[HN Gopher] Thermoelectric Stoves vs. Solar Panels
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Thermoelectric Stoves vs. Solar Panels
Author : MaurizioPz
Score : 16 points
Date : 2020-05-29 11:09 UTC (11 hours ago)
(HTM) web link (www.lowtechmagazine.com)
(TXT) w3m dump (www.lowtechmagazine.com)
| Animats wrote:
| _2.5 kg soft pine wood per hour ... average power output of 4.2
| watts_
|
| That's 1.68wh/kg of wood.
|
| Pine has a stored energy of about 15 million BTU/Cord (2380
| lb)[1], or 4,396Kwh / 1080 kg, or 4000 wh/kg of wood. 0.04%
| efficiency.
|
| That's terrible by the standards of 19th century steam engines,
| let alone anything newer. It might be a way to get enough power
| to charge a cell phone from a stove used for other purposes. But
| burning wood just to make electric power this way is going to
| need a lot of forest for very little energy.
|
| Note that the article has drawings, but not pictures, of a vacuum
| and scooter being powered with a thermoelectric unit. They
| probably can't do that.
|
| Thermoelectric systems are often used to power heating controls,
| where little power is required. Some bigger ones can power
| heating fans as a backup. The U.S. Army has a portable heater
| with a fan powered this way.
|
| [1] https://www.engineeringtoolbox.com/wood-combustion-heat-
| d_37...
| makomk wrote:
| Huge losses at every stage, I guess. A good chunk of the heat
| is going to go right up the chimney, then most of the heat that
| doesn't escape is going to directly heat the room the stove is
| in without going through the thermoelectric elements, and then
| only a tiny fraction of the tiny fraction that passes through
| them is going to get converted to electricity.
|
| What might be better is something more like a steam engine,
| except without the complicated maintenance and operation
| requirements and the annoying tendency to explode if not
| carefully maintained. Sadly no-one seems to have been able to
| design such a device.
| neltnerb wrote:
| I just want to comment that the author for this one is a
| fantastic writer. At each section I was wondering, "wait, why
| wouldn't you..." and it was consistently literally the next
| section.
|
| Very impressive ability to predict a reader's interpretation of
| what they're saying.
|
| But back to the article -- totally makes sense to me, as a
| materials scientist with a smidge of chemical engineering, for
| places that already use a wood stove for heating. I can't really
| imagine people redesigning gas stoves and obviously electric
| stoves are a non-starter. Though a gas boiler for central HVAC
| could probably generate a little bit.
|
| Getting say 100W out of a boiler in your basement seems like a
| pretty minor increase, but I suppose it does add up over time
| since themoelectric modules are practically indestructible as
| long as you don't exceed the temperature limits. I liked the idea
| of retrofitting places that already use wood stoves to also heat
| water a lot though. A replacement for an existing wood heating
| system makes a lot more sense if you're off the grid already
| (which in my observation is often true even for US homes with
| wood heating).
|
| But I love the idea of a subsidized (or unsubsidized if it's that
| easy) retrofit if it brings people enough power to charge their
| phone and some lights and such to get access to communication
| services.
| [deleted]
| makomk wrote:
| The trouble with this approach is that the thermoelectric modules
| are expensive and don't generate much power compared to solar.
| Also, whilst the fact that they can theoretically generate power
| regardless of the time of day or the weather is nice, you're
| probably not going to want to run your stove all day and produce
| twenty times as much heat as electricity in the middle of a
| baking hot summer.
| chewbacha wrote:
| I think the flaw here is that historically, we have quickly
| stripped the land for firewood: https://www.history.com/news/the-
| firewood-shortage-that-help...
|
| While it might be more efficient now, it's still a slightly more
| locally finite than the sun is.
|
| In addition, operating a wood stove is still a manual process
| that needs to be tended to constantly, making the solar panel
| much easier to operate, and likely much safer as there is no
| deliberate heat source in a solar array.
| joshdance wrote:
| Pellet stoves are almost 100% automatic. Pellets can be
| produced from junk wood, and if we really wanted more wood, we
| could plant and harvest the forests.
| close04 wrote:
| Wood has the slight disadvantage that it grows slower than it
| burns. Wood stoves still need active input for the "supply
| chain", you have to deal with some additional complexity,
| maintenance, and extra safety concerns.
|
| A solar panel on the other hand is passive, with no
| maintenance, or safety concerns.
| biomcgary wrote:
| Unfortunately, most pellet stoves depend on electricity for
| the fan and controller and stop if the power goes out.
|
| Gravity fed pellet stoves exist but have problems with
| consistency (and avoiding backdraft fires).
|
| I've thought about building a pellet stove with an integrated
| Stirling engine generator, but it's a bigger project than I
| have time for. It should be more efficient than
| thermoelectric.
| [deleted]
| ekr wrote:
| Funnily enough, just the other day I was thinking of a wood gas
| generator. It would be interesting to see an efficiency
| comparison, as the wood gas generator also gives out a lot of
| waste heat. The internal combustion engine is itself not more
| than 25% efficient so you won't get great efficiency there
| either, if you add up the losses from generating the wood gas.
|
| But it should still be much better than these thermoelectric
| generators.
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