Pre-assembled post-tensioning tendons secure the world largest wind turbine, Germany

Installation of vertical post-tensioning tendons into the E 112 wind energy plant, with a height of 180m, Wilhelmshaven, Germany

The three pillars of a sustainable energy supply are: renewable sources, generating efficiency and energy conservation. Water, wind, sun and biomass offer an energy potential that exceeds worldwide demand many times over. Wind power is no longer a niche source of energy. Its dynamic market sets new economic impulses in new, structurally weaker regions. Wind energy now accounts for approximately 4% of the net current consumption in Germany.

Wind energy plants are modern high-tech power plants,that function very simply: The kinetic energy of the wind is taken up by rotor blades and converted first into mechanical rotation energy and then, similar to the dynamo principle, into electrical current by means of a generator. The amount of current produced is considerably dependent of two factors: the wind speed and the diameter of the rotor. Wind speed significantly increases with height and the energy yield can be considerably increased with large rotor blades. The E 112 wind energy plant is designed for large capacities. The concrete tower of the largest wind turbine in the world (4.5 MW) has the gigantic height of 112 m.

The hub height of the E 112 rotor is 124 m. With a rotor diameter of 112m, the overall height of the structure is 180m. Each rotor blade has the span length of a jumbo jet, and together the three blades cover a rotor area of about 10,200m² - the size of two soccer fields. Rotor blades, hub and generator have a weight of approx. 200t.
The tower was constructed with slipforms, with a speed of about 4m per day. The pre-assembled post-tensioning tendons were placed into the tower shaft in stages. The anchor which was later placed at the level of the tower head was premounted on the post-tensioning tendon in the shop. 48 post-tensioning tendons are placed in the cross-section of the tower in equal distances.

Grouting of the up to 121m long tendon ducts was difficult. Developments in the field of mix design and in the field of the grouting technique contributed to achieving settlements of 0.5 to 1%. Pumping the grouting up to a height of 120m posed high requirements of the grouting technique (high-pressure grouting). After the post-tensioning tendons had been installed, the tendons were partly or fully post-tensioned. An optimization of the post-tensioning technique contributed to an acceleration of the schedule.