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I'd like to know who funded this test. With an average wind speed of only 8.5 MPH no wonder the output was maginal. In most cases a small turbine would not be installed in average wind speeds below 12 MPH. Looks like somebody is trying to give the small wind industry a bad name, could it be the utility comanies???



The test was funded by:

- Stichting Zeeuwind (wind energy)
- Greenlab (small scale renewable energy, focused on wind energy and tidal energy)
- DELTA NV (gas, electricity, solar, internet, tv, water)
- Provincie Zeeland (government)
- Gemeente Sluis (local government).

This test was not designed to give the small wind industry a bad name, on the contrary. These small windmills are designed and promoted for use in a built-up environment, where the average wind speeds are almost always lower than 8.5 mph. They were friendly enough to install them in an unobstructed area, and they decided not to include the results from November 2007 to March 2008, when many windmills showed problems.

See the windmap of Holland and the article we published before:





Talco - or is it reporting the facts ... Do you work for one of the companies that makes the small windmills maybe? :^)

Ave 12mph wind ... man I'd hate to live there!

These windmills are designed for urban areas right?? I would love to see them out perform larger designs, cost little and run forever, but they don't (yet?) so we're stuck with large farms in minimally inhabited areas.

Brian Miles


These results are not shocking. As the previous commenter stated an 8.5 MPH average wind speed is a marginal resource. That said, some of the turbines, for example the Skystream did quite well, and exactly as Southwest Wind's power curve predicts. Buying one of these turbines to offset 50% of a Dutch household's electricity use would make sense if the cost of electricity were high enough.



All the little birdies slaughtered oh the shame. What horrors for little birdies at that place.

Tom Hogarty


This report has blown away my idea of, one day, having a windmill installed in our back garden. The results are remarkable, especially seeing that smaller is really less efficient, something I suspected all along.

Whatever about any potential bias and variances that we haven't seen in the English only summary, the test was an excellent project and the presentation of the results extremely clear.

Thank you and well done on to all involved.



Brian: click on the name of that "previous commenter" and you will see that he is trying to sell a small wind turbine priced at $ 75,000. An 8.5 mph average wind speed is not a marginal resource in a built-up area.

Yep, the Skystream did quite well, but it has a rotor diameter of 3.7 meters. Check the many articles on "revolutionary" urban wind turbines on sites like Ecogeek, Ecofriend, Treehugger, and the like: they are all talking about machines with rotor diameters of around 1 meter.



The report is misleading. It should talk about the average power produced as X watts, saying it is continuous is misrepresenting an intermitent power source. There will have been days when no power was produced.



Of course, Dennis, wind turbines do not generate energy on calm days. Are you suggesting the test should have ignored that fact? That's kind of weird. Maybe you are confused by terminology: a continuous output of X watts = the average power produced, calm days included.



I replaced the word "continuous" by "average". It is more correct, indeed.

Mark Durrenberger


Once you understand the physics of a turbine, you see that small machines are only for show. The power output of a turbine is directly proportional to the swept area. However, when you double the radius of a turbine, you increase the swept area by a factor of four. And doubling the radius does not double the cost. Bigger is better.



The problem here is not the efficiency of the small windmills but the cost of the windmills compared to the power output. Until there is a significant drop in the cost of these machines they will not be a viable option for most people. It is important to note that many people are building their own small windmills from scrap parts for very little money and getting decent results.



"Until there is a significant drop in the cost of these machines they will not be a viable option for most people."

But this won't be the case if petroleum (and energy in general) becomes more expensive.

Higher energy costs => More expensive to manufacture, install, and maintain.

Kevin L. Hughes


A small wind turbine designed to produce electrical power for a dwelling unit requires operation in a high-wind area; certainly greater than the 7 knots prevalent in this test.
Just as there is only a finite amount of calories of energy in a gallon of fuel, and a pint of ethanol will NEVER produce the energy available in a pint of gasoline, there are only so many calories available for conversion from kinetic energy into electricity at a given wind speed within a given area.

As for the 'conclusion" that the amount of energy available from a small wind turbine is inadequate to power a home, I beg to disagree. I have powered my home with a single 1-meter diameter wind turbine and two average-sized solar panels for nearly ten years. There is obviously a bit more to this, so let me touch the high points:

Ø Using both wind and solar power provides a more reliable daily flow of electricity.

