DIY Stovetop 100w TEG build, design input wanted

[natdak]

TEGs should have a relatively stable temperature across their surface - if you leave a portion of it "open" rather than pressed up against a heatsink/metal plate, then over time you'll find it fails due to thermal expansion and it's very brittle nature.

Clamping is preferred, again because thermal expansion means the TEG and item it's attached to will need to move relative to each other, otherwise the TEG will crack over time. I have seen some say that thermal epoxy worked fine for them, but I don't know enough about their application or yours to say either way. Use some bolts with some shoulder washers, tighten them evenly so the pressure is constant across the TEG(s), and use thermal paste to improve heat transfer to/from the TEG surface.

If you can't protect the wires from the hot side, you can use crimped connections. Make sure they are tight enough to exclude oxygen, otherwise they will fail over time with the increased temperature - even inside insulation.

-Adam

Adam, those are good tips.
So what kind of thickness on the baseplate? Aluminium?
Will a thicker baseplate make the TEGs cooler and loose energy?
So we are clear, I was meaning that the TEGs would hang off on the hot side, but the cool side would be covered and only about 10% off.
But I guess a baseplate would solve that issue completely?
I found out that I can fit 10 56x56mm (216w) modules on a single cooking plate!! so, depending on the price they come back with, it wont be an issue for my design. 5 modules (108w) is closer to the size of a powerpot. But then why can a powerpot only make 10w??

https://www.amazon.com/NIUXX-Cookware-Charging-Backpacking-Equipment/dp/B07TNJTH3X/ref=sr_1_3?keywords=powerpot&qid=1663188540&sr=8-3

 

[natdak]

Sure, but you don't need the pump to cool the modules and generate energy.
My rig is meant to heat the room.

Are you meaning that you dont need the pump to cool the modules? It would be good if I didnt need it for energy production..
My questions about the pressure still remain.

 

[natdak]

I am starting to warm up to your water cooled suggestion as it turns out that some of the units you linked me to are reasonably priced and of course amazon was good enough to suggest a nice 4.3 watt submersible water pump. And I have to wonder which would provide better cooling, a 5 watt water cooler or a 20 watt dual fan blowing over a tower heat sink. Air is easier but water might provide faster cooling and that is important because the Peltier module is thin and even if you get the unit to cool well, it has to be able to keep the cool side cool at the place of reaction or the module doesn't work. I am going to wind up with something that looks like a rig from ghost busters if I keep this up. Thanks again.

The air cooled ones are really noisy, right? Since its meant to be a passive system in the middle of the house and sanity is golden, then I want it silent! Or close to silent...
You are going to need to watch not to get your modules too hot, they are quite low temperature. You could still make a device and upgrade modules in the future! Sorry about your dog.

 

[fblevins1]

The air cooled ones are really noisy, right? Since its meant to be a passive system in the middle of the house and sanity is golden, then I want it silent! Or close to silent...
You are going to need to watch not to get your modules too hot, they are quite low temperature. You could still make a device and upgrade modules in the future! Sorry about your dog.

At the moment I am using two PC cooling fans, since they were abundant and free as were the heat sinks. Basically once I get the initial testing done and can see that the technology is viable for emergency survival applications, I will play with other cooling options.

 

[natdak]

These are the prices of the TEGs from Thermonamic.

Getting 10 pieces of 40x40mm seems the cheapest option per watt. Each module is 9.8w, they are graphite coated so no need for thermal grease, and notice that 10 pieces include shipping!
The rest of the options are getting kind of expensive. Ive now asked for the price of the 35mm in case its cheaper.
And Ive asked what 30 pieces of 40x40mm will cost. If 3 people chipped together it could be even cheaper.

 

[MattiFin]

Adam, those are good tips.
So what kind of thickness on the baseplate? Aluminium?
Will a thicker baseplate make the TEGs cooler and loose energy?
So we are clear, I was meaning that the TEGs would hang off on the hot side, but the cool side would be covered and only about 10% off.
But I guess a baseplate would solve that issue completely?
I found out that I can fit 10 56x56mm (216w) modules on a single cooking plate!! so, depending on the price they come back with, it wont be an issue for my design. 5 modules (108w) is closer to the size of a powerpot. But then why can a powerpot only make 10w??

https://www.amazon.com/NIUXX-Cookware-Charging-Backpacking-Equipment/dp/B07TNJTH3X/ref=sr_1_3?keywords=powerpot&qid=1663188540&sr=8-3

216W peltier cooler generates maybe 5 to 10 watts of electricity if you push it to limit.
Cool side cooling is not trivial, you would need to keep theegu coolside temperature rise at minimum level while dissipating 2kW of power without wasting your precisious electricity on powerfull fan.

proper thermoelectric generators(compared to peltier coolers) have much higher temperature tolerance allowing bigger temperature delta(better efficiency) and higher cold side temperature(easier cooling)

get real TE-Generators and biggest, baddest cold side heat sink you can imagine. For example performance CPU coolers one for each TEG module. After that you need to fiqure out suitable hot-side ”coupling” or standoff distance to couple maximum heat energy from stove top without overheating the peltier.
more regulated heat source like gas flame would be easier to drive the TEG closer to optimum without worrying of frying it.

