The London Array is a massive 630 MW windfarm, comprised of 175 Siemens 3.6 MW turbines located about 20 km from the coasts of Kent and Essex. After 28 months of construction and a €2.2 billion cost, the farm was officially inaugurated on July 4th 2013. Dong Energy (50%), E.ON (30%), and Masdar (20%) are the stakeholders for this project, which will supply energy to an estimated 500,000 homes. It is the largest windfarm ever constructed, followed by UK's 504 MW Greater Gabbard windfarm. However, planning consent was granted on July 11th 2013 for an even larger 1.2 GW windfarm, the Triton Knoll.
As the world tries to move away from fossil fuels, offshore wind has been making a serious dent. Estimates from the European Wind Energy Association predict that 14% of the European Union's electricity needs could be met from offshore wind by 2030. In this offshore environment, wind is stronger and more consistent than terrestrial wind, and turbine size can be much larger because ships are more efficient at erecting turbines than trucks. As offshore windfarms continue to increase in size, they will play a major role in balancing grids and providing clean reliable electricity.
More information on the London Array can be seen here.