ok this might be a stupid question, but could you make the whole exhaust a peltier? by the way a much better way of doing one off pieces and getting WAAAAY better accuracy is to make a wax piece, put it in the sand that has a binder mixed into it. compress the sand, with something as simple as a stick, bake the mold to remove the wax and harden the binder in the sand. pour your aluminum in. aka the “lost wax” method. also its good to see that it was done outside, fumes off of molten metal can be quite nasty.

/ex-iron molder

Umm… free air aluminum casting? Maybe I’m missing something but doesn’t this require an oxygen free environment?

Couldn’t you just strap the thing to a wider part of the exhaust system, like the muffler? That should be relatively flat enough to make good contact on such a small surface as the Peltier, and still plenty hot.

Not that I get the idea here anyway. Pulling 1 volt out of the heat hardly seems worth it, could probably do better spinning a little turbine in the tip of the pipe.

Doesn’t the oxygen sensor after the catalytic converter require it be heated to 600F? Leeching heat may ruin his emissions quality or cause spurious sensor faults.

I agree about the turbine in the exhaust, it’d probably be a more efficient way of generating electricity as long as it didn’t constrict exhaust flow enough to affect engine performance.

And short of styrofoam this is how things have been cast in sand for centuries.

He is simply doing things the way every foundry has been doing it forever. Although the Styrofoam is a bad idea, it’s contaminating the metal and possibly causing gas pockets in the metal casting.

Metallurgy 090 stuff here. I can build you a forge for $20.00 in junkyard crap.

I would think that the added weight would negate the voltage gained vs just using a high-output alternator.

However, good idea, and nice execution.

when making the casting, I’d also make sure there were run-off pads. just pockets that would fill up first with the impurities and porosity. In forge type casting like what he’s doing its not really all that necessary for them to be there. But when you’re using injection molding, it’s a must. Worked in an aluminum/magnesium plant for 2 years. fyi for all the tards out there, NEVER mix hot molten metal with water. Even if you’re cooling down the casting. A large hunk of aluminum like that could stay gelatinous in the center for up to 10mins at least. I’ve saw 10 pound slugs of explode and almost kill a man because a water line broke open on it. if water is trapped in molten aluminum it can expand into steam to be at least 10x the original size, and magnesium can instantly explode and flash back at you. Dangerous stuff, just take the proper steps for safety and you’ll keep all your fingers and eyes.

Just the energy needed to cast the aluminum heat sink is going to wildly exceed the energy derived from the peltier.

Lost foam casting is a pretty neat process. It’s being increasingly used for things like engine blocks and other complicated high-precision parts. It works better if you coat the foam with a thin coat of plaster before packing it in sand. There’s not really any contamination — the metal is so hot it quickly drives off the foam.

As for his furnace set up, dear god. It doesn’t take much to build a decent one.

HAHA why put a turbine at the end of the pipe when you could put one attached to the exhaust manifold, inthe car world we call that a turbo!!! BOOST! haha who needs 1v extra power when you have 80 extra horsepower

@ Alan The advantage is after the input energy no additional energy is needed for these devices to produce energy in motor vehicle applications. Unlike the a conventional alternator, that adds a load to the engine, a peltier generator use energy that normally dissipated to the air, as the engine goes about it’s prime purpose of moving the vehicle. electrical load. Will a person, lacking deep pockets be afford to build a good peltier generator in their home shop? Probably not, but in this case it’s personal recreation. Most likely using less energy than other recreational activities.

@vince. idk(about temp. requirements) but he’s really insulating the exhaust, so it wont get cooler.
this would go alot better with a much thinner heatsink, he is only pulling upto 1v because of that massive hunk of aluminum. copper would transfer the heat better, and the aluminum being used on the cool side to dissipate heat faster.
a much more efficient method would be to have copper (or aluminum) (or any metal that wouldnt melt really), formed to be flat on one side, and hugging the exhaust pipe on the other, about 1 inch thick, so you have a flat mounting surface for the peltier, cutting out the additional weight and the extra distance the heat has to travel to reach the peltier.

