World's largest wind farm, London Array, brought fully online


April 10, 2013

The 630-MW London Array is now online and generating

The 630-MW London Array is now online and generating

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Phase one of the London Array usurped the UK's Greater Gabbard to become the largest operational offshore wind farm in the world when its final turbine (its 175th) was commissioned on Saturday afternoon. Though construction was completed back in December, it is only now that all of the farm's turbines are supplying the UK's national grid with electrical power. The array has a total capacity of 630 MW.

London Array is located some 20 km (12.4 miles) off the Kent coast, England's most south-eastern county which borders Greater London to its northwest. The 3.6-MW turbines are spread over an area of 90 sq km (35 sq miles).

Government backing for the farm was granted back in 2006, though construction didn't begin until March 2011. The farm has been completed to schedule.

"London Array is a significant achievement in renewable energy," said Tony Cocker, CEO of E-ON UK, joint owners of the array along with Dong Energy and Masdar. "The world's largest operational offshore wind farm will be capable of generating enough energy to power nearly half a million homes and reduce harmful CO2 emissions by over 900,000 tonnes a year," he added.

Though initially conceived as a 1-GW wind farm, it's now thought that a possible second phase would bring capacity up to 870 MW.

It was little more than a year ago that we reported on the opening of the second phase of Walney wind farm, making it the then-largest farm at 367.2 MW of capacity. The London Array looks set to remain largest for a little longer, as no larger farms are yet to emerge from the proposal stage. However, 2.5 GW offshore farms are planned for Sweden and South Korea.

Source: Dong Energy

About the Author
James Holloway James lives in East London where he punctuates endless tea drinking with freelance writing and meteorological angst. Unlocking Every Extend Extra Extreme’s “Master of Extreme” achievement was the fourth proudest moment of his life. All articles by James Holloway

Interesting, but... 1. how many hours is it expected to work at full capacity? 2. what happens when there's no or not enough wind? Do we have to use coal plants to keep everything running?

Freyr Gunnar

Wind turbine gearbox reliability is very low. I live near many wind turbines that are in Iowa and there are are always a large percentage not turning because they need mechanical attention of some sort. This English water based wind farm will be no different except that sharks will be waiting below for a tasty meal of wind turbine gearbox fixer and all the birds that meet their demise. Hard to believe that we can't just tap the geothermal energy that is essentially inexhaustible and waiting to be tapped. Large upfront cost but won't kill millions of birds and won't need a fleet of boats to maintain. Geothermal is a way better answer to any energy question.


It would be nice if the article gave yearly TWh, ave MW and capacity factor but we have to calculate it from expected CO2 saved

900,000 tonnes / yr divided by 8,760 gives 102.7 tonnes ie 226,450 lbs /hr of CO2 saved.

A quick search says UK ave CO2 /kWh is 0.527 Kg /kWh ie 1.16 lbs /kWh

So Averaged power is 226,450 / 1.16 ie 195.2 MW Yearly production is 1,709 TWh Capacity factor is 195/630 ~= 31%


The name plate capacity for a wind park has to be multiplied with a capacity factor, usually something from 0.3 to 0.5 to get real-world numbers. Maybe it is close to 0.5, this being off shore. Not bad!

"Gearboxes": While some newcomer manufacturers have had problems with gearboxes, some of the established brands like Enercon don't even have gearboxes, but run a direct drive system. These systems used to be in need of rare-earth magnets and were problematic for that reason, but there are some very good efforts underway (and succeeding) to build high-efficiency direct drive generators that don't even need such magnets.

Keep working. Don't drop the ball!

For the storage problem, look at synthetic methane. Gas distribution and storage networks are already in place in industrialized nations. The natural gas grids in cities and its storage tanks can serve as de-facto batteries. There's a lot of work being done already in the E.U. and China, and a bit in the U.S.


"It would be nice if the article gave yearly TWh"

It would, but there's a reason it doesn't. It's a new farm and we don't know. Sure, you can do a back-of-the-envelope calc derived from the estimated CO2 savings, but you've missed a key part of that quote: "The world's largest operational offshore wind farm will be capable of generating enough energy to..."

So the CO2 savings would seem to be based on the farm's capacity, not on its expected output.

James Holloway

There towers are tall and the average wind speed for the site is 9.2 m/s. The rated power of 3.6 mw is around 13 m/s and above with shut down at 25 m/s.

the rated power at 9.2 m/s is slightly over 2mw. with out looking at a wind profile its hard to say how much power these will produce but my estimate would be 2mw X 24hr X 365 or about 17.5 GWh. Assuming 10 cents per kwh (yes high I know) that would be 1.75 million dollars us? or 100k of power per turbine. The expected length of operation is 20 years.

So each turbine will generated about 2 million dollars worth of electricity.

I used 10 cents per KWh because I expect carbon taxes and other factors will increase energy cost. Really its tough to say what the power will be sold for, but I suspect the total cost of the turbines and towers would be less then 2million dollars (us).

How much is wholesale electricity going for in the UK?

Michael Mantion

Buellrider, there are many new WT's that are gearless.

