Our operations

Project development

The major construction work on the Lynn and Inner Dowsing offshore wind farms was completed to schedule in 2008.

Foundations for the 54 turbines were installed during 2007, as were the power cables connecting the turbines and the wind farms to shore.

Installation of the 3.6MW wind turbine generators, supplied by Siemens Power Generation, commenced in March 2008 and was completed in July 2008. The wind farms became fully operational with the completion of commissioning in March 2009.

Installation of the foundations and turbines was carried out by the M.V. Resolution, a purpose-built wind farm installation vessel, owned and operated by Middlesborough-based firm MPI Offshore Limited. The 38m wide ship uses six legs to secure its position on the seabed prior to installation.

Different foundations can be used depending on the nature of the seabed. The Lynn and Inner Dowsing wind farms used monopiles, cylindrical steel foundations which form a firm base for the turbines. These were driven or piled to the required depth using a large hydraulic hammer.

Geotechnical survey work was carried out in advance to determine the nature of the seabed and in some cases, due to the geology, some drilling was used to allow the monopile to reach the desired design depth.

The distance of the work from the coastline and the prevailing wind direction helped to minimise the risk of any disturbance due to noise. Certain environmental conditions can allow noise to travel greater distances on occasions, so noise monitoring was also carried out during certain stages of construction.

Once a foundation had been installed, a transition piece was lifted into position, slid over the monopile and secured with a cement grout. The transition piece includes a boat landing arrangement, ladders and a platform to allow access for turbine maintenance during operation of the wind farm.

Cable laying within the wind farm was carried out during 2007 and 2008. The six cables which were laid to transmit power to shore consist of copper conductors as well as a number of fibre optics for communication and control purposes.

These subsea cables, manufactured in Norway and Germany, were laid and buried using specially designed cable burial machines. The six export cables, which transmit power from the wind farms, were buried up to 2m deep in the seabed using an underwater cable plough weighing 21 tonnes.

The array cables, connecting the wind turbine generators, were laid using a Remotely Operated Vehicle (ROV) controlled from the installation vessel, Resolution and a cable laying barge pulling a plough along the seabed.

The turbine towers were lifted into position and bolted onto the transition pieces. The remainder of the turbine assembly consists of a nacelle (the housing at the top of the tower that contains the generator, gearbox and transformer) hub and blades. Each turbine tower is approximately 80m above mean sea level and has a rotor diameter of 107m, giving a total height to the blade tip of 134m.

The blades are made from reinforced glassfibre. The turbines cover an area of 20km² with the closest row of turbines being 5km from the coast and the furthest being 9km offshore. The wind farms will have an operational life of 20 years.