Consigned to Oblivion - Wind Power for the World: The Rise of Modern Wind Energy - page 375

Ole Hansen found that the gearbox was under-dimensioned,
the fibreglass hybrid blades disintegrated, the tower was too low,
and the light flashed of and on. Improvements led to the Kongsted
windmill which obtained system approval and consequently
became eligible for subsidy. This did not please Riisager, says Ole
Hansen, but he wanted to develop a well functioning windmill.
“That can best be done by building on experience. Riisager did the
same by building on the experience from the Gedser windmill,”
says Ole Hansen. It was quite true that the concept had been taken
from J. Juul, who designed the Gedser windmill.

16.11 The Fascinating Egg Beater

Special interest was shown in vertical-axis windmills, VAWTs,
which for some years attracted and fascinated a great number of
developers in Denmark and abroad, and resulted in many experi-
ments. The belief in the VAWT concept as the rational, simple, cheap
and reliable windmill, was so strong that it was often overlooked
that the wind is more turbulent, and the energy contents lower,
when the rotor was placed down on the ground and not on a high
tower like on a horizontal type windmill.
The designers and inventors of the many varieties of VAWTs
often were focused on having the generator placed on the ground,
in order to facilitate servicing. Meanwhile, they forgot that the
component that needed to be developed was not the generator,
as the technology was already well-known, but the vertical rotor
technology, which was new and yet unknown.
After 40 years of experiments and testing the situation by 2012
is almost the same. The VAWT concept still has to demonstrate
reliability and efficiency. That was the reason that windmills of
the Darrieus type have in fact been abandoned as commercially
irrelevant.
The preliminary successful research, testing and practical
experiences of Johannes Juul and Ulrich Hütter were available for
the designers of horizontal-axis wind turbines. However, people
involved in VAWT design had only the idea and theory of an
ideal wind turbine but no real operational experiences. And that
caused great problems, particularly because of the vibrations and
durability of the various configurations of VAWT rotors. Yet, the