Ø The penultimate key to the system is the largest battery system one can afford.

Ø Far and away the greatest factor in achieving this goal is conservation.

If there is more interest in my particular situation, I will send another short post with further details.



According to this article (published half way theough the trial) they had expected wind speeds to be around 6 m/s average. In end it turned out to be about half that.


Julian Patrick


I tend to agree that his must be funded by someone who has a reason to give micro-wind a bad name. The windspeed on this site is simply too low. It is the equivelant of putting solar pv panels under a tree!
It is the industry standard to never install a turbine on a site with an annual average windspeed of less than 5 m/s as a minimum. The power available in the wind is proportional to a square of the speed so if you install in a low wind speed area you are wasting your money. There will be no environmental or economic benefits whatsoever.
The only reason a local turbine would do well would be if it was on a much taller mast and therefore experience higher wind speeds.
Microwind does work, we see paybacks under 5 years! You just have to make sure you get good advice and use an accredited installer.



Colin: the higher expected wind speeds you mention seem to correspond with the information on the wind map of the Netherlands. So I guess you are right. I based my sentence "wind speeds were slightly higher than average" on information from Jeroen Haringman (link at the bottom of the article) and he must be wrong. I will correct this.

However, does this change the conclusions? Not at all.

To all those thinking that this research tries to give small wind turbines a bad name: Please check the wind map of the Netherlands.


The turbines were placed in the windiest part of the most windy country in Europe. As you can see on the map, only a very small part of the windiest country in Europe has wind speeds of 6 m/s.

These machines were tested in the most optimal conditions, rare in Holland, and even more rare in the rest of the (inhabited) world. They were installed in a sparsely populated area, on an open plain without any obstacles around, on a 15 meter high pole.

If the wind speed would have been 6 m/s, as expected, this would have said nothing about the usefulness of these machines, because almost nobody lives in such conditions.

The fact that the wind speed was much lower than expected, gives a much more realistic idea of how they might perform in a built-up environment. Because even in windy Holland the average wind speed inland is 4 m/s - on an OPEN PLAIN. And you will never get permission to install a pole of 15 meters.

So, these machines might be interesting for a very small minority of people, but for most of us, they are not. You will never even get an average of 3.7 m/s in a suburb or a city.



------ IMPORTANT UPDATE ------

The information on the average wind speed during the test is contradictory, which means that the performance of the turbines is probably even worse.

The statement of Jeroen Haringman (see comment below) is supported by measurements:


This concerns another location, but it is not that far away from the testing spot. Wind speed was slightly higher than average.

Even more interesting, the following article (also in Dutch, unfortunately) describes how a weather station of the Dutch meteorological service only 14 km off the test field did measure the expected wind speed of 6m/s.


The author of this article confronted the organizers with this information, and they answered that the given wind speed at the testing field is only "indicative".

In other words: the wind speed at the test location was possibly much higher than 3.7 m/s.

Which would make the performance of the turbines even worse...



- DELTA NV (gas, electricity, solar, internet, tv, water)
- Provincie Zeeland (government)

are funders of this research. I am not sure about the Provincie Zeeland, but Delta is the owner of a nucleair plant in Zeeland, and they want to build another one....they sure are not fans of windenergy!

Kevin L. Hughes


Sorry, I did not realize Europe has a complete lack of wind. You may be right: you'll be dependant on fossil fuels long past the point America is powering up with the wind.

Seeing I was raised in Milwaukee, and currently live in the Caribbean on a sailboat, I thought wind was available everywhere, including Europe. Guess it is only for the other 89% of the people in the world - HEY that's still enough to make it a good idea!

Below are the US cities that have an ANNUAL AVERAGE wind speed of 6 m/s or greater. There are 75 of them.




Walter, come on. Look at the energy return of the wind turbines. You think this will scare the owner of a nuclear plant?

If DELTA sells nuclear energy, like you say, then of course they were eager to fund this research. They know these machines don't work. For them it is a chance to run down the image of wind energy as a whole. But they don't have to tamper with the results to achieve that goal.

For many people these test results might have been a surprise, because small windmills have been hyped to death. But any wind energy expert would have told you already years ago that these machines are useless. The problem is nobody asked them.

