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



wind turbine

Vertical axis wind turbines aren’t quite ready for the masses.


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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?


stuttle
8/12/2013 11:38:17 PM

I have never seen an apples to apples study of both the VAWTs and HAWTs with the same footprint in same wind conditions.  I intend to do just that, and will report what I find.  Half of the wind exposure is of not motive power with a VAWT and that must be addressed.  Also, the misconseption is that the VAWT blade is like that of the typical Air Foil.  It clearly isn't and furthermore, has not been designed to take advantage of external and internal air flow on the half that is exposed to power extraction.  So I have a lot to do.  I'll keep you informed.


daedryn leviathos-young
2/1/2013 1:37:01 AM

what about the bats?


ananda wijesinghe
7/28/2012 12:07:30 AM

As an engineer who has built and tested several VAWTs (and HAWTs), I concur with most of the author's statements: VAWTs are indeed less efficient because all of the blades are not optimally oriented to the apparent wind during rotation, they are heavier and use more materials, the wind resource is generally poor in built up areas, and theVAWT rotor is subject to greater pulsating stresses. Having said that, if one is constrained to use a built up urban location with gusty turbulent wind, the inherent independence of VAWT designs of the wind direction is a distinct advantage. In such locations, small HAWTs fail to rapidly re-orient themselves to the fluctuating direction of the wind and accelerate long enough to produce sufficient power and capture the wind energy. Thiscontinual hunting for the wind is a distinct drawback of HAWTs in such locations. Therefore, it makes sense to build VAWTs ... specially designed to exploit both low and high speed albeit gusty winds .... in urban built up settings, even at the higher cost of energy required to assure increased efficiency and reliability. For many people, such a VAWT can often be justified on a cost-benefit basis, given that they have to use the site they have access to setup the turbine.; This is the goal of most people working on small VAWTs today.


alpha
7/15/2012 9:43:12 PM

This article reminds be of the 99 scientist out of 100 scientists who said the a wind powered land vehicle could not go faster than the wind speed. They were wrong. Its just his bias to see things in one way. Even if a machine is only 10% efficient, if is works 24 hours a day then you have a viable power source compared to solar or horizontal axis that is not going to be installed in anyone backyard anyway. The loses of centralized power generation are huge. So the horizontal axis generators in Palm Springs are less then 10% effcient by the time the power gets to San Francisco. To read Steve Jobs' biography was enlightening. Nothing that eventually made Apple computer successful was possible according to engineers.


leahcimsor
3/23/2011 6:58:00 PM

I think Mr. Segrillo is qualified to comment as he has. He seems to favor renewable energy. He dosen't seem to be anti any particular technology just taking a fact based stance : http://www.greenenergyohio.org/page.cfm?pageID=198 He has many years of experience with wind and other renewable energy systems for home use. His understanding of the physics seems good, and when he states an opinion he says that's what it is. He lays it on the line what it would take for him to change his mind - test results. I will venture my own opinion now. VAWT look very nice (until they start to come undone). If you look at one in a low wind setting it is hard to imagine what they are subject to in a good wind resource. You can go to NREL and see what happened to the first Mariah Power Windspire that was tested. http://tinyurl.com/4d3oc22 They get sustained 50mph winds there. I have done some product design and a million operations of even a small and lightweight mechanism may have trouble with a million operations. If a VAWT spins at 30RPM that is one million stress cycles every 23 days. 15 million cycles a year and 315 million cycles over a 20 year payback period. Given the forces that are involved and the huge number of repetitions, it makes a lot of sense that VAWT have a harder time with durability than HAWT. And given that handicap in order to too survive they use materials less efficiently, cost more, require greater development time, and more maintenance and repair. Cou


tony deckard
1/28/2011 9:08:55 PM

Seems to me this article is the antithesis of what MEN has always stood for. Whether vertical is feasible or not, the idea that one must have degrees and a proper background to come up with, and implement, good ideas is ignorant. I sincerely hope this author has learned something in the last three years.


