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# Slipstream Power Generation

Post-hoc net fuel efficiency boost
 (+5) [vote for, against]

Place little windmills by the sides of highways, where they would be powered by the slipstreams of passing vehicles. In addition to generating electricity, they could be used to measure the speed of traffic, taking into account ambient wind conditions.

If nothing else, they'd be fun to watch on long trips.

 — ytk, Mar 29 2011

These turbines thrive in turbulent air http://www.aerotect...om/documentary.html
[Klaatu, Mar 30 2011]

The Umbrellas http://en.wikipedia...apan-USA.2C_1984-91
[rcarty, Mar 30 2011]

http://www.mywindpo...ay-wind-turbine.jpg [2 fries shy of a happy meal, Mar 31 2011]

Turbulence
 — pocmloc, Mar 29 2011

Would this slow the vehicles, ever so slightly? Or would it recover energy which otherwise would only have warmed the atmosphere ever so slightly?
 — mouseposture, Mar 29 2011

The slipstream behind a vehicle is created by air rushing to fill in the empty space behind the vehicle as it moves. So it wouldn't slow the vehicles at all, because the only windmills that would turn are ones that have already passed. The energy recovered would essentially be part of the energy required to move the air out of the path of the vehicle in the first place.
 — ytk, Mar 30 2011

//air rushing to fill in the empty space behind the vehicle as it moves// So, this would impede (marginally) the movement of air to fill that void? Wouldn't that make the partial vacuum behind the vehicle ever so slightly less partial (more nearly complete)? Increasing drag?
 — mouseposture, Mar 30 2011

These would increase drag but most of the energy would be taken from movement that would otherwise have been wasted.
 — Voice, Mar 30 2011

I meant, in turbulent air, the blades of wind turbines tend to stall, meaning they are remarkably inefficient. Hence all those feelgood house-roof-mounted turbines sitting doing nothing much most of the time.
 — pocmloc, Mar 30 2011

I've seen this before but vertical. Gimme a sec.
<later>
I can't find the link I was looking for, which was for rows of red vertical windmills in some tunnel in Japan, but this one is pretty cool too. [link]
 — 2 fries shy of a happy meal, Mar 31 2011

 [Voice] OK so, in effect, a sort of gasoline tax. [+]

Edit: no, wait. You could put these in places where drivers brake, and the energy captured by the windmills would be energy which would otherwise only have heated the brakes. The only drivers subject to the "gasoline tax" would be those who didn't brake where they were supposed to.
 — mouseposture, Mar 31 2011

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