BAT KILLER: The zone of low pressure behind wind turbine blades seems to be responsible for killing migrating bats--though it remains unclear what is attracting the bats to the wind turbines in the first place.
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Scientists have known since 2004 that wind farms kill bats, just as they kill birds, even though the flying mammals should be able to avoid them. Many biologists thought that the bats, like their avian counterparts, might be falling victim to the fast-spinning turbine blades. But an examination of 188 hoary and silver-haired bats killed at a wind farm in southwestern Alberta in Canada between July and September in 2007 showed that nearly half showed no external injuries—as would be expected if the giant blades had smashed the flying mammals to the ground.
Instead, 90 percent of the 75 bats the researchers ultimately dissected had been killed by burst blood vessels in their lungs, according to results presented in Current Biology—suggesting that the air pressure difference created by the spinning windmills had terminated them, not contact with the blades.
"As turbine height increases, bat deaths increase exponentially," says ecologist Erin Baerwald of the University of Calgary in Alberta, who led research into the deaths as part of her master's project. "What we found is a lot of internal hemorrhaging."
As the wind moves through a wind turbine's blades, pressure drops behind them by five to 10 kilopascals (a pascal is a unit of pressure), and any bat unlucky enough to blunder into such an undetectable low pressure zone would find its lungs and blood vessels rapidly expanding and, quickly, bursting under the new conditions.
The Summerview wind farm, which Baerwald studied, kills hundreds of bats every year, particularly during the fall migration period that has just begun. But bats that find their way via sonar should have no trouble detecting fast-moving objects like the 200-foot- (60-meter-) long blades on the 300-foot- (90-meter-) tall turbines that spin as quickly as 160 miles (255 kilometers) per hour. And before the installation of these new, taller turbines bat kills had been practically nonexistent.
Pressure drops of as low as 4.4 kilopascals kill common lab rats and all the bats autopsied showed internal damage and bleeding consistent with this type of death, known as barotrauma. "If bats have a lungful of air as they fly through the air-pressure change, there's nowhere for the air to go," Baerwald explains. "The small blood vessels around the lungs burst and fill the lungs with fluid and blood."
This may also explain why, although some birds are killed by wind farms, the majority of casualties are bats. Birds' lungs are much more rigid and their capillaries are stronger, making them capable of withstanding extreme pressure changes, according to Baerwald. Those birds that are killed typically show damage from being struck by the actual turbine blade. "This offers an explanation of why bats, once they come across these turbines, are so likely to end up dead," says research biologist Paul Cryan of the U.S. Geological Survey, who has studied the issue but was not involved in this study. But "we don't have a satisfying explanation for why we're seeing such large numbers of bats. It seems they're being attracted to turbines."
Wind farm owners are well aware of the problem—and the potential hit to their environmental credibility. The corporation that owns Summerview, TransAlta Wind, along with ENMAX, Suncor Energy, Alberta Wind Energy and even Shell Canada teamed with Austin, Tex.–based Bat Conservation International to fund this study led by Baerwald. (TransAlta did not return calls for comment.)
It is unclear what measures, if any, can be taken to eliminate this pressure problem other than stopping turbines from spinning during times of lighter winds at night when bats tend to be most active. Of course, that would also curtail their electricity production: An experiment in August 2007 that stopped 19 of Summerview's turbines when winds fell below 18 feet (5.5 meters) per second cost TransAlta at least $50,000 in lost electricity production.
In the future, bat conservationists suggest, wind farms should be built away from known bat migration flight paths. The problem is: bat migrations are poorly understood at best. "We don't even know if they use migratory routes," Baerwald says, though she plans to begin looking for them in September.
"We don't have a clear idea of what a bad site for wind turbines is in terms of bat fatalities," Cryan adds. "We're not to the point yet where we can suggest solutions."
The full impact of these bat-killing pressure zones extends far beyond the wind farm, however. Such migrating bats travel from Canada as far as Mexico, eating thousands of insects en route, including crop pests such as moths and beetles. "They are one of the only things that fly around at night and eat bugs," Baerwald notes. "Bats killed in Canada could have a detrimental impact in America or Mexico. It's not local. It's an ecosystem-wide issue."
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42 Comments
Add CommentAha, the old dilemma arises again. How much is life worth? Well often there is a solution with little cost. Although I do have the answer, I am sure it exists (or can be made). If the wind farms were to install a deterrent, be it sound. ultrasound, strobe light or whatever, the bats and possibly birds could be directed away from the danger zone.
