an average annual basis. The 20 percent value is quite optimistic. That means it will average between one and two kilowatts over the year. Since there are 8,760 hours in a year, the turbine might produce between 8,760 and 17,520 kilowatt-hours of electricity per year.

I do not know what the town is paying for its electricity, but let's say it lies between 10 and 15 cents per kilowatt-hour. Thus the potential annual savings in purchased electricity will range from a low of $876 to a high of $2,628. Thus the simple payback period will range from a low of 24 years in the optimistic case to over 72 years. The estimated mean payback would be about 48 years.

With such a long payback period, so many unpredictable things can take place over so many years that sensible investors would refuse to put their money into such a venture. Most people would like to get their money back within their lifetime to leave time for some return on their investment.

Tiny turbines on short towers may make people feel good about generating "green energy," but they make no sense economically. The fact that the real cost may be hidden or spread out over millions of payers does not change the basic economics.

It is becoming clear that for land-based wind turbines to make economic sense in SouthCoast, they must be sited a few miles at most from the shoreline or be on high hills, be mounted on very tall towers, say 265 to 330 feet, and have substantial power ratings of at least 1,500 kilowatts.

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