The Great Lakes form one of the "North Coasts" of the USA - the other north coasts being in Alaska, the northern part of the Atlantic and Pacific shorelines of the continental USA, as well as those tropical isles such as Hawaii and Puerto Rico. The coasts tend to experience stronger winds than inland areas, and as one proceeds offshore, the winds get even stronger. Here is a map (from the Canadian Wind Atlas).
There has been a lot of activity with regards to Great Lakes wind energy lately, including the passing of the Feed-In Laws in Ontario (Green Energy Act) and NYPA's recent foray into buying offshore electricity made in NY (Lake Erie, Ontario or and/or offshore of Long Island). As you can see in the map, the areas with the best winds (orange/red colors) tend to be on the waters, especially where a decent fetch can take place. If you have the time, check out the Atlas at http://www.windatlas.ca - it has some new features that allows a decent estimation of the winds at any given site (and by season, too).
For a "typical" offshore turbine, about 60% of the cost is associated with the "offshore" part (foundation, ship/barge/crane rental, underwater electric cables, and environmental aspects associated with the offshore aspect), with 40% going to the turbine manufacture - including some "extra" aspects - like a helicopter pad - needed so that these can operate in a marine environment. The economics greatly favor large scale, and also large turbines. And this trend is accentuated by placing the turbines further and further offshore.
Today, Europe is undoubtedly the leader in this technology - most installations are in British and Danish waters, but Germany will soon be the leader in offshore wind installations. Here are some really handy sites for information on existing (1463 MW), under construction (2599 MW) and planned (13,320 MW) projects. The offshore wind turbine business will soon become one of the dominant forms of marine construction, and significant contributors to the German economy. And at about $4 million per MW installed costs, these are big investments, and lots of business/employment opportunities arise. Consider it a Keynesian economic stimulus that is done with essentially zero expenditure of tax money. Such installations are financed via either long term Power Purchase Agreements (PPA's), or by a special form of a PPA that is allowed by Feed-In Laws. The price for offshore wind in Germany is about 13 Eurocents/kw-hr, or about 18 c/kw-hr in US money (June, 2009).
When it comes to offshore wind, the water depth is a matter of great concern. Here is a site that shows the Great Lakes bathymetry (depths). The shallowest is Lake St Claire (maximum depth is 6 meters), and the average depths (shallowest to deepest) are in the following order - Erie, Huron, Ontario, Michigan and Superior. The faster winds move across Superior and parts of Lake Huron.
Here is a map of the Great Lakes, depth wise. The red area is the 0 to 20 meters range (0 to 66 feet), yellow 20 to 40 meter range, green is 40 to 80 meter depths light blue is 80 to 160 meters and dark blue is deeper than 160 meters (> 525 feet).
Most offshore wind turbines have been installed in less than 20 meters of water. The most common way this is done is the monopole approach - where a giant pipe is rammed into the seabed, a transition piece is placed on that, and then the turbine tower/nacelle/rotor/blades is attached. This "pipe" is made by rolling 2" thick or more steel plate into a cylinder, welding that, and then welding these "cans" into a long cylinder. These can be 50 meters or more (164 feet) long and are at least 4 meters (13+ feet) in diameter, and weigh a lot. For example, a 2.5" thick wall by 164 ft long monopole (50 meters long) would weigh over 324 tons - and that's just the pole coming up to a bit more than the waterline for a 2 MW or so wind turbine. About 90% of exsiting turbines are installed this way; the others use a "caison" approach. This is suited to shallower waters near a port, where the 1800 ton concrete system can be floated out to the location, sunk to the seabed, and the turbine tower placed on that. In Finland, one recently constructed in the Baltic Sea (Kemi Ajos I+II) involved making artificial islands for 8 x 3 MW WinWinD "multibrid" low speed generator units (also made in Finland).
One of the main purposes of the foundation is to prevent the turbine from tipping over, and for offshore turbines, there is also the need to keep water sensitive parts high enough above the water level (including tides and waves) to avoid water damage - for example, to the generator and transformer. For places like the Great Lakes and the Baltic Sea, the foundation must also be able to resist the push of icebergs, and wind driven pack ice.
In the last few years, offshore turbines have started to get really big. One of the more popular models (as of June, 2009) is the Siemens 3.6 MW S-107 unit (107 meter blade length). However, there are three 5 MW units (RE Power, Multibrid (Areva) and Bard), and two 6 MW units (RE Power and Enercon) now commercially available. These 5 MW units tend to need a different approach to foundations, especially in waters further out to sea, where winds are better but waters tend to be deeper. Many of the proposed wind farms in Germany are in 40 meters or more of depth, but where winds average 9.5 m/s (which is really fast). The most popular foundation for these "big boys" is the tripod. For water depths between 50 to 120 meters, the jack-up foundation (very popular for offshore oil and gas drilling platforms/oil and gas processing centers) seem like a good choice.
However, water depths less than 50 meters deep with high wind speeds near populated areas (with an already established electrical transmission grid) are not uniformally dispersed. In fact, the U.S. Pacific coast is characterized by steeply plunging seabeds (the Atlantic coast tends to be shallow for a considerable distance offshore). Thus, a new type of turbine foundation is needed for such areas. For our region, these would be ideal for Lake Ontario, a lot of Lake Michigan and most of Lake Superior. Here is a bathymetric map of this lake (numbers in meters).
As can be seen, most of Lake Ontario's waters in the New York part are more than 100 meters deep - the main exception being the Thousand Islands region at the exit of the lake/beginning of the St Lawrence River. And for those regions, the islands may be a great "pseudo-offshore" platform - such as the recently completed 198 MW Wolfe Island (Ontario) project, or the proposed Gallo Island (NY) project.
But, the NY portion of Lake Ontario measures about 2500 square miles, and the average wind speed is near 8 m/s at 80 meter heights above the water. That is enough wind resource/area to power up most of NY State (averaging more than 16 GW) on average, were there a will to do it (at present, no sign of that, however). This poses a problem - how could this wind resource get tapped in waters so deep?
Well, one solution is called a spar platform - an approach commonly used in the offshore oil and gas drilling/platform business. In Norway, Siemens and Statoil (Norway's nationalized oil company) where a humongous offshore oil and gas business exists, an experiment called the Hywind project is underway. A Siemens 2.3 MW wind turbine was attached to a 100 meter long spar/foundation - basically a hollow pipe weighetd on one end and anchored to the seabed. At this location, winds average near 9.5 m/s - like the North Sea, a nasty piece of water that is rarely calm. So, check out the videos at the Hywind website.... Should this come to pass in NY, we are talking about tens of thousands of jobs. In fact, too bad NYPA couldn't run the experiment offshore of Rochester.....
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