Woodstove Efficiency Reimagined | A Whole New Approach
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- เผยแพร่เมื่อ 7 ก.พ. 2025
- I’ve just built a reimagined woodstove with the goal of creating a much hotter fire in the fire box to create a more efficient, complete burn & cleaner flue gases. I’ve designed it so that instead of radiating out, the heat can be channeled into whatever application you want, like a radiator for heating houses or a a water heat exchanger for heating water.
Sorry about the editing error at 20:34, it should read 1700F / 927C!
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Hey guys, sorry about the editing error at 20:34, it should read 1700F / 927C 👍
You could try to add a base youtube annotation to that point in the video, I think I've seen it done elsewhere. Not sure though.
This man is bringing our daydreams to reality, epic videos
Very quickly becoming my favorite channel
So happy I found this channel, no cringe no clickbait no BS
Never going to build my own stove but alas
I recon it's easier to make a oven/furnace/fireplace by modeling it from clay+brick. It would have to be a permanent location though, not portable at all. Or make a very sturdy design from some very hard but light insulating material.
I'm LOVING your content. I find it the perfect balance of education, engineering/tinkering and mechanical building skills presented with great video/audio quality. You're giving me "my mechanics" vibes.
Really loving the explanations you're providing in these videos, thanks for making them!
Good lord, thank you! Finally somebody that understands how a woodstove works on youtube, that is not basically trying to watercool his firebox... Great video/project/everything! ;)
Bro this is one of the best new channel Ive come across, love it with the straight forward and to the point videos, keep up the great work
Amazing video again this week, I can't believe how you're keeping the quality and tempo up!
I am rather confident I am never going to build my own wood stove nor even heat my home with one but I enjoy your channel and I am commenting to help you get more attention.
It could also be interesting to design a heat radiator that takes advantage of this new stove’s energy efficiency to convert all the heat produced in the exhaust pipe into radiated and emitted warmth.
Great video as always, your building and pratical skills are simply amazing!
I'll do a radiator at some point. I hope to heat my workshop with this thing. Thanks!
ive always wondered why stove pipes with radiator fins arent the norm. im in spain and ive never seen them. i guess it never really gets cold enough to appreciate the extra heat efficiency, on the other hand wood fuel is expensive here.
@@toddberkely6791 I think it has to do with the condensation temperature of creosote in the average woodstove's inefficient burn. The 75-80% efficiency of the classic woodstove leaves enough material in the exhaust to cause a big problem quite rapidly if you cooled the gasses with a heat exchanger.
@ very interesting, makes sense
It was cool to see in the thermal how much hotter the legs were than the outside of the firebox as they are connected directly through the insulation
Very nicely done. Your builds are practical but also push innovative concepts. Love watching.
If weight is a concern, consider using phase change as your thermal battery. Wax is an easy, accessible option.
Also, capturing energy from high temperature quickly is probably a problem that's been solved in other applications. Heat exchangers come to mind but I'm sure you'll find something.
Thanks for your videos, they're helpful, no BS and you show the process and why.
Wax is flammable. I would use tin as a thermal battery or some other soft metal.
@@derghiarrinde Aluminum has a much higher heat capacity than tin, and even higher than sand (and tranfers heat all through itself much, much, much better than sand), while being fairly light weight and fairly inexpensive.
So a big aluminum bucket filled with multi sized aluminum particles (to fill in as much space as possible) or just a large, thick piece of aluminum even better yet.
Put an insulator over the aluminum (not so much that it could melt). Take off the insulator when you need/want the heat.
@@justinw1765 I understand what you want to say but I am not sure if you take phase transition into account. Tin has phase transition (it melts at 183C I think or 231C, not sure which) and it means that it might have much higher storage capacity for heat than either sand or aluminium. You want it to melt since when heat stops and it gets colder, it will literally need to radiate the heat out so that it can solidify. That's the battery capacity we're after here.
@@justinw1765 Hey, it's me again. I made a review of the tin/aluminium options for a stove-top heat battery and the results are mixed. Someone definitely needs to make a test which material makes more sense for stove-top heat battery. Al has more heat capacity but tin has a lower phase change temp and also is slower to release heat. So while Al might store and release more heat, tin might store less heat but release it for longer. Definitely needs to be tested for real use application.
Fantastic work again dude. The efficient editing and explanations to shave all the fat off and get it down to just a completely understandable process.
