It's like the question I came up with when a pre-teen many yrs ago.. "Why don't they just hook up a generator on a wheel and drag it behind the electric car to keep it charged, daddy?"...
"Harry K" wrote in
*** Free account sponsored by SecureIX.com *** *** Encrypt your Internet usage with a free VPN account from
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.
Harry K
All based on the Conservation of Energy law.
Energy in must equal energy out plus energy stored, and energy can not be created or destroyed.
Ok.....
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.
Harry K
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 the car).
Harry K
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.
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 wind resistance...correct? 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 amount..... So perhaps we will never agree on this one but hey....it's been an interesting debate!....Ross.... :>)
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
I have seen those studies a couple times back when. IIRC leaving the gate up does improve mileage but not enough to amount to much.
Harry K
---------------------------------------------------------------------
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.
Harry K
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.. ;)
*** Free account sponsored by SecureIX.com *** *** Encrypt your Internet usage with a free VPN account from
I thought of doing something like that.
I believe my variation would work.
---------------------------------------------------------------------
True...there would be little gain....I guess I should have said that originally....Ross
They could build electric roads. Every car would have a battery and a coil under the car. Coils would be buried under all major roads. As you drive along the road would charge the vehicle.
VERY COSTLY to implement, but no exhaust.
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.
Harry K
And at a great loss in energy time you add up all the losses involved at the generating plant, the transmission lines, driving the car, etc.
Using electricity to charge batteries, then converting it to driving power is a lossy proposition. Those proposing hybrids or even all electric overlook the economics of the process. Unless gasoline goes really outragious, IMO the internal combustion engine will remain the most economical way to power a car.
Note that the current rebates and tax write offs for hybrids are disguising one major problem. Cost originally becomes competitive with standard cars but then comes time to replace the batteries...
Harry K
I think fan usage is getting turned around. Some seem to be talking about a driven fan used to drive cooling air through the radiator and others are talking about a fan being driven by air to drive a generator.
Regardless both fans take energy from the engine.
As a kid I had this idea of making an electric driven car and putting generators on the wheels to create the electricity. Then that spoil sport, Issac Newton went and ruined the whole idea!!
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.