Environmental Engineering Reference
In-Depth Information
17.2
The Dream of Flying and First Theoretical
Works for Wind Energy
The academic work on wind energy for Hütter, as for many other
pioneers, was closely related to the dream of flying. Hütter, born
in Pilsen in 1910, became a great fan of gliding with unpowered
aircraft. Together with his brother he had designed a few light-
weight gliders in the thirties. The company Sportflugzeugbau
Schempp-Hirth in Göppingen built them in series. During the war,
he was the head of the construction department of the aviation
research institute “Graf Zeppelin” near Stuttgart. In summer 1944
he took over a chair for fluid mechanics and flight mechanics at
the Technical University of Stuttgart.
After the end of World War II the allied forces prohibited
aircraft construction in Germany. This was a hard blow for many
engineers who had dedicated their entire professional career to
aviation. For the aircraft designer Ulrich Hütter this ban was reason
to return to another subject he had pursued with great attention
several years before: wind energy.
Hütter had completed his doctorate proceedings already in
1942 at the University of Vienna with the thesis “Beitrag zur Schafung
von Gestaltungsgrundlagen für Windkraftwerke” (“
A contribution
to creating the design principles for wind turbines”
). Back then he
worked as a lecturer at the college of Weimar. On a test field of the
local company Ventimotor GmbH he collected valuable experience
with small wind turbines working according to the aerodynamic
principle. The design of their rotor blades used aerodynamic uplift
to drive the rotors instead of air resistance as in old type windmills.
The benefits of such machines have been undisputed ever
since the fundamental analyses of the scientist Albert Betz in the
1920s. At that time, Betz had analysed wind roses with diferent
numbers of blades in the wind tunnel of the Aerodynamic test
station in Göttingen. From these tests he derived the physical
principles of the conversion of wind energy. He also determined
the upper limit for the theoretical maximum value of wind power
performance, known today as “Betz's factor”, which is 16/27.
According to this factor, a maximum of 59.3% of the total perfor-
mance of airflow meeting the rotor of a wind turbine can be converted.
Betz's theoretical works have been the base for the calculation of
wind turbines ever since.
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