One of the major trends in wind power is ever larger turbines for offshore use. This raises many technical challenges, including how to transport and install such large components at offshore sites.
A2SEA is a Danish company that has expertise in precisely these challenges and has developed technology for it. The company’s Sea Installer is a wind turbine installation vessel designed to operate in deep offshore waters.
A2SEA owns at least one U.S. patent and several international patent applications, including U.S. Patent No. 6,808,337 (337 Patent) and International Publication No. Wo2006/076920 (’920 Application).
The ’337 Patent is entitled “Vessel with vertically elevational support legs” and directed to a ship (1) which has a hull (2), a deck (3), and two auxiliary cranes (10) positioned on the deck. A console (5) is mounted on either side of the hull (2), and support legs (9) are disposed in the console (5).
There are two support legs (9) at either end of the console (5), and they are connected to a winch wire (8), which provides for the right pressure on the support legs (9) via a hydraulic system. A large crane (11) having a loading capacity of about 450 tons is positioned on either side of the hull (2).
During mounting of a wind turbine, the support legs (9) exert the proper pressure to lift the ship (1) and the winch is locked to maintain the stability of the elevated ship:
During the mounting of a windmill the ship will thus on all four legs exert a pressure of 300 tons, which will lift up the ship, whereafter the winch is locked such that a possible wave will not give rise to instability.
The ’920 Application is entitled ”Lifting device for a wind turbine generator” and directed to a lifting device comprising a yoke (5) connecting the hook of a crane (11) with a collar (17) on the tower (8) of a wind turbine (9). The yoke (5) surrounds the nacelle (113) of the turbine (9) and is designed to lift and move a complete wind turbine.
According to the ’920 Application, the yoke (5) provides a stable lift because it is attached at a particular point of the wind turbine (9) that represents the turbine’s center of gravity:
In a suitable crane 35, the lifting yoke 5 can be mounted and designed to lift the WTG 9, which is attached at a predeteπnined point near the top of the tower 8 and below the nacelle 13. By lifting the WTG 9 at the top of the tower 8, it will be conveniently close to the centre of gravity that will make the lift of the WTG 9 a stable but heavy lift.
Eric Lane is a patent attorney at McKenna Long & Aldridge LLP in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at elane@mckennalong.com