Those of you interested in melting metal:
http://www.backyardmetalcasting.com/forums/
http://www.abymc.com/forum/

The reason the casts are so rough is he isn’t using green sand, he’s just using straight sand. Green sand is fine sand mixed with either water or oil bound clay to hold its shape and give smoother castings.
Also depending on the source of the aluminum there could be mass impurities. It’s really best to cast from ingots rather than directly from scrap.
It takes 20-32 aluminum cans to make one pound of metal, excluding losses to dross. 20 if they’re all from beer cans, 32 if its from lighter weight soda cans. If you’re going to cast from light gauge scrap it’s best to get a pool of metal going and add the scrap to that to limit the exposure to oxygen, otherwise you’ll get mad amounts of dross.
And as others have said you can make a charcoal foundary for well under $10 if you already have a leaf blower or other high volume air source. Propane ones aren’t that much more expensive if you build your own burners.
Also unless he laps the exhaust mounting block the heat transfer is going to be abyssmal.

Check out http://www.backyardmetalcasting.com/ for some indepth discussion and lots of pictures.

Dont forget that though it’s only 1v in this case (and that’s fairly low in comparison with whats possible), TEGs are fairly high current devices. It might only be 1v, but it could well be 1A too, and they can be stuck in series and/or parallel to make any combination you like. Just horrifically ineffient (4%ish). But if it’s wasted heat that’s extra for nothing (assuming your pumping losses don’t increase due to more dense gas in the exhaust system).

Enjoy your alziemers disease later in life

@Barry99705

what kind of hard drives are you using? Last time I checked the platters were metal, platinum plated to be more specific.

@ not me, There is no concrete link between aluminum and alzheimers disease. Yes alzheimers patients have elevated aluminum in their brains but no one has proven that it got there and caused the alzheimers it could very well be due to the disease.
In a healthy person the aluminum atom is too big to pass through the blood-brain barrier, let alone an aluminum ion.
Besides the amount of aluminum vapor cause by hobby casting that would be absorbed by a person would be so small compared to other environmental sources ie; deoderant, pill filler, paint, cooking utensils &ca.

PS: Teflon pans don’t hurt you either.

and there is a unlimited supply of scrap aluminum….check out places like automotive repair shops (old pistons, warped cylinder heads, seal carriers and so on), glass shops, the 2 pane windows are housed in a aluminum frame, they usually give the old ones away if they are not taking it in as scrap for money.

here is another idea i just had, if you had a big enough peltier, could you put it on your radiator?

I tried this years ago. This is not an easy project and will require a heck of a lot more than installation of a heat recovery system. You need to greatly reduce the electrical consumption of your vehicle to make this worthwhile. LED conversion for all lights would be the easiest. There have been a number of studies and a ton of research in industry has gone into this exact application for peltier devices. I feel that this is worthwhile however the physics are a bit disheartening. The surface area in terms of consumer-grade peltier elements that is required to drive a typical car is impressive to say the least. After I had already bought a whole slew of peltier elements I ran the numbers. If memory serves the area required was measured in square meters. Not reassuring.

Now, for all the braindead morons who are shitting on this guy saying that this has no application; an automotive alternator consumes a massive amount of energy. 10 – 15% on a typical car. …more if it’s a small, efficient car. The engine will rev much more freely and your vehicle will consume less fuel if the alternator is eliminated. Today manufacturers are scrambling for fuel savings that amount to less than 1 mpg. Elimination of the alternator amounts to much more than this. There is huge incentive to eliminate the alternator entirely.

Volts do not equal power. 1 volt could provide enough power to run a city if you had a lot of amps behind it. Practically yes, this might be difficult to accomplish however theoretically it’s possible. I don’t see why you guys are bitching about how 1 volt is not significant. I mean, James called you guys out on the series connection thing earlier but he shouldn’t have had to. That is amazingly basic electrical theory.

Magnets on any rotating equipment is simply creating a generator. That is not free energy. A joule of energy will cost you at least as much in gasoline as a joule from the alternator.

First of all, the exhaust absolutely cannot sustain a peltier element. It’s a hateful environment and although it seems good at first you won’t be able to get it to work. Scavenging waste heat from the cooling system is much, much better. Your peltiers will live a much longer, happier life and will thank you for it. You should be able to achieve at least an 80C temperature differential across the peltier, which is much healthier.

Funny enough, cooling the exhaust is actually a bad thing, even on a naturally aspirated engine.

As for my experiment it ended in complete failure. I got my ass handed to me by the laws of physics. Oh well. My alternator still ended up being a fixture on the garage floor. My car’s electrical system is now solar powered. It works well and has been for nearly 2 years.