The London Array - wind power on a massive scale

The London Array is a huge planned offshore wind farm that will be situated about 40km from Southend-on-Sea where the Thames estuary mingles with the North Sea. It'll be huge- 271 turbines spread out over a skewed shape about 11×20km. It promises to deliver between 1 and 1.3 gigawatts of electrical power to the UK National Grid¹. This is not much when compared with the currently active generating capacity in the UK; but as recently as 2003, global wind power capacity was only 40 gigawatts in total. It will be built on a commercial basis by The London Array Ltd; a private consortium of energy companies.

The Site

The site is said to offer reliably strong winds, shallow waters, low shipping traffic but several suitable ports for the construction effort, proximate National Grid connection points and a major concentration of electricity users (i.e. London).

Its remoteness from the coast means that it's just about over the horizon from the nearest accessible coastline; but it still falls entirely within UK territorial waters. Shipping will be accommodated by a marked channels past the site. The port authority continues to feel that radar reflections from the turbine blades and support poles have the potential to confuse navigation.

The Plan

271 offshore turbines will be erected in 4 phases; at the end of each phase, those turbines will be connected to the grid and begin delivering power - the whole thing should be complete and running by 2011 at the latest.

Each turbine will be mounted on a pole about 100m above sea level with massive blades sweeping down to 25m and then up to 175m high; getting on for twice the height of Big Ben's mighty clock-tower.

Six cables will run from the array's offshore substations to Cleve Hill near Canterbury. The substations will increase the voltage (decreasing the current and therefore the resistive losses in the cable) used for the transfer. Buried about 2m below the sea bed, the cables should be protected from the currents of the channel, and maybe even occasional light anchor impacts². A large onshore substation will provide the final voltage boost to 400kV matching the local National Grid lines.

How Much Power?

One Gigawatt sounds like - well unless you're heavily involved in the electricity biz, it probably won't mean much to you. Popular science articles typically convert watts into "homes", a curious unit to be sure. On their press release, the consortium convert their power output to 750,000 homes. Your electricity bill will probably be in kWhs (kilowatt-hours, the amount of energy expended at one kilowatt during one hour). The London Array promises 3100 gigawatt hours, three thousand-million times that. My last electricity bill was for about 3200 kWh per annum³, so I can coin a new unit and claim that the London Array could power one million spiregrains, or 1 Megaspiregrain.

This will be around 1% of the the UK's electricity needs.

By comparison, the UK's largest power station, the massive Drax facility at Goole in Yorkshire generates 4 gigawatts; but it burns imported coal to do it.

In these environmentally conscious times, the consortium also find it important to point out that the London Array will offset the emission of about 2 million tonnes of carbon dioxide per annum from conventional power stations.

How Much Money?

The consortium claims that the whole thing will cost £1.5 billion. Looking back over my electricity bill; the 3200 kWhs cost me about £250. At that rate, the consortium stands to take in about a quarter of a billion quid per annum. Although of course they'll be selling at wholesale rates to the grid, not at retail rates to the domestic end-user, this back-of the envelope calculation suggests that the consortium is in with a chance of turning a profit.

2007-era Timeline (now hopelessly out of date)

  • 1997- The UK signed the Kyoto Protocol, which committed signatories to cut greenhouse gases by 5% by 2012 compared with 1990 levels, inter alia. The UK government set an additional target of a 12.5% reduction over the same period. The thing about targets is that they focus the mind of committed parties to consider all options, rather than to glibly "do their best" until they get bored. The gauntlet was thrown down to government departments, planners and the electricity and transport industries to get in line.
  • 1999- An Npower study was commissioned to identify the most suitable locations for off-shore wind farms. It looked not just at average windspeed and reliability, but at practical measures such as water depth at the appropriate distance from shore, and proximity of National Grid infrastructure. Troublesome factors like shipping lanes and environmental impact were considered. The area of Thames estuary between Kent and Essex was identified.
  • 2000- The "UK Climate Change Programme" is unveiled, outlining the specific strategies and supporting policies that will fulfil the Kyoto targets. It commits to a 10% use of renewable resources for electricity generation by 2010, a 15% use by 2015 and a 20% use by 2020.
  • 2005- After extensive planning and design works, London Array ltd, a consortium of E.ON UK Renewable ltd, Shell WindEnergy ltd and CORE ltd, submitted their plans for approval. The plan is opposed by the Port of London Authority and the usual NIMBY and BANANA outfits; but the group are widely congratulated by environmental campaigners.
  • 2006- Planning approval is granted for the forest of windmills, but not initially for some of the key on-shore infrastructure, in part due to construction traffic. This permission remains outstanding as of February 2007.
  • 2007?- April- Construction begins.
  • 2008?- Phase 1 complete; phase 2 and 3 begins.
  • 2008- Shell pulls out of the consortium.
  • 2009?- Phase 2 and 3 complete, phase 4 begins.
  • 2010-11?- Phase 4 complete.

¹ - The National Grid is the UK's national electricity distribution network, owned and operated by National Grid plc.

² - Anchor impacts and dragging are the bane of the unburied telecommunications cable's existance.

³ - Approximate 2005 figures for a two-bed flat with gas central heating, communal gas-fired hot water boiler, and no hair-dryers but containing two technophiles.


  • London Array website -
  • Drax Group website -
  • The BBC News Website -

Log in or register to write something here or to contact authors.