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General => General Forum => Topic started by: paul wheaton on August 14, 2010, 08:53:31 PM

Title: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on August 14, 2010, 08:53:31 PM
I just now uploaded this.  Ernie Wisner talks about using four cords
of wood every winter using a wood stove.  And now he uses a half a
cord of wood each winter with a rocket mass heater.   Since he uses so
little wood, it ends up being just tree trimmings from his urban lot.

http://www.youtube.com/paulwheaton12#p/u/0/_jfag47dRCs
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: NM_Shooter on August 17, 2010, 06:40:15 PM
Do you think this might be because the exhaust gasses are cooled by the rocket heater mass, and most of the heat is kept in the building?

I wonder if it would be possible to make a "mini" rocket mass heater.  If I could figure out a way to build one in a 1'X1'X6' space....My cabin is so small, that a regular wood stove would blast me out.

Probably not... unless I wanted to be constantly feeding it small pieces of wood....  Hmmmmm......
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on August 17, 2010, 09:20:25 PM
QuoteDo you think this might be because the exhaust gasses are cooled by the rocket heater mass, and most of the heat is kept in the building?

Yup!  Exactly!

A traditional wood stove is pumping heat out of the house in order to get the smoke out.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: MountainDon on August 17, 2010, 09:35:52 PM
Quote from: paul wheaton on August 17, 2010, 09:20:25 PM


A traditional wood stove is pumping heat out of the house in order to get the smoke out.


Depends on how traditional the traditional stove is. If it is outfitted with an outside fresh air inlet no air from the interior will be leaving the cabin and no cold air is being unnecessarily introduced to the interior. It'll still use more wood than a rocket, but the air inlet works very well. Especially nice when fitted with a air inlet booster fan for getting a fire going.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on August 17, 2010, 10:08:40 PM
Actually, I'm thinking about the 600 degree smoke going out the top of the chimney as opposed to the 100 degree exhaust dribbling out of the vent for a rocket mass heater. 

As for air intake, I used to be of the camp you are talking about.  But when I attended the RMH workshop, there were five instructors there having a bit of an instructor re-union.  They tried really hard to not roll their eyes.  After about 20 minutes I could see their point.  Now that a lot of time has passed, it makes even more sense.

First, a rocket mass heater can be set up with an external air intake - no problem. 

Second ....  well ...   it would take 20 minutes to say it I suppose.  Let me just say that they convinced me with stuff like "do you want to live in a ziplock bag?" and then the reminded me about radiant heat and conductive heat.  And then the told me about a place in sweden that had a three inch gap to the outside all around the house, but everybody felt plenty warm inside.  They also said "do you want to burn stale air or do you want to burn fresh air?"

That all probably just sounds crazy - as it did to me the first time I heard it.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on August 17, 2010, 10:45:11 PM
Quote from: NM_Shooter on August 17, 2010, 06:40:15 PM
I wonder if it would be possible to make a "mini" rocket mass heater.  If I could figure out a way to build one in a 1'X1'X6' space....My cabin is so small, that a regular wood stove would blast me out.

Probably not... unless I wanted to be constantly feeding it small pieces of wood....  Hmmmmm......

You're right about constant feeding... I've seen many "pocket rockets", but it's a full-time job sitting over them with a pile of sticks.

A traditional rocket mass heater really takes very little space, though, when you consider that the mass is in a very usable form (such as a bench), and you need a place to sit anyway. It's a multi-tasking stove.. :)
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on September 13, 2011, 02:21:02 PM
Moments ago I uploaded a video where a rocket mass heater combustion chamber is mounted on top of a conventional wood stove. 

Ernie Wisner has built over 700 rocket mass heaters and this is his third hybrid.  In three minutes he covers a lot of detail about the efficiencies of conventional wood stoves, rocket mass heaters and hybrids.  Including some enlightening information on how rocket mass heaters can heat a space using 90% less wood.

http://www.richsoil.com/rocket-stove-mass-heater.jsp#hybrid

Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Squirl on September 13, 2011, 03:13:29 PM
I understand the physics, but I am a little off on some safety issues.  There is no way to get a 100% burn.  So whatever volatile gases (creosote), no matter how small, cool as the smoke cools in the chamber collect.  Is there a way to clean the piping?  What happens if there is a fire in the pipe?


