A real-world test performed by the Dutch province of Zeeland (a very windy place) confirms our earlier analysis that small windmills are a fundamentally flawed technology ( test results here , pdf in Dutch). Twelve of these much hyped machines were placed in a row on an open plain (picture above). Their energy yield was measured over a period of one year (April 1, 2008 - March 31, 2009), the average wind velocity during these 12 months was 3.8 meters per second (note: update on the wind speed ). Three windmills broke. Find the disappointing results of the others below.

Picture: Jeroen Haringman.



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Small Wind Turbines

- Energy Ball v100 (4,304 euro) : 73 kWh per year, corresponding to an average output of 8.3 watts

- Ampair 600 (8,925 euro) : 245 kWh per year or an average output of 28 watts

- Turby (21,350 euro) : 247 kWh per year or an average output of 28.1 watts

- Airdolphin (17,548 euro) : 393 kWh per year or an average output of 44.8 watts

- WRE 030 (29,512 euro) : 404 kWh per year or an average output of 46 watts

- WRE 060 (37,187 euro) : 485 kWh per year or an average output of 55.4 watts

- Passaat (9,239 euro) : 578 kWh per year or an average output of 66 watts

- Skystream (10,742 euro) : 2,109 kWh per year or an average power output of 240.7 watts

- Montana (18,508 euro) : 2,691 kWh per year or an average power output of 307 watts.

Keep in mind that these windmills would perform considerably worse in a built-up area.

47 windmills to power a household

An average Dutch household consumes 3,400 kWh/year. Listed below is the amount of windmills required, and their total cost, to power a Dutch household entirely using wind energy:

- Energy Ball : 47 windmills (202,288 euro)

- Ampair : 14 windmills (124,950 euro)

- Turby : 14 windmills (298,900 euro)

- Airdolphin : 9 windmills (157,932 euro)

- WRE 030 : 9 windmills (265,608 euro)

- WRE 060 : 7 windmills (260,309 euro)

- Passaat : 6 windmills (55,434 euro)

- Skystream : 2 windmills (21,484 euro)

- Montana : 2 windmills (37,016 euro)

An average American household consumes almost 3 times more electricity than a Dutch household. Simply multiply the above figures by three.

Rotor diameter

At first sight, the results seem to indicate that the design of the windmill matters. However, if you combine these figures with the rotor diameter, it becomes clear that the concept of small windmills is fundamentally flawed. The turbines that score best, are simply the largest ones:

- Energy Ball : 1 meter

- Ampair : 1.7 meter

- Turby : 2 meter

- Airdolphin : 1.8 meter

- WRE 030 : 2.5 meter

- WRE 060 : 3.3 meter

- Passaat : 3.12 meter

- Skystream : 3.7 meter

- Montana : 5 meters

Windmills with a rotor diameter of 4 or 5 meters do not fit on most roofs, and are not easy to integrate in a built-up environment.

Size matters

Close to the test site stands a (relatively) large windmill with a rotor diameter of 18 meters. It delivers 143,000 kWh per year, or an average power output of 16,324 watts. It can power 42 Dutch households. This large windmill costs only slightly more than all small windmills combined (17 percent more, to be exact, or 190,000 euro), but it delivers almost 20 times more energy. This comes down to 4,523 euro per household.

Wind power rules, but small windmills are a swindle. Bigger is, in this case, better.

© Kris De Decker (edited by Vincent Grosjean)

Thanks to Jeroen Haringman & Jaap Langenbach / Dutch readers can find a longer version of the article here.

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