ABSTRACT
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
Figure 13.2 Mark II water brake windmill: Section (left); Yaw system and power security (right).The measurements were recorded in the report “Wind Energy-Heat Generation” and presented in 978 at the Second International Symposium on Wind Systems Energy in Amsterdam. Ricard Matzen’s many experiments and measurements with water
13.2.2 Gunnar Broe and Værløse GroupGunnar Broe was the main member of a group of experimenting engineers from Værløse, active from around 970 onwards. The group was developing wind-powered water pumps for developing countries. They were made very simple and consisted of simple parts that were produced in big numbers. Parts came from the automobile industry, and were used or new components at a reasonable price. Broe developed a simple turbine with a three-bladed rotor. The rotor diameter was 5 m and tower height was 8 m. The nacelle was made of second hand car parts. The tower was bolted lattice. The blades were upwind of the tower and were held up against the wind by yaw blades.The windmill was later converted into a heat-producing windmill with an open water brake, based partly on results from the experiments held at the Institute of Agricultural Engineering. 13.2.3 Windmill Group ECO-RAThe windmill group ECO-RA continued the development of Gunnar Broe’s ideas with water brake windmill experiments. The group consisted of Gert Ottosen and Jørgen Krogsgaard. The prototype wind turbine used parts from a car and the open water brake that looked like the one from the Agricultural Technical Institute. The entire windmill was of a very simple construction. After taking some measurements and testing of the water brake windmill, a design manual was created in 1976. It was very brief with three pages of text and drawings, which was sold in 00 copies.Then in 977, Jørgen Krogsgaard designed a much better water brake windmill. It had three blades with the profile from the Gedser wind turbine. The rotor diameter was 6 m. For the transmission in the nacelle, second-hand car parts were used. The tower was a tube held up by four wires. The blades were placed downwind. The power was limited by mechanical pitch regulation. The speed of rotation was variable, which gave a constant tip-speed ratio until the pitch regulation set in and the tip speed was constant. The water brakes were of the closed Culver-type and mounted in a special lattice
Figure 13.4 The 3-bladed ECO-RA water brake windmill (left); ECO-RA water brake windmill built by Ib Grosser, Odder (right).In 978, Ib Grosser from Odder used this construction manual and built a water brake turbine with 6.4 m rotor and a tower height of m (Fig. 3.4 right). It ran very well and the pitch regulation could keep the rotation speed nearly constant. After four years of operation it was taken down for revision and was not put up again. Also other windmills were built in accordance with the
13.2.4 The Calorius WindmillHans Henrik Ekner from Slagelse developed a -bladed house-hold windmill with a water brake, the Calorius windmill. It was approved by the Risø test station for windmills. The windmill was mounted on a 9 m tube tower held up by four wires. The rotor diameter was 5 m. It was upwind and held by a wind vane. The water brake was of the closed Culver-type. The power limit was set in the way that the water brake changed characteristics in a very clever way. When the maximum effect was achieved, the rotor stalled. The windmill had variable rotation conditions with constant tip-speed ratio until the power limit stall takes over and the tip speed was held constant. This wind turbine-Calorius type 37, was the only water brake windmill approved and tested at Risø test station and documented in the reports “I-986” and “I-1205”. The measurements showed that the maximum capacity was 3.5 kW at about m/s. The company Acoustica conducted the noise measurements: The Calorius windmill was very quiet. The safe-guard against run away was a mechanical brake activated by too high speed. However, it was difficult to adjust and this caused some problems.
