Car Alternator as Human Powered Generator

Yes, such an efficient battery. I run my entire home off vinegar cells.

A check on Google finds some people who have experimented with this kind of thing. Basically, you put a belt over the bare rim and drive the alternator off that. Some designs allow the field coil power to be reduced so the alternator is more efficient at light loads.

Some have also had success building windmills that will produce even more power. This one is made of Volvos, wood, magnets, and wire:

They even have a hamster wheel that runs a pair of LEDs :)

Yesterday I was out in far east Mesa where the predominant business is still growing oranges.

I observed a modern two-bladed windmill being used to pump irrigation water.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

have them eat more beans! :))

Rob> Hello All,

If you're going to buy stuff, how about, um, a generator?

Good Luck! Rich

Well, yeah, that's what "battery acid" does. The reaction between the acid (in this case vinegar) and the metal (in this case, iron) releases electrons, or something like that.

I suppose you'd have to use fresh vinegar regularly, and as that other person said, scrape the iron vinegaride off the plates. ;-)

Cheers! Rich

I thought that the beauty of an alternator as opposed to a permanent magnet generator, is that the field voltage is regulated, so it can produce an appropriate voltage at any speed. A 120V DC 10,000 RPM permanent magnet motor will produce 12V at 1000 RPM only - faster will produce higher voltages and slower will produce lower. Since we need to generate about 13.5 to 14.5 VDC to charge batteries, that puts the cyclist to task for riding only at a very specific speed. But using an alternator, a slower cylist will only produce lower current, but still the ideal voltage.

If I am wrong about the theory of alternators, let me know.

Sage

[snip]

You are correct, the field current and rotational speed determine the output capability.

Other posters seem to imply that there's no control mechanism... except for some types of motorcycle alternators, that shunt the output with zeners, they are wrong.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

In the olden days, when cars had generators, they still had regulators, which were just choppers. But the generators didn't put out enough at idle to keep the battery even on float charge. I could see how today's magnet technology could make a better generator, but it seems the consensus is that a car alternator might be the cheapest, but it's about the least efficient thing you could use.

Good Luck! Rich

Here is the basic plan I am following:

This includes a rheostate which I will mount on the bike handlebars, to allow the rider to regulate the voltage. That rheostat in turn regulates a TIP-120 transistor, which in turn regulates *another* TIP-120 transistor, which feeds the field coil of the alternator.

(I asked the above website's owner to email the designer of this little system, but the designer refused to help because he thought that Nepal was a Maoist country. Yes, there's a Maoist insurgency there but I'm not working for them. In fact, they make this work much more difficult because both the State and the insurgents are suspicious that any equipment with capability will be used for their enemy's benefit.)

Why are car alternators less efficient that permanent magnet generators? By how much? Is this a trait of alternators versus generators, or is it simply a matter of design because car alternators are designed to run off of an abundant power source? Where could I get a more efficient alternator? So much to learn.

I am also confused about the relationship of current to voltage in the field coil -- an increase in voltage increases what? The voltage output of the stator coils? An increase in field current increases what? The physical resistance of the alternator and the stator output current? These are my questions and my hunches. Now for more research.

In the meantime, the bicycle is all built and the alternator is mounted. Now I am only waiting for the long belt to drive it. I ordered a segmented belt from Woodworker's Supply, which may work very well for this application.

Sage

Sad...

Well, cost is important, there is energy to spare, and the alternator is designed to deliver around a thousand watts, not a hundred.

There is nothing wrong in principle with alternators, though the large volume of iron to be remagnetized has higher hysteresis losses than if the alternating field is in the internal iron.

A higher field current and voltage give a higher magnetic field. This will mean a higher voltage for a certain speed.

If you want to be more efficient, use a chopper to drive the field coil:

+12 ---- T ---+---+ | | | drive - 3 ^ 3 | | gnd ----------+---+

T is the power transistor: you will pulse it on. Note the freewheel diode (this 'kees the current going' in the field coild then the transistor is off. Without it, you blow the transistor and you do not gain any efficiency.

Interesting to hear how things work out. Keep in mind that what you are making is not a demo. While someone building an excercise cycle may be happy with a demo cycle that delivers 15 watts out with 100 watts excercise, you might want to aim higher.

I'm also curious how your belt drive works out - I assume it is a V-belt. Toothed is better than plain, but a chain or a toothed flat belt may be improvements. Or use a 'poly V belt' - here often used in washers and dryers. Especially dryers use long belts.

I also just read a bit about using a series connected washing machine motor (with windings on rotor and stator) - the poster claiming/guessing that is 12 volt was connected to the stator, the rotor would be abouve

12 volts at speeds below 1000 RPM.

These are all from Euro style washers with horizontal axle and high spin speeds.

