One of the more curious arguments "pooted forth" against offshore wind farms in the Great Lakes concerns the fact that the Great lakes are freshwater bodies. To date, most offshore wind farms have been located in salt water (Baltic Sea, North Sea, and the waters around northern Europe), so people could say that only salt water bodies have had wind turbines placed in them (some of the inland water bodies in The Netherlands may also be brackish/saline). But since most of those claiming that there is a big difference in the impacts of offshore wind turbines between freshwater and saline water situations have been opposed to offshore wind turbines (or to all wind turbines, for that matter), well, some skepticism is warranted.
Last year, a wind farm composed of 10 x 3 MW wind turbines was installed in Lake Vanern, which is the biggest lake in Sweden. The water body has a surface area of 5650 km^2, or about 2207 mi^2. It is somewhat elliptical in shape, but if it was perfectly circular, it would be 53 miles in diameter. It has 22% of the surface area of Lake Erie, or 29% of the area of Lake Ontario. In terms of water volume, Lake Vanern has 32% of the water that is in Lake Eire, but only 9% of the water volume of Lake Ontario. In terms of average depth (27 meters) and maximum depth (106 meters), it is similar to Lake Erie (19 meters and 64 meters maximum depth). A brief summary of the lake can be found at http://en.wikipedia.org/wiki/Vänern.
It does have a couple of other similarities to Lake Erie - it freezes up in the winter, and it is one of the few places in the southern part of Sweden that is not covered with trees and buildings, or other obstacles to wind flow. But, the average latitude of Lake Erie is near 42 north; Vanern is 59 North. Sweden's big pond (Baltic Sea, and 3 wt% salt) routinely freezes up in the winter even near the southernmost part of Sweden, and Lake Vanern's surface is a solid pack for a considerable part of the year. There have even been epic battles conducted on the ice of the lake - see http://en.wikipedia.org/wiki/Battle_on_the_Ice_of_Lake_Vänern. However, because there are no significant obstacles to the wind on the lake (frozen or liquid), the wind speeds tend to be faster than over land. And since most of the trees tend to be conifers in Sweden, they don't lose their wind resistance in the fall/winter/spring.
The wind farm commenced commercial operations in May of 2010. The opening was a big deal, and even royalty got in on the act. The details of the project can be seen at http://swentec.se/en/Start/find_cleantech/Plants/Wind-farm-in-lake-Vanern-/ and http://www.4coffshore.com/windfarms/vindpark-vanern-gasslingegrund-sweden-se06.html. In many ways, this 30 MW facility is a pilot project, mostly done to investigate how freshwater and salt-water wind turbine arrays might differ or be the same. And odds are, there are many more turbines planned for the lake. And because it is located in that bastion of Socialism and eco-consciousness (they decided to phase out all their nukes - how's that for eco-friendly!), permitting was extensive. The turbines are located in about 10 meters of water (from 1 to 22 meters), on average 7 km from shore (3.5 to 10). The turbines use a gravity foundation (large mass of concrete built onshore/then sunk at the location) similar to what was used at the Middlegrunden wind farm that is located in Copenhagen harbor. Odds are, the foundation was especially designed to deal with pack ice.
The wind turbines employed are somewhat unique, as they use what is called "multi-brid" technology. They are made by WinWinD (Finland - http://www.winwind.com/), and these use a 90 meter steel tower and ~ 50 meter long blades, with the estimated net yield will be 34%. The multi-brid" approach uses a medium speed 2 step gear arrangement to increase the rotor speed from ~ 10 (5 to 16, depends on wind speed) rpm to a generator speed of near 200 rpm. The multipole generators also use a permanent magnet rotor, so these tend to be more energy efficient and reliable than ones that have an electromagnet core that requires rotor electrical connections. The lower speed transmission/gear box also results in less wear and tear, and is also more energy effiicient than the traditional 3 step gear speed increaser. Details are found at http://www.winwind.com/Documents/Press%20Kit/WWD-3_Fact_sheet.pdf.
Sweden also has many Baltic Sea wind farms in operation, and a lot more are being built or being designed. In addition, one of the world's biggest onshore wind farms (using concrete towers at more than 113 meter heights and Enercon gearless turbines) is being built in the northern forests - it will be rated at about 3000 MW capacity, and have an average output similar to a 1 GW nuke (see http://www.renewableenergyworld.com/rea/news/article/2008/06/markbygden-enercon-to-erect-3-gw-wind-farm-in-sweden-52877), but of course, none of the actual (such as grotesquely high capital cost/actual operating costs) or potential downsides of a nuke, like Chernobyl. Fun factoid - the Chernobyl meltdown was actually detected first in Sweden when a worker at one of Sweden's nukes walked INTO the facility. He was radioactively contaminated with the fallout from Chernobyl (about 2000 miles to the southeast), but that set off all kinds of alarms, so to speak. And it is one of the reasons why Sweden has decided to use wind, hydropower and biomass as their sole sources for electricity, with hydropower also being the preferred way to temporarily store any excess electricity (from windy times) for those not so windy times.
Anyway, next time some yahooey tells you that wind turbines cannot be placed on freshwater, well, you can try to talk sensible with them. Or you can walk away, since this person is brim full of ignorance, and they might be one of those ferocious "low-information type" teabaggers looking to pick a fight with you. Your choice... but don't say you weren't warned....
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