Keep it up man! Also I hope you are into some version of stirling engine tech, I'd love to see it.
Puttin' in the work & effort. Thanks for the video
Very nice! Looking forward to see the next one
Thanks for including us in the development and build....I envy your metal working skills...watching this while my wood stove is working to keep my off grid cabin warm, wondering if I can do more to for heating efficiency with less frequent stoking...etc
That flat self adhesive fire rope is great I use it too 😊
Complete combustion is extremely important. I am a firm believer in secondary combustion. One of the stoves I am burning now has multiple secondary burn tubes that when set up and burning right was the glass with secondary burn. Bring it up to temp and enjoy a strong low slow burn ,
Just discovered your channel and absolutely loving it. Well presented and informative. Keep it up.
Excellent presentation. Thank you. You are really doing a nice job on these. The content is excellent and your presentation/video work/editing is also excellent. A lot has to come together for these video uploads to be useful. A person can be a PhD+ in welding/science/chemistry/metallurgy but they still have to film the mess, edit it, narrate it and post it online. A lot has to come together to produce non-garbage content. Nice job. That all said, I didn't see any credit given to the beautiful chicken appearance during the testing.
Thanks! We all know she's the real star.
Great vid!
Some food for thought: my wood burner has an outer shell around it with a small fan underneath the shell to direct air up around the hot inner shell, and out a gap above the door. The brand is Coonara if you need to see photos. It heats the house very well once the inner firebox is hot enough, as it blows hot air through the rooms. It’s also much more child safe. You can’t cook on it, but that’s not its job.
Cheers.
I made a stove like that for a school bus/motorhome conversion I did years ago. It worked really well and could be right next to the wall.
Im just loving every single video you make. Thank you very much! Would love a shop tour and some background in a video sometime, your place seems really cool!
.really nice hearing that you did some research. really interesting stuff
We had similar designs here about 30 years ago. Much more efficient double and triple burning units here now with minimal particles being released
This stove has a secondary burn chamber. I'll do some efficiency testing soon.
This series earned you a subscription from me. Please continue improving the design. You might be missing a tall rounded steel mesh mantle inside the chimney close to the fire for super efficient burning of secondary gases (CO). You would also need to add some more oxygen/holes at that point (when the fumes leave the fire area). It's just like you said, you need more heat and also more oxygen.
Something tells me temps could go even higher if you preheated the air intake with the chimney radiating heat to some pipes that would serve as air intake. The air you currently take in is cool and it effectively cools the fire even if it brings more oxygen. Imagine what hot air would do.
Also, you want to keep the stove going for a few hours, so that insulation heats up. Then measure surface temps. When placed on inside, depending on these temperatures, you might be missing metal heat reflectors on wall behind the stove and on the floor where the stove stands. Also, a ceiling metal reflector would take care of heated air that is exchanging heat with ceiling.
You could also try to burn charcoal for possibly higher temperatures burn, it would be an interesting video. For charcoal you might also want to add even more oxygen.
If you haven't seen the first woodstove build video you might like it. It has an additional air supply at the secondary burn chamber. th-cam.com/video/al_UNeEeaQw/w-d-xo.html
@@GreenhillForge I have seen it, I think you're missing that mesh though? Don't remember anymore.
@@derghiarrinde Yeah no mesh, just additional oxygen supply. I'll look into the mesh.
first time watcher. impressive build, a very nice and calm video :) I dont have a workshop but now i want one!
Good stuff
very nicely done!
Hi There, I have a couple of comment: 1 - Amazing content; I could watch this all day It takes some amazing skills to build this. 2 - Check your fire for secondary burn; I didn't see it from the video and that is something you want to explore 3 - Please use 'The Suisse Method' to light your fire. If you want to build an eco-friendly wood stove this is almost an obligation to your audience. Thank you !
Thanks! There should be a second combustion happening, especially with the high temperatures it was hitting but I'll try to get some more efficiency testing done. I am of two minds about top down burning, but agree that one area that it is better is that it's a cleaner way to start a fire.
If you make the shell to your firebox bigger, you could add a swirl of pipes going up and around on the inside surrounded by sand, this would make a sand heat battery and give you instant hot water access that wouldn't cool down immediately. It would make it bigger but you'd have great efficiency. I used ChatGPT to run the math and you'd have long lasting heat if the outer layer was made deep enough.