Reply | Report Abuse | Link to thisAbsolutely. Just as there are deer warning whistles one can put on one's car to forewarn the four-legged critters of the car's approach, we just velcro the bat version onto the tips of the wind turbine blades. Ta da! I do hope to hear of a solution nearly as simple. Let's not make this any more complicated than it has to be. This is a serious problem. Let's find a simple, ingenious solution quickly.
Reply | Report Abuse | Link to thisDepending on the size of space behind the windmill that is causing this low pressure system, perhaps a screen of some sort could be installed behind the windmill that prevents the bats and birds from entering "the danger zone".
Reply | Report Abuse | Link to thisAll animals have a way of signaling danger to others of their spiecies, find that signal for bats and sound it off on the turbine to deflect the bats away from harm.
Reply | Report Abuse | Link to thisA warning system, not a bat idea.
Reply | Report Abuse | Link to thisjust place some hanging light paper strips on the blades, with some light colours that the bats can see at night. If the blades are turning, the paper surely will make a sound that might alert the bats.
Reply | Report Abuse | Link to thisI remember that the US invested 10 millions on a pen to use upside down while in space.... the Russians use a cheap pencil... a simple solutions might be the best solution.
I was just curious if this would have any affect on mayor Bloomberg's envision of New York's skyline of windmills .... Could this pressure drop create a problem only to flying species?
Reply | Report Abuse | Link to thisThis means that the more wind farms there are the more children will die. Bats eate the mosquitos that might be carring West Nile virus... so, more West Nile virus. Our childeren are at greater risk of dieing from disease so...
Reply | Report Abuse | Link to thisLook at how many cildren die from malaria each year.
I will bet that the reason the bats like that location trailing the blades is that there are lots of insects there. I'll bet if the researchers look, that insects will also be seen to be dying in large numbers because of the same effect, and the bats sense a concentration of them. Plus the insects will be tumbling, and falling, dead, and that will make them easier to catch.
Reply | Report Abuse | Link to this@ FERNANDO58 "I remember that the US invested 10 millions on a pen to use upside down while in space.... the Russians use a cheap pencil... a simple solutions might be the best solution." This is a common urban legend. I'd suggest reading this article on Snope.com. (http://www.snopes.com/business/genius/spacepen.asp)
Reply | Report Abuse | Link to this"Just place some hanging light paper strips on the blades, with some light colours that the bats can see at night." Also bats can't see colors, they use sonar to navagate. The phrase "blind as a Bat" comes to mind.
Can't do much to change the pressure difference either since this is what makes the props turn. You lower the pressure change so that bats surrvive and teh props won't turn with as much force slowing the generator and electricity output. Need somthing that would reflect the sonar of the bats to make them see the turbine blades as a solid object that the creature couldn't fly though. This would be better than a warrning signal I'd think.
A similar problem occurs underwater where fishes are molted by ship turbines. There are already prototypes of effective turbines that do not produce intensive underwater turbulences, preventing killing fishes in the see surface area. Maybe the shape of wind turbines could also be somehow modified...
Reply | Report Abuse | Link to thisPerhaps what we need are wind turbines of a different design like fernando says. Say some type of "mesh" that reflects enough of the sound waves to fool the bats into withing "wall!". The blades would need to still funtion correctly.
Reply | Report Abuse | Link to thisThe solution may not be stopping all avian deaths. But reducing the loses to an "acceptable level"
The bats are inately drawn to the area of low pressure as their normal habbitat in the cave when they hibernate. The pressure must be low in the cave due to low or negative temperatures and little movement. As the wind turbine prooves and low pressure that occurs with a looming hurricane.This detriment to the bat's is also a detriment to the enviroment obviously.Which is more important the natural enviroment or the material value of this wind turbine? I know, that was a silly question.
Reply | Report Abuse | Link to thisI agree that an ultrasonic approach might be the best. The bats are more than likely attracted to the insects around the turbines. So obviously research needs to be done to determine what the insects are attracted to (perhaps heat). I think it is also possible, as john_toradze suggests, that the insects are being killed the same way as the bats. If the same ultrasonic approach could be used to repel the insects then that would be preferable. To cut down on cost, I would suggest that the systems not be on during the day. Depending on the effective range of the devices, it may only require that an emitter be placed on the top of the "stem" of the turbine so that it can remain stationary. Otherwise it should be in the center as well as the tips of the blades and perhaps a perimeter set up around the entire wind farm to help keep them out. I think that's probably the most effective solution. It shouldn't be difficult to find the right repelling frequencies (especially if the devices do quick sweeps of a range of frequencies). The fact that bats are already sensitive to ultrasonic frequencies should make it a rather easy implementation.
