Rising winds

As a new generation of larger, higher, wind turbines become commonplace around the world, wind farm developers will need to look at employing larger lattice and telescopic crawler cranes to install them. Will north reports.

10 years ago, a typical wind farm job may have required no more than lifting a 120-tonne nacelle to a height of 80 to 100 meters. that is all changing, the machinery housing alone on wind turbine generators such as Enercon's 7MW e-126 or repower’s 5MW 5M can weigh around 120 tonnes. Add to this its contents, such as the 220-tonne generator and a rotor and hub that can add a further 320 tonnes and you have a fully assembled nacelle that weighs more than 600 tonnes. All of which will need to be placed on top of a 135-meter high tower, ideally all in one go. While such turbines are still very much at the cutting edge of the market three to four-megawatt turbines are rapidly becoming the norm.

This demands both a step-change in lifting capacities at height and new approaches to performing the job. A 120-tonne nacelle could still have been delivered to the site complete using fairly standard trailers or transporters. Today’s larger nacelles must usually be delivered separately and assembled on-site, ideally on the ground, but if not then at height.

Both approaches have their own risks. Assembling the nacelle on the ground reduces the risk of working at height, or installers working in the machinery housing being crushed as the generator drive train is lowered into the open machinery housing at 130 metres. But lifting a fully assembled nacelle requires a substantially larger crane.

Material handling and assist