Posts Tagged Wind Turbines

US wind energy turbines killed 600,000 bats last year, study says

From the South China Morning Post: http://www.scmp.com/news/world/article/1352671/us-wind-energy-turbines-killed-600000-bats-last-year-study-says.

More than 600,000 bats were killed by wind turbines across the United States last year, with the highest concentration of kills in the Appalachian Mountains, according to new research.

In a paper published in the journal BioScience, University of Colorado biologist Mark Hayes used records of dead bats found beneath wind generators and statistical analysis to estimate how many bats were struck and killed by generator propellers each year.

“Dead bats are being found underneath wind turbines across North America,” Hayes wrote. “This estimate of bat fatalities is probably conservative.”

The new estimate is among the highest yet for generator-related bat deaths. Previous studies have calculated mortality rates of between 33,000 and 888,000 a year.

The bat deaths were calculated on a per megawatt basis, and the highest rates were associated with generators in the Appalachian Mountains-Buffalo Mountain, in the state of Tennessee, and Mountaineer, West Virginia.

Hayes said his estimates were conservative for several reasons.

Little information on bat mortality was available for wind generators along the Sierra Nevada ranges and Rocky Mountains, he wrote, and scavenging animals likely carried away a percentage of dead bats before they could be counted.

Hayes also said that if a range of bat deaths were listed by a facility, he used the lowest one for his calculations.

There are 45 known bat species in the continental United States, but biologists do not have a firm handle on their total population. Experts say the animals’ small size and nocturnal habits make them difficult to survey.

Nonetheless, biologists suspect their numbers are decreasing because of changing climate and diseases such as white-nose syndrome.

Even under the best circumstances, bat populations grew slowly, as they give birth to one pup per year, and the mortality rate for young bats was high, Hayes said.

While they are not generally beloved by the American public, bats perform two highly valuable services: they eat enormous amounts of flying insects, and they help pollinate crops like peaches and avocados.

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Well Blow Me Down

In a world of climate change we are all (well, maybe not the coal and oil companies) looking for alternative ways to generate energy that do not produce greenhouse gases. It seems ironic that the nuclear industry has seen this as a potential opportunity to appear green and a viable alternative to coal power. Apart from the fact that plutonium is still deadly for 250,000 years and countries like Germany appear to be winding their nuclear programs down in the wake of the Fukushima disaster, nuclear is no more sustainable than coal or oil. Uranium will run out just like all the fossil fuels, so why go down a potentially lethal path for the sake of a few years of power? Forget the nuclear nonsense and head straight to the technologies that will keep my computer alive and active long after I’ve nourished a few thousand worms.

Which brings me to wind farms and turbines. As usual, a lot of nonsense is being spouted by both sides. One memorable newspaper article described opposition to turbines because they would negatively affect the migrating orange-bellied parrot, with a lovely full colour photo of the parrot accompanying the article (http://www.theage.com.au/articles/2006/04/05/1143916574751.html). Interestingly these turbines were destined for a site east of Melbourne, in an area not visited by OBPs, who prefer the saltmarshes west of Melbourne for their overwintering grounds.

Nevertheless turbines do kill birds and bats, 100,000 to 440,000 birds each year according to the US Fish and Wildlife Service (http://www.nature.com/news/the-trouble-with-turbines-an-ill-wind-1.10849), generally through direct collisions. This is, however, considerably fewer than are killed by cars (60-80 million), building strikes (100,000 to 1 billion), power lines (up to 175 million) and our old friend, the pussy cat (365 million to 1 billion). Very rubbery figures to be sure, but significant nonetheless.

Bats, however, die in a more interesting way. The movement of the propellers generates a significant area of low pressure behind the turbine (five to 10 kilopascals less than the surrounding air). As nature abhors inequality, when the unsuspecting bat flies into this low pressure region the relatively higher pressure inside its body attempts to equalise with the lower pressure outside its body. It does this by expanding outwards, which leads to ruptured blood vessels and lungs filled with blood (http://www.scientificamerican.com/article.cfm?id=wind-turbines-kill-bats). I can certainly attest to this, having necropsied affected bats. There are no external signs of damage but their chests are certainly full of blood, caused by this barotrauma.

What to do? Do we sacrifice some birds and bats on the altar of climate change, because none of us want to return to pre-electricity days but we also don’t want our planet to heat up? You can’t make an omelette without breaking eggs, and all that. Rather than scrap a potentially important source of sustainable power one suggestion is to be smarter about placing wind turbines away from bird and bat flight paths in the first place. While this is sensible in principle we don’t know enough about their pathways to make this work reliably.

What shows more promise is redesigning the turbines themselves. On a recent ski trip to Copper Mountain in Colorado I saw some wind turbines on the very top of the mountain. But these turbines were different to the traditional horizontal axis turbines we are all familiar with. They were vertical axis turbines. Instead of having a big propeller spinning on a pole, they had vertically orientated blades which spun around the central pole. I had never seen this design before, but it could be the answer. According to a report these vertical turbines are less dangerous than the horizontal ones because they don’t use propeller-like blades to capture the wind, but rotating open-framed cylinders (http://www.msnbc.msn.com/id/44627832/ns/technology_and_science-innovation/t/upright-turbines-breathe-new-life-wind-farms/). The downside is that they don’t generate as much electricity as the traditional turbines. However, according to the article, “putting windmills upright and spacing them more tightly together can generate more electricity on less land, and kill fewer birds or bats than traditional horizontal rotating wind turbines.” These vertical turbines are also only 30 feet high, which is below the migratory level for birds and bats.

It is amazing how resourceful we can be when we have to. It’s just a shame that resourcefulness only materializes when we are faced with a catastrophe. But that is how we operate, I guess. Why waste time on things that might happen, like Y2K, when there are so many things that are happening to worry about? It does make preventative medicine particularly hard to sell, however.

Dr. F. Bunny

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