Reply | Report Abuse | Link to thisI am interest in why bats are attracted by wind farms but the article does not figure it out. I think it is more constructive than seeking migratory routes of bats.
Reply | Report Abuse | Link to thisSounds like every wind farm will need to be a Super Fund site because of the added polution. Nobody will live near the wind farm... on one will want to live near the power lines that run to the wind farm... no one will want to see the wind farm, example: "The four-year-old battle started heating up last summer when Greenpeace USA staged a demonstration against well-known eco-activist Robert F. Kennedy Jr., who's been an outspoken opponent of the proposal for a 130-turbine wind-power project in Horseshoe Shoal, a shallow portion of Nantucket Sound south of Cape Cod." Do people really care about saving the world, I don't think so. I can not get people to drive the speed limit in Boulder CO the self proclaimd capital of environmental concern. If someone can not even take control of there lives enough (self control) to drive the speed limit do you think they will have YOUR best intrest in mind when making decision about the environment.
Reply | Report Abuse | Link to thisultrasonic beacon, like a dog whistle, should be easy enough.
Reply | Report Abuse | Link to thistwo words: ultrasonic beacon
Reply | Report Abuse | Link to thissince bats navigate by sonar and radio waves or some sort of electrical wave can be detected by sonar why can't we have those waves surrounding the turbines so the bats will see them as a wall or something to avoid so they wont get killed by low pressure? i mean, i'm no scientist and my facts aren't always straight but with all the geniuses around here, cant we work off of that somehow?
Reply | Report Abuse | Link to thisLet's hope it doesn't take 10 years of studying the problem. If it was for me, I'll start testing possible solutions in a month, and check which one is more effective, made some improvements, and distribute the solution A.F.A.P. (i.e. as fast as possible). We need those bats to avoid being invaded by insects.
Reply | Report Abuse | Link to thisOld world bats do indeed have vision the blind as a bat saying is based upon myth, most bats have very acute vision and are used in conjuntion with biosonar. And bats don't have actual radar they use echolocation using their own vocalizations they listen for the response of basically their own voice. Its closer to sonar, its actually biosonar. No human has the same voice as do no bats. There is a frequency range at which they vocalize within, from about 14000 hz to over 100,000 hz, however there has already been lots of research in the area of keeping away bats and by the time a bat could 'see' the turbines it would most likely already be in the low pressure area. And the bats will indeed affect Canada because they are also plant pollenators, not to mention mosquito control! They do avoid lights though. Either way us humans will only spread more pollution in one form or another its our nature. The turbines completely change the environment, as will any further sounds high frequency or not, and lighting pollutes the night skies. Netting is labour intensive and still harsh on the bats body. I would think a good solution would be the old scarecrow method. Except use artifical owls. Bats avoid owls. They avoid the sounds and looks of owls.
Reply | Report Abuse | Link to thisThis is the first "measurable" unintended consequence of so called "free energy" - which we all should actually know better as being non-existent...
Reply | Report Abuse | Link to thisI have been wondering for quite a while now what effect windfarms have on the "upstream" weather.
Conventional "wisdom" would dictate that if one wind-generator generates X KW of energy, then the wind it took that energy from now has X KW less energy to travel to it's previously unimpeded destination to - say - deliver moisture laiden air for rainfall...
The so-called "butterfly" effect, although not proven, does make some sense if one think about it, hence my fear that wind energy is not such a good idea untill we can unequivocally prove that it has no effect on the regional/global weather patterns.
I guess the same argument can be made against wave/tide energy (but here with a possible direct ecological impact on tidal species).
IMHO, the only "safe" and renewable energy with arguably no possible climatic impact is solar energy ( not in the form of large solar farms though, because even those have been proven to effect the local climate ).
I fully realize that wind energy, wave/tidal and solar energy are all infinitely "better" than our current methods of generaing power, but it does not automatically make it "right". If we don't do the science correclty from the outset, then humanity may end up with similar problems 300 years from now?
I posted a similarly worded question on the Ask The Experts sections quite a while ago, but nobody ever answered it. - am I completely "nutters" in my thinking? I would be interested to hear what others think.
