How does an offshore wind farm work, you ask? A wind turbine is analogous to the old windmill, which harnesses wind energy to produce mechanical work; movement of the wind over the blades causes the rotation of the blades to turn mechanical machinery that pumps water or grinds grain, for example. Wind turbines may be thought of the opposite of fans, which use electricity to produce wind. Instead, wind energy is harnessed via mechanical machinery to produce electric current. Offshore wind turbines are built into the seabed with a platform for maintenance access. Sensors in the wind turbine detect the wind direction and turn the head towards the wind to facilitate the maximum wind energy consumption. The wind movement causes rotation of the aerodynamically shaped turbine blades around a horizontal hub, which spins a shaft inside the head that, in turn, through a gearbox, powers an electrical generator. The generated electrical current runs through subsea cables back to an off-shore transformer where it is converted to high voltage electricity and from there it is run 5-10 miles to a utility grid.
The Powergen electricity group owned by the German consortium E.On, oil giant Shell, and Danish group Energi2 will build the 300 ft. turbines 12 miles off the cost of Kent. The work will begin in 2008 and is scheduled for completion in 2011. The turbines’ 1,000 megawatts (MW) of power output is claimed to be equivalent to a large conventional gas or coal-burning power station and enough to supply 750,000 homes. This so-called the London Array project is said to double the U.K.’s wind-based electricity manufacturing capacity and to provide a clean and renewable alternative to sole dependence upon fossil fuels used by conventional electrical power plants that cause pollution and use up scarce resources. However, citing wind limitation and the need for a constant, predictable supply of power, opponents argue that because the wind is not dependable, the output of the offshore wind farm will be far less on average than claimed. Furthermore, opponents assert that the equivalent power station, which can run at peak output continuously for all but a few weeks of the year, would supply over a million MORE homes than that purported for the wind farm by its proponents.
The British government hopes that by 2010, 10% of the nation’s electricity needs will be produced by renewable resources. Other European countries, however, already have a much greater usage of wind farms. Germany already has more than 19 GW of wind power capacity and is the world leader in the field, with certain areas such as the Schleswig-Holstein province generating 25% of its power from wind turbines. With over 10 GW of electricity, Spain has the second largest wind-based power capacity. Denmark has the capacity to produce over 20% of the electricity from wind turbines, the highest percentage of any country in the world. However, because of wind intermittency, opponents claim much lower average outputs. In the U.S., wind power recently passed the 10 GW mark and now supplies 0.4% (1.6 million households) of total electricity in the U.S., up from less than 0.1% in 1999. US Department of Energy studies are said to have concluded that building wind farms in just three of the fifty U.S. states could provide enough electricity to power the entire nation, and that offshore wind farms could do the same job.