Sand is inefficient compared to wax or tin, I think. They both take and radiate a lot of heat for phase transitions. Sand does not do that.
Maybe you should have a look at what is called "kakelugn" in Swedish (I believe the english term is "masonry heater"). They capture a lot of the heat from the exhaust gases and radiate it into the room.
You should look into plasma candles for heating water, low voltage input, but 5000 degree flame output.
not sure if you mentioned it (sorry if you did) but you could put a catalyst in the exhaust as an afterburner as that would help extract almost all the heat and alsl help reduce buildup. although not a woodstove in norway/ sweden they have these pellet fired heaters, as the draw is through the ashes on the bottom there is no smoke and no creosote, almost a 100% clean burn, so they use it to heat water for their homes. this was a great design too, would be excellent for a camper or something as you dont risk setting anything nearby alight
Hi, have you considered making and using vacuum insulated panels for the ultimate in insulation? With your welding skills etc, it shouldn't be too difficult. Essentially what you do is make a steel panel with between a half inch to an inch of space in between the top and bottom panels. Drill a small hole on one side of the panel. Heat up the entire panel to at least 500* F so (the more hot, the better) that most of the air inside expands out of the panel, and while it is still hot, weld-fill in that hole.
If you want to use thinner steel, you will have to use a core spacing material like perlite or fumed silica. These also act as a nice backup in case the vacuum ever gets compromised so that you still have decent insulation. But if you use thicker and stronger steel, you could forgo the core, spacing material which would make it more insulating (as long as the vacuum remains intact).
Btw, perlite is significantly less insulating in a conduction and convective sense than fumed silica, but is better at blocking IR transfer than fumed silica.
You would still want to use some vermiculite or the like on the inside to protect the steel from oxidation, but you could use thinner stuff. Speaking of IR, I mentioned this on one of your previous videos, but I think you really should consider the IR factor here. To put things into perspective, a research team made a forge out of, well wood, by coating the inside of the wood with a special IR reflecting material made mostly out of a type of Zirconium that is very good at reflecting IR.
They were able to heat it for hours with the wood just getting barely warm to the touch from the outside. That is how important IR reflection is when temps start to get very high. IR reflection with the above could be as simple as putting some aluminum foil inside the vacuum insulated steel panels. Or using a water based paste (with zirconium) to put on the vermiculite. They also make pastes that can bond to metal, and it would provide a two fold function of protecting the steel from oxidation while reflecting a large amount of IR. But these do eventually need to be reapplied, so the aluminum foil inside the steel vacuum insulated panels might be your best bet i.e. near permanent.
With a combo of vacuum insulation, IR reflection, and some kind of liner like vermiculite board, very little heat would get through the areas where you don't want it to get through.
I'll look into IR reflection. Argon filled panels would be pretty good too, but with both options there would be a lot of thermal bridging. How quick and easy is it to manufacture is also a big consideration.
Love the videos and love the lack of background music!
Fantastic video and impressive fabrication skills! In a house you would traditionally want as low smoke temperature as possible to limit the fire hazard of soot fire in the chimney, this could make this design a bit challenging to get safe for house use.
For the heat exchanger I think the best design would be to use a traditional industrial heat exchanger design where you can use a 200cm long and 15-20cm wide stainless steel tube with a lot of smaller tubes inside where the smoke passes through inn the small tubes, and the water will be in the space between the tubes inside the large tube. If everything is stainless it should be durable and possible to weld, and the tube design should be okay to clean which was the main problem of the coil design.
Thanks! In a house you traditionally want the flue gasses to be between 120C and 150C as they exit the flue in order to reduce creosote buildup. But if you've had a more complete burn then less creosote can actuallu build up so you could probably go lower than that. If you essentially had a radiator right above the woodstove that heated the room then the gasses would be significantly cooler before they went up the flue. It's all theoretical at this point and would need a lot of testing but I think it could work
@GreenhillForge Yes, looking forward to see the results! From my knowledge the old wood stoves here in Norway had a exhaust temperature of 500c and often more. Combined with a incomplete burn this caused a lot of fires in the chimneys.
In 1998 the requirement for clean burning stoves was introduced and now these stoves have a exhaust temperature from 200-300c and a much cleaner burn.
