A government-sponsored study examining bird and bat deaths from wind turbines found that newer, slower spinning turbines don’t necessarily ease the killings.
The report by the National Wind Coordinating Collaborative and funded by DOE may not end the controversy surrounding older turbines and the fear they are to blame for more than their share of deaths. But it will sound the call for more study.
Study finds modest number of bird deaths - fewer than 14 annually per MW hour of electricity.
The report found that wind farms in total are responsible for relatively few deaths – fewer than 14 bird deaths annually per MW hour of electricity. Many farms have fewer than four.
This is lower than deaths from other sources, such as vehicles, transmission lines, windows and cats.
More uncertainty appears to exist about bat deaths. Some farms report a relatively high death rate while others find few fatalities.
But perhaps its most significant observation is that taller turbines with wider blades are no pancea. The potential impact on birds and bats is uncertain, the report stated.
In the past, many blamed the high level of bird deaths at older wind farms, such as Altamont Pass in California on the outdated turbines that spin there.
The study, by in large, should ease the worries of some environmentalists. As wind energy expands in the U.S. and massive killing of wildlife isn’t expected. But that doesn’t mean continued technological efforts to reduce collisions aren’t needed.
This is especially true when considering that most birds killed at wind farms in the United States are smaller songbirds – three-quarters of the total. The most dangerous times of the year are spring and fall, when the birds are migrating. Often they fly at night and above the reach of wind turbines. It is believed they are most vulnerable when they land.
The most at-risk bats are tree-roosting species, such as the Eastern Red Bat and the Hoary Bat. The most dangerous periods are in the late summer and fall, again when migrations occur. But direct collision with a turbine blade isn’t the only danger for a bat. Some likely die from the trauma of suddenly having a spinning blade alter nearby air pressure.
In the past, Altamont Pass in California was often thought of as the killing for birds, in particular predators, such as hawks and golden eagles that hunt there. This was believed due to the older turbines and the large bird populations.
But newer towers aren’t off the hook. Today’s wind turbines stand 260 feet tall with blades that stretch 260 feet in diameter. Older turbines were no more than 80 feet high and blades only 60 feet in diameter.
While these monster turbines spin slower (20 or so revolutions a minute) their span is huge, sweeping more than a acre of sky. In three years, the sweep will expand to 1.5 acres. This broader reach increases blade tip speed to 150 miles a hour or more.
As it turns out, this may be no deliverance for birds and beasts.
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