Last Thursday the wind eventually dropped enough to allow more progress at T2. The top tower section was the next in line to be lifted.
Both cranes are required for the first stage; the main 500-tonne capacity crane lifts the top end and the 200-tonne auxiliary crane lifts the bottom end off the ground with a special clamp attached to the lifting strop. This allows the main crane to gradually raise the top end until it is taking the full weight and the tower is vertical.
Once the auxiliary crane is disconnected the tower is lowered temporarily onto supports on the ground so the installation technicians can perform final checks and cleaning. They also attach a bag of the huge nuts and bolts that will be used to connect the tower sections so they don’t have to carry these up the ladder to the top of the section already built – you can see this in the picture above along with a generator to power some of their tools. Around lunchtime you can often see bags of sandwiches being clipped on and lifted so the engineers don’t have to climb back down to get them!
The tower is then hoisted up and carefully maneuvered into position to be bolted down.
Next comes the nacelle; in the photo above you can just make out the taglines used by the technicians on the ground to control the angle it is lifted at. With such large components it’s easy to see why low wind conditions are needed at this stage.
The drivetrain may look like a small component, but it weighs 46 tonnes, nearly as much as the nacelle itself (50 tonnes), and more than the top tower section, which is only 30 tonnes.
The drive-train is comprised of the main shaft which supports the rotor blades and hub, and the gearbox, which converts the low-speed rotation of the blades into the high-speed rotation required to generate power.
You can just see one of the technicians in the nacelle waiting to pull the unit into place.