@@TheJensss Yeah 500C is crazy hot. That will definitely ignite creosote but also what a waste of heat. Woodstove tech has come a very long way since the late 70s. I wouldn't be surprised to see 90% efficency in common stoves before too long
@@GreenhillForge Yes the designs and efficiency has fortunately been improved the last 20-30 years.
MAN GOT SKILLS
Excellent build, extraordinary burn temps. Wondering about life span of baffles at that high a burn temp? You don;t mention how you used the baffle vent control to fine tune the secondary burn. Rocket stoves often have fine control for 2nd burn chamber, once tuned you set and forget. With your open flue test, what will temps be like once you slow down your flue flow to capture all that heat? Over all great video showcasing great fabrication skills, Thank you.
That coil could augment an in floor water heating system. Would be great to see your design put into a real world application.
You explain that to be efficient, the fire needs to get very hot but you also say that a hot burn will be a fast burn - not what we want. Is there a case then to reduce the size of the very hot burn chamber so that it runs for a longer period from the same quantity of wood ?
Compared to your original designed stove is more for stove pipe heat for a water jacket etc. or room heat? I mean by insulating the stove box are you trying to block the radiant heat or heat loss? I also see you eliminated the fresh air return above the baffle.
20:34 you have an error. 1700°F is 927°C, not 2160°C.
I was really thinking for a moment , 2.160°C should have liquified that stove :D
😬
Look up Valco wood stove if you want a good idea for an efficient stove. The best stove I ever owned, too bad they went out of business long ago.
I appreciated the rocket comparispn ay the start. Couldn't a rocket just burn a smaller amount per time to spread out the heat over a longer time? Maybe if you go too small it doesn't get the temp high enough?
I am just wondering about using that water heat system with thermoelectric generators together as the water will help provide the temperature differential. Crazy thinking maybe haha but taking efficiency to a new level perhaps too. I enjoy your videos, thanks. Have a great day.
All good and beautiful, but less efficient in burning wood. The fire must be lit from above for greater efficiency and for a longer duration
If you're giving it less thermal mass and maybe a smaller hotter fire, it's going to diverge quicker from the ideal burn and become impossible to manage effectively with a person in the control loop. You might want to consider an active (probably electronic) control system. This is how an unstable process would be brought under control in an industrial setting.
I've now watched the video and I love the stove and I like your thinking. Referencing my earlier comment above, what would I do? I'd have a box under / next to the stove with servos in it, coupled to the air wash, flue damper etc. The servos would be controlled by either a PLC or an Arduino. This would also have thermocouples at various points and maybe a pressure sensor to measure the pull from the flue. Then it needs a software effort, and I don't know whether that is your thing, but in my view it's what is needed if you're chasing 10 percent of performance with the aim of getting within 10 percent of optimum.
I have a few arduino videos I'm working on now. None are fire related but when I have time I might add that to the list
Im at the very beginning of the video im curious how this progresses however since your last video ive been asking myself why you simply dont scale down the rocket stove so that it is in-line with your heat capture setup? More efficient means you can get to the same thermal output with a smaller stove.
Rocket stoves generally get less efficient as they get smaller. To get the really high temperatures needed for super high efficiency requires either a big fire or some other addition like forced air or different fuel. I have a 4 inch rocket stove with a very similar build design as the 6 inch and it doesn't get anywhere near the temperatures I can get with the 6 inch. But yes, either the heating coil could be sized up or the rocket stove reduced to try and bring them more in line, but there are several additional reasons I don't favor rocket stoves.
Seems like the thermal camera display range is not able of "coloring" above 150°C?
I think the temp ranges are adjustable, I haven't really played with it much yet though.
If you pull all the heat out of the exhaust gas, will it still float out the flue?
there are rocket stove mass heaters that have exhaust that is basically room temperature but the designs are really well thought out
🤘
If the problem with the rocket stove is that it's too powerful, isn't it possible to just build it smaller?
rocket stoves generally are less efficient as they get smaller. Of course there's probably a good balance in there somewhere. But I aslo have other reasons that I don't favor rocket stoves for this kind of application.
Hi. I don't understand the difference between the initial two bullet points "What's the purpose?" and "What are the applications?".
The purpose could be heating water for example and the applications could be feeding the flue gasses through a water jacket system vs feeding the flue gasses through a heat exchanger coil.
