Hi All,

I think the issue of bats and wind energy has been discussed a bit on this forum, but I saw this on the interweb and though it might be of interest...

http://www.planningresource.co.uk/appea ... tect-bats/

I am not proposing to initiate a discussion on the impacts of turbines on bats (unless someone else wants to!) but was more interested on the technicalities of this, as wind energy is not something I am particularly familiar with (but hopefully will be geting to grips with at some point soon). Basically, the planning inspector allowed the turbine to be erected as long as it was immobilised during bat foraging periods (basically dusk to dawn between spring and early autumn). Has anyone else had similar conditions imposed, or does anyone think that technically this is possible / practical to do, possibly via a timeswitch, light-sensitive switch or similar? My immediate thought was if the blades were immobilised and a summer storm blew up one night, would the resistance result in the wind blowing the pole / turbine over and damaging the house?

Cheers!

I'm sure there must be some research somewhere that shows that bats don't fly as much in bad weather. They certainly don't come out here in very wet conditions.

Summer evenings are usually characterised by very low wind conditions in any case, so not having the turbine move during these times probably results in zero lost energy. I'd want the planning conditions to allow the turbine to run in high winds though to reduce the likelihood of damage.

Any research done about whether wind turbines pose a threat to bats?

It's not obvious that they would. Birds might not be able to see the fast moving blades but might be very "visible" to a bat since that's sonar and there would be Doppler effect shifts to the frequency of the echos.

No, I meant research into under what conditions bats judge the weather is too poor to try to catch insects.

that's totally batty!!
Reckon the bats have more sense than the PO , see M&Ps comment on Doppler!
Has anyone even checked that there are bats about in sufficient numbers to justify such a restriction?
and if so, what species?
Sounds well dodgy to me!!
Greenwash?
Hogwash?
Mike.

I'll see if the bat researchers I know are able to shed any light on it.

They did some work locally on bat flight routes when a new road went in.

The result was that some types of bats flew high enough for the road not to bother them & others flew low so they did tunnels & that some could be guided over by the use of obstacles / lights if I remember right.

I wonder if they have the right type of bat in mind for the risk?

Justme

Has anybody here ever hit a bat? (I never have; have bounced plenty of birds off the windshield)

I understand; they observed some bats flying low over the road. But was that in the presence of absence of a vehicle?

Bats often fly pretty fast, so echo patterns as made by a moving object not more than say twice their max speed ought to be familiar to them. One bat flying toward another and a bat flying perpendicular to the way a car is moving not much different in terms of Doppler shift. Remember a car is a large reflecting surface compared to what bats are usually "looking" at. It's the angular dimension that counts for the size of the echo. If the bat can hear the reflection of something as small as a moth at ten feet ought to be able hear something the size of a car at hundreds.

Good points! Although I was initially interested in the technical aspects of this, I have done a bit of internet reading in the meantime... I think bats can only 'see' about 10-20m in front of them due to the limitations of echolocation, and can only 'see' in front of them (about 40degree arc, I think) when they recieve an echo back (so can't 'see' when sending out a signal, which happens about 10-20 times a second, and increasing when they are zero-ing in on a moth) - so probably wouldn't 'see' a car a longer distance away, but would do when it got closer. I think this would explain why I have had a couple of near misses in my car with bats, but never hit one (yet!), despite there probably being a lot more bats actually flying around country roadside hedges at night than there are birds in the day. M&P, you are right I think to mention the Doppler shift - I think bats are good at using this to assess fluttering moth wings.

I reckon that there would be most risk to bats when the blades spin faster, but as you say, at fast wind speeds, bats would seem to be less likely to be out and about - doesn't seem to be a lot of conclusive evidence for this, but it seems that moths aren't flying too much when it is windy, so it is not energy efficient for bats to be out hunting, rather than bats not being able to fly.

Cheers
Adam

(to help people understand)

The distance calculation based upon the speed of sound in air (somewhat over 300 m/sec) so at ten chirps per seccond you get about 15 m since the sound has to go both ways. But the big assumption there is that the bat is only hearing the echos from the latest chirp and that wouldn't be the case. From the latest chirp the bat is hearing echos returning at various times (depending on how far the reflecting object) but would also be hearing returing echos from previous chirps (from more distant objects) and all these echos would be overlapping. Obviously bats and other sonar using animals have brains that can sort these signals out and interpret them in ways far exceeding a human operator of sonar gear.

Surely there's a low tech answer to this?

Has anyone here who has a WT flying ever found dead bats under/near it?

If so how many, how often, and at what time of the year?

I'm particularly interested as we have many bats living in our barns and we intend to put up a WT this year.

Debbie

We have a 6kW wind turbine that has been operating since Mar 07 and we have never found any dead bats or birds in the vicinity.

Thanks Janco, thought not

Amazing what a low tech approach to a subject can do

I'm afraid that chirps per second leave me a bit cold and yes ... I do know what a Doppler shift is

Debbie