In September Siemens signed a reservation agreement with Greater Gabbard Offshore Winds Ltd. (GGOWL) for the construction of the world’s largest offshore wind farm off the British coast.
The agreement, by far the largest ever reached for offshore wind turbines, involves 140 Siemens 3.6-MW turbines for delivery in 2009 and 2010.
Once connected to the power grid, the Greater Gabbard Offshore wind farm, located 25 km off the coast of Suffolk in the Outer Thames estuary, will produce green electricity with a maximum capacity of more than 500 MW. It will be the first UK offshore wind farm to be built outside territorial waters and will provide power for more than 415,000 homes.
Since the acquisition of Danish wind-turbine manufacturer Bonus Energy at the end of 2004, the Siemens wind business has been growing rapidly. The total employee headcount of the Siemens Wind Division has quadrupled to more than 3,200 employees worldwide today. The number of its wind turbine installations has tripled since 2004. In 2007 Siemens expects to install 1,500 MW of new capacity worldwide, of which 200 MW will be offshore.
Offshore wind energy plays a key role in the Siemens strategy and the company can look back on many years of experience within this sector. In 1991, the first offshore wind farm in the world was installed by Siemens in Denmark. The 165 MW Nysted wind farm, erected by Siemens in the Baltic Sea in Denmark in 2003, is still the largest offshore wind farm in the world.
In the future the importance of offshore wind power will increase even more for Siemens. In 2007 alone, the company is realising two major offshore projects. In July, Siemens successfully completed installation of 25 wind turbines for the Burbo Offshore Wind Farm in Liverpool Bay. The turbines, with a capacity of 3.6 MW each, were erected in less than 1.5 months, well ahead of schedule. Commercial operation will commence at the end of the year.
The Burbo Offshore Wind Farm has a total capacity of 90 MW and will be operated by SeaScape Energy Ltd., a company owned by the Danish utility DONG energy A/S.
Burbo is the first offshore project using the Siemens SWT-3.6-107 turbine, the largest serial wind turbine available on the market for offshore applications.
The SWT-3.6-107 was specifically designed for offshore applications, but works equally well onshore. A rugged, conservative structural design, automatic lubrication systems with ample supplies, climate control of the internal environment, and a simple generator system without slip rings provide maximum reliability with long service intervals.
Power conversion is implemented with Siemens’ NetConverter system, ensuring compliance with all relevant grid codes and offering high flexibility in the turbine response to voltage and frequency control, fault ride-through and output adjustment.
The 52m blades are made of fibreglass-reinforced epoxy in Siemens’ proprietary IntergalBlade manufacturing process. In this process, the blades are cast in one piece, leaving no weak points at glue joints and providing optimum quality. Major components, such as the rotor hub, the main shaft, the gearbox and the yaw system are all of particularly heavy dimensions and the safety systems are fail-safe.
The installation of the Siemens 3.6-MW wind turbines at the Burbo Offshore Wind Farm was not only a technical but also a logistical challenge. For onshore operations, Siemens leased a 45,000 square-metre area in the Port of Mostyn, located in North Wales.
The 65 m high steel towers of the wind turbines were assembled upright and all internal and electrical systems were tested before they were loaded onto the installation vessel. The purpose-built vessel carried towers, nacelles, hubs and blades for three turbines per trip to the site area, which is located approximately 12kms from shore. At the site, each wind turbine was erected in five heavy lifts with a maximum weight of approximately 185 tons. The average erection time per turbine, weighing almost 500 tons each, was less than half a day.
The Burbo Wind Farm is the first in a series of offshore projects to be built by Siemens. In August, erection of 48 turbines of the SWT-2.3-93 type commenced offshore at Lillgrund near the Swedish city of Malmö. With a capacity of 110 MW, this will be the largest wind farm in Sweden. The Lillgrund project will be operated by the utility company Vattenfall.
In 2008, Siemens will start erection of the Lynn and Inner Dowsing Offshore Wind Farm on the East Coast of Great Britain. The project comprises 54 SWT-3.6-107 wind turbines and will have a maximum capacity of 180 MW. The wind farm will be operated by the British gas provider Centrica. Once finalised, the Lynn and Inner Dowsing wind farm will be the largest offshore project in the world – until the Greater Gabbard Offshore Wind Farm goes into operation two years later.
In 2009, Siemens will also install and commission 25 of its STW-3.6-107 type turbines for the Rhyl Flats Offshore Wind Farm off the Welsh Coast. The customer is RWE npower plc, the UK arm of RWE AG.