**ANY** energy that you would generate by wind on a vehicle would cost 100%
plus the inneficiencies of the devices used, no matter WHERE in the stream
it's placed. There is NO free lunch. Energy generation = drag.
Why use a wind generator? Put a generator on the front wheels
and an electric motor on the back wheels. Put two generators
on the front wheels and you will go twice as fast. Just make
sure all the parts are bolted on real good so that nothing is
dragging to slow you down. :) :)
Fans should not heat up an engine whether they are hooked to a generator or
not when placed behind a grill...Of course, you wouldn't want to block the
radiator but are we not speaking of a hybrid here?....
The air going through the grill is that intended to go through the
radiator. Block that and you are cutting down on cooling capacity.
Now take a hybrid running on the electric only. No extra fans, you get
x mpg. Now intall the fans running generators you get x-y mpg (due to
increased drag) which will be way more than whatever gain you get from
the electricity you generate. It's basic physics - no free lunch.
No matter where you put the fans, as someone else said, it causes drag.
If it didn't the fans wouldn't turn.
So you are saying that wind already blocked by a vehicle and run through a
fan would cause more wind resistance than it would be worth?
I am talking about air that is blowing into the engine compartment and is
ALREADY a waste of energy since it hits the engine and firewall and then the
ground and using it to generate power. Not trying to create energy or break
the laws of Physics....Ross
But you are trying to 'create engery..." That wind is blowing
_through_ the engine compartment. You seem to understand that. The
fact that it already is causing some drag is immaterial. Adding the
fan adds _more_ drag. It still comes down to no free lunch. Any time
one thinks they have found a free lunch it should be a warning to stop
and try to spot the fallacy.
It is somewhat the same as adding a turbo charger. On first glance it
looks like you are getting a free lunch since you are using waste heat
to boost HP. It doesn't. What it does is compress the intake air
which allows you to burn more fuel and it is that extra fuel that
increases the HP. An energy audit going across the turbo _only_ would
show a net energy loss until you get to the 'adds more fuel' point.
On the surface that is correct....
Now...if you were to place a tube that would redirect the air coming into
the grill area and port it behind the car there would be an improvement in
So now if you place a fan in that tube connected to a small generator it
very well may have the same, or close to it, wind resistance of the original
setup with wind just hitting the firewall and then the ground. That is where
I have been going with this. Reduce drag, the increase it at the same
So perhaps we will never agree on this one but hey....it's been an
interesting debate!....Ross.... :>)
Interesting idea with the tube. I don't know if it would be possible
to engineer one that would decrease the drag but assuming you can...
You are still stuck with the lousy energy conversion factor of
somewhere around 30-40% from generator-storage-use. Thus I suspect you
would still be on the losing end of the proposition.
On Sat, 25 Mar 2006 20:10:38 -0500, Ross Mac wrote:
How about the P51's radiator? The radiator was in a scoop on the bottom
of the airframe with a ramp exhausting the heated air rearward. The
heated air provided more than enough thrust to offset the drag of the
cross-section of the scoop.
Good point...I'm an old P51 fan....used to go see them yearly at the
Watsonville Fly In....They flew support back in WWII and will always be
remembered by the fantastic roar of their engines.......not to mention their
great contribution to the war effort....hope all is well. Keith....Ross
OOOPSS. I should have pointed out that the wind entering the engine
compartment is not reduced to zero when it hits the fire wall, it is
deflected downward with much of it's original velocity (in respect to
I think there may be even more things involved. For some or maybe many
vehicles, the designer may in trying for the least air resistance, size
the opening for the air intake just large enough so to pass the
necessary amount of air to do it's necessary job of cooling. A fan
would slow down the air movement.
What seems obvious is not always true. There are nets being marketed to
replace the rear gate of pickup trucks thereby reducing drag. Several
years ago a test was run at a Lockheed wind tunnel. They measured
amount of drag with a tail gate in place and none at all. It was found
that there was less drag with the tail gate. With the gate in place,
the air in the pickup box formed a sort of bubble and directed the flow
over the gate. With the gate gone, turbulence created a vacuum behind
the cab creating additional drag.
Hey, that is quite interesting...do you have a link with some data on that
one? I know some years ago there WERE a whole bunch of nets showing up on
pickups and I always wondered if the numbers were there. I put a tonneau
cover on my pickup and figured it would make a difference. Well, I drove
that Dodge Ram for months both ways, with and without the cover, and my
experience was the same...mileage still sucked to put it lightly!
Enjoyed your posts on this thread.....take care, Ross
True. Probably similar to putting a fan in the front of a car.
However, the bottom line is the nets are only good at removing weight
from your wallet. Those slotted gates are useful if you are frequently
hooking up a 5th wheel.
Hmm... You say that fans inside the grill would lower the cooling effect for
radiaters and then go on to say why you couldn't put "windmills" on the
external side of an electric-car... Why do you "avoid the obvious?..."
With most of the batteries removed (less need for so many with wind-power),
there'd be LOTS of room under the hood of an electric-car for fans and no
need for a radiator at all...
Not that I can't see why it wouldn't work, but..
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Errrm. What part of cooling the internal combustion engine are you
missing? We are discussing hybrids.
I didn't say you can't put fans outside the car. I said that it
doesn't matter at all -where- you put them, you will get less energy
out of the fans than the vehicle puts into pushing those fans.
You point about removing the batteries is, to put it rudely, ludicrous.
Using that theory, you could mount a fan facing a fan with the second
one driving a generator, connect them up and get perpetual motion, nay,
even produce more electricity than you put into the system.
To repeat. A fan will not run just sitting there. It has to have air
flowing through it. The car makes it turn by pushing the fans through
the air. That takes energy. That takes more energy than the fan(s)
would produce. Basic physics. It does not matter -where- those fans
are positioned it still takes energy to push them.
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