Birds Bats Bugs Bees and Wind turbines

A tale of the Double Stall.

A lot of my friends get extremely animated about the slaughter of bats and birds by wind turbines.
This Canada Free Press Report indicates that in Spain alone around 6 - 18 million birds and bats get chopped every year.

But compared to the numbers of less fashionable critters that get chopped, the slaughter of the birds is small beer.

So do the bugs matter?

Well, to the wind energy companies it matters greatly (although for all the wrong reasons).

As the bugs get slapped by the rotor they do roughly what they do when they hit your windscreen.
They splat. Having splatted, they stick to the offending aerofoil. This increases what is known as the rugosity (or roughness) of the blade. The rougher the blade, the less effective it is at  taking energy out of the wind. (A bit like the difference on pushing a wood block across the carpet then trying to do the same with it wrapped in sandpaper.)

This rugosity has an astonishing effect on the output and can decrease the output by nearly 50%. It is mooted that this accounts for a problem that the wind industry has kept quiet for about ten years. The problem has become known as the Double Stall.

This graph from HERE shows the effect of the Double Stall phenomena.
So what exactly is the Double Stall? The problem came to light when numerous identical turbines, positioned in equivalently windy locations produced massively different output. (up to 50%). Initially various ideas were mooted for this. Most came down to some form of operator incompetence.

But it looks like the problem is not the operator error. The problem is the layer of bug DNA smeared over the leading edge of the aerofoil. See  This Paper  by Corten and Veldkamp. Also link to Nature report Here

(If the above link to the paper by Corten & Veldkamp is problematic  - try this direct link

Various cleaning methodologies have been investigated but most can only be done in low wind speeds with the thing stopped. Even then, dangling 200 feet up in the air while scraping off dead insects is not for the faint hearted.

The down time can be anything up to three days at a time. For a larger turbines (bigger than 1MW) I suspect it might be considerably longer.

But of course, scraping off the DNA to boost your profits hardly addresses the millions of critters that must get splatted in the name of Green fashionability. But as they are not "pretty" they get ignored. Even by the anti-wind compaigners.

It is just an hypothesis, but it would be interesting to find out the effect IWT's have on the local bug/bee population. After all, most of the time IWT's are spinning idly in low wind, producing little but the murder millions of insects. That must have an effect on bird food supplies and I suspect insect populations. Maybe this is even part of the recent drop in Bee populations?

So next time you lament for a bird like this:

(image from Daily Mirror HERE)

Please remember the billions of insects that met a similar fate. Spare a thought for our ugly bugs, wasps and bees as well as our bats and birds.

They are all just as important to our countryside and environment.

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