Wind Farms in the Thames Estuary

The map below shows wind farms in and around the Thames Estuary. The most northerly one is Gunfleet Sands off of Clacton, the largest is the proposed London Array and construction started in March 2011, bottom left is Kentish Flats (the green area on two sides is a proposed extention) and finally the bottom right one is the Thanet Offshore Windfarm.

Wind Farm




Gunfleet Sands (1&2)


48 x 3.6MW

172 MW

Kentish Flats


30 x 3.0MW

90 MW



100 x 3.0MW

300 MW

London Array


175 x 3.6MW

630 MW

Kentish Flats extention

10 - 17

30 - 51MW

The power generation capacity of the installed three windfarms is 562 MW. So far (for Kentish Flats windfarm of 90MWh capability) the average production for the first two years has been less than a third of the potential for each year, for the third just over a third. An interesting note on the Kentish Flats web site regarding usable generation:-

Average industry capacity factor for offshore wind: 35%

This percentage seems to backup the real output of a windfarm from the maximum output, which in earlier years used to be the headline figures. Part of the conditions of the subsidy given to the builders of Kentish Flats, was that they have to provide detailed information about the power production for three years. Annual Reports are available on the internet (they take some finding), but are quite telling. The 90MWh wind farm could potentially produce 788,400MWh in a year, using the capacity factor (as above) would give an expected yearly production of 275,940MWh. In 2006 (the first full year of operation), it produced 227,977MWh (28.9%), in 2007 it produced 209,444MWh (26.5%) and for 2008 it produced 269,267MWh (34.1%).

So for the first three years, Kentish Flats has under-performed, although the first two years were lower due to technical problems, it was about par for the third year. The production figures are no longer available, which is shame, as it may have shown that the windfarm was now performing better. Dec 2010 was one of the coldest months we've had recently, but part of the problem causing the cold snap was a 'high' sitting over the UK which meant little wind and when we needed power, there wasn't the wind to drive the turbines.