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The Dutch Windmill



After the Chinese Windmills arose in Europe the propeller windmills. It is not quite clear who had first the idea. Belgium or Ireland are possible, too. Because Europe has not light bamboo but hard and heavy oak they took oak and the propeller with four blades went common. Plentiful the propeller windmills arose in the Netherlands where they used it to drain the fields to gain land from the North Sea. The technique was developed as far as wood allows here and therefore the propeller windmills became the name Dutch Windmill. Foremost the steam power lets this type of windmills take out of service.

Because propeller windmills move close hauled the towers are made out of massive oak or stone to stand the pressure of the wind. The Dutch Windmill is a pure buoyancy runner. Buoyancy runner have a higher efficiency than pure resistance runner because they do not move into the direction of the wind. The performance of a windmill depends with the cube of the velocity of the virtual wind and the virtual wind of a resistance runner is lower.

A varietal form of the Dutch Windmill is the American Windmill, the so called Western Mill. It appears in many Western movies. Typically is, that the American Windmill has many blades out of metal. After inventing the radio the farmers do want to have one, therefore they needed electricity. But the electricity net was still not extended and the Western Mill came in frequent use at the beginning of the 20th century.

Also known is the Spanish or Greek Windmill. Here rotate mostly eight triangular fabrics which are mounted towards wooden sticks. A spanned rope outside stabilizes it.

The upcoming of the actual propeller windmills with the long and small iron masts is a comeback attempt of this deprecated technique. After inventing the airplanes and getting the wisdom about aerodynamics aerodynamically formed blades got their entrance into the windmill technique, too. Because the Dane company Vestas was strongly involved in this, it is allowed to call the propellers with aerodynamic shaped profiles the Dane Windmill.


today┬┤s propeller windmill

Bild "Home:Windmuehle.gif"

And here I list some disadvantages of the modern Dutch (or Dane) Windmill:

Disadvantages:

  • the high speed of the blades kills directly birds, bats and insects
  • the insect-dying due to the 20 to 30km long wake turbulence. In the Karman whirlstreet insects cannot fly because of the many changes of the direction of the wind and of the pressure. The nuptial flight cannot take place.
  • with the insects as source of food are not only songbirds dying but also amphibians like frogs or fire salamanders
  • depending of the direction of the wind
  • the turning moment comes into being where it is not wanted (e.g. in 100 m highness).
  • the sound there can cover the landscape
  • because of the movement of the profiles close hauled and the lever rule propeller windmills do need an huge groundwork
  • the material of the blades must be very stable
  • the groundwork gets some rifts with the time in which water can come in and bring the iron of the mast within the cement to rust but you cannot see that
  • because of the mass of the propeller the ball bearing must have big dimensions
  • therefore a high need for lubricating oil
  • danger of resonance for the mast
  • while the blade comes near the tower, the propeller receives a hitch because the wind gets jammed there
  • problems of getting started because of the heavy weight
  • "dirt" on the blades, the dead insects stick on the blades and lower the efficiency
  • problem of the waste heat
  • the need of lots of materials
  • about every 4 years a serious damage
  • short usage for about 20 years
  • after that lots of special waste
  • problem of transport and building
  • problem of repairs
  • shadow
  • strokes of lightning
  • at fire no fire fighters can help; danger by falling and burning parts
  • icicles in winter can fly hundreds of meter


Advantages:
  • jobs for the sake of themselves
  • "greenwashing" of the money-stream from "bottom" to "top" by higher electricity costs
  • politicians can play good humans and the media has a theme to write about
  • the solvent customers of the anthroposophic driven organic grocery stores buy not only food but also the feeling to support "clean" energy