Foundation and Tower - Installation

Foundations

• Onshore Wind Turbine foundations can be compared with traditional foundations for large buildings. The fixation into the ground is achieved by piles, which are hammered or drilled into the ground, or anchors in case of rocky ground conditions. Subsequently, the base construction is created as an immense cage of metal reinforcement bars, which is finally filled up with concrete. The final result is a well anchored conical base, up to 25 meters in diameter, and 4 meters high, on which the actual wind turbine tower can be installed.
• Offshore Wind Turbine foundations are diverse, and depend on seabed depth. Currently, the majority of development efforts for Offshore Wind Turbines is focused on Monopiles, which can be used up to 30 meters of  water depth. The Monopile has a thick walled (>100 mm) steel tube with a large diameter (8-11 meters), and is piled / hammered into the seabed floor by large offshore piling hammers. 
  Once the Monopile is fully anchored into the seabed, the Transition Piece is placed on top of the Monopile. During installation, this Transition piece slides a few meters over the Monopile until both flanges fully align. After bolting of flanges, the wind turbine tower can be installed on top of the Transition Piece. 

Lifting equipment

• Onshore Wind Turbine installation can use relatively standard mobile cranes, although the increasing hub-height can pose a challenge. 
• Offshore Wind Turbine installation requires a fleet of vessels, which can perform steady lifting during high seas, and on which special offshore cranes are mounted.

Power line

The power line is the aorta of the wind turbine, as it will transport the generated energy towards the users. In order to prevent damage, several systems protect the cable in the hostile offshore environment.

Trenching

In order to protect the submerged power lines from damage by anchors and other objects, they need to be buried at underneath the seabed. This operation is performed by a trencher, which digs a deep trench (several meters deep), positions the cable into the trench, and then closes the trench again. All in one operation.

Trenchers can be towed passively by a boat, or can drive autonomously on the seabed. In the latter case, the required traction is derived from Nylatrack® track shoes with heavy-duty grousers.

Expertise in Onshore & Offshore Solutions for Foundation and Tower