@@GreenhillForge Ok, understood in principle, thanks, but what I meant is that asking yourself what the application is would seem to be sufficient to drive the entire design process without having to also ask yourself what the more general purpose is.
@@nicknelson9450 I understood what you were saying. What I'm saying is that considering the problem from multiple levels and perspectives is important to achieving the simplest and most holistic answer. As I see it anyway.
i build steam locomotives and the only way you're going to approach high levels of thermal efficiency in heating water using fire is by insulating the firebox with the waterjacket. most of the work is done by the radiant heat of combustion itself and a relatively small amount is in the combustion gases which is what you're focused on. to me it essentially looks like you're taking a very roundabout way of converging your design with a briggs (dry leg) boiler, so.... why not just cut to the chase and build a wet leg vertical fire tube boiler, except using it as a water heater instead of as a pressure vessel? by not using it as a pressure vessel it means you wouldn't really have to worry about it blowing up or melting down if you run it dry like if it was a pressure veseel, so you wouldn't need to worry about pressure vessel construction regulations. build it out of 3/8" hot rolled steel all around and use schedule 80 seamless steel (or copper) pipe for the tubes and you'll be fine. you can use a cylindrical unstayed firebox. if you want i could make up a quick CAD model of something that would work very well for your purposes.
if you really want to get extremely fancy and reach peak efficiency then you'll want to design it to use producer gas combustion, but that would require a level of engineering in the firebox that is beyond my meager abilities.
I'd love to see anything you're willing to draw up. I made a basic off-grid shower water jacket setup but with flue gasses again, not the actual firebox. you can see that here if you want th-cam.com/video/pP_2A5Wdvqg/w-d-xo.html. I'd also love to hear more about what you do. Feel free to take this over to email if you'd like info@greenhillforge.com
Does it cook hot dogs good?
You ain't never had a better dog
what kind of glass did you use for the door?
It's just standard woodstove glass
@@GreenhillForge thank you! : )
I don't get it... to me, insulating it means heat is trapped inside and cant warm up the house.
Someone needs to explain to me this Counter intuitive build.
That's exactly the goal. Hotter fire = more efficient. Then you'd run the exhaust through a radiator to warm the house. Using the woodstove itself as a radiator causes it to have a less efficient fire.
Isn't vermiculite board asbestos? I thought that was banned.
No, they're different things. They are offten confused with each other though. They are both mined and can sometimes be found near each other so vermiculite is now tested to make sure it doesn't have asbestos in it.
@@GreenhillForge What is the difference between Vermiculite board and Ceramic Fiber board?
Try a box rocket stove
that verm. board is fragile. i doubt it will hold up where it is not protected. great stuff though for high temp. insulation. overall it would be better to use pumice firebrick. not as good of an insulator as verm. board but much more durable and practical. the verm. would be best for baffle still. this would be a compromise but again much more practical. could always put 1/2 inch ceramic board behind the brick and under the brick on base. that would be the best overall actually. ..... admire your skills, effort and willingness to test your ideas
One idea I have had while watching your videos. Boiler systems leverage a water jacket method. Essentially the firebox is wrapped in water.
It's not great for your use case, but perhaps instead of the copper in the chimney. What if you used a water jacket on top chimney at an angle rather than straight up. On the top/water bath side you can add downward flats to cause turbulence in the exit gas, improving heat transfer surface area and slowing the exit gasses in the wider flatter chimney.
It could be a water tight steel water jacket with fitting for your water hoses at the top and bottom.
I made an off-grid water jacket woodstove for outdoor showers. I show it in this video if you want to check it out th-cam.com/video/pP_2A5Wdvqg/w-d-xo.html
Your F to C isn't correct - 1700F is 926 C
Y WOULDNT U WANT HEAT COMING OFF THE SIDES??
because that's effectively removing temperature from the fire, which reduces the effectiveness of the combustion. He's trying to maintain as much heat as possible to maximize the efficiency of the burn.
1700°F is 926.6°C not 2100 🥴
Your bagel should be made of ceramic, in fact inside the firebox should be no wimpy metal!
Look into a Google search of flameless combustion, and why it is superior.
Then post your interpretation build of a flameless wood stove?
A rocket stove is 90% so you can’t get 90%
Rocket stoves can get to 95% or even a bit higher. But I've never seen anything to say it's impossible to get a woodstove to 90%, I just haven't seen it done yet.