“Wind Doesn’t Work” (or Does It?)

I frequently get queries from the buying public or inventors about non-traditional wind turbine designs, “non-traditional” meaning anything but three (or two) bladed horizontal-axis models on very tall towers. These take a variety of shapes, from roof-top ventilators to shrouded or ducted designs to vertical axis style turbines mounted in a variety of different orientations. Invariably each turbine, usually mounted on a building or very short tower, is portrayed as a “breakthrough technology” by the inventor. Unfortunately, the media picks up on and propagates these press releases, resulting in considerable confusion on the part of interested people that really want to be part of the climate change solution by supporting renewable technologies.

…the unusual designs, which differ from the 3-blade norm, were all tried and abandoned years ago as grossly inefficient or unreliable, yet have been recently resurrected because of their unique appearances.

Indeed, there are hundreds of web sites offering all manner of these types of “alternate” wind turbine designs. Most of these websites also include a video of the gizmo spinning. Many websites tout turbines with very small rotors and enormous generator capacity as a means of portending that the device will generate lots of electricity, enough to power your entire home or even “megawatts of electricity.” When I explain that “megawatt” is a unit of power, not energy generated, and that people and their houses consume energy, not power, the inventor or sales person is always befuddled. Nowhere on any of these websites is there any mention of actual documented and confirmed energy production.

There are three fundamental principles of wind power as a source of kinetic energy that can be converted to useful work (like electricity). These are:

• The power in the wind that is available to a wind turbine to convert to electricity is proportional to the cube of the wind speed. This means that a 10% increase in wind speed results in a 33% increase in power available in the wind. Going from an eight mile per hour average wind speed to a 10 mph average wind speed results in nearly a 100% increase in power available to the wind turbine.
• Wind speed increases with height above the ground. This is akin to water in a river flowing faster as you get away from the bank towards the center of the river. The friction between the stationary river bank and the flowing water diminishes with distance from the bank. Similarly, wind speed increases above the ground, trees, and buildings due to reduced friction with height above the ground.
• Turbulence caused by trees and buildings robs a wind turbine of power by compromising the wind flow, resulting in decreased energy generation and increased wear and tear on the equipment. Remember the last time you flew across the country in a jetliner, suddenly hit a pocket of turbulence, and dropped 3,000 feet? After a frantic search for the “comfort bag” in seat pouch, you recall that airplanes don’t fly well in turbulence. Neither do wind turbines; there is very little usable “fuel” in turbulence.

These are principles of fluid dynamics, a branch of physics that describes how wind flow works. Over the past 8-plus decades, wind turbines have evolved to look like they do because what they currently look like takes best advantage of these principles, reliably surviving what the environment throws at them, and doing what they’re intended to do: converting the kinetic energy in the wind into usable electricity.

A fundamental principle of wind turbine technology is that the amount of energy you can extract from the wind and convert to electricity is directly proportional to the swept area of the “collector.” In the case of the wind turbine, the “wind collector” is the rotor, the blades that spin. Yes, there might be small efficiency differences that allow one rotor design to perform slightly better than another, but for the successful designs that are out there, the comparable efficiencies are very close to one another for the standard 3-bladed horizontal axis designs. A detailed search of ‘historic wind turbine” reveals that the unusual designs, which differ from the 3-blade norm, were all tried and abandoned years ago as grossly inefficient or unreliable, yet have been recently resurrected because of their unique appearances. However, changing the orientation of the blades or the design of the collector or downsizing the rotor area, does not, because it cannot, change the extractable energy in the wind. At least not on planet Earth.

Can you actually build one of these unconventional contraptions and will it generate electricity? Perhaps. But the web sites touting these technology breakthroughs leave several unanswered questions that must be asked before clicking on “buy now!” These include:

• How long will the new design last? In other words, what’s the reliability of the wind turbine?
• What’s the installed cost of the entire system? (Not just the cost of the wind turbine in a box on the manu- facturer’s shipping warehouse.)
• How much electricity will it generate over its lifetime? (After all, isn’t that why you are buying a wind turbine?)
• What’s the cost of electricity generated?
• Is the turbine certified to an internation- al standard like AWEA 9.1-2009 and that confirmed by an independent agency like the Small Wind Certification Council or Intertek?

These questions are actually all inter-related. If a device generates electricity, but only limited amounts due to a short life, the purchase was not a wise one. If the energy predictions by the manufacturer are wildly enthusiastic, or perhaps even fraudulent, disappointment will be followed by the conclusion that “wind doesn’t work.” Any breakthrough rotor design that was abandoned decades ago as useless or ineffectual is, well, another useless self-proclaimed breakthrough technology.

There are several axioms of wind technology that must occur for a system to be acceptable by the buying public.

• The wind turbine must be reliable, and generate electricity as advertised for decades. The most expensive wind turbine you can buy is the one that cost one-tenth of the price of a conventional tower mounted model, but only lasts a couple of months before disintegrating in the first storm, as opposed to the 20 year design life.
• It must be tower mounted high enough so that the entire rotor clears all obstacles within 500 feet by at least 30 feet. This gets the rotor up into the laminar flow of the faster winds and reasonably minimizes turbulence.
• It must generate electricity cost effectively. Most breakthrough technologies perform so poorly that the payback period is in the thousands to tens of thousands of years. And this is without operation and maintenance. We’re approaching the half life of some radioactive elements with these payback periods!

At the Small Wind Conference this past June, I was approached by a gentleman who is designing a new wind turbine, but not the type normally seen—three bladed and on a tall tower. The sole criteria for the design is that “it will not look like common wind turbines”. The designer proudly proclaimed that he is “thinking outside the box.” Asked if he understood why wind turbines today look like they do, the inventor responded “no, why, what difference would that make?”

I’m always stunned by such proclamations. This is akin to your dentist announcing that he or she is going to try a new untried procedure on you, nothing that is proven, accepted, or common practice, solely because it will be different. In other words, he or she is thinking outside the box. Who wants to be the first to sign up for that procedure?

Don’t you think that before one thinks outside the box, one ought to at least know what’s inside the box? And why is it in there?

Don’t you think that before one thinks outside the box, one ought to at least know what’s inside the box? And why is it in there?

Which is why nearly all of these unconventional rotor breakthrough technologies are failures in the field and disappointments for the owner, and give bona fide wind technologies a black eye. Most of these designs were abandoned decades ago as dead ends. Darwinian economics at its best: if doesn’t generate electricity cost effectively, then it’s out of the gene pool.

We know how to make wind technology work reliably and for decades. And it’s not with an unconventional rotor configuration or breakthrough technology, or mounted on a building or short tower. If you must buy a “spinny thing”, buy a whirly gig at a craft fair. They’re a lot cheaper. But if you want to buy a wind turbine that generates usable amounts of electricity for years, choose wisely. Of the hundreds of different designs available on the web, the only ones that I can recommend are the eight small and four medium wind turbines listed on the Interstate Turbine Advisory Council’s list at http://www.cleanenergystates.org/ projects/ITAC/list/.

Mick Sagrillo (msagrillo@ wizunwired.net) has powered his family’s home with all manner of wind turbines for the past 35 years.