Environmental Engineering Reference
In-Depth Information
3.7
Technological Development during the
Second World War
When the breakout of the Second World War in 1939 limited the
supply of imported fossil fuels, the Danish knowledge of wind
power was not far away. A few windmill producers had survived
since the “golden age” 20 years ago and statistics from 1935 showed
that more than 15 000 windmills were still installed in Danish
farms. Some of them were out of service, but many farmers still
considered wind power as useful means to reduce electricity bills
in times of crisis. In most cases the windmills were used in the
traditional way with a mechanical drive to the farm machines, but
more than 1 400 farmers established their own electricity production
during the war, either by connecting a dynamo to their old windmill
or buying one of the new small (<1 kW) propeller-type windmills
produced by a number of Danish companies [8].
Among the commercial electricity producers, the war also
gave wind a new chance. The number of local power stations using
wind power grew from 16 in 1940 to around 90 at the end of the war.
Most of the windmills were delivered by the Lykkegaard Machine
Factory and followed the la Cour tradition using four blades with
wooden shuttered sails. The “standard model” for small power
stations had an 18 m diameter, a 20 m steel lattice tower and a
30 kW generator.
Though, the basic principles were 40 years old, details in the
technology had been modified throughout the years. Light running
ball bearings were used instead of the traditional white metal
bearings, and at the bottom of the tower, the combined pinion- and
belt-drive to the dynamo was replaced by a sturdy gearbox. On
windy locations along the west coast of Jutland or at one of the
small Danish islands, this type of windmill could have had a yearly
production of 60 000-70 000 kWh.
However, the problems caused by the war also initiated
development of quite a new type of “wind turbine” with aerodynamic
blade profiles, taking up the legacy from the ill-fated Agricco 20
years before. In May 1940, the big Danish industrial company
F. L. Smidth & Co., the world-known producer of machinery for the
cement industry, decided to enter the wind power market. The FLS
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