eric b
9/20/2010 10:14:42 AM

Link with 2 brief excerpts: http://www.theoildrum.com/node/6954 12 Small Wind Turbines Tested in the Netherlands The Dutch coastal province of Zeeland (a very windy place) placed twelve of these much hyped machines in a row on an open plain (picture above)…. Two real-world tests performed in the Netherlands and in the UK confirm our earlier analysis that small wind turbines are a fundamentally flawed technology. Their financial payback time is much longer than their life expectancy, and in urban areas, some poorly placed wind turbines will not even deliver as much energy as needed to operate them (let alone energy needed to produce them). Given their long payback period relative to their life expectancy, most small wind turbines are net energy consumers rather than net energy producers. The machines face two fundamental problems: there is not enough wind at low altitudes in a built-up environment, and the energy production of a wind turbine declines more than proportionately to the rotor diameter. Wind power rules, but small wind turbines are a swindle.


tom_54
9/17/2010 6:46:54 AM

This gentleman is biased. He probably works for a HAWT manufacturer and is using outdated information. Not once does he mention problems associated with the horizontals, such as blade flutter and fatigue, exploding blades due to over spin,(http://www.liveleak.com/view?i=cdd_1203701257) etc. This, in addition to being bird and bat killers makes the HAWT a poor choice no matter where it is installed. There have been, and continue to be many advancements in VAWT's, including verifiable performance testing. Typical performance failures are due to improper siting. When people hear these are good for the urban environment, they think it means VAWT's can be installed anywhere. Since the engineer spews his opinion throughout the article, I'll take my turn. In my opinion, the VAWT is superior to HAWT in that it produces very little vibration, produces usable power in low wind conditions, operates silently and doesn't kill wild life. Oh, yeah, and the blades don't explode!


tom_54
9/17/2010 6:46:53 AM

This gentleman is biased. He probably works for a HAWT manufacturer and is using outdated information. Not once does he mention problems associated with the horizontals, such as blade flutter and fatigue, exploding blades due to over spin,(http://www.liveleak.com/view?i=cdd_1203701257) etc. This, in addition to being bird and bat killers makes the HAWT a poor choice no matter where it is installed. There have been, and continue to be many advancements in VAWT's, including verifiable performance testing. Typical performance failures are due to improper siting. When people hear these are good for the urban environment, they think it means VAWT's can be installed anywhere. Since the engineer spews his opinion throughout the article, I'll take my turn. In my opinion, the VAWT is superior to HAWT in that it produces very little vibration, produces usable power in low wind conditions, operates silently and doesn't kill wild life. Oh, yeah, and the blades don't explode!


john m carter
5/11/2010 12:33:35 AM

Savonius rotor, the design being just to barrels cut in half. If the machine is built the way it was originally designed to be Mother Earth New's would think twice about their statement . my late Grand father Galen B. Schubauer was a physicist who worked for the Burrow of standards in Washington D.C. Dr. Schubauer redesigned the old version of the Savonius wind rotor so it would allow the air to flow through easyer with less drag . His redesigned is very simaler to ex. of what Fitz Water Wheel company gave by improving on an old design. To the water driven grain mills . G.B. Sububauer put a copywrite on his redesigned s-rotor , so The Schubauer s-rotor with a long shaft attached to the shaft with a special designed propeller, kept our dock free of Ice! for close to ten seasons . My Grandfathers invention saved close to $1500. per year. If we relied on a traditional eletric Ice eater ,it would have costed us alot more then just minor fixes . Sincerely yours, John M. Carter


tom kregel_2
5/7/2010 10:24:32 AM

Isn't it about time for Mother Earth News to compile a spreadsheet of costs and efficiencies for all the brands and models available for residential use? Let the numbers speak for themselves. One column could be Vertical vs. Horizontal. Others are maintenance costs, initial set-up costs, required height, wattage at various wind speeds, noise level... Where can one go for this across-the-board type of data? Even better would b a competition where many different brands and models are set up in the same field and see who makes the most wattage. I am in the market and do not know who to believe.


