I know it won't be a massive amount of power, but given it will be 24/7 for about 6 months of winter when the wood stove runs, I think it will be a useful amount.
Does anyone know where I can buy TECs that will handle extremely high temperatures like this?
All the ones I see say they're rated at about a max temp delta of ~67C-72C
You'd get much better result by making a small steam plant with the same setup: boil water on stove, drive plant (turbine or piston), condense outside, repeat.
However, if you really want to do this with TECs, stack them to lower the per-unit temperature differential, or distribute the heat energy over a larger area and run them in parallel.
It got beat out by subsidized Chinese-produced PV panels (SES was forced into bankruptcy).
I ended up consulting with leather plant for their hot water needs via solar thermal. At least that is still viable.
Amazing how China came along at the time it did. The hardball politics aimed against US solar startups since Carter has been a fascinating tale with little mainstream coverage.
(A homemade setup would not be very efficient regardless of technology chosen, so I'm ignoring complexities of elaborate high-performance boilers.)
I think it'd certainly be fun to play with. Some bits of warning - most TECs are physically quite fragile. Not in the sense that you need to be super careful when handling them with your hands, but that heat stresses can totally wreck them. Do NOT hard mount both sides (hot and cold) to different materials - the differential thermal expansion on the two sides has a potentially of ripping your TEC apart. You may be able to get away with a hard mount (such as solder) on one surface, and some sort of thermal transfer material on the other.
Also warning, your hot side is hot enough to start doing weird things with normal solders, which might be the bigger limiting factor.
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.
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?
> 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.
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.
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.
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.
You could adjust the distance from the stove to keep things within operating range.
Yes. You want to have the "cold" side indoors where the heat is going anyway. You might think it's all going outside in the end, but we dont want to create a new path for it to get there.
BTW a sterling engine running a generator seems like a good idea in this case.
Wouldn't a home made Sterling Engine be easier and cheaper? Then use the motion to power a small generator.
But like others commented you may just end up cooling your stove. The Yukon can get pretty cool.
Maybe an old washer motor, a prop to generate power from wind? Or solar in the summer when light is ample.
Sounds cool... I'm always interested in off-the-grid living arrangements.
Many people up North have solar setups and are off grid, usually with older lead-acid battery setups which work just fine.
Solar is great in the summer when the sun is up for 20+ hours a day, but slim in the winter when we only get ~4 hours of sunlight. Most people supplement with a generator for a couple of hours a day which is what I really hope to avoid with ideas like this TEC on the woodstove.
The stove is already pumping out so much heat, and it's so cold outside I feel like the temperature difference is just begging me to do something with it!
My other dream is to by land on moving water (river, stream) and make a little water wheel that turns an old pickup truck alternator. It will be killer in summer, but it's a problem in the winter because the water will be solid for ~5 months.
By the way, I wonder if it's possible to use waste heat from a generator to warm your house, so you can turn down the stove.
(Also, I was curious about your project idea too and it turns out they do already build wood stove thermoelectric generators if you Google that term...)
I came across this link because I want to build cheap small sensor stations using LoRa to transmit data (gps location?, temp, humidity, air quality) to a central server.
Solar is not really an option because it needs to be cleaned once in a while.
You could also use the coolant to pull heat off the stove (obvs with appropriate safety built in) and run the hot side of the TEC within spec.
I’ve seen wood stoves get red hot after an incorrect damper setting runs for 5-10 mins, direct heating might fry your circuits.
There is a company making beautiful camping stoves with TECs and fans: www.bioliteenergy.com
Essentially, it's just to supplement the solar which as I said isn't so crash hot in the Yukon in winter. It's a hobby, and I'd like to see what I can get out of it.
Again, because it's 24x7 for ~6 months I think it might be a fun side project to play with and watch what I can get out of it.
> As much as possible.