I was looking for an environmentally friendly way to give supplemental slow release heat in a greenhouse.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on September 13, 2011, 03:20:04 PM
QuoteThere is no way to get a 100% burn.

I'm confused.  What is your point here?

Quotesmoke cools in the chamber collect.

I'm confused again.  What are you talking about here? 

QuoteI was looking for an environmentally friendly way to give supplemental slow release heat in a greenhouse.

Have you seen this:

http://www.youtube.com/watch?v=qtFvdMk3eLM


Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Squirl on September 13, 2011, 03:39:13 PM
Whatever flammable gases (creosote) that don't burn, and will collect as they cool. All be it a small amount of gases, in a normal wood stove or fireplace, the pipe or chimney can be cleaned with a brush.  How is this dealt with in a rocket stove?  It looks like once it is built, it is a solid piece and you would have to destroy it to clean it.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on September 13, 2011, 03:46:10 PM
For a rocket mass heater:

1)  zero creosote.  for the thousands built, there has yet to be a report of creosote in one.

2)  I have yet to see one that doens't have a way to clean out the ash. 

Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Squirl on September 13, 2011, 03:57:41 PM
How do you clean the piping?
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: davidj on September 13, 2011, 04:07:03 PM
Modern wood-burning stoves are supposed to have efficiencies in the 60%-70% range (although I'm guessing it's more like 50% in real life).  A rocket mass heater has got to be a lot less than 100% efficient, so at best it could use maybe 2/3 of the wood of a modern stove.  So it may use 1/8 of the wood of a really inefficient, inappropriately-installed stove but it's unlikely to be much better than a modern stove that's been installed sensibly (i.e. away from draughts and in the part of the house you are trying to heat).
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Native_NM on September 13, 2011, 04:15:10 PM
We built a bio-mass stove for a science project a few years back using old steel cans, an old computer fan, rivets, and some other common junk. Note that the new paint cans, like the unused ones from Lowes melt. You need steel. If you have a welder you could put one together pretty quick.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on September 13, 2011, 04:20:30 PM
I have the footage for another video along those lines. 

Basically it starts off with:  the whole 75% efficient thing turns out to be one big steaming pile of lies.  First, the scale goes to 116%.  Sometimes higher - this is because of the amount of heat that is allowed, in the system, to go up the chimney.  Next, the labs are competing with each other to do the ratings for the stove manufacturers.   So the numbers are mysteriously higher at some labs than others.  And so then the manufacturers will only use the labs that give the higher numbers.  The labs with ethics go out of business.   There is a lot more wackiness down that path.   Finally, the average wood stove owner tends to run their stove much less efficiently than what the labs do.  Probably a lot closer to 10% than the claimed 75%.

Next, the rocket mass heater has fewer ways to be operated inefficiently.  Plus, it doesn't try to push the exhaust out the roof, so it can extract more heat from the exhaust.  Conventional wood stoves usually have smoke leaving the roof at 300 to 600 degrees F.  Rocket mass heaters have exhaust leaving at about 90 to 110 degrees F.

And that's just the beginning. 

The bottom line is that folks that take out a conventional wood stove and replace it with a rocket mass heater, typically experience burning 80% to 90% less wood.



Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Squirl on September 13, 2011, 04:31:37 PM
Modern EPA wood stoves have a re-burn feature similar to the concept of a rocket mass stove.  The purpose is to get a complete and hot burn of all the gases in wood.  I understand capturing the additional heat lost from the piping of the hot exhaust.

There is always some creosote, even if it is a small amount.  In your videos the description even states that the first 8 minutes or more of firing it is not efficient.  Then to trust my life to the idea that it will be 100% efficient in burning all volatile gases for the entire life of the stove would be fool hardy.  I watched many of your videos on the stove.  Some had vent pipes snaked all around a room with, from what I could see, no clean outs?  Do people assume there stove is 100% efficient all of the time?  I didn't see a way to clean the vent pipes addressed in any of the videos, just an ash clean out.