 

[natdak]

216W peltier cooler generates maybe 5 to 10 watts of electricity if you push it to limit.
Cool side cooling is not trivial, you would need to keep theegu coolside temperature rise at minimum level while dissipating 2kW of power without wasting your precisious electricity on powerfull fan.

proper thermoelectric generators(compared to peltier coolers) have much higher temperature tolerance allowing bigger temperature delta(better efficiency) and higher cold side temperature(easier cooling)

get real TE-Generators and biggest, baddest cold side heat sink you can imagine. For example performance CPU coolers one for each TEG module. After that you need to fiqure out suitable hot-side ”coupling” or standoff distance to couple maximum heat energy from stove top without overheating the peltier.
more regulated heat source like gas flame would be easier to drive the TEG closer to optimum without worrying of frying it.

Hi Matt,
The TEGs Im looking at are proper high temp modules designed for power generation. They have a working temp of up to 330c and 400c intermittently.
http://www.thermonamic.com/pro_view.asp?id=801 Check out the specification sheets if youre interested. There are some nice graphs.
Too hot has worried me a little bit. If I cram the stove full, which I never do, I can get one of the plates to glow red, indicating 460c or so. But I have 3 different plates that get different temperatures so it should be fine in my situation. I want to make it easily movable and removable for that reason.
Do you know about water cooled systems? Thats what Im designing for. Im guessing that its just a question of how big of a radiator you have?

 

[MattiFin]

Hi Matt,
The TEGs Im looking at are proper high temp modules designed for power generation. They have a working temp of up to 330c and 400c intermittently.
http://www.thermonamic.com/pro_view.asp?id=801 Check out the specification sheets if youre interested. There are some nice graphs.
Too hot has worried me a little bit. If I cram the stove full, which I never do, I can get one of the plates to glow red, indicating 460c or so. But I have 3 different plates that get different temperatures so it should be fine in my situation. I want to make it easily movable and removable for that reason.
Do you know about water cooled systems? Thats what Im designing for. Im guessing that its just a question of how big of a radiator you have?

OK, those look much better than cooling peltiers someone else was talking about.
Red glow is 600c or above. I'd implement some sort of overheating warning buzzer and possibly emergency cooling fan of some sorts?

I have played around with the water cooled overclocked CPU's and turbocharged car engine air-to-water intercoolers a bit so I might have some ideas what works and what doesn't work.
Maybe small 12v powered pump and one or more "peltier water cooling block"s from aliexpress. BIG central heating radiator to cool the water. Or largest truck radiator you can cheaply find.

 

[natdak]

OK, those look much better than cooling peltiers someone else was talking about.
Red glow is 600c or above. I'd implement some sort of overheating warning buzzer and possibly emergency cooling fan of some sorts?

I have played around with the water cooled overclocked CPU's and turbocharged car engine air-to-water intercoolers a bit so I might have some ideas what works and what doesn't work.
Maybe small 12v powered pump and one or more "peltier water cooling block"s from aliexpress. BIG central heating radiator to cool the water. Or largest truck radiator you can cheaply find.

Good ideas with the overheating warning. I have access to 2 car radiators, do you think that will do the job?

 

[natdak]

This is more prices from Thermonamic. If 5 or 10 people got together then the ready-built 100w generator is a very good option indeed! It would probably be cheapest in the end and hassle free. Otherwise getting 3 people together to get 10 40x40mm modules each is another good option, especially as it includes shipping. Anybody interested?

 

[Ted leaf]

Hi folks, tripped over this discussion while looking at a DIY teg.
I live on a canal narrow boat.
Small wood burner is basically on 24/7/365,even in middle of 40°+ heat waves, just shut right down when not needed for cooking.
I use a dewalt battery chainsaw for wooding, all my wood is free, what I would like to do is set up a teg to re-charged the saws 18/54 volt 9ah power pack,canals often in valleys, with trees, so today, 3/2/23 we will get about 3 hours of decent light, not enough to keep batteries properly topped up, so we have to run a small petrol generator 2-3 times a week to keep them healthy.
Water supply for cooling is obviously not a problem, but would prefer no fans or pumps, stove is withing a foot of the Hull, so I was thinking of big fat copper pipes full of water or lead and connecting cool side of teg direct to inside of 6mm steel hull, or possibly down to 10mm bottom plate..
Also need to run a dumb parasitic radiator to move heat about 20 foot to further end of 40 ft cabin, stove can't take a back boiler, so a simple small square bathroom radiator clamped to back of burner is nice and cheap/simple, 2 very vital things to bear in mind, I have almost zero budget and a simple fit n forget setup, going to use convection/gravity for transferring hot water, works perfectly well on many boats.
A quick look on ebay UK shows I can get 12volt/400 watt/26 amp peltier plates for about £13 each,TEC1-12726.
Any ideas, advice etc gratefully accepted.

 

[stienman]

This paper suggests you can expect about 0.5W of power for a 75C difference using a 40mmx40mm TEC: https://ieeexplore.ieee.org/abstrac...CgAffPkn-BUPoHp_2cu0RxZqAei0F6x5IA4S0aKEzCxXB

But it does indicate that the more expensive TEGs don't perform much better than the cheaper TECs at the low temperature differentials you're going to have.

If your dewalt packs total 18v 9AH, then you need 162WH three times a week, and the stove is hot 24 hours a day, then each module, properly used - meaning that the voltage output and current are set to maximize total power output - will generate 12WH a day. You need to generate 162WH every 2-3 days, so five modules might be sufficient. If you run your fire less, or the movement of the cool/heat is sluggish, etc, then it will be worse. If your temperature difference is 200C then it'll be better.

Note that I have no first hand experience with using TECs as generators, and I'm gathering this information through research papers. Keep looking around for further confirmation of the above numbers, don't rely on this post alone.