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Re: bats and wind turbine blades....follow up  David I. Johnson
 Oct 13, 2005 11:40 PDT 

Unfortunately, I do not think that any policy should be made on this
small of a sample size. It certainly does suggest that further study is
necessary though.

At 02:05 PM 10/13/05, you wrote:
The following is an excerpt from
the final research report by Jessica Kerns and Wally Erickson, dated June

Thermal images indicated that bats are attracted to and investigate
both moving and nonmoving blades. Thermal images of bats attempting to
land, or actually landing on stationary blades and turbine masts, suggest
possible curiosity about potential roosts or use for gleaning insects.
Images of bats chasing turbine blades rotating at slow speeds suggest
possible attraction to movement out of curiosity. However, most of the
observed collisions (7 of 8) were between bats and fast-moving (17 rpm)
turbine blades. Thermal imaging observations of bat and insect activity
support the conclusion that fatality occurs primarily on low wind nights,
but when blades are pitched into the wind and powered to rotate, which
may be at or near their maximum speeds of 17 RPM, despite modest or no
power production.

This is potentially valuable information for protecting bats in
Michigan's UP. Since the Bowling Green wind farms maintain their turbines
a constant 16.8 rpm for compatibility with grid transmission, we may be
able to operate wind turbines in the UP at a similar speed with minimal
I believe that if turbines are to be allowed in the UP, especially within
a mile of bat hibernacula, the state should require a study to confirm
the impacts of blade speed and pitch on bat fatalities, and then require
that blades be kept below the threshold for causing significant harm.

Kerns and Erickson's final report is now available at

Daniel Alberts
Lawrence Tech's Wind Energy Delphi
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