Wood-fired camp stove that generates electricity

[Analog Kid]

Just ran across this thing I had first noticed several years ago which still intrigues me.
It's a small wood-fired camp stove that, in addition to letting you cook with the fire, generates electricity through a USB port.

I like the idea of the wood-fired stove part of the product alone; you can use twigs and whatnot to fuel it. What I'm not sure about is just how much electricity this thing can generate. What do y'all think about that? How much juice could you expect to get out of this, assuming it uses a thermocouple for generation? I guess if it's enough to recharge a cell phone then that could be worth the price ($200, not cheap).

https://www.bioliteenergy.com/products/campstove-2-plus

[cunningfellow]

I have one.  I think it would take between 5 and 10 hours to recharge a modern phone.

It is useful as a fan assisted fire that recharges its own battery.

[Psi]

Peltier's work pretty well to turn fire into electrical energy. Less because they are efficient and more because fires are friggen hot

A large fire could generate quite a large amount of power, but that doesn't mean the product was engineered to be the best it could be. Likely engineered to maximize profits.

Could probably DIY something that generates way more power with an array of peltier's and some PC water cooling parts.

[jpanhalt]

The Voyagers are powered by TEG's.  Digikey lists some with currents of a few amperes.

[Psi]

Digikey lists some with currents of a few amperes.

A standard peltier module works pretty well in reverse. No idea about the long term reliability through.
You obviously have to make sure you don't exceed the temp delta, but they work fine in reverse.

[coppercone2]

there is some ancient picture of a soviet? wood, or perhaps fuel stove that used many 'thermocouples' to power a radio.

https://swling.com/blog/2020/05/soviet-era-kerosene-lamp-generator-gives-new-meaning-to-lets-fire-up-the-radio/

fuel

[Ian.M]

http://www.douglas-self.com/MUSEUM/POWER/thermoelectric/thermoelectric.htm

[coppercone2]

need kerosene thermoelectric radio digital mode mod

[Analog Kid]

I'm still interested in this device, the wood-fired camp stove, but really only for its use as a camp stove, not as a source of power for charging stuff. For that, solar might be much better.

I'm wondering what it would take to DIY such a thing: the stove itself shouldn't be that hard, maybe using stainless steel sheet for the body and wire for the grill parts.

The electrical side would consist of
1) a thermocouple or Peltier junction or whatever to generate the electricity,
2) a simple battery w/charge controller and
3) a small fan

The stove might be able to operate without the fan, so that might just be icing on the cake.

Anyone care to suggest what it might take to build such a thing? This would just be for my own amusement and use, not for production.

I'm guessing it might involve some welding, although if it could be done instead by riveting, so much the better. (Might not last as long but would be far simpler to build.)

[cunningfellow]

Analog Kid,  I have pulled mine apart to look at it a long time ago. The only thing that was not obvious (peltier, hot heatsink cold heatsink) was the SHAPE of the hot heatsink that goes into the flame.

It was a copper round that had a slot cut in it.  This slot was out of the flame area and the whole copper part was slopped up.

This looks to me like it was engineered to limit the rate of heat going into the peltier.

[Gazz_292]

Wonder how many smoke alarms i'd need to take apart to turn one of these into an RTG 

[Analog Kid]

Wonder how many smoke alarms i'd need to take apart to turn one of these into an RTG 

A micro-nuke, eh? Fabricate your own fuel rods, moderator rods. Micro-turbine.
Don't think any amount of americium will power such a thing, though. Pity.

[Psi]

The hardest part of building a DIY one is probably regulating the temperature delta.
Because the intensity of a fire is not static is rises and falls as you add fuel and it burns down.

You need a temp delta close to the max but never over it. You need something close to the fire to get the heat and bring it to your TEK and then something to get the heat from the TEK and pull that away and dump it into a cooler area.

One way to do this might be liquid cooling, but you don't want to melt the tubes.
You'd probably want a bypass loop so if there's too much delta it can regulate how much goes through the tek.

Another way to do it might be with heat pipes, since they are copper they can handle the heat better than liquid cooling tubes.  But you have to figure out how to regulate the heat if the delta gets to hot.

[coppercone2]

for this application you can use a special high temperature peltier too.