Edit:
I reread this and thought the tone could be misconstrued.  I am just curious how this is dealt with.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on September 13, 2011, 07:07:37 PM
In a good design, you have a cleanout located at every sharp bend. The ash buildup is so slow that you only should have to scoop/vacuum the pipes after 5-10 seasons. I wouldn't think that you could have a chimney fire in the thermal mass section of the system, (and it would be well contained if you have the pipe buried deep in cob), since the oxygen is consumed in the burn chamber. ??? We did have a small chimney fire at the base of our exterior vertical stack once, and it completely baffled me.. There was hardly any creosote buildup, and the temps are so low out there, I don't know how it started.. But all we had to do was cap up the stove and it snuffed right out. Wish we didn't have that vertical stack... You really would never experience creosote if you exited the building through the roof with a short section of insulated pipe.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Squirl on September 13, 2011, 07:17:32 PM
I could also see the massive savings in wood, depending upon the structure or individual.  In practice the way to get the 60% efficiency out of a wood stove is to burn it as hot as and fast as possible.  In practice most people don't do this.  In a modern well insulated home, the heat could easily become uncomfortable very quickly.  Most people I know try to get a slow burn out of there wood stove at night so that it releases heat all night.  This way it doesn't over power them in the beginning and leave them freezing in the wee hours of the morning.  The added benefit is they don't have to get up in the middle of the night to refuel.  I have been guilty of it too.  This is the least efficient way of burning wood and wastes a lot of its energy.  So the stove may be super efficient, but the users don't want that. 

In theory, and by testimonial, the higher thermal mass of a rocket stove is supposed to work as a heat sink, slowly dissipating the heat into the room over a long period.  By the design of burning as hot as possible for a more complete burn with the distribution method, in practice it is supposed to use far smaller amounts of wood. Masonry stoves are supposed to do the same thing, but without the gas re- burn chamber.  I would love to see more engineering data on these, other than mostly anecdotal.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on September 13, 2011, 08:27:25 PM
Well, my testimonial for the past three winters we've used the stove is as follows; we burn 4 loggers' chords (4x4x8) of Aspen, which is about the lightest (least embodied energy)  wood there is.. Our cobwood home is about 1200 s.f., and although the walls are 16'' thick, we have developed quite a bit of draftiness due to the greenish logs we had to build with. On a calm, 10 degree winter night, we only lose a few degrees from the time the fire is put out (10ish) to the time we start it up again in the morning (8-9ish). Windy nights are a bit cooler, but most of the house stays around 65 degrees, and if that is too cold for ya' the bench is always very warm, sometimes too hot, for up to 3 days after the fire is put out.

It would be very interesting to compare that to a regular wood stove for a while, but we have no acceptable chimney for a test..
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Squirl on September 13, 2011, 09:15:07 PM
Quote from: Ernest T. Bass on September 13, 2011, 07:07:37 PM
We did have a small chimney fire at the base of our exterior vertical stack once, and it completely baffled me.. There was hardly any creosote buildup, and the temps are so low out there, I don't know how it started..

That is one of my main concerns.  There are many more volatile gases discharged from wood other than creosote.  Turpentine and Methanol are two that I can think of off the top of my head.  Many of these gases you would never have worry about in a normal wood stove.  The exhaust gets so cool out of a rocket stove it complicates things.  At the temperature of close to 100 degrees these and many other gases become liquids or solids, yet are still very flammable.  Even if it is a very small amount of inefficiency, there is something there.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on September 14, 2011, 06:59:49 AM
Usually the exhaust is closer to 200 degrees, especially if the stove has been running for a while and the thermal battery is warmed up. Our exterior stack is currently a cheapy thinwall pipe that is 25' long (read: cold...).. A short section of insulated pipe would be ideal; I don't think that the gases would condense at all before leaving.

