Three of the RE Power 5 MW offshore units sitting atop jacket formations at this wind farm. For reference, it is 92 meters (302 feet) from the turbine hub to the average water level, and each blade is 61 meters long (about 200 feet). The towers are about 75 meters tall.
The Alpha Ventus wind farm is a "pilot" project, and it consists of 12 x 5 MW offshore wind turbines - six from RE Power and 6 from Areva (ex-Multibrid). The project cost somewhere in excess of $300 million, and is a partnership of 3 of Germany's 4 big grid operators/large power producers. These were set up to get real world data on what the new version (from a few years ago) of "commercial scale" would perform like in real world conditions. These are located in the North Sea about 30 miles offshore of Germany in about 30 to 40 meters of water depth. It's really windy here, with an average wind speed at hub height near 10 m/s. Data was obtained from a nearby offshore meteorological tower for several years as a part of this project that documented the very abundant wind resource as well as dangerous wave conditions.
Like any pilot project, there were things learned - especially with regards to the "jacket foundation", where 4 large (2 to 3 meter diameter x 30 meter long) pipes are rammed into the seafloor (sand and mud, in this case), and the 4 legged support structure is then lowered onto them/attached to them. There was some mechanical issue with the Areva units, so they had to be dis-assembled, brought back to shore, repaired and then re-installed. That does not come cheap, as the vessels to do that have to remain stable and be able to lift a 350 ton object off a 4 meter diameter pole that is 92 meters above the water (75 meter tower plus the 17 meter above the water jacket structure) and then do the opposite once repairs were made.
But, it worked out. And as reported in many places (including here - where the picture came from - http://www.rechargenews.com/energy/wind/article306656.ece), the wind farm just completed 1 full year of electrical generation. A total of 267 GW-hr of electricity was delivered to the mainland in 8760 hours, for an average production rate of 30.48 MW, and an average net efficiency of 50.8%. The turbines were operable for 97% of the year. Anyway, the owners and turbine manufacturers were quite happy with that result, and they called a press conference/gave out a press release.
The RE Power units feature a 126 meter rotor and a "conventional" 3 stage gear speed increaser/ 6 pole generator (750 to 1170 rpm). The power ratio (swept rotor diameter to generator capacity) is 2.49 m^2/kw; on the basis of experience like this RE Power upped the generator size to 6.15 MW (new power ratio would be 2.02 m^2/MW). More information on these can be found at http://www.repower.de/fileadmin/download/produkte/RE_PP_5M_uk.pdf.
The Areva units feature a 116 rotor diameter (power ratio = 2.11 m^2/kw). They feature permanent magnet generators that operate at 45 to 148 rpm and a single stage gear speed 10:1 gear speed increaser - all designed to minimize weight. Areva recently introduced a "medium wind speed offshore turbine" with a 135 meter rotor diameter and power ratio of 2.86 m^2/kw - these would be quite appropriate for places like the Great Lakes. More information can be found here: http://www.areva-wind.com/1/m5000/technical-data/.
Since the Alpha Ventus project was started, several wind farms in the North Sea/French coastline have been announced. Areva (mostly owned by the French government, and also actively involved in selling new nukes) has plans to take the German designed "Multibrid" and manufacture in large scale in France. France recently tendered 3 GW of offshore wind proposals, and the winners should be announced soon.
And not be be outdone, the French company Alstom announced their 6 MW wind turbine (gearless) is also ready for sale: http://www.offshorewind.biz/2012/03/20/france-alstom-inaugurates-largest-offshore-wind-turbine/. The Haliade unit was installed on the French coastline; it features a 150 meter rotor diameter (power ratio = 2.94 m^2/kw). The first offshore units will be installed near the Belgium/French coastline later this year. They and Areva are strong contenders for the French initial 3 GW tender.
All of these offshore units feature helicopter pads to land maintenance people/facilitate minor repairs. These are not toy turbines by any means, and as has been shown by the Alpha Ventus site, these are serious power generation systems.
And certainly not to be outdone, Germany announced a 200 BILLION Euro intention for offshore wind (http://www.bloomberg.com/news/2012-03-19/germany-s-270-billion-renewables-shift-biggest-since-war.html). After all, when 22 nukes get shut down (17 so far), the make-up electricity has to come from somewhere. This should be about 50 GW of capacity, and about 25 GW on a delivered basis. So it looks like ditching that vile and potentially nasty nuke habit was...good for employment and business opportunities. That translates into about $US 260 billion, and is about 400,000 direct job-yrs of employment/close to 2 million job-years once "spin-off" jobs are counted. And that is Germany's jobs program, economic stimulus program, and a big part of their export drive. That's roughly 200,000 jobs, with ZERO expenditure of taxpayer dollars, Not bad, eh?
All done via that infernal Feed-In Tariff system of theirs. Hey New York, get the hint?
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