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intelligent and creative artisans. The windmill was erected at
Stagstrup in Thy, where it heated Hans Svaneborg's house for
years. The two brothers had gathered all accessible knowledge on
that kind of windmill and gave it three fibreglass blades. The angle
gearbox came from a Mercedes vehicle; the home-made liquid
brake was placed at the bottom of the tower. From here the pipes
led to a water storage container inside the house. The Svaneborg
windmill was demolished but not shredded. When restored it will
be part of the Folkecenter Renewable Energy Museum where the
blades are already exhibited.
16.6
The “Folke” Windmill: One Blade Suffices
“From the point of aerodynamics more than one blade is really
almost wastefulness,” according to civil engineer Burmand Jensen.
Together with Finn Jensen and Søren Olsen, who had harvested
inspiration at a sail-blade-windmill-course at Kolding Folk High
School during the spring of 1977, they wanted to design an ideal
windmill for the people. It was super light, of 6.5 kW and had an
enormous swept area for its size of 95 m
. It was calculated to be
able to produce more than 20 000 kWh annually. Other people
also worked on one-bladed windmills, among those the German
weapon giant MBB. They shared similar problems and fate: the
fewer the blades, the faster they have to rotate in order to utilise
the wind efficiently. And that creates noise and problems of counter-
weights for proper balancing of the rotor.
The group was good at getting money grants, Burmand was
an excellent theorist, the others could turn theory into practice.
This resulted in several prototypes which did not, however, get
past the experimental stage. Burmand recounts that the last type
was erected next to the old Harreby Co-op outside the town of Ribe.
This place also had a workshop where the pioneers could work.
But one windy day things went wrong. Some of the ingenious
mechanical bits in the hub had got stuck, and the windmill began
to race. The long laminated wooden blade hit the tower and was
splintered so that the bits of the blade flew as far away as 250 m!
Of the three pioneers, Søren Olsen later founded his own
blade factory, Olsen Wings, which became a leading supplier of
blades for 3 kW to 30 kW wind turbines.
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