A 100-metre prototype was installed in 2012, near Hanover in northwest Germany, with a 1.5MW Vensys 77 turbine. Windpower Monthly's Eize de Vries visited the firm.
"Wood as raw material has a favourable price level, while price fluctuations are minor by comparison. The same is true when wood is compared with concrete, again on raw materials basis. Our towers can be up to 20% cheaper compared with concrete-steel hybrid towers. Our next steps are constructing a wind farm with five towers of 140-metre hub height each and develop plans for 160-metre towers," said TimberTower head of engineering Carlo Schroder.
TimberTower is also developing a project to use five 140-metre towers in Bavaria, southeast Germany. The second tower design would be a 12-sided wood and tubular steel tower. The base of the tower would be 80-metres wide. These TimberHybrid towers are designed for 2.5MW Vensys nacelles with 112-metre diameter rotors. The project is expected to complete this year.
A third design is planned for a project in north west Germany, for which TimberTower owns the rights to develop. This will comprise three turbines of 2.5-3MW, with 140-metre hub heights. The firm will use a largely wooden tower section of 132 metres and a five-metre long steel adapter to accommodate the yaw bearing. The remaining three metres is from the yaw bearing bottom interface with the tower up to the centre of the rotor.
TimberTower engineers and external experts developed a functionally comparable joining solution for the steel adapter (with octagonal-shape) bottom flange, which serves as an interface between the tower top and yaw bearing, which requires a circular mounting base. The adapter used for the 100-metre tower of the 1.5MW turbine contains a total of 176 perforated steel sheets welded to the adapter bottom flange, which weighs 7.6 tonnes and has a height of 3.65 metres.
TimberTower gained a type certificate for a 20-year design life, through German certification body TUV Nord. This matches the certified design life of tubular steel and concrete-steel hybrid towers.
You can read Windpower Monthly's full feature on the wooden towers here.