Nobody even bothered to read the claims of the manufacturers. Check the website of the manufacturer of the Energy Ball, for instance. According to their own figures, the yearly electricity output of the Energy Ball v100 (the machine tested) is 100 kWh at an average wind speed of 4 meters per second.

In the real-world test described in the article the Energy Ball delivered 73 kWh at an average wind speed of 3.7 m/s. I don't see any fraud here.



@ KEVIN L. HUGHES : could you give the source for your information, please?

Because you need to look at wind maps that give wind speed for a height of 10 meters (like the one from Holland I have linked to).

99 percent of windmaps out there describe the wind speed at a height of 75 meters or more.

That's a huge difference.

Kevin L. Hughes


I apologize for the sarcasm, and do not disagree totally with the viewpoint of the article, only it's spirit.

Wind energy is a viable resource most everywhere, and needs to be utilized to it's fullest potential because of its clean nature.
The following link provides a basic mapping of average wind speeds for the whole planet, excluding Antarctica (which is by far the windiest place on earth):

My US data came from:
published by Dr. John Horel, Mesoscale Analysis Committee Co-chair, National Weather Service, Office of Science and Technology and the Director of the NOAA Cooperative Institute for Regional Prediction, University of Utah. Pretty much, a guy that should know wind.

If you average only the seven windiest months of the cities on this list, well over 200 of them have higher wind speeds than the test site in the Netherlands.

True, Europe isn't as blessed as other locations, but there is enough wind to go for it using the big boys in appropriate places.



Kevin, the link you give only shows cities and wind speed, not the height at which the wind is measured.

Judging from the numbers, however, I am quite sure that these average wind speeds for American cities concern the wind velocities at 80 meters. So they describe the potential of LARGE WINDMILLS.

The other link you posted states that the worldwide average wind speed at a height of 10 meters (the information we need) is 3.31 m/s. That is considerably lower than the average wind speed in the Netherlands, and also lower than the wind speed in the real-world test.

Wind speed goes up fast when you go higher, that is why some people think "flying" windmills are the answer, and why kites are more powerful than sails:



Kevin l. Hughes


Kris, you are skewing the data a bit, " . . . worldwide average wind speed at a height of 10 meters . . . " is not an important piece of data. Who cares if the "average" number of batteries/square-foot in a room is .004 when I only need two for my flashlight?

You might have missed this in the summary:
"Assuming that statistics generated from all stations analyzed here are representative of the global distribution of winds, global wind power generated at locations with mean annual wind speeds ≥ 6.9 m/s at 80 m is found to be ~72 TW (~54,000 Mtoe) for the year 2000. Even if only ~20% of this power could be captured, it could satisfy 100% of the world's energy demand for all purposes (6995-10177 Mtoe) and over seven times the world's electricity needs (1.6-1.8 TW). Several practical barriers need to be overcome to fully realize this potential."

This is, of course, utilizing wind turbines at appropriate heights.

Concerning the 10-meter measurements, what we are interested in for 'small' wind turbines, is wind velocity greater than 6 m/s; therefore we are interested in stations defined as "class 3'" or above, because:

"Mean velocity for class ≥ 3 stations (AT 10-METER HEIGHT!) = 6.53 m/s"

"Approximately 12.3% of all stations worldwide belong to class 3 or greater (i.e., annual mean wind speed ≥ 6.9 m/s at 10 m) and are therefore suitable for wind power generation. This estimate is conservative . . . "
-----this is 12.3% of 8321 stations worldwide----
" . . . Europe and North America have the greatest number of stations in class = 3 (307 and 453, respectively), whereas Oceania and Antarctica have the greatest percentage (21 and 60%, respectively). Areas with strong wind power potential were found in Northern Europe along the North Sea, the southern tip of the South American continent, the island of Tasmania in Australia, the Great Lakes region, and the northeastern and western coasts of Canada and the United States."

Regardless of the potential at 80-meters, there are MANY places where MANY people can do as I do and live ENTIRELY on wind & solar generated electricity at only FOUR METERS ABOVE SEA LEVEL! The proof is in the pudding, Kris, and I have been doing it for ten years over the course of a 15,000 mile journey (thus surviving in MANY locations with my lighting, refrigeration, navigation, computing, 2000-watt sound system, and all-electric galley [microwave, rice cooker, toaster oven, griddle, & electric fry pan]).

