Wind Power: Are Vertical Axis Wind Turbines Better?

Wind expert Mick Sagrillo discusses vertical axis wind turbines, a recent innovation in wind power.


| February/March 2008


Worldwide interest in renewable energy options has given rise to a rash of new wind turbine designs. Some of the most recent models on the market are vertical axis wind turbines (VAWTs), which manufacturers claim are quiet, efficient, economical and perfect for residential energy production, especially in urban environments.

We asked Mick Sagrillo, veteran residential wind power authority, to answer our questions about this technology and its future in the realm of alternative energy.

First of all, how does a vertical axis wind turbine work?  

There are actually two different designs out there. One’s called a Savonius rotor, which essentially, if you take a 55-gallon drum and cut it in half, then offset the two halves and put them on a shaft that rotates, you’ve built a Savonius rotor. It’s similar to an anemometer. A lot of what we see today are Savonius rotors. They’re very crude, very low-tech, very inefficient. We’re talking about something that operates in the, say, 5 to 10 percent efficiency range. People have been able to tweak the efficiency rate — ideally, they might be as high as 15 percent.

Then there’s the Darrieus model — the type that resembles an egg beater. Essentially, you have two vertically oriented blades revolving around a vertical shaft. But the Darrieus models use an airfoil design. A wind turbine airfoil works in the same way as an airplane wing. An airfoil has a flat side and a curved side. The result of air passing over the two sides is a force known as “lift.” When an airplane speeds down a runway, air passing on both sides of the airfoil wings, the lift force literally lifts the airplane into the air. This will continue as long as there is forward motion over the airfoil to generate the required lift.

A wind turbine uses this same principle, but instead of flying up and away, the airfoils are secured to a hub, which in turn is attached to a generator shaft. The air passing over the airfoils (wind turbine blades) are converted into rotational momentum which spins the generator.

Conner
8/5/2015 5:56:15 PM

I was hoping for a good comparison of the two types, and some of your article was well-written. However, this piece was so ludicrously biased against VAWTs that it became a rant against these turbines, the principles behind them, and even the people who build them. I was quite disappointed. I did read the full article and agree with some statements made. However, when you when you assert your status as an expert, you should actually know what you are writing about. For example, you claim that centrifugal force on the turbines causes more wear on a vertical as compared to a horizontal, and say this is a fluke of physics. However, any physicist, and even most high-school students, can tell you that centrifugal force is not a real force. Rather, it is a misconception many people have about circular motion and how inertia works. In reality, CENTRIPETAL force acts on rotating objects to keep them IN the circle, as they would otherwise be thrown out due to their inertia. For future reference, please do more research on your topics so that readers will not be misinformed. Thank you.


Aland
7/27/2014 9:39:32 PM

I am interested in the cylindrical type of wind generator mainly because it is compact & possibly because it would be simple to make. A number of small ones of say, 600 high & 350 dia would not be such a dominating feature on a domestic home roof. How to size generators & connect to the main power supply. Alan Davies (mech.eng) Melbourne Australia


Vawtman
6/6/2014 9:34:32 AM

I’ve researched VAWTS for nine months and the Change Wind Corporation’s 36 kW VAWT appears to have no equal. Go to: http://changewindcorp.com/ There was also a press release last week in the Hartford Courant(Front Page) Business section. Go to: http://articles.courant.com/2014-06-01/business/hc-change-wind-turbines-jewett-city-20140530_1_wind-turbine-cheaper-wind-power-low-wind-speed I can’t find any VAWT that even comes close to the output of this machine. Their prototype has been in operation since 09 with no failures and constant data streams documenting the output. Has anyone ever heard of these folks?






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