Water Brake Windmills - Wind Power for the World: The Rise of Modern Wind Energy - page 319

wind turbine with constant tip speed. That is optimal in a smaller
range of operations. Thus, in principle a water brake windmill
is producing more than windmills running at constant speed of
rotation.
Water brake wind turbines produce hot water, which can be
circulated into a nearby house by an insulated pipe network. In
the house, there is often a heat storage tank to compensate for
the consumption and production.
There are few disadvantages of water brake turbines. Pumps,
used for circulating water into the nearby houses usually cause
some efficiency losses. Also, transmission loss in the pipes limits
the distance to maybe 0 m to 50 m or more but this is enough
to enable the turbine to be sheltered by buildings or trees. Noise
and too close to neighbours can also be a problem.

13.2 Developing Water Brake Windmills

13.2.1 Institute of Agricultural Engineering

As a result of the energy crisis in 973 Svend Sonne Kofoed and
Ricard Matzen from the Institute of Agricultural Engineering in
Taastrup, became interested in wind power. They began to develop
an experimental windmill Mark I with a water brake. It was at
first a turbine with a blade diameter of 6 m, two blades made of
wood, and a m lattice tower. It was downwind rotor and was
running anti-clockwise. In the nacelle there was a gear with a
shaft down to the water brake at the bottom of the tower. A number
of measurements were carried out. These measurements resulted
in reports “Wind energy as an opportunity for agriculture” and
report no. 36 of the Institute of Agricultural Engineering.
The next windmill Mark II had also a diameter of 6 m and two
blades shaped out of one piece of wood and the same as Mark I. The
tower consisted of three wooden beams and could rotate according
to the wind as the yaw system was on the ground. The blades
were placed upwind and held up in the wind by a yaw vane. The
rotor was connected to a gear at the top and a long shaft to the water
brake at the bottom of the tower. The water brake “k” factor was :3.
The tip-speed ratio was :0, so it was quite a fast-running -bladed
rotor.