It wasn't the hot, raging chimney fire that you typically hear about... Just a few flames visible though some gaps and some ash flying high..
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Alan Gage on September 14, 2011, 09:01:40 AM
Squirl:

I've got the same worries about the rocket stoves as you. The reason to keep the chimney hot on a wood stove is to keep the gasses from cooling and condensing inside the chimney, which causes creosote to form. That's also why heat recovery units built into the chimney aren't recommended, they cool the gasses too much. If the exhaust was 600 degrees leaving the stove and 100 degrees out the chimney I'd be very worried about what was building up inside those walls.

Alan
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Squirl on September 14, 2011, 10:21:36 AM
Yes, creosote boils at 400 degrees Celsius.  Because wood stove exhaust can hover between 300 and 600 degrees creosote is the main gas that can condense in a wood stove.  Because of this and the familiarity of wood stoves, it is what most people are familiar with.

Many of the videos and promotions of rocket mass heaters state the exhaust exits around 90 degrees F. Almost all other flammable oils and alcohols in wood condense by 150-160 degrees F.  Combine this with the greatest statement that I could find is a 90% efficiency of burn (anecdotal "Rocket Mass Heaters: Superefficient Woodstoves YOU can build" (Ianto Evans and Leslie Jackson, Cob Cottage Company p.80), and you have serious safety concerns.  Even if it were 99% efficient, that 1% can be alarming built up over time or just based on the contents of that 1%.  Anyone that has run a backyard still knows the flammability of a condensed alcohol (methanol).

I'm not saying that a wood stove is a better, but it takes these factors into consideration in the design.  It wastes the heat up an insulated pipe to cut down on condensation of flammables.  There are manufacturer guides and whole organizations devoted to the design of dealing with its drawbacks.  It also is a requirement that they have easy access to clean the pipes with a chimney sweep, and promote regular cleaning.  In a sense it trades efficiency for safety.

This is one criticism I have of many of the publications promoting rocket mass heaters.  They don't seem to address any of these issues.  Either they don't know or understand them, or they don't care.  Saying these issues don't exist would defy physics and sense.

I'm sorry if some of this is redundant, I was just trying to be clearer with my thoughts and concerns.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: JRR on September 14, 2011, 10:33:38 AM
On the question of what air source to use for combustion air, fresh air or "stale" air, ... I would choose fresh air piped directly into the location of the heater.  Stale air should be removed through other proper ventilation devices and should not be dependent on the heating process.  The heating process should be as "stand alone" as possible.  Supplied combustion air in, heated exhaust out...with flows properly controlled.  Separate breathing air ventilation should be "as needed", heating season or not.

A tightly built, well insulated small residence that has been choosen to fit well with its environment ... will make any heat source seem to perform at its best.

A rocket mass stove certainly looks like a interesting, fun project ... not sure I have the craft skills to do a good job.  Think I will go with the store-bought heaters for now.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on September 14, 2011, 10:44:35 AM
Many rocket stoves have been in regular use for over a decade, and so far none of them have exploded... Like I said before, the chimney is buried at least 6'' deep in cob, so even if you did have a chimney fire, I can't see how it could be a serious danger. From my observations, very little if anything condenses on the pipe inside the house. The interior pipe is always very warm, being shrouded in hot thermal mass. The gasses don't condense until they hit a cooler surface.

We've used efficient air-tight wood stoves, crummy franklin stoves and old wood cook stoves, with insulated pipe and temporary thinwall pipe. Our lousy 25' feet of furnace duct (creosote magnet) that has been our temporary exterior stack for the last three years has had less buildup any of the other chimneys, about the same as burning a conventional stove hot through an insulated chimney.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: John Raabe on September 14, 2011, 11:13:04 AM
There have been a number of posts and experiments with rocket stoves that have been reported on this site.

Here is a link to Glenn's project from 2006.

(http://www.countryplans.com/images/Rocket_stove/Notes-1.jpg)
http://countryplans.com/smf/index.php?topic=2350.0
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: PapaBear on September 14, 2011, 11:21:55 AM
Great discussion on rocket stoves.  I think this is the second or third time I've watched some of Paul's videos as I've been reading up on this for a year or so.  I'd like to build one to heat my shed/workshop if I can ever finish all my other projects.  I don't have any first hand experience, but I can share what I've learned from reading.

