Kentish Flats Extension

Location

The Kentish Flats Extension 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 7.8 km away from the north Kent coast, adjacent to the existing Kentish Flats wind farm. The nearest points to the wind farm are 8.9 km from Herne Bay and 10 km from Whitstable.

Ownership and Operation

The Kentish Flats Extension is owned and operated by Vattenfall, a Swedish energy company. The maintenance and operation of the wind farm are managed from Vattenfall’s existing maintenance base on the west quay of Whitstable Harbour.

Installation and Commissioning

The permission to extend the existing Kentish Flats Offshore Wind Farm was granted in February 2013. Main offshore construction works for the extension project began in May 2015, with the installation of the turbines. The project became operational by December 2015, and all 15 turbines were connected to the National Grid by September 2015.

Turbines and Capacity

The Kentish Flats Extension comprises 15 Vestas V112 wind turbines, each with a rated capacity of 3.3 MW. This adds an extra 49.5 MW to the existing Kentish Flats wind farm. Each turbine has a rotor diameter of 120 meters, with 54.65-meter-long blades, providing a swept area of 9,852 square meters. The turbines are mounted on towers fitted to 6-meter-diameter transition pieces, which are fixed to 6-meter-diameter monopole foundations laid up to 45 meters deep inside the seabed.

Energy Production

The extension project is expected to generate around 150 GWh of clean electricity per year. This is sufficient to power up to 35,000 UK households and offset up to 64,500 tons of CO₂ emissions annually.

Infrastructure and Grid Connection

The turbines are connected via 33kV inter-array cables, which are linked to subsea export cables. These export cables transmit the power to the shore near Hampton Pier, at the western end of Herne Bay. From there, the electricity is supplied to the Red House Farm substation on Thornden Wood Road, Herne Bay, for transmission to the national grid. The total length of the inter-array and subsea export cabling is approximately 30 km.

Construction and Costs

The offshore components of the project were installed using jack-up or floating dynamically positioned vessels. The subsea cables were buried in the seabed using ploughing or water jetting techniques. The project was anticipated to be completed at a cost of more than £150 million.

Monitoring and Control

The turbines are controlled using microprocessor controls and are monitored by a centralized supervisory control and data acquisition (SCADA) system. The SCADA system and other communication requirements are linked to the onshore communication network via optical fibre cables (OFC). Each turbine is equipped with internal emergency stop facilities activated by local control systems in case of component or system malfunctions.

Environmental Impact and Contribution

The extension of the Kentish Flats wind farm is part of the UK's efforts to increase renewable energy production. Combined with the other Vattenfall wind farms in Kent (Thanet and Kentish Flats), these wind farms produce enough electricity to power more than 400,000 UK homes annually.