BioLite electricity from a stove

[Jags]

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.

 

[Thomas Anderson]

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.

 

[Jags]

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

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

 

[stoveguy2esw]

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

 

[Thomas Anderson]

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.

 

[stoveguy2esw]

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

 

[Dune]

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.