BioLite electricity from a stove

Post in 'The Green Room' started by MishMouse, Jun 12, 2012.

  1. MishMouse

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    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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  2. Adios Pantalones

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    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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  3. Slow1

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    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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  4. MishMouse

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    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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  5. Adios Pantalones

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    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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  6. Jags

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    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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  7. MishMouse

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  8. Jags

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  9. Adios Pantalones

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  10. Jags

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    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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  11. Adios Pantalones

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

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    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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  13. Adios Pantalones

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    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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  14. begreen

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    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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  15. Jags

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    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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  16. Jags

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  17. begreen

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  18. Corey

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    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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  19. begreen

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  20. blujacket

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    Super Cedars would be great fuel for that BioLite.
     
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  21. semipro

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    I have one of these and have been impressed. http://www.zzstove.com/sierra.html
    [​IMG]
     
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  22. Thomas Anderson

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    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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  23. woodgeek

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    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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  24. Jags

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    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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  25. woodgeek

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    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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