That is not a useful response. Would it be worth doing if "possible" turned out to be 0.1 mW? 1 mW? 10 mW? 100 mW? 1 W? 10 W? 100 W? 1 kW? 10 kW? Presumably somewhere in that sequence your answer goes from "no" to yes" and that point determines what tradeoffs you're going to be willing to accept in order to increase your power capacity.
People have suggested steam engines. Those would definitely produce more power than TECs, at least twice as much and potentially six times as much. But they are far more likely to kill you. Is that tradeoff worth it to you?
TECs are pretty expensive per watt. Are you really willing to spend tens of thousands of dollars if it will increase your energy output a little? How about hundreds of thousands?
There are tradeoffs in any engineering design. It's obvious that more power is better, but without some idea of the shape of your utility curve, it's impossible to evaluate those tradeoffs in a useful way.
The idea of putting my phone, or any lithium battery really, that close to fire... this plan is not for me.
Slapping a Stirling engine on a rocket stove just seems like a really good idea to me. My major concern would be the in-backpack weight and volume.
It's all just an idea right now, first I have to find TECs that are up to the heat directly touching the stove.
The hot exhaust also helps create airflow that moves the combustion products out of your living space.
It would be neat to recover otherwise totally wasted heat, just be careful.
The idea that the crystalline structure plays a large role in the bulk thermal conductivity of the material is kind of mind-blowing at first and then retrospectively obvious.
Let's see how well I can explain this (haven't read the article, yet, sorry! Waiting for a plane...)
So you're no doubt familiar with the physics of a vibrating string; it resonates at wavelengths (length of string, 2 * length of string, 3 * length of string... n as n->inf). So you can express any vibrational state of the string as sum(intensity * wavelength); so you can represent the state of the string as a vector of intensities on a basis of allowable vibrations of the string.
Let's call these _vibrational modes_. Let's assume occupancy of these modes is quantized. It's (sort of...) the same as energy levels of atomic orbitals in electronic structure, if you remember that from chemistry classes; the way it's not the same is important (bosons vs fermions) but not at this level of handwaving :-)
So this is how solids store energy, and we call this energy "heat".
A reasonable approximation for a crystalline structure is balls – point masses – connected by springs, where the springs are covalent bonds, plus electrostatic effects between point charges. Intuitively, you can follow that the same kind of _vibrational spectrum_ will arise from this arrangement (in the same kind of way; the solutions of the differential equation of this system of forces under periodic boundary conditions). So materials have resonant frequencies in the same way guitar strings do.
Therefore, this vibrational spectrum defines the thermal behavior of a material; heat capacity, thermal conductance, etc etc etc etc. Each of these vibrational modes is also tied to a collective motion of the particles in the material, which (if sufficiently violent) will tear the structure apart – there's the solid-to-liquid phase transition – or, more subtly, if lost will lower the symmetry of the crystal structure, which gives rise to solid-to-solid phase transitions (an example would be alpha to beta quartz, which will crack your crockery if you leave it in the oven on a cleaning cycle; https://en.wikipedia.org/wiki/Quartz_inversion).
There's a lot of depth here, as you can imagine!
The incoming light wave causes an avalanche of secondary waves through electromagnetically perturbing the individual atoms, and the superposition of all these results in a wave that seems to travel slower than the speed of light.
Thanks! This is a great analogy.
Also, (and I may be totally wrong about this!), the concept of Annealing from metallurgy -- seems related to that of Quartz Inversion:
Any suggestion to read ?
To you the simpleness of the final result is surprising, but that simple result was discovered after a long and exhaustive search. A search into a wide and shallow space can be just as impressive and difficult as a search into a narrow and deep space.
Engineer here btw.
We don’t have good theory for materials science. Our understanding is closer to a list of observations (“effects”) than anything unifying. That almost ensures there will be surprises in the gaps.
At the same time, popular disillusionment with repeated claims of wonder materials has led to—in my opinion—underinvestment in basic research.
