The wood usage is actually 1/2 cord of wood per winter.

:thumb:

 

I have seen a number of rocket stoves, The problem I foresee with them is that you will have some smoke bleed over into the house.

 

I think I missed something.
How is the ash removed?

 

The "highly efficient" combustion reduces ash. One of the videos also shows a clean-out that is capped during operation of the stove.

 

Here is a forum I see a lot of discussion of this technology:
http://www.permies.com/permaculture-forums/10.0

 

I first opened this thread and got really interested in the video's. So I researched more and I've actually been swapping e-mails with another SB denizen about it. They seem to be incredibly efficient and have almost no combustion bi-products. (no smoke is a GOOD thing) They seemed to be "re-burned" in the second chamber. The way they heat the clay thermal mass seems to be the way to go for heat retention over time.

It doesn't seem to be a great leap to put water lines in the thermal mass to heat water with either. Or to cook on the barrel top. There also seems to be considerably less use of wood resources.

I see something I really like here and intend to look more into it. In fact I have already started to mentally change some plans to incorperate some of these techniques.

And for a posed 'better homes and gardens' look scroll down the page to the book cover
http://www.richsoil.com/rocket-stove-mass-heater.jsp

Good post. Thanx.

 

a RSMH is the best thing i've ever built.
no problems, no smoke back, hardly any ash, snakes all along my floor, super efficient and tons of warm thermal mass.

i plan on tearing it up a bit and sinking an earthen oven in next to the heat riser barrel (upon which i cook on) so that i can bake, make soup/casseroles, dutch it, dehydrate produce, make granola or yogurt, etc. i also want to sink a 30 gallon next to the earthen oven with a line along my exhaust to gravity feed into the bath tub which is sunked a few feet on the other side of the building...

did i missed the hippy-dippy bit? where was that at?

 

.

i plan on tearing it up a bit and sinking an earthen oven in next to the heat riser barrel (upon which i cook on) so that i can bake, make soup/casseroles, dutch it, dehydrate produce, make granola or yogurt, etc. i also want to sink a 30 gallon next to the earthen oven with a line along my exhaust to gravity feed into the bath tub which is sunked a few feet on the other side of the building...

I was thinking something along that line myself. For a few sticks of wood you could heat the dwelling, bake the bread and have a hot bath all at the same time. Now thats efficient use of resources!

 

It requires a big commitment to space. Pretty cool seeing them lay on the pipes.

 

It's an interesting technology though in many respects a house has to be built around it.

If I'm building new, though, I'd be more likely to build superinsulated and have two heat sources, a very small woodstove (on which cooking could be done), and perhaps a propane device.

The idea behind superinsulation is that you don't need much heat to keep them comfortable.

 

Cool!
Thanks for the post.

 

WOW!

Uhm, what those folks built was a VERY BAD IDEA!

They MIGHT get one season out of it.

If anyone is seriously considering constructing one of those for long term usage in a retreat, by all means use stainless steel sealed flue pipe.

Folks can call it a "rocket stove" or whatever they would like, all it is would be an un-dampened natural draft furnace. The concept they built it on relies solely on the buoyancy of the air. That has issues and if the flue temps drop below the due point some really corrosive byproducts of combustion will eat that flue up in very short order.

The comment when the girl referred to the smoke as "unburned fuel" and at the end of the video when they said they checked outside and all that was coming out was "steam" are a direct reflection of the idiots whom built that contraption and it is a very dangerous setup.

That video served a very good example of what NOT to do.

 

I think they've been using these for quite a few years now. I don't know anything about how long they last though. I think I'll write to that Paul Wheaton fellow and see what the skinny is. :thumb:

 

Ok. I saw the pic in one of the links above. Why would the hot smoke move downward once it is out of the chimney? Heat rises, it doesn't fall, and there's not enough room for the smoke to become cooler than the ambient air and move downward.

 

I think it is a cool technology. But I agree the hippies building it out of galvanized stove pipe and mud are going to have to fix or repair it frequently. This stove should be built completely out of fire brick, stone, mortar (not mud), and stainless stove pipe.

They need to balance the length of their horizontal runs vs the height of the vertical pipe. It is very easy to install a wood stove that only works most of the time. It is even easier to instal one that condences flue gasses and results in a chimney fire.

I like the idea. I don't much like this version of it.