One is invited to go to and download the entire 10-page report. LOTS of math, informative graphs, and pretty pictures of the wind velocities across the globe.

p.s. I have sent an emailio to Dr. Horel to discover his data gathering methodology; I will post any response I receive.

p.p.s. I obviously enjoy your magazine and find MANY topics relevant, for example: I was anchored next to the Maltese Falcon last month at Jost Van Dyke, BVI (did you know it is for sale?); and discovered last week that the VLA telescope on St. Croix, USVI, where I am currently staying, uses "Sneakernet" to collect the data from its ten radio astronomy locations.
Very cool stuff, but we can agree to disagree, no? ;-] (don't get me started on the electric car issue . . .)



Kevin, the wind speeds at a height of 80 meters are completely irrelevant here. You don't have to convince me of the potential of large windmills, I agree with you on that.

We are talking about small windmills. The figures you link to, confirm that the potential of these machines is very limited. Of course, there are places in the world where you have sufficient wind speeds at a height of 10 meters, but not where most of us live.

Contrary to large windmills, mini wind turbines have to be placed right next to where your house is standing. So these "Class 3" locations you are referring to are of not much use. What counts, is the average wind speed in our cities and towns, where we live. You live on a sailboat, roaming the Caribbean. Most of us, unfortunately, not.

You make one very good point, though: energy conservation is a way to deal with the limited energy output of these machines. If you live a low-tech life, a small windmill combined with a solar panel can give you all the power you need.



Why do people always think they need a windmill in their house? The idea that they would never work in urban areas is a mute point - we have something called high voltage power lines. Build the mindmills in windy areas, transform the voltage and put it into the grid. Don't even bother trying to put windmills where you happen to live - go looking for a good place to put them.

The idea that small windmills are useless may not be true. Its a simple exercise in math. Work out your up front and maintainance costs, and work out what wind speed you will need on average for it to break even over a reasonable period of time, given a reasonable cost of energy.

I have a 2.5m 500W windmill on a property directly on the beach (not my property, but they let me use it because they interested). It cost me just $650US for the windmill and another $200US for a grid inverter. But I installed it myself. I would say I did $500US of work in total. The power company had to hook it up for free to the grid, which is paid for by a goverment bonus grant thing for green energy.

I luckily have a position on the slope of a hill in a fjord that is almost constaly 10 to 15 m/s and is about 50m above sea level. The generator makes 200W at 8m/s and upto 500W at 12m/S, and can max out at 600W at over 15m/s in storms. So far in the first 3 months I have pulled in 650kw-hours. I get paid about 31 US cents per kilowatt hour because its green energy, my first months check was about $190US. At this rate it will pay for itself in about 18 months.

However not everyone is as lucky. If the average wind speed was only about 8m/s I would probably only pull in 100kw-hours instead of 600. If the goverment doesn't pay you for green power, you might only get 10 cents per kilowatt hour, instead of 30 cents. If that was all true it would probably take 20+ years to get pay off (I doupt it windmill would last more than 4-5 years without having to spend on parts, new blades are about $100 US each).



Basically bigger is better, which we all kind of knew anyway. Tell that to these campaigning morons who object to them because they damage the scenery... Huge campaigns in Scotland to NOT have windfarms. Each of them should be strapped to the arm of a giand windmill for a few days to help power it - with their hot air and arm flapping.



I have constructed and owned large wind farms for almost 30 years in California. I have no economic interest in small wind but thought I might add a comment here.

As a previous commentator mentions, there is an exponential increase in the power of the wind as its velocity increases. All windmills need a wind of at least 14mph (6.25mps) to achieve rated ouput. Many need more. The issue is not the average wind at a site, rather how many hours of wind exceeds 13mph. It is the higher winds which produce power. That is why the earlier comment that the more batteries the better for home use is correct. Charge them in high wind, use the power in calm or low wind times.

Second, the array of small windmills is appropriately designed if the wind is unidirectional as it is in Palm Springs California, where I operate my windmills. If the direction from which the wind blows varies significantly and blows much in a direction parallel to the array, the windmills will mask wind from each other and the downwind windmills will receive great and damaging turbulence.

kris de decker


"The issue is not the average wind at a site, rather how many hours of wind exceeds 13mph"

I think the former is a good indication of the latter, no?

"If the direction from which the wind blows varies significantly and blows much in a direction parallel to the array, the windmills will mask wind from each other and the downwind windmills will receive great and damaging turbulence."

