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PowerPedia:Offshore Wind Power Drawbacks
Wildlife Impacts of Offshore WindFarms
In all the proposals for offshore windfarms, the authors focus naturally enough on the technology itself. For example, the MIT proposal doesn't refer to environmental and wildlife-impact assessment, and among the oil companies and electric utilities which are said to be enthusiastic about their tensor-leg platform there's no listing of any environmental group.  Nor is any effect on resident or migratory bird populations mentioned in relation to the other floating or offshore wind generation projects.
The risk of something being out of sight of land is that it's also out of mind. Way out at sea, there won't be bird bodies lying on the ground around such turbines to be counted. Feathered corpses would likely be eaten by any number of hungry sea-creatures before they even floated very far.
Can Land-Based Statistics be Extrapolated to the Ocean?
Although the industry tends to dismiss concerns with their own statistics, land-based windfarms are accessible, so that the death tolls can be and have been be tallied. The Center for Biological Diversity brought a lawsuit against windmill owners in California, stating that thousands of birds were being killed at the Altamont Pass windfarm annually, including protected raptor species: <http://rppi.org/groupsues.shtml> That environmental group didn't even want to stop wind-power harvesting, but launched this legal action to urge that measures be taken to reduce the carnage.
Risk Factors for Birds
The question to be posed in the case of oceanic windfarm environmental-impact assessment would be: "Do any bird species use those specific offshore high-wind corridors for migration?"
Logically, they might. Land-based species of birds are known to rely on favourable winds, which assist them in going long distances at sea which they must cover without eating until they reach land again. Sea-birds which hunt for fish are not governed by this type of necessity.
So is it only the routes followed by land-based birds that should be of concern? Not really.
There are sea-birds that migrate as well. Arctic terns are known to migrate the longest distance of any bird. But do they fly close enough to land to encounter a floating windfarm? Another factor would be the height above the waves at which the species typically flies. Given the huge sizes of some of the proposed floating turbines, a seabird scanning the water from close enough to the surface to observe and pounce on their finny prey would be within the danger zone from the sweeping blades.
Given that developing wind-power is one of the ways to reduce damage to the environment from emissions, some protection for living creatures in the environment must also be part of the picture. Regardless of what type of platform or tether or floating-pole anchoring rig is adopted, there should be some effort at mitigation.
Ornithologists should be consulted for information about bird species distribution, typical flying heights, and their most-frequented fishing grounds and flyways. If possible, the windfarms should be located outside the critical feeding and migration zones.
The proposed rotor designs should be examined to find the one(s) least likely to cause damage to the types of birds flying through or living and feeding in an area where a windfarm is proposed.
Which design kills fewer birds per turbine? The huge, slow-moving trio of straight blades that are most commonly seen? (<>, <>) Would vertical turbines such as the Windaus spiral (<http://windausenergy.com/>) be more easily avoided by birds, or does that type of design need a rigid fixed base? Would the flat-panel types that deter birds by presenting a solid barrier (even if it's a moving one) function on a floating base? Could those styles withstand storm conditions at sea?
Would the many smaller mini-blades lying closer to the surface as proposed by Selsam? (<[www.selsam.com]>) Or would the both-end-mounted blades of a unique Dutch design spare avian life even if a bird should be drawn inside its wind-concentrating sphere? There's an animation of that one at: <> Both of these are smaller in overall size due to unique design features (multiplicity or hollow core, respectively) that enable them to drive a more powerful generator than expected.
One might be willing to guess that simply due to a smaller swept area, the smaller sizes of rotors would reduce the odds of birds flying into them. However, without comparison studies and statistics based on bird casualties observed on land, there's no way to know.
Accurate Data Already Available
Due to studies being conducted in recent years with tiny transponders carried by birds, their migration routes can be accurately traced by GPS satellites, and some species which live at sea for long periods have also been traced in this manner. Therefore, a lot of the data needed can be extracted out of already-collected information, doubling the value of studies already conducted by marine scientists and ornithological researchers.
Part of deciding which technology to use in a given ocean location, therefore, should include not just cost-based factors, but also an environmental impact study based on solid scientific data, most of which is already collected.
Various control attempts on land
Land-Based mitigation at airports, where bird flocks endanger both themselves and jet engines, has included releasing predators into the area. At some airports, falconers have flown their trained birds of prey to frighten off the pigeons and other natural prey. Or herding dogs have been used in some cases to chase them off. Other measures to deal with birds in areas where they are not wanted have included playing the hunting calls of predators, or even recordings of humans firing shotguns (with occasional reinforcement from a real shotgun) to frighten away huge flocks of crows that tend to congregate in one area.
These approaches, using controlled predators or sounds associated with danger, would be harder to apply on the ocean than they are on land. Would there be any type of sound or signal that birds can detect and which can be heard above the natural sounds of wind and water, which could frighten them away from approaching a windfarm?
If a technology can be developed that is capable of keeping birds away from a danger zone, and safe to use in ocean conditions, this might be the best mitigation of all. Then the merits of each technology would be the main determining factor in the choice of a system for capturing windpower and bringing it back to shore.
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