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0 pointsgrecy6y ago0 comments

> Won't this reduce the thermal output of your stove quite significantly

I'm going to chime in and say that I think it will be insignificant. I don't know for sure, but I really doubt you could do much to cool the stove. When it's cold in the Yukon, I'm literally stuffing in ~8-10 big logs every ~12 hours.

It's not at all uncommon for the base of the chimney to be glowing red. Obviously not ideal, but it happens.

When it's past -40, I set my alarm for 1am to get up and put in more wood. The stove would just last the night if I didn't, but it's a pain to light it again from scratch every morning, so it's easier to just keep it going.

All of that is to say the wood stove is absolutely pumping out heat 24x7 from ~September to ~April.

If I already have batteries and charge controllers and inverters, why not wire in a handful of TECs.. even if I only get a combined total of 100W, that's worth having over those months the sun is not up for long, and not strong.

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bradknowles6y ago

Glowing red?

As an Amateur Blacksmith (and lifetime member of the Blacksmiths Guild of the Potomac), I was taught that color meant you were hitting 500-600 degrees Fahrenheit, which is usually about the lowest temperature you normally want to have when working on a piece of metal.

If you’re hitting those kinds of temperatures, I’d think you would need some substantial work done on the thermo electric components to keep them from melting, much less being able to operate.

Or am I missing something obvious here?

arghwhat6y ago

> Even if I only get a combined total of 100W

Quoting Wikipedia:

> The typical efficiency of TEGs is around 5–8%

To get 100W out at 5% efficiency, you'd need to put 2kW in, 1.9kW of which has to be moved away to keep the cold side cold with perfect cooling.

Realistically speaking, the cooling will not be that efficient, and will probably cost you a bit more energy. I'd ballpark that to 2.5kW lost total for 100W of charging.

That's pretty significant.

starpilot6y ago

Thermoelectrics have terrible efficiency, that's why they're hardly used despite the fact that waste heat is literally everywhere. Your computer, your phone, your car engine, everywhere there is energy to be recovered. In theory, any heat-based powerplant could use them, but instead they all boil water and drive steam through turbines, which is much more efficient.

scottlocklin6y ago

Thermoelectrics you can order from a catalog have real world efficiency ~6%, which is on the order of what a well engineered practical Sterling engine will do for converting heat to electricity without any moving parts to wear out, exotic working fluids/seals, or ... complete lack of supply chain for any of the above. If this new material pans out it could be on the order of 24% efficient, which would be preposterously better than any heat engine you can fit in an Alaska cabin.

I hate the computer programmer weeb meme of suggesting a Sterling engine for every damn thing. None of you jokers suggesting this has ever built a real world heat engine, let alone attempted to engineer an efficient one from scratch, which is what you'd be doing in the case of log cabin Sterling engines. There are excellent reasons they're not commonly used, and less thermodynamically efficient external combustion engines (like steam) are used. The problems with making them work efficiently are immense.

trhway6y ago

>would be preposterously better than any heat engine you can fit in an Alaska cabin.

Or a cabin on Mars. Solar and nuclear would be used on Mars. For nuclear - with 20% efficiency i think it would allow to use simple RTG (Matt Damon style) instead of full blown nuclear reactor with working fluids, pumps, turbines, etc.

grecyOP6y ago

> Thermoelectrics have terrible efficiency

I agree with what you're saying, but the point is that the woodstove is running 24x7 in the winter, and the solar is very pool. Whatever energy I can get from the TECs is an order of magnitude more than I'll be making without them - i.e. zero.

lgats6y ago

I think you could build a panel of TECs and just set it up near your wood stove. The radient hear from the stove would be enough to keep the TECs at high temp on one side and room temp (maybe with some heatsink) on the other side.

You could adjust the distance from the stove to keep things within operating range.

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