Winds in that area of the Netherlands are predominantly south-west.

Kris De Decker


The Oil Drum runs an extended and rewritten version of this article - including additional tests results from the UK.


Brian Barghout


I would like to respectfully disagree with the broad sweeping statement that small windmills are a fundementally flawed technology, and I will detail below a different perspective on this issue:

1. maintenence. Depending on the quality of the parts used, the working life will vary, For example at my factory Barplas we carry out scheduled maintence and keep a history of when parts need changing. Its often the case that a part may cost 2 to 3 times more than a comparable part, but have 5 times the working life. Add to this the downtime to replace the parts and the labour and this is the real cost. ie, certain parts may be cheap in the short term and more expensive in the long term This needs to be analysed properly before a decision is made.

2. Regarding the costs of windmills as stated in the article. I feel obliged to point out that with my experience of living in Asia that the costs of Windmills in Europe and the USA are about 5 to 10 times the costs of getting the same spec machines from China or other far east sources. Ultimately, the parasitical nature of Goverment duties, import taxes etc, has be held to account. We either pollute our planet to death, by falsely hiking up prices of alternative energy sources, or else start dealing with the true and much more economical prices of Windmills. I'm not trying to sell windmills from asia here but I can tell you that when I compared prices in the UK to the prices in China there was a 10 fold increase in price. Also some of the Windmills were Chinese but re-branded.

3. I follow that a Dutch house hold uses 3,400 kWh/year and an avereage American household consumes almost 3 times more electricity than a Dutch household. But please don't forget that millions, if not billions of people in third world countries would love to have just 100 watts per household, so that they have a little light and security at night, and for their children to study with a light bulb instead of a candle or an oil wick. Let's not deny all of these people the technology for a small windmill based on the fact that we in the west need big ones for ourselves.

4. Again regarding costs. We've built Windmills in Beirut, and run a small garden center from it. Without going into lots of details, I just want to mention, as I believe one of the other comentors here has, that we built it from scrap.

In closing, I would say say is that there will be a place for many different solutions, Big, Medium, and Small Windmills. the determining factor will be the eventual location/country and the actual users (first world heavy users vs third world light users)

I also think there should be very heavy pressure on our goverments to have zero duty on Windmills and other alternative energy sources because its a joke when the duty, and taxes end up with a 5 to 10 fold difference in the price of the technology. (Although I'll admit that some companies have to bear some of the blame as they are demanding a big profit margin out of sheer greed)

Brian Barghout



Small Windmills are inefficient, for many reasons:
1. Windmill companies, have become like the Standard Oil companies. Huge monopolistic behemoths. They are one of the reasons, why good quality dynamos are not available, at affordable prices.
2. Most people who construct cheap windmills, Only understand a small portion of the dynamics, of windpower. They are unable to tap, even a fraction, of the wind energy, of big (and expensive) windmills.
3. Most of the DIYs, on windmills, only deal with how to make a windmill, and Not, how to increase the output of the dynamo.
As, a matter of fact, since most smaller windmills are much lighter, they should have faster moving parts, and should require lesser wind, to move them. Also, the scope of dealing with ergonomics, and wind-mill design, is far greater, in smaller windmills.
Only, if people didn't get fooled, by all the wind-energy generating companies.

Bas Groot


The report itself is even more misleading than the article already suggests (I'm dutch so I can read it).

On the one hand it says that in one of the windiest outposts of one of the windiest countries in Europe, the wind 50% of the time just doesn't blow hard enough at a 12m pole to get a small wind mill going at all!
In other words, it's just not gonna work. Mere physics.
This brings the scientist to a surprising conclusion: let's pump more R&D subsidies in it, so that the pysically impossible becomes possible. And these wind mill companies stay afloat. Again: says a scientist!

Keith Cockburn


A lot of these comments and indeed the artical entirely missed the important point that most of the energy generated by wind power is wasted. Not going round at the right speed to generate 50/60 Hz and 250v or whatever multiple is the most limiting factor. Home units and indeed the one I am planning for my workshop can be variable speed and make use of suplus enery as heat (it is ussually coldest when the wind is blowing hard). Not to mention energy harvesting and having the blades at the most efficient speed.
I am for more scientific investigation.
Keith Cockburn for Calenterprises

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