On the creosote issue, my understanding is that in a rocket stove the fire burns hot enough (600+) and long enough (through the cob whatever) to effectively eliminate (burn up) any particulates in the exhaust.  Therefore you get a more efficient burn (is this the 75% vs 90% efficiency thing?).  In other stoves (conventional wood stove) the fire and heat is less contained so a lot of the combustion heat is lost and the fire just never gets hot enough to burn everything.  I think this is similar to why pellet burners are labeled as more efficient, because they contain the combustion better (I've got no source on that other than my own interpretation of what I've read).  Along these same lines, it makes sense to me that increased efficiency (less leftovers in the exhaust) would lead to a safer system.

The other advantage I think rocket stoves have is more efficient retention of heat.  When the exhaust is snaked through a cob something-or-other more useful heat is retained.  I think a typical wood stove relies more on air convection (very low thermal mass) to heat a space than it does conduction and radiation as in a cob bench.  Similar to why radient heat flooring is more efficient at overall BTU retention than a heat pump (makes sense intuitively anyway).  As for the safety issue, in what I've read there is often guidance to make sure you can clean ALL of your ductwork out, cause it'll need it eventually.  

So, I guess the way I think of it, heating stove efficiency is two-fold.  One, completeness of burn or how many BTUs can you recover from the wood itself; and two, how many BTUs you can recover from your exhaust and get into your space.  It seems to me that a rocket stove with cob bench wins on both accounts.  (remember, no experience here, only book knowledge)

PapaBear

EDIT: 1st post!?  I've been lurking for so long I didn't even realize I've never posted   ::)  Hello from Maryland!
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Squirl on September 14, 2011, 02:24:53 PM
 w* Papabear. I'm glad you finally joined the discussion.

There seems to be a nomenclature issue.  The "rocket stove" I am a big fan of.  
http://www.iwilltry.org/b/build-a-rocket-stove-for-home-heating/
These work like a regular wood stove, only hotter and faster.  They get a large amount of the energy from the wood, and vent the exhaust safely.

It is the "rocket mass heater" seems like a more efficient, yet unsafe alternative.

Quote from: PapaBear on September 14, 2011, 11:21:55 AM
 As for the safety issue, in what I've read there is often guidance to make sure you can clean ALL of your ductwork out, cause it'll need it eventually.  

I guess this is one of the things I haven't seen.  All I have seen are limited access to clean out ashes from before and just after the combustion chambers.  Also most seem to have pipes snaked under benches and through cob, that you would have to break the cob to clean the pipe.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on September 14, 2011, 04:45:30 PM
You make a lot of good points MD; those reasons are why the stove really isn't for everybody. I would never put one in an occasional-use cabin/home. Heck, it might even take days to heat up! And I'll have to admit, I really like to be able to watch the fire--my biggest pet peeve of the traditional-style rmh. The heated bench is super luxurious, but being able to lay back on it and watch the fire would be even better! I've been throwing around lots of ideas for a window.. Trouble is how hot the burn chamber gets. It would have to be placed so the flames were getting sucked away from the glass..

Squirl, cleaning isn't any different than any other masonry stove. Lots of cleanouts. Sounds like a pain, but you rarely need them.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: MountainDon on September 14, 2011, 08:13:35 PM
I had something happen when I was huuriedly modifying the post ETB refers to above. I lost the whole thing.

What I was commenting was that I had no interest in a rocket mass heater myself. Our cabin sees 2 to 3 days use at a time in the cool/cold weather seasons. A RMH would be next to useless as it would take very long to warm up itself and then the cabin interior. In the coldest weather even if the RMH came to temperature while we were there, then in the nearly 2 weeks before the next use everything would most likely return to the ambient temperature.


