use the air we drive through

[Patrick]

If you only need to go downwind, you could build yourself one of these:

http://www.youtube.com/watch?v=aDzWh...e=mfu_in_order

[NachtRitter]

That might really annoy the folks waiting behind you at the light... The guy otter have a manual boost to get the machine going! (pedals or Flintstone slots or some such)

[ShadeTreeMech]

I have to disagree with many people here about this.

The common philosophy is to go alternatorless will save buckets of energy. My question is, if an alternator is drawing no power, how much gas does it consume? The answer is very little in comparison to the gas usage of the vehicle needing to move down the road. If a 100 amp alternator is drawing full power, how much gas does it consume?

@100 amps output, we could assume 50% efficiency, which make 200 amps effective draw from the crank.
750 watts=55.6 amps @13.5 volts
13.5 volts (roughly the voltage of a running alternator) times 200 amps = 2700 watts
2700 watts divided by 750 watts (or 746 for those who are particular) = 3.6 hp.

At cruise the Scanguage calculates I am creating 50 hp from the gas I burn. So 7.2 percent of gas burned at cruise goes to the alternator ASSUMING the battery is dead and requires a recharge, which would require all the alternator has to give. However, generally speaking, with a topped off battery and a healthy alternator, it would be a fraction of that draw. Lets say half that, I'm sure it's less, but half makes easy math.

7.2 hp required divided in half = 3.6% required from my 50 hp output at cruise. At cruise I can easily exceed 30 mpg, so we'll stick with 30 mpg. So if I delete the alternator and ignore any possible side effects from a lower voltage requiring more amperage to components (higher amps = more heat) I'll save 3.6% of 30 mpg which equals 1.08 mpg and a nearly dead battery after a healthy drive.

Where's the benefit when I can allow the alternator to efficiently create electricity on the fly and hardly if ever open the hood to recharge a nearly flat battery?

[3-Wheeler]

Originally Posted by ShadeTreeMech

I have to disagree with many people here about this.

The common philosophy is to go alternatorless will save buckets of energy. My question is, if an alternator is drawing no power, how much gas does it consume? The answer is very little in comparison to the gas usage of the vehicle needing to move down the road. If a 100 amp alternator is drawing full power, how much gas does it consume?

@100 amps output, we could assume 50% efficiency, which make 200 amps effective draw from the crank.
750 watts=55.6 amps @13.5 volts
13.5 volts (roughly the voltage of a running alternator) times 200 amps = 2700 watts
2700 watts divided by 750 watts (or 746 for those who are particular) = 3.6 hp.

At cruise the Scanguage calculates I am creating 50 hp from the gas I burn. So 7.2 percent of gas burned at cruise goes to the alternator ASSUMING the battery is dead and requires a recharge, which would require all the alternator has to give. However, generally speaking, with a topped off battery and a healthy alternator, it would be a fraction of that draw. Lets say half that, I'm sure it's less, but half makes easy math.

7.2 hp required divided in half = 3.6% required from my 50 hp output at cruise. At cruise I can easily exceed 30 mpg, so we'll stick with 30 mpg. So if I delete the alternator and ignore any possible side effects from a lower voltage requiring more amperage to components (higher amps = more heat) I'll save 3.6% of 30 mpg which equals 1.08 mpg and a nearly dead battery after a healthy drive.

Where's the benefit when I can allow the alternator to efficiently create electricity on the fly and hardly if ever open the hood to recharge a nearly flat battery?

Hi ShadeTree,

I like what you said above, but I do question the 50 hp at cruise. Of course this does depend on what speed you are going.

Cycle magazine used to use a third wheel to measure various factors such as acceleration, braking, hp at 60 and so on.

Back then the motorcycles of the day used to use something like 6 hp to go 60 mph. Of course a motorcycle has less frontal area and less weight, but a much higher Cd.

Based on this, your car should use something around 20 hp to go sixty. That 50 number sounds too high if you are really going 60 mph at the time.

EDIT: If your driving the van, well, then maybe the 50 hp might be accurate.

Originally Posted by ShadeTreeMech

Where's the benefit when I can allow the alternator to efficiently create electricity on the fly and hardly if ever open the hood to recharge a nearly flat battery?

As fuel becomes more scarce, I believe the 3% increase in fuel mileage will become more important to all of us. And I still like your analysis.

Jim.

[user removed]

Smokey Yunick modified his Daytona car when he found that the under hood pressure was making the fuel injection system go super rich. He added two relief flaps in the floorboards that allowed the high pressure air to escape the engine compartment.

Good for an additional 20 MPH on the Daytona Beach qualifying. Qualifying in 1957 was a max speed run down the beach with the fastest car getting pole position.

This was before fuel injection was illegal.

regards
Mech

[KamperBob]

Wind generators are not efficient. Only a fraction of the kinetic energy of wind can be captured mechanically. Converting to electricity is lossy: alternators and wires heat up. Storing energy electrically is lossy: batteries leak due to internal resistance. Far better to forgo the weight, expense and complexity and focus on reducing drag. That will pay dividends ALWAYS and the return on investment increases with speed!

I installed a digital amp meter on the battery of my truck. Cranking the engine over saturates the draw above 200A for a second or two. The initial (peak) recharge rate is around 50A initially. That drops quickly and exponentially to 10A within a minute and 1A (steady state) within an hour. When you integrate the area under the curve the total energy to recharge the battery after a start is low. Parasitic power to do the deed is high fruit. Pick it last IMHO once your Cd is under 0.2 for example.

Cheers
KB

[talldudenumber5]

so squash using mini wind generators to produce electricity sounds like, well not to be discouraged that easily i will research using the numbers you guys gave me and see if wind is usable numerically and if it can be combined with solar to ease my mind.

[gone-ot]

...anything you "hang" out in the breeze is gonna effectively become an "air-brake" because the lowest air resistance is to have NOTHING hanging in the air.

[Ryland]

I used to have a tachometer on my car that was also an hour meter, I made note of the odometer reading at time of install and a few times a year check to see what my average speed was, turns out it was about 28mph, after I bought my electric car and started using that for 90% of my shorter trips my average went up to 32mph.
I know that there are figures for how much energy is in a given area of wind at a given speed but I couldn't the specs that I have once seen, I did however do some quick math from wind turbine out puts at 25mph and figured you get about 10-12 watts per square foot of rotor area, the ECU for my car uses around 60 watts, then add to that the fuel pump, radio, lights and you need closer to 250 watts or more.

[redyaris]

I don't think drilling an exta hole is a good plan, however if you already have an opening for cooling air that goes through the radiator you could use any energy left in the radiator exit flow to drive a mini air tubine then duct the exit air from the mini turbine to a low pressure area it might work. The experament is well worth a try. If nothing else you will find out what doesn't work. The process will teach you a whole lot of other stuff that may become useful in some other experament.