 

Can you point me to some reading materials that would help me understand how to balance the horizontal runs vs. the vertical rise? Could you use clay pipe instead of stainless pipe? Would that capture and transmit enough heat into the mass of a floor or bench? What is wrong with using cob to surface the bench? Thanks for anything you might be able to tell me. :thumb:

 

lot of work for a wood stove.

 

You ever tried to make a cast iron one from scratch? I discommend it heartily unless you just like casting iron.... I build one of these a while back for one of the neighbors, and she is still using last year's wood in it. And she probably can do that again next year as well.

 

I've built a version of the RMH without the "mass" part, using a 55-gallon drum. It's extremely efficient and heats very well.

Mine is more experimental than permanent, so I used cheap metal. If I were making it permanent I'd use triple-wall stovepipe combined with pearlite on the innards.

There are quite a few RMHs out there that have been used for 5 or 6 seasons without needing a rebuild. The experimental nature of them, however, means people build them incorrectly and then claim the idea doesn't work or won't last. Done correctly, however, >95% efficiency can be achieved with longevity.

 

Flue design is NOT for the amateur at ALL!

The purpose of the flue is to get the gases out that are poisonous.

I am not going to have any kind of debate with anyone on it. The principals that a flue operate on are fairly simple while at the same time being very unforgiving.

Delta Pressure = Cah(1/t1 - 1/t2)
C=0.342 constant
a = atmospheric pressure
h = Flue height in meters
T1 = absolute temp
T2 = Absolute mean temp in the flue

Now as you lose flue temp, you lose lift. The design of this stove is to a degree fine as long as you do not steal so much heat from the flue that you lose the proper amount of lift.

The flue should NEVER run horizontal as they did for the warming bench and that lends itself to a LOT of cooling on the flue gases resulting in a loss of lift, when that happens the production of the combustion byproducts does not stop, it leaks into the space.

Unless a flue is specifically designed for condensing the vapors, the results can be disastrous. They did not even assemble the pipe properly from the looks of the video.

Using double or triple wall flue pipe would defeat the purpose and would not prevent the problem either.

Will it heat the space? YES it sure will. Will it get the poisonous gases out of the space in a safe manner? Without any doubt I can answer that NO.

These are the kind of folks you read about whom die from CO poisoning every year, literally hundreds.

Put the fire brick on the ground, cut a door and air dampers into that barrel, attach a proper flue with a manual damper on it like so many of you have seen on pot belly stoves and you can absolutely maximize the heat extracted while maintaining proper exhaust flow. When you try and extract too much heat from the flue you are flirting with going overboard and the result is death, simply not a good survival idea.

One of my employees spent a great deal of time in the hospital this spring from a similar set up in their hunting cabin, his father was not so lucky and passed. There is a reason it is called the silent killer, you simply go to sleep and never wake up.

 

I think you're misunderstanding the basic concept of how the RMH works, NedReck.

The "burn chamber" and "heat riser" are both insulated to concentrate and keep the heat in the gasses. This is why RMHs burn so cleanly. The insulated heat riser keep the air good and hot which gives it plenty of updraft (an internal flu which drives the airflow). Once all of the fuel is burned (smoke is simply wasted fuel of which a RMH emits very little), it exits the heat riser into the "secondary burn chamber" (which is a misnomer since all of the fuel should be already burned if the system is properly built) and can be dissipated into the living space.

The air is channeled downward and some of the heat is dissipated by the barrel into the living space. The dissipation of the heat allows the air to sink inside the barrel, causing a downdraft which helps keep the air flowing. Once it exits the barrel it can be either fed into a mass to capture the rest of the heat or exhausted outside.

The air inside the RMH won't be cooler than room or outside temperature and therefore is easily able to maintain airflow (if the system is built properly). Even if that weren't the case, the insulated heat riser is the heart of the system and drives the airflow.

You can try to disprove the efficacy of the RMH design with all of the math in the world, but at the end of the day the thing will still work.

If properly built there is no concern for CO poisoning (as long as their are no leaks) since the exhaust is channeled outside.

EDIT: I want to make sure I'm absolutely clear: The key to an efficient RMH is to have the burn chamber and heat riser as well-insulated as possible to maintain gas temperatures since this is where the airflow comes from. I agree with you, that if you steal heat from the flu, the airflow will slow down. Luckily, though, in this design the "flu" (heat riser) is insulated and should lose very little heat.

 

Let me add that I want to measure Gage pressure and flow velocities at various places in the combustor sections and the stack. The notion that the stove might be at a positive pressure vs the room (like an axial flow rocket) just sent chills up my spine.