Why not send out a supersonic alarm call to deter the bats?
Reply | Report Abuse | Link to thisA bat does not "see" the actual blades with their sonar. Because of the movement of the blades they would recieve a "softer" signal return. It would probably appear to them not unlike a large swarm of insects. This is attracting them to the moving blades. The body damage to the bats is not caused by air pressure, but more likely the bats are flying directly into the front of the blades. The blade isn't hitting the bats, the bats are hitting the blade and there is a "big" difference.
Reply | Report Abuse | Link to thisThe bats are not actually "seeing" the blades with their sonar. The are receiving back a softer return signal because of the movement of the blade. This movement would appear not unlike a swarm of insects. This is attracting the bats to the blade area. The body damage to the bats is probably not being caused by pressure change. More likely is the blades are not hitting the bats, but the bats are actually flying into the blades, a big difference in trama. Or if you watch a bat in super slow motion they turn of a dime. The bats may be trying to avoid the blade at the last second and reducing the trama to their bodies, but still being killed.
Reply | Report Abuse | Link to thisWhy not just have a net which will stop all bats ??? !!!
Reply | Report Abuse | Link to thisStick to burning coal and oil. The bad effects from CO2 only exist in the virtual reality computer world of Al Gore and not in the real world. The earths temperature has been dropping sense 1998 even with an increase of CO2 in the air. Global warming from CO2 is a lie (along with everything else from the mouths of environmentalist) and mother nature is proving it.
Reply | Report Abuse | Link to thisPassive whistle 'screamers' can be put on the blades, at no significant additional cost. Individually they're less than $2 each, and in bulk will likely cost much less than $5 to make each turbine safe for avians.
Reply | Report Abuse | Link to thisThese whistle screamers are the same thing truckers, rural commuters and outdoorsmen put on their transportation to keep rabbits, birds & other small animals from stepping in the path of moving vehicles.
This is a NON-issue.
BUILD WIND FARMS, AND BUILD THEM NOW!
The "exploding lungs" headline here is pure speculation, not science. Scientific American shouldn't present this malarky as news simply because a researcher was too dull to explain observations and failed to test hypotheses. Yet the headline is on thousands of sites poisoning minds against wind energy.
Reply | Report Abuse | Link to thisSo "scientists": did you measure the pressure drop and it's duration? Did you elicit laboratory results showing that these conditions could account for "exploding lungs?" The pressure drop on these blades would be on the order of 20 lb/sq ft (based on what I know of maximal wing loading of aircraft that operate at similar airspeeds). This is a truly trivial decompression relative to the ambient pressure of 2200 lb/sq ft. I can't believe that a sudden pressure drop on the order of 1%, and therefore a maximal sudden lung expansion of 1%, would be uncomfortable, let alone lethal, to a bat. Human passengers in a decompressing airline cabin will experience a sudden drop of 8 lb/sq in (1200 lb/sq ft -- lung expansion of 100%!) and survive. A smaller creature should be less susceptible than a large one in such conditions, since the accumulation of forces is much greater over a larger tissue mass.
As mentioned by others here, these bats are being struck by the blades and hemmorhaging due to mechanical, not pneumatic trauma. You don't see the impact injuries because the blades are smooth, blunt, and featureless with respect to the bat's size, just as you don't see external wounds or broken bones on the small birds that hit your picture window. Blunt impact is a well-known and documented cause of pulmonary contusion.
I won't believe the pressure drop theory until I see a laboratory
demonstration of such a small, brief decompression producing measurable injury. Let's not start solving this problem we establish what the problem is. And let's not start abandoning windfarms until we realistically weigh the carnage caused by competing energy sources. Certainly bats are dying, and we should do what can be reasonably done to minimize that, but virtually ALL human activity destroys wildlife in one way or another--do you eat, own material goods, use electricity, drive a car? If any of the above, you're killing plants and animals by the thousands, and you're destroying habitat every day. Every kWh of energy NOT made by wind costs the planet something, too. Go visit a strip mine or an oil field before you draw conclusions about how murderous a wind farm might be.
Responding to Piie: as far as I know, there aren't any sane people who proclaim the existence of "free" energy.
Reply | Report Abuse | Link to thisIt all costs something. I, too have wondered about the effects of windfarms on the circulation of the atmosphere, climate, heat transport, etc. BUT...