(I ordered them that way because Voyager 2 was launched first)
Wiki also tells me that the best TEG modules currently lock in around 8%, so we're looking at like 10-11% at best with the new material.
So from a bulk scale electricity standpoint... the needle probably hasn't shifted at all. From a small scale? In the IoT like applications (as mentioned in the press release), that extra 30-40% is nothing to sneeze at.
Would also point out that for the IoT like applications, the assumption of T_c ~= T_h isn't so bad. For example, if you wanted something powered off residual body heat, you're looking at something like 293/310 = 0.945. For
This does not imply that 1.4% efficiency is enough to be useful for most applications, of course.
The peltier effect is just down right awesome, you put power in and now it’s cold!? Reality steps in at some point when you need to drive down the efficiency even further to get large differentials and ugh. They’re insane to deal with, any amount of thermal load worth speaking of means you have to use a phase change system.
It is very handy for camera sensors though and other scientific gear. There’s a world world of CCD sensors that act in a vacuum with peltier devices driving them below -30c to reduce the noise produced by the sensor.
It's used to power space probes that can't use solar panels. https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
That's why you have to use a real fridge to do the work before starting the journey. And at that point, those electric fridges are only slightly more useful than a pile of ice packs.
that's more a function of the insulation , rather than the cooling ability. The wattage needed for 'thermal maintenance' is far lower than needed for actually removing heat from the system.
Peltiers' are kind of on the same scale of efficiency as using your car (on purpose) to cook food in the engine bay.
As a side note, look up the book 'manifold destiny'. It's all about cooking with one's engine bay. An amusing read!
However, thermoelectrics have an efficiency well below 10% (maybe a bit better with this improvement but not much). For that reason, future reactors in space will likely use Stirling engines instead.
*I spent part of my career working on these devices and saw many of them running in labs
So now you’ve got a very thin chip and all the power comes in on the side with pretty much nothing else on it. I wonder if you mount the chip backside up, put these little peltier devices on the hot spots, if you can maintain a higher heat transfer rate.
But there are an awful lot of mobile processors with passive cooling or complex heat pipes, and it would take more convincing that such a scheme would also fail there.
I'm also wondering if it might be useful for 'race to idle' situations by extending the time until thermal throttling kicks in.
I can't imagine why anyone would be more inclined to use a peltier as wattage increases. Higher wattages make that idea progressively worse unless you have some very specific and strange requirements.
The worst spots aren't much worse than the median spots (over calculating silicon, not cache). Anything big enough to be a hot spot, like a big ALU, is big enough to represent a large portion of your power budget. The main goal is to get all the heat away from the chip, and putting peltiers on a large portion of the chip gives you more heat to take away. For anything significantly smaller than that, the heat bleeds out without the need of a peltier. There might be a middle ground where peltiers could make a real life difference, but I'm skeptical.
> or it could mean circuits with far more layers than we can manage now
That sounds like you're cooling the entire chip, which is the worst time to use a peltier.
Our galaxy and others appear to be missing most of the mass i.e. stars that they should have in order to rotate as fast as they do. We put the figure for missing mass at about 80 to 90 percent for our galaxy. What if our galaxy and others are already colonized by advanced civilizations that make maximal use of the power output of stars so it simply looks like we're missing most of the matter that should exist. This could explain why there is a variation in the amount of missing mass between galaxies with some galaxies apparently containing 0% 'dark matter'. No advanced civilization = no dark matter, different amounts = different stages in development of the galactic civilization.
Could this be a solution to the Fermi paradox?
You would still see infrared:
> Such a feat of astroengineering would drastically alter the observed spectrum of the star involved, changing it at least partly from the normal emission lines of a natural stellar atmosphere to those of black-body radiation, probably with a peak in the infrared.
