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I just did a Search here for "underwater" and "windmill" and it came up blank, so if this idea really has been posted here using some other verbiage,
Anyway, this Idea should be somewhat obvious in hindsight. We build ordinary windmills to extract useful power from wind energy. We put turbines in rivers (usually accompanied by dams) to extract useful power from downhill water flow. The second is more "energy intensive" than the first, which is why we all know that dams are great sources of electrical power, while electric-generator windmills spent decades in the economic doldrums (return on investment --ROI-- is relatively tiny, and only recently proved viable on a large scale).
Anyway, putting the equivalent of a windmill in a steady ocean current, say the Gulf Stream, should have an automatically-viable ROI that is intermediate between windmills and ordinary hydropower. This is because water is something like a thousand times denser than air, so a volume of flowing water contains a thousand times the energy of an equal volume of equally-flowing air.
Do note that the ocean has different currents at different depths. I once read somewhere that near the seafloor underneath the Gulf Stream is another current going the opposite direction. If true, then we can build towers on the seafloor, just like ordinary windmills, to extract power. Being so deep will protect them from ships, and most sea life is found at other depths, so they won't be bothered. Also, another thing that protects sea life is the fact that underwater windmills will have a SLOW rotation rate, due to that same greater density of water over air. This means we can also put windmills in the rich-life upper ocean currents; animals will have time to dodge the blades. (Some life forms, like barnacles, need to be discouraged; probably everything needs to be coated with Teflon or something even more slippery.)
Consider buoyant windmill modules can be anchored by cables to the bottom. They float up to perhaps fifty meters beneath the surface, in the midst of the ocean current. There they stay and generate power (which flows down those same anchor cables, and then toward shore).
Finally, it may be necessary to build all underwater windmill modules in counter rotating pairs. Again, this is because the water is denser than air; and for every unit of force that tries to rotate the blade, there will be reactive force against the generator assembly, Counter rotating blades will let such forces be canceled.
Tidal currents are being recognized as a resource to be exploited for the sustainable generation of electrical power. The high load factors resulting from the fluid proper- ties and the predictable resource characteristics make marine currents particularly attractive for power generation. These two factors makes electricity generation from marine currents much more appealing when compared to other renewables. Marine current turbine (MCT) installations could also provide base grid power especially if two separate arrays had offset peak flow periods. This characteristic dispels the myth that renewable energy generation is unsuitable on a large scale.
The global strive to combat global warming will necessitate more reliance on clean energy production. This is particularly important for electricity generation which is currently heavily reliant on the use of fossil fuel. Both the UK Government and the EU have committed themselves to internationally negotiated agreements designed to combat global warming. In order to achieve the target set by such agreements, large scale increase in electricity generation from renewable resources will be required.
Marine currents have the potential to supply a significant fraction of future electricity needs. A study of 106 possible locations in the EU for tidal turbines showed that these sites could generate power in the order of 50 TWh/year. If this resource is to be successfully utilized, the technology required could form the basis of a major new industry to produce clean power for the 21st century.
Although the energy in marine currents is generally diffuse it is concentrated at a number of sites. In the UK, for example, tidal races which exist in the waters around the Channel Islands and the ?Sounds? off the Scottish west coast are well known amongst sailors for their fast flowing waters and treacherous whirlpools. The energy density at such sites is high and arrays of turbines could generate as much as 3000 MW in the spring tides.
In spite of the advantages offered by MCTs, it is rather surprising that such technology has not received much attention in terms of research and development. There are many fundamental issues of research and various key aspects of system design that would require investigation. A major research effort is needed in order to expedite the application of the marine current kinetic energy converters. Virtually no work has been done to determine the characteristics of turbines running in water for electricity production even though relevant work has been carried out on wind turbines and on high speed ship?s propellers and hydro turbines. None of these three well established areas of technology completely overlap with this new field so that gaps remain in the state of knowledge. This paper reviews the fundamental issues that likely to play a major role in implementation of MCT systems. It also highlights research areas to be encountered in this new area and reports on issues such as the harsh marine environment, the phenomenon of cavitation and the high stresses encountered by such structures.
Related Topic Windmill
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