I also added a personal note, that I would actually like to burn more wood that we do now rather than burn less. When thinning a forest as we have been doing we find ourselves with more wood than we can even give away. Some folks express interest then back down when they realize they'll have to drive 60-70 miles to pick it up. Free is free so I don't understand those folks. Right now we have a couple cords of seasoned pine ready to go. Plus another several of 3 to 4 foot lengths of freshly cut pine. And some folks are picky when they come to get their free wood; they leave the 3 inch and smaller behind. I don't ask them back.   Anyhow we end up burning up piles of it over the winter in bonfires so as to reduce the fire danger. Maybe some day in the distant future we will run out of trees to thin. But then I'm going after the neighb ors lands. They would like to see their trees thinned, but never get around to it and are too cheap to hire out the work. I'll do it for free after we're done just to keep busy and slowly beat back the fire danger on theiur lands that abut ours.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: MountainDon on September 14, 2011, 08:16:30 PM
ETB, re the window..... The flames on our Aspen with window in the door actually lick towards and up over the glass as the air flow is up the front and then back in the secondary burn chamber.  Good quartz glass should do the trick.   ???

Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on December 12, 2011, 02:39:47 PM
I just finished a major overhaul of my rocket mass heater article.  Nine new drawings, one new animation showing the path of the fire/smoke/steam, new videos and twelve new pictures.

http://www.richsoil.com/rocket-stove-mass-heater.jsp


Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on December 13, 2011, 09:57:35 AM
Really great page, Paul.. One of the most comprehensive collections of info on the web.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on February 21, 2012, 09:22:58 PM
I posted this video about ten minutes ago.

After building 700 rocket mass heaters, this is Ernie and Erica's
latest.  They are in the okanagan highlands where snow has been on the
ground, non stop, for months.  Two days earlier the temperature
dropped to 19 below.  They show how little wood is needed to stay warm
up there.  And they show some new innovations with their designs.

http://www.youtube.com/watch?v=4usXIAoy9us

Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: rick91351 on February 22, 2012, 09:24:42 AM
Thanks Paul!  Glad to see more on this concept!
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: umtallguy on February 22, 2012, 01:16:23 PM
have any of these been in use for long enought to see real safe lifespans on the combustion chambers? the thin walled barrells scare me
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on February 22, 2012, 01:33:40 PM
There are several that are ten years old or more and still getting regular use. 

I have heard of folks replacing a worn out barrel.  My dusty memory is suggesting that the barrel lasts about seven years.  But the concerns are not like the concerns you would have for a conventional wood stove because the design of the rocket mass heater is such that leaks are not as scary.  With a proper heat riser the exhaust is almost all steam and CO2. 

The key is that this contraption is a very different animal from a conventional wood stove.  The key to it all is the heat riser, which is designed to basically maintain a chimney fire for the whole burn. 

Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on February 22, 2012, 10:52:06 PM
Nice vid, but I was a tad disappointed to not get some design/construction advice from people who seem to have so much experience...
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: umtallguy on February 22, 2012, 11:23:33 PM
hmm that video is really interesting, I was expecting there to be some pressure in the stove, but i guess when it is drafting it actually is sucking down on the lid holding it in
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on February 23, 2012, 11:31:39 AM
A video that has all of the information would be a full two hour video.

I have other videos that have more information on the "how to" aspect.  And then there is a book.  Recently, Ernie and Erica have released VERY detailed plans for an 8 inch system and a 6 inch system.  http://www.permies.com/wood-burning-stoves.html



Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on February 23, 2012, 10:52:11 PM
Yeah, the basic info is readily available and any of us who are serious about these things already own the book.. I just meant that if you are going to bother interviewing someone who's built hundreds of these things they must have a few new ideas to share. ;) Not intending to harp on ya', just pointing out that I like it when your vids are more informative, that's all.
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on February 24, 2012, 10:50:48 AM
Ernest,

I hear ya.  And I have something you are gonna love.  Actually, I have a few things you are gonna love.

podcast 019 - rocket mass heaters (http://www.richsoil.com/permaculture/182-rocket-mass-heaters-permaculture-podcast-019/)

podcast 104 - rocket mass heaters (http://www.richsoil.com/permaculture/782-podcast-104-rocket-mass-heaters-with-ernie-and-erica/)

Both of these are with ernie and erica.  And we go into gobs of detail.

