# BioLite electricity from a stove



## MishMouse (Jun 12, 2012)

http://biolitestove.com/

One of my fellow co-workers just got one of the camp stove models.
Once it heats up it is able to generate enough electricity to run the fan and charge gadgets via a usb port.

I was wondering if this concept was buildt into a pellet stove would the stove generate enough heat to power the internal workings of the stove.  Thus making the pellet stove able to run without electricity.

Or if this was buildt into a wood stove how much power would it generate.
My thoughts are it works similiar to a eco fan in the way it uses a thermoelectric generator to provide the electricity.


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## Adios Pantalones (Jun 12, 2012)

That thing is sweet. Looks like rocket stove setup, so it should be super efficient as well.

A 5.5 kw fire puts out 4W at 5V.

So consider a 70,000 BTU stove: 70000 BTU= 20.5 KW
So a pellet stove would put out ~15W at 5V.
I think a pellet burner uses like 100-150W, so this would be short

Someone check my assumptions/math please


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## Slow1 (Jun 12, 2012)

I'd be quite interested in hearing how well that stove works out for your co-worker.  I'm really not all that interested in the charging aspect, rather I am interested in how well it works as a wood-burning camp stove.  I don't like that I have to carry fuel with me to burn when I camp in areas that don't allow ground fires - this would likely qualify as a 'stove' instead of a campfire (at least I'd make that argument until confronted).  

Being that the design seems to be a forced-air secondary burn of the smoke it should be fairly efficient and pleasant to cook on as well... but practical experience may be a different thing eh?


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## MishMouse (Jun 12, 2012)

Slow1 said:


> I'd be quite interested in hearing how well that stove works out for your co-worker. I'm really not all that interested in the charging aspect, rather I am interested in how well it works as a wood-burning camp stove. I don't like that I have to carry fuel with me to burn when I camp in areas that don't allow ground fires - this would likely qualify as a 'stove' instead of a campfire (at least I'd make that argument until confronted).
> 
> Being that the design seems to be a forced-air secondary burn of the smoke it should be fairly efficient and pleasant to cook on as well... but practical experience may be a different thing eh?


 
So far he is very pleased with it and told me that this is one of the first products that he used that actaully does what it is advertised.


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## Adios Pantalones (Jun 12, 2012)

Slow1 said:


> I'd be quite interested in hearing how well that stove works out for your co-worker. I'm really not all that interested in the charging aspect, rather I am interested in how well it works as a wood-burning camp stove. I don't like that I have to carry fuel with me to burn when I camp in areas that don't allow ground fires - this would likely qualify as a 'stove' instead of a campfire (at least I'd make that argument until confronted).
> 
> Being that the design seems to be a forced-air secondary burn of the smoke it should be fairly efficient and pleasant to cook on as well... but practical experience may be a different thing eh?


 
I'm surprised at how inexpensive these biolite units are, but if not interested in the power, they will be relatively large compared to some other options.

I am fascinated by efficient fire tech- it truly changes people's lives in third world countries.
You might look into gasifying coffee can stoves etc- should be fun and easy to make and experiment with.

Easy Plans: http://www.instructables.com/id/Woodgas-Can-Stove/

This one has a small battery unit: http://www.woodgas-stove.com/how_to_use_woodgas_stoves.php
I think there are other commercial units as well.


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## Jags (Jun 13, 2012)

The mental math works out about the same as AP's.  To completely run a pellet stove - probably not.  To run a very small fan or slow charge of some gadgets - I could see that.

The sterling engine (eco fan) and the TEG (Thermoelectric generator - this is what is used on the stove) are both very interesting to me.

Do some search on the TEG.  There are units that can be slapped to a stove.  There are basically two designs, one for lower temps and one for higher temps.  They work off of temp differential.


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## MishMouse (Jun 13, 2012)

My co-worker sent me this link on the break down of the BioLite http://zombiehunters.org/forum/viewtopic.php?f=14&t=90760&start=96


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## Jags (Jun 13, 2012)

Did you catch this link:
http://www.kickstarter.com/projects/1203647021/the-powerpot?ref=email


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## Adios Pantalones (Jun 13, 2012)

Jags said:


> Did you catch this link:
> http://www.kickstarter.com/projects/1203647021/the-powerpot?ref=email


I saw that- looks cool. I need mega TEG's for my kiln chimney- maybe with a thermosiphon cooling loop.


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## Jags (Jun 13, 2012)

Man - if you could get and keep the temp differential, you could really get those babies cranking.  Typically they do have a ceiling temp though.


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## Adios Pantalones (Jun 13, 2012)

I wonder if, for larger heat sources, one would be better off using a thermosiphon and micro-hydro generation.


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## Jags (Jun 13, 2012)

That might work, but you would probably need a home run to each TEG or you would have degraded performance of each unit in the loop (if in series).


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## Adios Pantalones (Jun 13, 2012)

I mean- just a closed loop of water pipe that would get heated, the water would thermosiphon, and that would drive a microhydro generator. I'd have to think a lot about pressure issues, relief valves, etc. Recipe for a steam explosion.