Also have a look at

(you are in the US?). The first motor claims to run at 850 RPM at 12 volts while drawing 850 mA. This means the losses at that speed are about 10 watts. Your problem when using this as a generator might be DC resistance though.

Thomas

Sage,

First of all, sorry about some peoples ideas about Nepal. I served with several Ghurkas during my time in Oman and elsewhere, and I can assure anyone willing to listen that the Neaplese are as intelligent as most people, if not more so.

If you have water buffalo available, why not use them as a power source instead of wearing out people pedalling a bicycle going nowhere. It will take an extra step of "gearing up" but it might be an interesting and useful next project.

With regard to the downspouts, by the time you've installed all the waterwheels, pulleys, small generators etc, it strikes me that you'd have a pretty haywire rig. All that water must run somewhere. Is it possible to direct the flow from the downspouts to a holding pond and then use the water in the pond to drive a single large wheel to turn your generator? How's the local supply of bamboo? It makes pretty good pipes and there should be people around you who have a lot of experience in using it to construct just about anything.

Speaking as someone who bears scars inflicted by heavily armed, socialist, peace lovers, I sympathise about the Maoists.

Regards

Cap

I think it's because they have to run in dirt, and crud, and shock, and heat, and vibration, and noise, and NOISE, and keep running for years.

I was thinking it'd be interesting to see if you could rewind one; I don't remember if it was here or some other thread or NG - but ISTR somebody said even rewinding it, although it would help, still falls way short of one designed for efficiency in a living room environment. It has something to do with pole gap spacing or some such Magnetic Black Magick Arcana.

Me, Too!

Borrow somebody's panty hose for the first smoke test. ;-)

Good Luck! Rich

All alternators consume energy in their field windings creating the magnetic lines of flux that must be cut (passed through) by the stator to generate energy. For example, look at that schematic referenced on the web page above. My numbers may be way off, but after you build & run the circut, you can measure and tell us where the energy is going. Let's say 2 Amps flow in the field winding of the alternator to create the required magnetic field. So that's 2A x 12V = 24 watts. That's 24 watts NOT being delivered to your batteries. (Purists - Yes I know that there's energy being lost in the darlington pass transistor, but we're still looking at 2 Amps in a series circuit feed by 12 volts.) If you're getting 100 watts to your load, then your efficiency is 100 watts out/ 124 watts in = 80%. And there's plenty of other losses that aren't factored in here (like IR losses, eddy currents.)

Good questions. My experience fails me. But you can't beat 0 field current for a permanent magnets. Haven't I convinced you alternators are not the most efficient way to go??? Cheap, available, yes. Efficient, not usually. Google for do it your self permanent magnet generators.

You left out the socially redeeming factor of cost. My guess is even a 100% efficient alternator (Impossible, see above) would help gas mileage by a minor amount, so manufacturers aren't even trying. In addition to the factors you list above that are competing factors against efficiency, weight & size probably rank high.

The bicycle powered alternator system I built was from an article in Ham Radio magazine. (Not _a_ Ham Radio magazine, that was _the_ name.) It suggested, and I used with great success, a couple of bicycle chains to loop around the alternator and the rim of the bike tire. Attached to the shaft of the alternator was a 5 speed gear cluster. The chain drive meant you didn't have any pulley belt slippage, at least at the alternator. Surprisingly, black electrical tape wrapped about the rim held up for many hours of operation. Now you may have to use leather or rubber to last longer, but there's so much contact area on the rim that there's really no slippage to speak of to rip up your "rim pad."

OK, now for the "flames." ;^) Unless I missed what the Original Poster eventually said, there's 3 - 75 Amp-hour 12 Volt batteries in this system. Let's see --- that's 75 Amp-hour * 12 V = 900 watt-hours. Times 3 batteries = 2700 watt-hours. If you can produce 100 watts of power from your bike power system, that's 2700 watt-hours / 100 watts = 27 hours of pedalling. Oh, don't forget, there's charging inefficiencies. So it's probably more like 35 hours to fully charge dead batteries. Fortunately, your batteries will & should never be dead, but we're still talking serious hours pedalling. Man, 3 - 75 Amp-hour batteries. I know I'd be dead after pedalling to charge 'em, even to 25%! IIRC, with my bike generator [sic - bike alternator] system I could power a 100 watt load for say 15 minutes.

50 watts, over an hour. 175 watts, expect to pass out in about 2 minutes. It was a steep power curve. I never did an efficiency estimate or measurement on my bike system, so YMMV. Good luck, I honestly think you may need it.

Seriously, please do some power budget calculations. See

How much KWH per day do those radios take? Can that power be replaced by humans each day? Not enough data given to tell.

Thanks, Steve