And there's more ....

Erica has drafting skills and has wrapped hundreds of hours into extremely detailed plans along with detailed builders notes:

Wood Burning Stoves 2.0 (http://www.permies.com/wood-burning-stoves.html)

If you sign up for my daily-ish email (http://www.richsoil.com/email.jsp) you would hear about all their new stuff as I hear about it, and all sorts of similar stuff.

Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Ernest T. Bass on February 25, 2012, 01:02:05 AM
Thanks for the links, Paul. Those two really know their stuff. Listening to you guys talk about the stoves makes me want to play with fire more and build another one... We want to build a sauna/summer kitchen, and I really want to make a rocket cooker with an oven that also heats water in its spare time... Tall order.. I keep drawing designs up. I also want to do more experimenting with radiant floor heating.. Got the bug. ;)
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: KLF on April 07, 2012, 03:40:44 PM
Quote from: Ernest T. Bass on February 25, 2012, 01:02:05 AM
Thanks for the links, Paul. Those two really know their stuff. Listening to you guys talk about the stoves makes me want to play with fire more and build another one... We want to build a sauna/summer kitchen, and I really want to make a rocket cooker with an oven that also heats water in its spare time... Tall order.. I keep drawing designs up. I also want to do more experimenting with radiant floor heating.. Got the bug. ;)

Magic word, sauna, mentioned! :D

My grandparent's summerhome had a sauna stove similar in idea to this one, just 40+ years older:
http://translate.google.fi/translate?sl=auto&tl=en&js=n&prev=_t&hl=fi&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.puuilo.fi%2Fcat%2Fproduct_details.php%3Fp%3D97   (sorry for google translation)

20 litres of hot water usable every time you heat the sauna. Makes bathing much more enjoyable, if the only alternative is cold-ish lake water... :D

Unfortunately that summerhome was sold few years ago, so I can't really go there and take pictures anymore. This is indirectly related to the topic, since I would have loved to share pictures of the house's fireplace (and house altogether, it was hand built by my grandfather in the 70's).

The difference I often see between finnish and american fireplace design is that here fireplace is usually built in the middle of the house (and it's massive, to store heat) while the american counterpart is often built on the outer wall or it's a small metal box in the room. Something that caughts my eye often :)
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on August 14, 2013, 03:30:54 PM
I did a kickstarter last spring.  It was successful, so now I am selling the DVDs of the rocket mass heater workshop with Ernie and Erica:

http://www.richsoil.com/rmh-dvd.html

And I've started a new kickstarter for permaculture playing cards:

http://www.kickstarter.com/projects/paulwheaton/permaculture-playing-cards

Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: Erin on August 15, 2013, 08:39:02 AM
It's really funny that you updated this yesterday, paul!   [cool]

Last night, my son was playing with the burn barrel, with a smaller one stacked in/on it (he backed the pickup into it this spring so there's a dent big enough to leave an airspace below the smaller barrel when it sits on the caved in part), and a stovepipe.  He discovered that by making this tall thing with an airspace below that he got a MUCH better burn.  The ash is almost gone. 
Then he sat down and sketched out a "real" stove complete with "bolted connections and welds and everything, Mom."  My son is 13.

But looking at his rough idea, it occurred to me that that's basically a rocket stove... So today he's researching (if he ever decides to drag himself out of bed lol)
Title: Re: rocket mass heater uses EIGHT TIMES less wood than a wood stove
Post by: paul wheaton on February 14, 2015, 11:28:19 AM
I just started another rocket mass heater kickstarter.

The last one from a few years ago was just a video of a workshop and we sold way more than I thought we would. So now we are making an effort to make something much more professional. These videos would be in addition to the videos from before - not a replacement.

https://www.youtube.com/watch?v=49khDHMqyUw

https://www.kickstarter.com/projects/paulwheaton/rocket-mass-heaters-4-dvd-set