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## begreen (Jun 13, 2012)

Adios Pantalones said:


> I wonder if, for larger heat sources, one would be better off using a thermosiphon and micro-hydro generation.


 
why dink around? with the heat your kiln produces go for full steam production. Only problem is that it's intermittent.


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## Jags (Jun 13, 2012)

AP - you create enough waste heat with that thing to go full blown steam power.
The thermosiphon idea would work, but to generate much usable energy I would think that you are getting into professional type pressures (and regulated).  Of course the same could be said about steam generation.


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## Jags (Jun 13, 2012)

The hearthdotcom of steam:
http://www.steamforum.com/

And sorry about the mis-read of your prior post.


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## begreen (Jun 13, 2012)

Back to the OP, there are a few older threads on TEG electrical generation including some products for wood or pellet stoves.

https://www.hearth.com/talk/threads/electricity-generating-heat-engines.74878/
https://www.hearth.com/talk/threads/energy-is-limitless-one-small-example.57867/
https://www.hearth.com/talk/threads/alternative-electric-source-for-blower-fans.73095/


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## Corey (Jun 13, 2012)

Adios Pantalones said:


> ...
> A 5.5 kw fire puts out 4W at 5V.
> 
> So consider a 70,000 BTU stove: 70000 BTU= 20.5 KW
> ...


 
Math looks good, though there is one catch...you say '5.5KW fire puts out 4W @ 5V'  that may not be entirely correct...  a more correct statement may be 'they capture 4W/5V out of a 5.5KW fire'

The kicker here is, they are using only one small TEG because that is all the power they want - not all the power the fire can produce.  A person could pretty easily line a stove with TEGs and make substantially more power.  The main drawbacks would be:

1) pretty expensive watts/dollar
2) best power generation is in a small temp range with a relatively low temp limit...typically 300-350F (though this would be easier to hold with a pellet stove vs wood
3) you may still need external power to get the process going...run things until the stove heats up and makes its own power.


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## begreen (Sep 19, 2012)

This material might put the TEG devices on steroids:

http://www.nature.com/news/out-of-disorder-comes-electricty-1.11445


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## blujacket (Sep 20, 2012)

Super Cedars would be great fuel for that BioLite.


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## semipro (Sep 20, 2012)

Slow1 said:


> I'd be quite interested in hearing how well that stove works out for your co-worker. I'm really not all that interested in the charging aspect, rather I am interested in how well it works as a wood-burning camp stove. I don't like that I have to carry fuel with me to burn when I camp in areas that don't allow ground fires - this would likely qualify as a 'stove' instead of a campfire (at least I'd make that argument until confronted).
> 
> Being that the design seems to be a forced-air secondary burn of the smoke it should be fairly efficient and pleasant to cook on as well... but practical experience may be a different thing eh?


 
I have one of these and have been impressed.  http://www.zzstove.com/sierra.html


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## Thomas Anderson (Sep 25, 2012)

I've been thinking about experimenting with TEGs and Stirling engines as soon as I have the time.  The problem with TEGs is they're not terribly efficient.  The problem with Stirling engines is you need a really hot fire.  You can buy TEGs online, but they're expensive for their output.  Stirling engines are hard to come by pre-built other than as toy models or massive beasts.  And building a Stirling engine from scratch will probably require forging parts from steel, which isn't exactly a weekend project.  For reliability, TEGs have no moving parts, although Stirling engines at least have less moving parts than internal combustion engines.  

Unless I can find a commercially available Stirling engine in a size that is amenable to mating to a wood stove, I'll probably concentrate my first experiments on an array of TEGs.  Attached to an MPPT charge controller, the TEGs can be easily connected in a series string or parallel arrays of series strings summing to 48V, 60V, or whatever the CC can handle.  They can either be mounted to the body of the stove (probably the top) or else concentric rings around the base of the chimney.  Overall output may be paltry compared to, say, solar panels of the same cost; however, efficiency can be improved if waste heat is captured for home heating, and the low efficiency of electricity production will be balanced by the on-demand nature of the source.  I.e. solar is dependent on the sun shining whereas a wood-fired TEG can produce whenever you need it, day and night.


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## woodgeek (Sep 25, 2012)

Agree completely about the TEGs on a woodstove....the design challenge is getting the coolth to the other side of the TEG, passively if possible.


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## Jags (Sep 25, 2012)

I have looked into TEGs and the difficulty is in maintaining the temp differential from side to side for long duration tricity production.  To the point that external cooling was almost a requirement if used long term on a wood stove body.  At that point the TEGs are basically a tricity neutral component.  Requiring darn near as much energy to keep them operational as they produce.  Short term is a different story.


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## woodgeek (Sep 25, 2012)

Agree that fans would have a bit too much parasitics.  I still think it should be possible with heat pipes to carry the heat away from the stove body (a shielded stove would be good) to the TEG and a bigazz heatsink to the ambient air on the cool side.  Design is non-trivial (steady state), but doable IMO. Mebbe I will try...