> A Dyson sphere, constructed by life forms dwelling in proximity to a Sun-like star, would cause an increase in the amount of infrared radiation in the star system's emitted spectrum. Hence, Freeman Dyson selected the title "Search for Artificial Stellar Sources of Infrared Radiation" for his 1960 paper on the subject. SETI has adopted these assumptions in its search, looking for such "infrared heavy" spectra from solar analogs. From 2005, Fermilab has conducted an ongoing survey for such spectra, analyzing data from the Infrared Astronomical Satellite.
There are (probably) other paths to avoiding this conundrum as well. Spitballing here, but perhaps the 'satellites' in this case can be pairs of orbiting black holes which emit the waste heat in a band we don't detect (gravitational waves).
If the person I replied to qualified their comment with "lets assume laws of physicis is not relevant" then sure...
The 2nd law is an observed fact with very shaky theoretical underpinnings (I am not talking about the behavior which has very strong underpinnings). It appears to be an emergent behavior rather than a fundamental one. It is a surprising fact given what else we know about the universe. It breaks the time symmetry of the other laws of physics. This is akin to learning that even though the laws of physics dont break position and rotational symmetries, there is a preferred direction and spin. In fact there is a preferred spin- all neutrinos are left handed. There are huge research efforts to understand why or if there are corresponding right handed particles. Broken symmetries mean big things because as far as we can tell the universe is ruled by what symmetries exist and in what ways they are broken.
And this is what we could do now with our technology.
The infra-red issue, imho, is based on current technology level. No light enters the depth of the ocean because life evolved to build photon-recepters of all wave-lengths, even the less fruitful.
Taking this into consideration, every maturing civilization WILL inevitably produce Dyson spheres at least transiently. We already started it! Just look at the solar moduls of the ISS, which are actually the beginning of a Dyson sphere.
If we're assuming a highly advanced civilization aiming for maximal efficiency I would hope that they have figured out how to make all of their electrical systems out of high temperature superconductors.
I mean, there's going to inherently be infrared, so how can you convert that to radio of roughly a desired frequency range without complex machinery?
In the particular case of solar panels, in order to have a workable thermal gradient, you need to have some sort of conductive path from the solar panel to the cold reservoir (assume the ground under it) - that's extra cost there. Then once you have the TEG running, what you're actually doing is adding an impediment to heat flowing from the solar panel to the cold spot, likely causing the solar panel to be a bit warmer (thus decreasing its efficiency). The increase in energy production per given investment is almost always going to be lower than just getting more solar panels.
You see this is most bulk energy production contexts. It's rare for these energy scavenging techniques to make economic sense. Where you start seeing them make sense is when you have other constraints come into play. You can see this with other aspects of solar generation like solar tracking.
It needs a nearby source of cool to work, and when a solar panel is hot, oftentimes everything surrounding it is hot.
I have no real data...
This opens up a quiet a few possibilities like buy a temperature sensor place it somewhere and it starts feeding data into your home WiFi. No wires, no batteries.
Edit : Method of producing said reactor left as an exercise for the reader.
In addition to being affordable the material is available in bulk and there exists an industry which knows how to work with it. Same with all the materials mentioned.
Or at least recycle some of the heat fridge/freezers produce back into electricity.
This was already possible. Now you could just do it more efficiently.
It's just a heat engine like any other electrical generator so it's not going to have fundamentally new kinds of applications.
Don't forget you can also use the waste heat from a device (like a computer) to run a mechanical heat engine to generate power to help run the device. But only partially. I guess we don't do that much because it's probably not economically feasible. That's kind of what turbochargers in cars do though.
Also, with a difference of 30C (60F) they increased the maximum efficiency from 1% to 4%, but that temperature difference is probably too hot for a phone in your pocket.
It's probably better to have a smaller phone, or to use the additional space/weight in a bigger battery.
There must be some heat flowing to generate electrical power because of the 1st law, so even if the effect is described as being due to a temperature difference, in practice, you also need a heat flow to be useful.
Your quote about "without any side effect" means without heating up a cold reservoir. But the article doesn't claim that.