Burbo Offshore Wind Farm, United Kingdom

Twenty five 3.6MW wind turbines have been installed at the 90MW Burbo Offshore Wind Farm in Liverpool Bay, Wales. The wind farm cost around £90m, and is owned and operated by SeaScape Energy, a company owned by the Danish utility Dong Energy A/S.

Siemens Power Generation (PG) erected the turbines in less than 1.5 months, well ahead of schedule. Following commissioning and connection to the power grid, the turbines started commercial operation at the end of 2007.

The wind farm is located on the Burbo Flats in Liverpool Bay at the entrance to the River Mersey, about 6.5km from the Sefton coastline. The total power output is enough for more than 75,000 households: 12% of Merseyside's electricity demand.

It could reduce CO2 emissions by over 300,000t (300 million kilograms) a year, translating over the 20-year operating life to savings of 6.4 million tonnes. There will also be smaller but still significant SO2 and NOx savings.

CONSTRUCTION AT BURBO

Siemens leased a 45,000m² area in the port of Mostyn, North Wales, for onshore operations. The 65m-high steel towers 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 about 12km from shore.

At the site, each turbine was erected in five heavy lifts with a maximum weight of approximately 185t each. The average erection time per turbine (which weighs almost 500t) was less than half a day.

Each turbine has a maximum blade tip height of around 130m from sea level, with the hub being around 80m high and the turbine rotor blades around 50m long. They are manufactured in Aalborg. The integral blades require no adhesives, with the blade produced in a single casting and so without seams which increases the blade strength.

A NEW TOURIST ATTRACTION

The sea bed is relatively shallow at the site, between less than 1m at low tide. It is one of a number of sites around Britain's coast which has been leased to developers by the Crown Estate. The wind farm takes up 10km² of the seabed, although the area of the turbines themselves is below 400m².

Turbine spacing is above 500m, so recreational users can still use the wind site; boats can sail between them as long as they avoid the turbine foundations and don't anchor on them. Scour protection material has been added, which could increase the marine habitat around the turbine base, and allow fishing, for example. It is thought the wind farm will actually become a visitor attraction, possibly with boat trips out there.

SeaScape Energy assessed the potential effects of the wind farm on radar installations. The company outlined a range of possible measures if it is found to be a problem, including radar-absorbing paints, software upgrades to remove false signals, an additional radar station, or a radar repeater station on a turbine platform.

The wind farm has needed subsea cables between turbines, and from the turbines to the shore. Seascape's Burbo Environmental Statement remarked that these would not interfere with any existing cables or pipelines.

FIRST OFFSHORE PROJECT FOR SIEMENS SWT-3.6-107

The Burbo Wind Farm is the first offshore project to use the Siemens SWT-3.6-107 turbine, and the first in a series of offshore projects being built by Siemens. Also in 2007, Siemens erected 48 SWT-2.3-93 type turbines at Lillgrund near the Swedish city of Malmö, the largest offshore wind farm in Sweden.

Siemens sees offshore wind farms as a key future market, and is currently the leading manufacturer of offshore turbines. The 165MW Nysted wind farm, erected by Siemens in the Baltic Sea offshore of Denmark in 2003, is still the world's largest.

In 2008, Siemens started erection work on what will replace it as the largest, off the east coast of Great Britain. The Lynn and Inner Dowsing project has 54 SWT-3.6-107 wind turbines and will have a maximum capacity of 180MW.