 

I think the "rocket" part of the system has been overlooked in this thread. Pinhead nailed it above. The airflow is driven at the front end, not the exhaust.

 

Rocket stove mass heater mod?

OK,
I'm completely new to the idea of rocket stoves as mass heaters. It's a must in my next dwelling I think.
What I keep seeing over and over again is how efficient they are, anywhere up to 95%.
So my question is has any one considered using the same basic design. With one modification, setting it up for propane or natural gas.

Yes, it would take a bit of engineering but ....

So you have all the advantages of the RMH with no ash, no baby sitting and maybe kicks on every other day?

Thoughts?

 

OK,
I'm completely new to the idea of rocket stoves as mass heaters. It's a must in my next dwelling I think.
What I keep seeing over and over again is how efficient they are, anywhere up to 95%.
So my question is has any one considered using the same basic design. With one modification, setting it up for propane or natural gas.

Yes, it would take a bit of engineering but ....

So you have all the advantages of the RMH with no ash, no baby sitting and maybe kicks on every other day?

Thoughts?

I'm also completely new to this design.
But... It seems to me that using a rocket stove to burn gas would go against the concept of the stove.
The rocket stove main advantage is to burn the gas and smoke (from wood) that normally goes up the chimney.

Since propane and natural gas burns so clean (compared to wood) there would be almost zero burnable gas in the exhaust.

 

I've always wanted to experiment with something like this, at least the thermal mass part, and probably will in my next cabin that I build.

My grandfather used a similar technology when he built his house, using a wood stove with an unusually large masonry hearth, through which the flue zig-zags at about a five degree upward cant on each turn.

The wood stove, itself, was already fairly high efficiency for it's time, at around 55% (Yes, I know they're -much- better now), and the masonry surrounding the flue increased the efficiency even more so. We've never had it tested to figure out just how much, but I know it's pretty good. He said that he based his idea off of the masonry stoves common in Germany at the time he left, and thus far it's worked like a dream. I certainly trust it a lot more than some of the designs I'm seeing.

 

Lets clear up an important point:
Is the pipe that goes from my car engine to my muffler called an exhaust pipe or a flue, and what is the difference?

From what I can tell, the rocket mass heater has an exhaust pipe, under pressure from the fire. So yeah, any carbon monoxide produced by the fire is going to want to get out of that exhaust pipe and into your house. Is hippy-mud impervious to carbon monoxide? I don't know. Does the magic hippy fire produce any carbon monoxide? I don't know - one assumes some amount is produce. Does it produce enough and does enough of it make it through the magic hippy-mud to be a health (death) concern? I don't know.

What is confusing to me is that none of those questions are addressed in the video. If this is so awesome why didn't someone pay some post-doc slaves to do a little testing on it? Maybe Bill Gates can fork over 100k to see how many lives this will save/end.

ETA: At great risk to my street cred, I have to admit I don't actually hate hippies, they are just an easy target to make fun of.

 

I earned a great deal of my tuition money measuring data and capturing flu gas from small scale coal burning stoves. So at least one university has been testing such designs. I am assuming that every reliable wood and coal stove pays some outside lab to test their designs before putting them on the market.

I am always skeptical when backyard mechanics promote ideas without subjecting them to the most basic level of testing. From what I saw on the vid, they did not seal the primary burn chamber where CO is produced. Mud drys out and cracks, so it does not count.

I see a benefit from thermal mass wood stoves. I see a benefit from building your own stove on site and incorporating it into the hearth of a new home.

But combustion science, thermodynamics, and heat transfer are the basis of Mechanical Engineering and Rocket Propulsion. You dont just slap this stuff together. You design, build prototypes, test, and modify.

I would not touch this contraption with a ten foot pole.

 

And draft, ya gotta have draft! Either higher flue temperatures or higher flue outlets create more draft. NedReck's analysis is sound. From someone who does this for a living on an industrial scale.

 

I've ordered the book by Ianto Evans and Leslie Jackson, the sort of inventors of the RMH. Mr. Evans was involved in a lot of projects to help people in third world countries use less fuel and clean up their environment by reducing the pollutants emitted through the burning of wood. I'm pretty sure he wouldn't want people to build heaters that would kill them. It's bad for your reputation. Since these heaters are homemade, I suspect that they can be made badly. But the technology seems to work well, and I haven't found any references to deaths due the using a Rocket Mass Heater. That doesn't mean there aren't any, just that I haven't found any yet. I am hoping to contact the authors of that book and ask them the questions you've asked in this thread.