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## Jags (Sep 25, 2012)

I was actually looking into a liquid cooling system.  Thermosiphon was the only viable solution that I found.  If using any kind of pump it went to the energy neutral state as explained above.


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## Thomas Anderson (Sep 25, 2012)

I would use liquid cooling, with the water coming from the bottom of my solar thermal tank and going into the top my solar thermal tank.  This way the waste heat would also contribute to the heat and hot water for my house.  I'd use water blocks like these: http://customthermoelectric.com/Water_blocks.html

If you could produce 300 on the hot side and cool with 30 water, you could generate 19.1 W with one of these TEGs: http://customthermoelectric.com/powergen/pdf/1261G-7L31-24CX1_spec_sht.pdf

String 18 of them together (perhaps 3 strings of 6) for 343.8 W.  Circulate the water with a 10 W El Sid pump: http://shop.solardirect.com/product_info.php?products_id=363

That's 8.25 kWh/day generated if burning for 24 hours.  My off-grid house uses around 6-8 kWh/day, so this would provide all the electricity I need.  Total cost would be around $3,000 for the TEGs, water blocks, pump, and charge controller.  Not including the cost of the stove itself.

That's under optimal conditions.  More than likely, I could not keep the fire at 300 constantly, not all the TEGs would have optimal position to receive that heat, and if I used only one circulator pump, the last TEG would have some pretty hot water on the cold side.  So maybe throw in a few more pumps and expect the net energy to be more like 5-7 kWh/day for an investment of like $3,500.  That would still be worthwhile in my situation, being off-grid.  A cluster of snowy but calm days in the middle of January would be a perfect time for such a solution to kick in.  It probably wouldn't make much sense for someone grid-connected though.


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## Jags (Sep 25, 2012)

Thomas Anderson said:


> It probably wouldn't make much sense for someone grid-connected though.


 
That is ultimately the same conclusion that I came up with.


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## stoveguy2esw (Oct 8, 2012)

i'd been playing with the idea of a teg assisted off grid pellet stove, havent been able to make the math work to gain enough energy from the fuel to power the system without a battery which would be needed anyway for startup and initial heat production. i figure if it was single auger single fan with a positve pressure air induction and a pulling chimney to draft the exhaust it could be done to the point where it would be able to extend the battery life for quite a while, but i cant figure out a way to make it self contained. just cant make enough power to resupply the battery at the same rate as it drains.

who knows, the technology is attainable and its an exciting idea for me to play with but the initial stove would have to be dirt floor primitive to attain equality between power use and generation


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## Thomas Anderson (Oct 9, 2012)

stoveguy2esw said:


> i'd been playing with the idea of a teg assisted off grid pellet stove, havent been able to make the math work to gain enough energy from the fuel to power the system without a battery which would be needed anyway for startup and initial heat production. i figure if it was single auger single fan with a positve pressure air induction and a pulling chimney to draft the exhaust it could be done to the point where it would be able to extend the battery life for quite a while, but i cant figure out a way to make it self contained. just cant make enough power to resupply the battery at the same rate as it drains.
> 
> who knows, the technology is attainable and its an exciting idea for me to play with but the initial stove would have to be dirt floor primitive to attain equality between power use and generation


 
You could put enough TEGs together to make the power, but the question is how much are you willing to spend, and can you find enough hot surface area on a pellet stove to put them? It definitely gets more expensive to get net zero energy the more energy it takes to keep the fire going. If you can get the fuel for cheap, then maybe it makes sense to spend on the TEGs and run your pellet stove a lot and make it self-sufficient. But if you're not going to run your pellet stove 24/7 anyway, the payback is going to be a long time coming. Better bet would be to just beef up your batteries and charge them from the grid to keep you going for awhile even without grid power. Or hook up some solar panels. For the amount you'd spend on TEGs, you could get 1kW or more of solar.

Renewable on-demand (instead of at the whim of the elements, like with solar and wind) energy production is very elusive. TEGs are an expensive solution; doable but impractical until $/watt comes down. Alternatives include wood gas generation to power a normal gasoline internal combustion engine or else external combustion engines like Stirling engines or steam engines. There are no commercial solutions available (on a residential scale). I've seen Stirling engines hinted at coming to market and then mysteriously disappear. So if you want to go down this path, as I do, and you're not trying to build a power generating station on the megawatt scale (with the budget to match), then the current options include only those of the do-it-yourself style. I'm always eager to hear success stories.


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## stoveguy2esw (Oct 9, 2012)

well, im kinda looking at it as a "can i do it"  project. so far though its just an "ink on paper" situation. i'd like to try it  for real but i just havent had the time or the approval of the boss to run with it yet


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## Dune (Oct 10, 2012)

One thing to consider with TEGs and wood stoves is to use and OAK and cool the cold sides of the TEGs with the outside air. 
Another thing is MIT is working on a massive TEG breakthrough, with the potential to change from 4% efficiency to possibly 20%, which, if the costs were comparable, would be a game changer.


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