jan steinman
4/30/2010 11:23:35 AM

Hi cites TWO DESIGNS and then writes off ALL vertical-axis machines? I might agree with him that if you limit yourself to Savonius and Darius designs, horizontals are better for most applications. But horizontals (and the author, it seems) are so mainstream. The real creative work is going into verticals. Here's an example (actually, the patent) created by a "guy down the street," "in his garage," that eliminates all of the objections Sagrillo raises: http://www.wipo.int/pctdb/en/wo.jsp?WO=2009018666


bob braafhart
10/1/2009 3:26:40 PM

Thank you Mother Earth News for all your great work. I have read this person's comments before and it is clear there is not love lost by him on VAWT. I believe one great thing they have done is to create interest and to sparked to life the inventor in many of us. Even more so it has fanned to flames interest in something that could create energy from an abundant renewable resource. In that arena, I believe they achieve a 90% efficiency rating.


gene_15
5/7/2009 6:46:37 AM

I am working for a custom sheet metal fabrications shop and I have been talking with engineer who doesn't know wind and an experienced HVAC designer that understands wind (airflow) but doesn't get everything with the Betz' Law, the concepts that I have, etc , etc... and I talk to them but they cock their heads to the side and think I am out of my mind. The author definitely has some bias in his words. I hope to field test this coming winter a variant of the savonius type out on the south shore of Long Island and a few on my roof (after I get a thumbs up from the Town supervisor) Stay Tuned!


jon_23
4/1/2009 1:29:44 PM

why is it that noone ever mentions the wind ship alcion launched over 25 years ago which proved vertical wind technology works it was completely self sufficient once the foreward movement was 2kts it powered all its electronic and drive functions, which it had or should i say has quite a lot. the only problem with it is that the custeau society seems to keep tight wraps on the design.


winter star
3/24/2009 10:00:49 PM

Seems this guy has not seen them all, after all. Waht about that double-helix config. unit in Chicago? They have measured and statted that, and it seems to be doing very well, turbulent winds and all. OR, maybe that one has such cheaply replaced membrane fins, that makes up for being short-lived?


larry _1
3/24/2009 1:57:08 PM

This article is awful. The writer is full of opinion. Im an engineer too but I don't use it to club young inventors over the head. Millions of guys have passed those tests pal get over it. It's really not true what your mother said about you being the smartest boy in the world. After accusing Vertical Turbine makers of failing to provide statistics the writer fails to provide us with any useful statistics of his own.. terrible engineering article


pedro_2
2/26/2009 5:37:06 PM

Great article! I had the chance to check out Mariah Power's Windspire since I live near their Reno HQ (http://mariahpower.com). What a great product: made in the US, pretty much silent operation, starts in low wind speeds, 90+% recycled materials (yes, made from YOUR Coke cans). Check em out and support a US company making clean energy products right here in the US!


pedro_2
2/26/2009 5:35:20 PM

Great article! I had the chance to check out Mariah Power's Windspire since I live near their Reno HQ (http://mariahpower.com). What a great product: made in the US, pretty much silent operation, starts in low wind speeds, 90+% recycled materials (yes, made from YOUR Coke cans). Check em out and support a US company making clean energy products right here in the US!


testing_1
11/21/2008 12:07:44 AM

testing testing


testing_1
11/21/2008 12:05:46 AM

testing testing


laurie_2
9/29/2008 12:02:17 PM

One aspect that should be weighed in any design review is the impacts on wildlife and environment. We know that traditional commercial sized turbine designs kill birds and bats. And despite some reports, the numbers can be quite high in some situations. New designs that reduce this environmental cost should be encouraged.


susumu
1/23/2008 9:16:25 AM

We completed an efficient vertical axis wind turbine after 18 years' development, see our website www.etllc.org.






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