Kentish Flats

Location and Overview

The Kentish Flats Offshore Wind Farm is located off the coast of Kent, England, on a large, flat, and shallow plateau just outside the main Thames shipping lanes. It is situated approximately 8.6 km north of Herne Bay and 9.5 km north of Whitstable.

Ownership and Operation

The wind farm is owned and operated by Vattenfall, a state-owned energy company based in Sweden. Vattenfall has a 100% stake in the project.

Initial Construction and Capacity

The initial phase of the Kentish Flats Offshore Wind Farm was constructed in 2004 and entered commercial operation in September 2005. It consists of 30 Vestas V90-3MW wind turbines, each with a rated capacity of 3 MW, totaling a nameplate capacity of 90 MW. At the time of its construction, it was the largest wind farm in the UK and featured the largest wind turbines installed in UK waters.

Turbine Specifications

• Each turbine has a rotor diameter of 90 meters and a hub height of 70 meters.
• The turbines are installed on fixed monopile foundations at an average water depth of 5-8 meters.

Extension Project

In February 2013, Vattenfall was granted consent to extend the existing Kentish Flats Offshore Wind Farm. The extension added 15 Vestas V112 wind turbines, each with a rated capacity of 3.3 MW, increasing the total capacity by 49.5 MW. The extension project began offshore construction in May 2015 and was operational by December 2015. This extension generates around 150 GWh of electricity annually, enough to power up to 35,000 UK households and offset up to 64,500 tons of CO₂ emissions per year.

Power Transmission

The power generated by the wind farm is transmitted to shore via three buried subsea export cables. For the extension project, the inter-array cables and subsea export cables total approximately 30 km in length. The electricity is transmitted to the national grid from an onshore substation at Herne Bay, specifically the Red House Farm substation on Thornden Wood Road.

Energy Production

The original Kentish Flats wind farm generates more than 280 GWh of electricity annually, which is sufficient to meet the electricity needs of approximately 61,000 UK households. When combined with the extension and other nearby wind farms (Thanet and Kentish Flats Extension), these wind farms produce enough electricity to power over 400,000 UK homes annually.

Maintenance and Operation

The wind farm is operated and maintained from Vattenfall’s existing maintenance base on the west quay of Whitstable Harbour. The turbines are controlled using microprocessor controls and monitored by a centralized supervisory control and data acquisition (SCADA) system linked to the onshore communication network via optical fibre cables.

Contractors and Suppliers

• Vestas Wind Systems supplied the turbines for both the original and extension projects.
• A2SEA was responsible for the installation of the turbines in the original project.
• ALL NRG is the Operations and Maintenance (O&M) contractor for the wind farm.

Environmental and Economic Impact

The Kentish Flats Offshore Wind Farm contributes significantly to reducing carbon emissions. The extension project alone is expected to offset up to 64,500 tons of CO₂ emissions annually. The project was developed with an initial investment of £105 million for the original phase and more than £150 million for the extension.

Technical Innovations

The project incorporated several technical innovations, including the use of stronger steel (S 355) for the towers, which made them lighter and less costly to handle. The nacelle design allowed for it to serve as its own transport system, eliminating the need for additional transport equipment. The turbines also feature extensive marinization measures, such as offshore class corrosion protection and remote monitoring and control systems.