I have to say that I was surprised at the intensity of emotion coming from the folks who spoke out against the RMH. :thumb:

 

Quote:
Originally Posted by Doc Simonson
I have to say that I was surprised at the intensity of emotion coming from the folks who spoke out against the RMH.
That is not hard to explain at all sir, it is the penalties for improper design that drive my passions about it. The "rocket stove" is a heat concentration device for cooking, very efficient and if designed properly as safe as can be.

The rocket stove "mass heater" is a real good example of what one should NOT do at all. You will find that the folks whom wrote the book make it clear that dropping the flue temps too low makes the stove "smoke out" or some similar term. In other words instead of coming out the flue, the exhaust gases spill out through the fire box.

CO poisoning is so pitiful a way to watch a person pass. Yes, I said WATCH. Once you have a 30% level in your blood stream there is NOTHING that can be done. The person can be fully awake and your talking to them and there is not a thing you can do to save them, even the hospital can only administer pure oxygen and hope.

There is a REASON building codes do not allow horizontal flue systems, they are VERY dangerous and can lose draft any time. In most states I think you would find a MINIMUM 1-12 pitch requirement meaning a minimum of 1 inch of rise for every foot of length absolute minimum, and then only if proper flue temps are maintained due to the increased friction and buoyancy losses. I have never designed a system with any less than a 45 degree angle myself simply due to the liability issues one would have for doing so.

Again in answering your question regarding the emotional response to it, while I may not be the most friendly person one would ever cross, senseless deaths from stupid ideas infuriate me. While I highly doubt this involves a rocket stove, I simply hope I am not contacted to perform an inspection or act as a professional witness for this recent event of 3 days ago:

ST. CLAIR, MO (KTVI - FOX2now.com) — A St. Clair, Missouri family is dead and carbon monoxide poisoning may be to blame. The bodies of four family members were discovered in their home in St. Clair Missouri around 11 p.m. Thursday. The youngest victim is 3 the oldest is 29. When 27 year old Ryan Yoder did not show up for work for a few days people became concerned.

Two individuals went to Yoder's residence and when they arrived they saw Yoder's body through a window inside the home.

They called police and a forced entry was made. The bodies of three others were also found. Yoder's two children, 4 year old son Devin and 3 year old daughter Tessa as well as 29 year old Angela Sohn. All were pronounced dead at the scene.

Photos and the rest of this tragic story are : http://www.fox2now.com/ktvi-carbon-m...,6469862.story

 

CO poisoning is so pitiful a way to watch a person pass. Yes, I said WATCH. Once you have a 30% level in your blood stream there is NOTHING that can be done. The person can be fully awake and your talking to them and there is not a thing you can do to save them, even the hospital can only administer pure oxygen and hope.

There is a REASON building codes do not allow horizontal flue systems, they are VERY dangerous and can lose draft any time. In most states I think you would find a MINIMUM 1-12 pitch requirement meaning a minimum of 1 inch of rise for every foot of length absolute minimum, and then only if proper flue temps are maintained due to the increased friction and buoyancy losses. I have never designed a system with any less than a 45 degree angle myself simply due to the liability issues one would have for doing so.

Nedreck, please don't call me sir. There is nothing about me that deserves that honor. Call me Doc (purely a nick name) or Dave. I certainly don't want to trivialize the dangers of CO poisoning. Being a biologist by training, I understand that the irreversible bond of CO to hemoglobin can be a very difficult thing to treat. And since it is a suffocation event, it is painful and horrible.

If building codes don't allow for a horizontal run, it seems to be a moot point. You can't legally install a RMH in your home I would assume. I am still interested in knowing what the facts are regarding it's performance. I'd like to see technical data on one in action. So far, I have found nothing. I am hoping the book I ordered will point me to something a bit more scientific in nature. :thumb:

 

The earlier point about using warm inside air to 'push' the exhaust out is a good one. The rocket stove is not just using interior oxygen, it is pulling a lot of warm nitrogen with it. Maybe a better design would be to a closed loop from outside (oxygen) to fire then through the mass (heat and waste gases) and back outside.
Assuming you can make a really closed loop (no joints leak under whatever pressure can occur), then the back draft problem goes away - it back drafts outside.
Some wood stoves have air tight gaskets on the loading door, so maybe the same could be used on the rocket stove for loading in fuel.