From Energy Crisis to Industrial Adventure: A Chronicle - Wind Power for the World: The Rise of Modern Wind Energy - page 235

blades to be tested on their small 18 kW windmill, the so-called PTG

windmill that was developed for this purpose. Tvind did not aim
for industrial production but allowed private builders to have a
blade for copying.

Figure 7.45 Tvind PTG wind turbine with first fibreglass blades (down

scaled Hütter-type blades), around 1977. Children playing are
the author's sons, born 1971 and 1974.

The self-built blades were installed on the windmill of electrician

Leif Nielsen in Gredstedbro, but already in the summer of 1977
the windmill lost a blade and the interest in self-made fibreglass
blades vanished. Erik Grove-Nielsen of Økær, Viborg, took over the
mould and he commercialised the Tvind blade, the first one from
an independent blade supplier. Thus, the component windmill
had become a reality.

From now on interested windmill producers
could buy blades where the manufacturer had the copyright. At a
stroke this made it much simpler to introduce a windmill to the

market.
The first set of 4.5 m Økær blades were delivered at the end
of 1977 to mechanic Svend Adolphsen in Knudstrup at Viborg.
However, the 4.5 m blade had two important shortcomings. It had no
air brakes, it ran too fast and was noisy which was not satisfactory
for the users. Soon the newly established blade supplier had no
customers.
This might have been the end of the independent sector of
blade production, if Erik Grove-Nielsen had given up at this point,
where his financial basis was rather weak. But various forces