Nordex has erected the first two N90/2500 turbines on hybrid towers. The hybrid tower comprises a concrete tower with a height of around 60 meters, which is mounted directly on the base at the location and then pre-stressed.
It bears the three steel tower sections of the modular tower with a total height of a further 60 meters. To achieve the necessary rigidity at hub heights of over 100 meters and to suppress resonance frequencies caused by turbine rotation, the lower part of the tower must have a diameter of over four meters. As this makes the tower too large to be carried on a conventional low-bed trailer, road transport is not a viable option. Nordex has solved this logistic and resonance frequency problem arising with towers with a hub height of over 100 meters by developing a special concrete/steel hybrid tower. The advantage of this is that the concrete tube is produced on site. The overall system has an adequate resonance frequency as the diameter of the concrete element fitted in the lower part of the hybrid tower is freely adjustable. 800 cubic meters of concrete and 130 tons of armoring steel were used for each of the two towers. The lowest section of the steel tower section is placed on top of the concrete tower head and fastened by means of anchor bolts.
