Why do a grill block when you could put excess air to good use?

[Sven7]

The device adds more drag to the car than the power it makes. Much like a classmate of mine who designed an electric car with giant wind turbines on the back to supplement battery power. Neat idea, not applicable to our universe.

[HighMPG]

Why not just add some solar panels on the roof.

[ConnClark]

Originally Posted by tortoise

A grill block giving the same reduction of internal flow as the turbine will reduce power required more than the turbine would have produced. Unless the turbine is greater than 100% efficient. Give up on this one.

If the drag reduction is due to reduction of internal flow then any form of blockage inside the internal flow intake that reduces the flow the same amount will reduce the drag the same amount. The case is we have a required mass of air that must flow internally to cool the engine. The dynamic pressure of the air is not needed for the cooling. So if we convert some of that dynamic pressure into energy we are not preventing it from cooling the engine. Turbine efficiency never enters the equation. The argument that since your generating something its going to create more drag due to thermodynamics doesn't apply here. Your just utilizing a resource more effectively.


If you don't buy that in the 80's nasa put wing tip turbines on a piper aircraft and showed you could generate electricity while reducing drag.

[slowmover]

At what cruise speed? (All in all I like the thread, thanks).

[CigaR007]

Aren't there vortices being generated on wing tips (due to lift) ? If so, it would beneficial to tap into that unused energy for power generation. A very precise application, in my opinion, which would be hard to mimic on a car.

[HighMPG]

Originally Posted by slowmover

At what cruise speed? (All in all I like the thread, thanks).

faster then a car can go usually.lol
I am only kidding and I thought of this before also, just invent a better one that creates less drag and has very low inertia like 3" in diameter for a car but I like solar panels better and it's better use of the cars roof and it works even when you aren't moving. + for hybrid cars.

[ConnClark]

Originally Posted by slowmover

At what cruise speed? (All in all I like the thread, thanks).

If I remember correctly when I read a report on it a few years ago it was something like 140 knots. But they did say that this test was by no means optimized, it was just the cheapest way to prove the concept. I'm sure it would work at lower speeds too.

Originally Posted by CigaR007

Aren't there vortices being generated on wing tips (due to lift) ? If so, it would beneficial to tap into that unused energy for power generation. A very precise application, in my opinion, which would be hard to mimic on a car.

Actually most cars generate a pair of vortices from the c pillar

see page 9 here

http://www.grandmarq.net/blaze/Blaze...of%20Autos.pdf

[Ryland]

I can't find it right now, but the last time someone asked this question I found a calculator on the energy that you can get out of the wind at a given speed and for 55mph I think you could get about 200 watts out of a turbine that was about 2 feet across, so how do they get around 100 watts out of a little 6" turbine? they are going over 85mph! just like it's going to take signifagently more energy to go 85mph, you can also get more energy out of the wind when you are going that speed! just like you can get 3/4 more out of a 12mph wind then you can out of 11mph wind.
So a turbine like that might be able to run your LED running lights, but not much else unless you are going above the speed limit.

[Frank Lee]

The "perpetual motion" thing pops up with some regularity.

Sure there is already internal drag through the engine compartment. I think a prop driven device would only add to it.

[euromodder]

Originally Posted by ConnClark

If you don't buy that in the 80's nasa put wing tip turbines on a piper aircraft and showed you could generate electricity while reducing drag.

The basic squarish wingtip design of the day created vortices and was so inefficient that the wingtip pods bettered it so much, it still reduced drag despite the turbines.

Wingtip Vortex Turbine Investigation for Vortex Energy Recovery

The inefficiency was already built into the baseline vehicle.
This experiment won back some of that energy.

It's better to avoid the inefficiency to start with, rather than try to recover some of the wasted energy later.