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Why Wind??? Mick Sagrillo
©1993 Mick Sagrillo
ind power has taken a lot of Wbashing in recent years, for a
variety of reasons. Some of the criticism has been justified, but most of it is completely unfounded. A fresh look at wind power and its place in a renewable energy (RE) system is in order.
Let’s take the most frequently used excuses for not considering wind power in an RE system and analyze the whys and why nots. By the time we’re finished, you will have clearer understanding of wind’s place in the whole RE picture.
“Wind doesn’t work”
One reason given for not wanting to use wind power is that the equipment apparently doesn’t work. “I drove past this wind generator and the blades weren’t spinning.” Well, maybe the wind wasn’t blowing, or maybe it was blowing too hard. Maybe the wind system was shut down for routine maintenance. Maybe the owners’ batteries were charged up and the power was not needed. Maybe...I could go on and on, but I’m sure that you get the picture. We humans are very visual yet blind creatures in that first impressions are often the most lasting impressions. When one glances quickly at a PV array, a solar hot water heater, or even a hydro plant, you have no idea if it’s operating or not. You can’t see what’s going on inside. But it is always obvious when a wind generator is or is not operating.
This isn’t to say that wind generators always work. In the late ‘70s and early ‘80s, there were scores of companies who set up shop building wind generators. In many cases, their motivation was greed. They were attempting to cash in on the 40% federal tax credit that was granted to buyers of RE equipment. Most states also offered tax incentives for RE purchases. Homeowners could get up to 70% of a $10,000 investment back from the government.
The problem was that there were no standards for most of the RE equipment that folks bought. Consumers were in the mood to spend lots of cash, and manufacturers were all too willing to take their money. No standards, lots of money,
32 Home Power #34 • April / May 1993
and the tax credits all combined for what would ultimately be a major setback for renewables. There is no question that a lot of junk was being sold. Many of these travesties still hang from their towers as a dismal reminder that their owners had been had. Not only wind power, but all forms of renewables got a black eye that is now just healing. Unfortunately, many people developed a sour taste for RE. Ronald Reagan even got a laugh at one of his State of the Union speeches by poking fun at wind farms and Jimmy Carter’s solar water heaters.
Six years after the sunset of the tax credits, virtually all of the 80 or so wind generator companies doing business in the U.S. are gone. Only a handful of manufacturers have survived the shake-down. And these survivors are still cranking out the same reliable equipment that the fly-by-nighters tried to emulate a decade ago. There is no question that the equipment available today is reliable, and their manufacturers stand behind their designs. These people know that a wind generator manufacturer is in the business to help generate renewable electricity, not just build and sell RE equipment. Today’s wind generators work!
Many folks have the misconception that there is no real power available in the wind. Therefore, why bother with a wind generator. Let’s look at this more closely.
The equation for determining the power available to a wind generator is as follows:
P = 1/2 d AV3
where P is the power in the wind, d is the density of the air, A is the swept area of the rotor, and V is the wind speed or velocity.
What we are interested in here is V3 or V x V x V. When we double the wind speed for a given location, say from 5 to 10 mph, we increase the value of V3 by a factor of eight! Multiply 5 x 5 x 5 and you get 125. Double it to 10. Multiply 10 x 10 x 10 and the result is 1000, an 800% increase.
There are two lessons here. The first is that even small gains in wind speed can result in enormous increases in the power in the wind. As the wind steadily increases, the power in the wind increases exponentially.
The second lesson is that, because the power gets so large so fast, it must be awfully difficult to build a wind system that will survive high winds. Any do-it-yourselfer who has tried to design a wind generator has learned this lesson, probably the hard way. So have all those bankrupt manufacturers that were mentioned earlier. But today’s wind generators know how to behave without self-destructing in high winds.
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