The ยฃ725m project will be powered to generate 270MW of electricity annually. The permitted annual capacity of the project is 250MW. The remaining 20MW will be constructed in the Lynn and Inner Dowsing wind farm area and connected to the transmission of Linc. When operational by the end of 2012, the wind farm will power the annual electricity requirements of approximately 200,000 households, with zero emissions.
The project is jointly owned by Centrica, Siemens Project Ventures and DONG Energy. Siemens Project Ventures and DONG Energy acquired a 50% stake in the project from Centrica, by forming a joint venture in December 2009. Centrica owns the remaining 50% stake.
The 35kmยฒnorth-south oriented wind farm will be composed of 75 three-blade turbines with horizontal-axis installed in a water depth of 10m to 15m in the North Sea. The Siemens turbines have a capacity of 3.6MW each, and will be equipped with a 120m diameter rotor and 58.5m-long rotor blades. The maximum height to the tip of the blade will be 170m and the turbines will be spaced at a distance of 500m. The hub height will be 100m. The nacelle and hub of the turbines will be installed atop a cylindrical steel tower that will be further supported by a foundation attached to seabed. For both the turbines and the offshore substations, the foundation will be either monopile, gravity base or steel jacket structures.
The project will be constructed between March 2010 and August 2011. The initial enabling works on the Walpole substation site have been completed, improving the traffic safety while entering and leaving the site. Between April 2010 and June 2011, two high-voltage cables will be installed from the landfall to the new onshore substation site.
“The 35kmยฒ, north-south oriented wind farm will be composed of 75 three-blade turbines “
Each of the 145kV cables will be 50km long and will be supplied by Nexans Norway AS. The cables will be drawn through cable ducts buried at distances of 1km along the entire cable route. Methods for duct installation will include direct buried, open cut or horizontal directional drilling (HDD).
Between April 2010 and August 2010, a substation to connect the wind farm with the national grid network will be erected. Piling will be carried out using Continuous Flight Auger (CFA), a less noisy method that also creates less vibration.
Works will also include construction of new access roadways, a road junction and civil works besides installation of steelwork, mechanical and electrical equipment.
Landfall works being conducted in 2010 include the installation of three 1,000m-long steel ducts beneath the sea wall and salt marsh. Two 16in diameter ducts will be used separately for two export cables. The third duct, with a diameter of 6in, will be employed for the mud return line during drilling operations. During the work period, a 60mx20m barge will be brought and moored approximately 1km from the sea wall. An on-board drilling rig will carry out drilling under the salt marsh found at pre-defined locations in the first field behind the sea wall. Each hole will be reamed out before a fabricated steel duct is drawn through the hole with the rig.
“Landfall works being conducted in 2010 include the installation of three 1,000m-long steel ducts beneath the sea wall and salt marsh.”
The main contractor for onshore works of the project will be Siemens Transmission and Distribution. The contractual scope includes design and building of the grid connection and laying of the cables onshore. The contract for the supply of turbines was awarded to Siemens in March 2009. Siemens Project Ventures was awarded the contract to design the offshore and onshore substations.
Fugro GeoConsulting has been chosen as the geo-technical surveyor. SGS-International Certification Services is acting as the risk management consultancy for the project.
The wind power plant will be connected to a new substation via two underground 132kV cables. Approximately 40km long, the cables will be partially buried within the seabed at a depth of 1m and 3m, and partially onshore. Before supplying the national electricity network, power will be increased from 132kV to 400kV at the substation located adjacent to the current substation at Walpole.
Power market in UK
The UK’s total electricity supply in 2008 was 400,671Gwh. Approximately 46% of this was contributed by gas-powered plants. Coal, nuclear, renewable, imports and oil accounted for 31%, 13%, 6%, 3% and 1% respectively. The installed electricity generation capacity of coal, gas, nuclear and other power stations stood at 83.5GW, with less than 0.5GW coming from wind.
In 2009, however, nearly 1,077MW of new wind capacity was installed in the UK, accounting for 10% of the total capacity installed in the whole of the European Union. By 2020, the target is to install approximately 33GW of wind turbines. With large expansion of offshore wind-power plants taking place in the North Sea, the Irish Sea and around the coast of Scotland, by 2020, nearly half of the UK’s current electricity consumption is expected to be met by wind farms.