David Anderton

Bad gearboxes? Go to China for better? (and rare earth magnets?) Capacity factor is 31% of a perpetual and infinite supply? Millions of Li or nano carbon super capacitor vehicles on the roads very soon, will ballast the intermittentcy ? Intermittency can over-lap - Wind, Solar, Wave, buffer against peak demand/off peak demand. Thorium LFTR styled reactor technologies from China about to "Alter Global Energy Maps Forever", may leave a wide open window for Solar, Wind, Wave, Hydro, Tidal, Geothermal. Biological, domestic local power generation? Anaerobic sewage digestion produces 'easy to store' Methane that can be burned to provide peak electric demand and power when the wind doesn't blow, the sun doesn't shine? Ironprior, Ontario, Dairy Farmer does this now! Meanwhile America Factory Farms waste animal shit, contaminate the land, need to be mandated to Anaerobic digestion electric generation? Many smaller 21st century Chinese (debut: 2017) Thorium technology generator plants: over the 20th century restrictions to single huge central generation enriched Uranium, plutonium and radio-active wastes producing systems? Remember: Saudis pump salt water to float remaining oil - and build enriched Uranium reactors from America and Solar Collector Arrays in the deserts as they have truly discovered that Oil is not eternally sourced from a pipe up &Allah's ass after all. Iran, coveted target for U.S. Oil moguls is in fact China's gasoline tank, and not really up for grabs as Israel would have you believe, and Iraq's oil already on the world market at world prices, and still out of reach for the average peon in U.S.A. Canada's Tar Sands well known for generations there and thought to be economically not feasible, are "mined" for oil today - not because there is a surplus, not because it is the preferred 'light sweet crude' - it is not, but because we face the end of the 'Cheap Oil Era' in the world today. Gasoline engines commonly (and foolishly) used by Americans today are in fact hardly 25% efficient from a fixed and expensive quantity of gasoline, while Wind Turbines are near 30 % efficient from an infinite and free amount of eternal, perpetual Wind? Solar Cells the same? Geothermal too? And as for Humanure and other Factory Farm manure, as long as we eat, there will be a constant(perpetual, infinite) supply ready for methane making, storing, and leaving a Top Soil Building fertilizer behind. Coal? finite, and hardly efficient? Seeking improvements? C02 capture and use ? My Question: where are the potentially energy saving super insulations that made the Moon Shot possible? We need them now as energy prices escalate, just to survive as a nation?

Bruce Miller

Buellrider Geothermal consumes massive amounts of clean water, that we just do not have anymore.

Robin McCabe

Bruce Miller, Please review & edit before sending. Aim for better, more grammatical sentences! Super insulation materials have slowly evolved and are now becoming useful! Aerogels, lighter than cigarette smoke have tremendous insulating values. Specifically there is an emerging class that are made by resin coating an underlying fragile aerogel which is then baked or freeze-dried to extract volatiles. They have insulation values in the range of R20 per 1/8th inch! Some have been used for clothing but were found to be too much insulation. The big deal is that a material can formed into a jacket is sturdy enough to be handled. Past aerogels were as light as cigarette smoke and about as durable as smoke. The remaining big question cost per square foot for a given application? The next Really Big Question is how to convince American policy makers and the public to energetically go after low-hanging fruit energy savers. Everyone can save tremendous amounts of energy by improving home insulation efficiency. This would be a great application for a blow in aerogel puff ball with maybe R60 for a standard stud wall. This would be a huge improvement over R19 glass or cellulose. Again, however, at what pricetag?


Wind turbine builders need to solve the problem of intermittent supply. It would have been done already but governments forced the utilities to buy the electricity produced.

Gearless wind turbines use a generator less efficient than running the mechanical energy through a gear train. However this solves the reliability issues and removes the cost of the gear train.

The reason that the gear trains are unreliable is that the wind is fickle. A turbine can be running at rated power and a transitory turbulence creates a gust that kicks the energy captured over the transmissions design limit. This both takes significant life off the transmission and puts a energy spike on the electrical grid. (Combined with the dips in production is why it cost so much to integrate wind energy into the grid.) To solve the gear train issues the manufacturers have A) Tried to create a algorithm that would accurately predict when the gear train would fail so it can be replaced just before failure. B) Set up wind sensors to detect gusts and built ultra-fast blade control to maintain energy input to the transmission. C) Designed and built more robust transmissions. A is just stupid. B helps with both gear train reliability and power fluctuation in generated electricity but it is not enough. C increases the cost of the turbines.

re; Buellrider Geothermal is not limitless and is often very expensive to tap.

re; Robin McCabe Geothermal does not require vast quantities of water in the fact that they recirculate the same water through the system repeatedly and some designs don't use water.


@ Michael Mantion Cost per KWH for electricity in the UK is at £0.14 ($0.22). This is for a home user.

Marc Browne

@Michael Mantion Your calculations are wrong in that you didn't figure the 17.5GWh is per year. So, if you multiply your expected lifetime of that windmill as 20 years then you multiply 17.5GWh by 20 to get 350GWh. Or you could say $1.75 million earned per year per turbine at $0.10 per KWh.

That's why the East Coast in the USA is pursuing windfarms when their utility rates are averaging over $0.13 near New England and Hawaii pays roughly $0.25 per KWh.

With subsidies and other incentives, the windfarms and their powerlines are quickly paid off. After amortization, the rates could drop as low as $0.02 or $0.03 per KWh and still make money. But you would need to see what the average turbine maintenance rates are for offshore (based on design) to determine how low you can go and still stay competitive.

The goal to increasing profit on turbines is to maximize lifetimes of each component. For instance, the foundation and tower portion can last up to 100 years if made with pre-tensioned concrete like those used in bridges over salt water.

Gary Richardson

I doubt if any electricity generator lasts for very many years before it needs to be changed. The thing is, it is perfectly feasible to store a windy day, or an underused night either by electrolysis . i.e. use the surplus to electrically split water into hydrogen and oxygen, which is perfectly capable of propelling motors, even cars. The other way is to use low demand high production periods to pump water into reservoirs to be released as hydro electricity when demand is high, but production is low. Reservoirs could quite easily be built out to sea near the pylons, using the coffer dam principle.

What does seem to be a terrible shame is that these electric pylons ,which hold the generators aloft, are also standing waist deep in tidal waters. Why, in heavens name, do they not have submerged tidal generators fixed to the pylon. That would work even if there is no wind at all for days !

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