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The Story Behind: Offshore Wind Energy
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A promising green energy source
The beginnings of wind energy were humble: The first windmills were built in Persia around 500-900 AD to automate the task of grinding grain and pumping water. In Western Europe, the earliest documented windmills surfaced in the 13th century. These mills used wooden cog-and-ring gears to translate the motion of a horizontal shaft to vertical movement to turn a grindstone.
With the advent of electricity, wind suddenly became a potential source of power generation. The first use of a large windmill to generate electricity was a system built in Cleveland, Ohio, in 1888 by Charles F. Brush. The 12 kilowatts (kW) produced by its 17-meter rotor pales in comparison to the at-least 100 kW produced by a comparably sized, modern-era rotor, but they were enough to run electrical appliances in Brush's house.
From grinding grain to producing power
In 1891, Poul La Cour, a Danish meteorologist and inventor, developed the first electrical output wind machine to incorporate aerodynamic design principles - low-solidity, four-bladed rotors incorporating primitive airfoil shapes. The higher speed of the La Cour rotor made these mills quite practical for electricity generation, and by the end of World War I, the use of La Cour's machines had spread throughout Denmark.
After World War II, engineers in the United States, Denmark, France and Germany dominated the advancement of wind energy. Austrian-German engineer Ulrich Hütter developed the wind power unit on which most modern-day units are based: The prototype of his highly successful 100-kilowatt StGW-34 was erected in 1957 at a test field near Geisslingen on the Swabian Alb.
Yet wind energy had to wait until 1991 to become successful on a greater scale. That year, the German Stromeinspeisegesetz required the large utilities to feed into their grids electricity from renewable energy sources. The Stromeinspeisegesetz and later its updated version, the EEG (adopted in 2001), propelled the construction of wind parks in Germany.
Today, the country leads the world in wind-energy expertise and is the globe's largest user of wind power: In 2006, Germany generated some 7 percent of its electricity through an installed capacity of 20,621 MW, ahead of Spain which had an installed capacity of 11,615 MW.
Currently, more than 25,000 wind farms are operating throughout Europe, and capacity is expected to double by 2015. Apart from national climate protection initiatives, wind energy will receive a further push from Brussel's recent decision to increase the share of renewables in the European Union's power generation to 20 percent by 2020. Judged by outputs in gigawatts (GW), wind power has been one of the most successful green energy sources up to today. By 2007, the cumulative wind power capacity operating in the European Union had reached some 50,000 megawatts (MW). In an average wind year, this will produce approximately 100 terawatts (TW) hours of electricity, equal to 3.3 percent of the EU's entire electricity consumption.
Offshore's enormous potential
While growth on land is limited by wind conditions and the space available, the seas still offer vast areas of constantly high winds and thus tremendous potential for electricity generation.
The history of offshore wind power generation is fairly recent: The world's first offshore park was built in 1986 off the coast of Denmark. Sixteen 55-kW units produced electricity for the 4,000 citizens in nearby Ebeltoft. Following the project's success, similar parks were built off Scandinavian coasts through the late 1990s. Danish and German firms are known for their expertise when it comes to offshore wind, and they will likely benefit from the current boom that offshore wind power is experiencing. Companies and governments are planning to build 25 offshore wind parks in five European countries with a total capacity of some 1,100 MW.
"The technical potential of offshore wind power is enormous," Jos Beurskens, a wind power specialist at the Energy Research Centre of the Netherlands (ECN), recently told the bi-monthly magazine European Energy Review. "Placed in a row along every European coastline, offshore wind would make it possible to produce 30 to 40 percent more electricity than needed in the whole of Europe. This is only a technical potential that never will be fully exploited because of practical impediments like balancing problems, but it is an indication of the possibilities sea wind has to offer."
There are still some hurdles offshore wind energy has to overcome - mainly the high costs connected to construction, maintenance and operation. Offshore wind units are constantly exposed to high winds, salt water and corrosive sea air, which makes them more vulnerable to damage than land units.
Corrosion protection is key
In Germany, Sönke Siegfriedsen was one of the first engineers to tackle the issue of corrosion in offshore wind units. He developed a system that, similar to the air system in a semiconductor plant, takes in outside air and filters out the salt and any other particles. Using the treated air, a level of overpressure is built up inside the tower, sealing the air circulation so that none of the corrosive outside air can get inside the unit.
Experts have lauded Siegfriedsen's system, which will be used in units equipping a 60-MW wind park off the German North Sea coast, as especially efficient. The development of wind energy is far from over, however. Engineers will continue trying to make offshore units as safe as possible; as risks diminish, so will financing and insurance costs, which will give another boost to offshore wind energy.
Read more about the inventor: Sönke Siegfriedsen (Germany)