Look through a list of modules and you will see some of them have a 400C temp rating. I suspect that using the low max temperature one (i.e. bismuth or indium solder) can make the design more difficult then it has to be, because you need to spread heat more and over-temp is easier to reach.

They are often sold as TEG not TEC. (generator type)
high end example
https://www.digikey.com/en/products/detail/thermoelectric-conversion-systems-ltd/MONTEG-4X4/13684286

https://www.tegmart.com/thermoelectric-modules/


Not having to design the entire system so the temperature gradient has to be between low and ambient is pretty liberating.
https://www.tegmart.com/thermoelectric-modules/22w-teg-module

[Psi]

22-Watt TEG Module at 7V sounds pretty nice for phone charging.

[coppercone2]

yeah I wonder if you can modify some sort of stove exhaust to use it. Finding the optimal thing would take some experimenting but it should work



I think alot of inventors are stuck on TEC which have strict requirements, compared to the rather wide specification of TEG, which allow you to 'half ass' things, instead of needing a 'electronics grade' thermal system. 60C or whatever limit is really easy to breach when there is fire involved. That is practically cold. Its mostly a limitation due the solder type used. Thats it, all these experiments are being held back by low melting point solder, pretty much. (their still bismuth telluride! its just the packaging, you would proboly get better performance if you can get one of the other junction types though, but I think thats NASA stuff)

[Psi]

yeah I wonder if you can modify some sort of stove exhaust to use it. Finding the optimal thing would take some experimenting but it should work

Maybe a heat pipe/pipes from the fire area onto a heatsink and then liquid cooling from that to bring heat to the TEG and then a second liquid cooling loop from the TEG to a cooler heatsink area. Then you can regulate temp by the speed of the two pumps.

(Note i'm more thinking about how to build something with off the shelf parts than i'm thinking how best to design a system)

[coppercone2]

IDK that is kinda taking away the appeal of wood stove alaska technology, but I think you can get high temp heat pipes.

I think it would need to be alot more then 20W to justify pumps. Something with power outputs compared to one of those small power stations might be appealing though, I think they start at 300W

I don't have a wood stove, so I don't have a feel for how it would be implemented, or what the temperatures you find in it, etc. I noticed some people really love them though (especially if they get pallets)


A unique problem might be the gasses, IDK if they are corrosive. or soot

[coppercone2]

they have some variation on the website
https://www.tegmart.com/thermoelectric-generators/wood-stove-air-cooled-45w-teg


you just put it on the stove lol. it sounds like they need a supervisor circuit to disconnect bad loads that cause t he fan to stop spinning. I suspect the main flaw is the 45W, the problem is gonna be people getting mad when their 200W laptops don't wanna charge and stuff


they got a water cooling one
https://www.tegmart.com/thermoelectric-generators/wood-stove-water-cooled-100w-teg


I thought it would have to be like a heat exchanger that you put on the exhaust pipe

[cunningfellow]

That is the hot end that pokes into he flame.

The cold end is a normal ally heatsink that is in the path the fan draws cold air past to blow into the fire.

I can't find a long enough screwdriver right now to pull the main body apart.

[cunningfellow]

I think if you are getting up to the 300W mark you are into the territory of those newzeland stirling generators that are washing machine sized (and car priced)

[coppercone2]

their 100w unit is not that big, but it probobly can't handle the high end laptop the rich boss in the cabin would have lol


230w thinkpad

[paulca]

Wonder how many smoke alarms i'd need to take apart to turn one of these into an RTG 

A micro-nuke, eh? Fabricate your own fuel rods, moderator rods. Micro-turbine.
Don't think any amount of americium will power such a thing, though. Pity.

The radioactive boy scout story.

In an RTG there are no rods.  It's all just decay heat.
https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator

[nali]

Wonder how many smoke alarms i'd need to take apart to turn one of these into an RTG 

A micro-nuke, eh? Fabricate your own fuel rods, moderator rods. Micro-turbine.
Don't think any amount of americium will power such a thing, though. Pity.

The Soviets did that for powering remote lighthouses, trouble is some folks decided to pilfer them for scrap or free heating...

https://englishrussia.com/2009/01/06/abandoned-russian-polar-nuclear-lighthouses/

[Analog Kid]

Keep in mind that this li'l stove is small and light enough to be carried in a backpack.
Someone wrote something above about a system with 2 pumps; I don't think so.