All about the blade

National offshore wind capacity and emissions reduction targets, increasing global power demand, and the expanding energy mix are propelling the offshore wind industry. As the industry rapidly grows and wind farms move farther offshore and into harsher environments, so do the size and complexity of the turbine towers, nacelles, and blades. Larger offshore wind turbines have reduced the levelized cost of energy, but they present installation, transit, and logistical challenges.

Wind turbine installation vessels (WTIV) – with ever-increasing lifting and carry-ing capacities – currently install all the components. However, these large jack-up vessels have high day rates.

Since blades are highly susceptible to wind loads, they take the most time to install. While blades weigh less than 100 t, these vast and costly jack-up vessels feature heavy-lift cranes with lifting capacities of up to 2600 t, resulting in inefficient use of resources.

In response, GustoMSC and NOV Lifting & Handling in Norway have developed a new wind blade installation (WBI) solution that makes blade logistics, transportation, and installation safer, faster, and more efficient while minimising the environmental impact. Sjøhest, Norwegian for ‘seahorse’, consists of a newbuild GustoMSC^TM NG-5500XL self-propelled jack-up vessel, or a smaller converted jack-up, with integrated equipment dedicated only to blade installation, loading, and transport.

Enhancing logistics

The Sjøhest WBI solution creates the opportunity for logistics flexibility by splitting the tower/nacelle and blade mobilisation into separate onshore hubs. At more than 120 m (394 ft) in length, larger blades require more staging space. But unlike the heavy towers and nacelles, blades do not need a crane for loading.

On the quayside, 3 – 4 blade sets (9 – 12 blades) are rolled onto the deck from the aft of the vessel and stored longitudinally. GustoMSC created more deck space – 2000 m² (21 528 ft²) – on the NG-5500XL jack-up vessel by splitting the accommodation. Storing the blades in the same direction as the jack-up’s heading enables faster loading and allows the Sjøhest WBI vessel to sail and manoeuvre safely through the harbour. It also enhances wind loads on the jack-up during transit, thus, saving fuel and reducing carbon emissions.

WTIVs, however, transport blades transversely to accommodate the vertical towers and nacelles on deck. As a result, more than half of the blades, including the tips, hang off the vessel, obstructing harbour traffic, escalating the risk of collisions, and increasing costs.

Alternative installation approach

The new WBI solution also offers an alternative offshore installation methodology. While the high-capacity WTIV installs the towers and nacelles, the smaller Sjøhest WBI jack-up – equipped with a telescopic leader boom, knuckle boom crane, blade-handling tool, and trolley – simultaneously installs the blades in another part of the wind farm.

Precision is vital but challenging for offshore wind turbine installation operations because of rising hub heights and harsher weather conditions. The installed tower moves separately from the blades during installation due to wind and waves. These dynamics not only increase downtime, installation time, and costs, but also risk damaging the blades and harming technicians and other crew personnel.

Just as a seahorse’s strong grasping tail enables it to resist ocean currents, the Sjøhest uses the telescopic leader boom to connect and align with the installed tower’s movements, reducing the effects of the wind and waves. By moving as one unit, the firm connection creates a stable platform for lifting operations. It also extends the weather window and workability of the jack-up vessel while enhancing the safety, speed, and precision of blade installation.

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