Over the last three hundred years, people have cleared hundreds of thousands of square miles of forest, thus removing a vast natural source of resistance to surface winds. Wind farms and the energy they take from atmospheric circulation could therefore be seen as helping to restore the natural order, and no time in the coming 1000 years could we erect enough windmills to equal the energy damping of those now-cleared forests.
As for the butterfly effect, I think you're refering to nonlinear phenomena in which tiny inputs produce vast results. Since no one can predict WHICH tiny inputs might produce WHAT vast results, there's nothing to gain by thinking like that--if a butterfly can produce a hurricane by turning left rather than right, it could also produce one by not turning left. So what're you gonna do about it? Sticking a windmill on a hilltop is just as likely to prevent a tornado as to cause one (zero likelihood in both cases, if you ask me). On the whole, natural systems are stable and absorb small fluctuations of every kind. No sense in anyone being afraid to blink in order to thwart a tidal wave.
Maybe a screen covering the blades, on both sides, would prevent bats from flying through them. It would be expensive to enclose the blades entirely, like a room fan, but even partial enclosure might reduce casualties.
Reply | Report Abuse | Link to thisWouldn't nets, designed to deter bats without breaking the wind, mitigate the problem?
Reply | Report Abuse | Link to thisSigh, the bats use bloody sonar right? hows about some high pitched sound transmitters placed around the turbines to stop the little buggers?
Reply | Report Abuse | Link to thisEvolution will solve this one. But I like the idea of putting something on the blades. It would look cool from a distance. Like LED's turning on and off would create maybe advertising for the owner's of the wind farms and put the birds and bats off, maybe?
Reply | Report Abuse | Link to thisOK, maybe evolution can handle this one? But, before we go crazy here, let's do some tests. And, see what is causing, not correlated with, the death of the birds and bats. By, attaching LED's to the blades, it would look cool and maybe, just maybe it would act as a warning to birds, bats and humans too. I am assuming that the FAA is looking into this too? Hello FAA are you there? These things are very tall and could interfere with low flying human craft too!
Reply | Report Abuse | Link to thisCould the bats be chasing water droplets being shed by the blades?
Reply | Report Abuse | Link to thisThe reported pressure drop behind the blade would cause adiabatic cooling, and perhaps the condensation of water vapor into an aerosol, in the air behind the blades. If the back side of the blades was cooled by this pocket of cool air, then perhaps water would condense on the back side of the blades as well.
Perhaps the bats are chasing water droplets and not insects. Wind turbines, like your car, probably cool faster than the ground and become wet as the temperature drops at night. The movement of air over the blades and the angular acceleration of the blades would probably fling the water off the blades air behind as droplets.
Reply | Report Abuse | Link to thisAlso, the reported pressure drop behind the blades causes adiabatic cooling of the air, and could potentially cause condensation of water vapor into an aerosol. If the cool air cools the back of the blades as well, then water might also condense there even without ambient cooling.
Here is a new technology for trapping wind energy in large-scale.
Reply | Report Abuse | Link to thisPlease visit:
http://www.geocities.com/newideasfromtelewise/windbarrier.htm
http://www.physics-edu.org/tech/wind_barrier_system_for_generating_hydrogen.htm
Here is a new technology for trapping wind energy in large-scale.
Reply | Report Abuse | Link to thisPlease visit:
http://www.geocities.com/newideasfromtelewise/windbarrier.htm
http://www.physics-edu.org/tech/wind_barrier_system_for_generating_hydrogen.htm
The solution seems to be to turn off the turbines at night when bats are active. I am confused by the the results of the experiment performed in August 2007 that stopped 19 of Summerview's turbines when winds fell below 18 feet (5.5 meters) per second. This supposedly cost TransAlta $50,000 in lost electricity production. How exactly did this cost 50,000? Did this company have imaginary money on the books from predicted profits that were not made due to the turbines being shut down? If so, that's what I call BS. You earn what you earn not what you are projected to earn. you can't lose what you don't have.
Reply | Report Abuse | Link to thisHow about using a energy source that doesn't kill wildlife. How about putting our emphsis on nuclear energy? That seems to work in France just fine and is less costly.
Reply | Report Abuse | Link to thisNope, the pressure hemorrhages their lungs, which is what kills them.
Reply | Report Abuse | Link to this"Instead, 90 percent of the 75 bats the researchers ultimately dissected had been killed by burst blood vessels in their lungs, according to results presented in Current Biology—suggesting that the air pressure difference created by the spinning windmills had terminated them, not contact with the blades." -SA