CO2 released from fermentation can be used wonderfully for plant/algae but I don't think that exhaust from a rocket will be clean enough. Can algae handle CO not to mention the plethora of other compounds that will be present in the exhaust at different times/stages/conditions? Perhaps some small scale experimentation is in order before too much investment in plannning and construction. I appreciate the approach of not wanting "waste" so don't let my doubt get in the way of your mission. Please share your results for us fellow "gleaners". Canyon
I am a beer brewing rocketeer (just did a batch on tuesday) and can relate to your quest. I made a 1/2 barrel keg rocket wood stove conversion that works well as a hot liquor tank or brew kettle. But for real hot h20 making you need more surface area than just the bottom of a keg "barrel". So I built a tube shell heat exchanger but it is a bit of work,$, and more complicated. I added copper pipes in my mass bench so that I can extract hot h20 low tech for brewing or otherwise , or add hot h20 from my solar flat plate collectors to add heat to the mass. I think the pipes in a bench are a good low tech heat exchanger for lower temp heat (preheat) of brewing liquor. Rocket kettles are tall so must be built sturdy and stable even more so if you are going for a full three tier gravity system. Are you a welder? I think a bell with large enough copper pipes embedded in the top would be a sweet way to go for hot h20. Anyway, lots of ways to do it, just depends on your particular needs and $ and skills and time! My best advice, get rid of the plastic mash tun right away!
I assume you are talking about a barrel of an insulated heat riser? If so, it gets plenty hot, like a barrel stove. I have measured 900 F at the exit point! Of course the top(cooking spot) gets red hot.
Cleanouts are key for long term maintenance. Any flue run needs to have an opening where you can stick a flue brush/shop vac hose into to clean even if it isn't that often. I only need to open mine up and clean every other year unless I burn less than ideal wood (I only had to do that once to learn that lesson). I thought one of my runs would be accessible from one end (it has some twists and turns) and when it came time to clean I found out that I really need another cleanout so now I have to add one after the fact which is a pain. So, if you have any u-bends to do, make them H's with two tees and you have cleanouts or figure out what it takes. Breakup is kind of starting I guess (it is melting a bit in the latter part of the day these days but we still have feets of snow!). Yes, what an awesome winter!
Andrew Parker wrote:Jason,
The internal heat riser in the RMH is not what makes it a rocket stove.
A rocket stove is, IIRC, an insulated (though not always insulated) duct or flue of relatively constant internal cross-sectional area, in the shape of an L or J (though not restricted to those shapes). The constant cross-sectional area keeps the gases moving. The insulation helps to keep the flue gases from cooling before combustion is complete and maintains draft. (Those are the rockety parts)
In an RMH, the internal heat riser, made by putting a barrel over a J-shaped rocket stove, is used to help passively pump hot flue gas through the labyrinth of ductwork.
I am not sure if you really want to have a nomenclature discussion (I am frequently challenged discerning when people are serious or sarcastic) but I am interested in clarification of these terms as I teach people this stuff and would like to be accurate. I have been teaching that the main defining feature of a rocket is the insulated "heat riser" or "internal chimney". The internal heat riser is made by insulating the internal VERTICAL chimney (which the L or J shapes inherently have), not by putting a barrel over it as that is just one option for heat exchange or flue gas path. I like your effort to simplify the rocket stove definition but I would say that it could be simplified further by dropping the words "chamber of constant cross-sectional area" and adding the word vertical. So the description of a rocket stove could be simplified to an elongated, insulated combustion chamber with a vertical leg. An evolved design without that vertical insulated heat riser would indeed be at the point of difference to warrant its own label and NOT be considered a rocket. Feedback?
Jason Munzke wrote:I have the same type question. Is there more about converting woodstoves into Rocket Heaters. I want the efficiency (or near the efficiency) of the RMH with the quick radiation heat of my cast iron stove, to be used as a sauna.
You can build a RMH without the mass ( a rocket air heater) by adding lots of surface area for heat exchange after the heat riser (like extra barrels). I have converted woodstoves to rockets by adding insulated heat risers and have this problem of looking at every woodstove I see and imagining how I'd rocketfy it. There have been alot of fun ideas but I much prefer to build rockets from firebrick as it is generally much less work and lasts longer and I believe more efficient. Canyon
Somewhat similar to Matt Walker, we have been building rocket combustion systems that double as masonry ovens up here in Alaska. Our heating needs are pretty great so we have been building more batch style rockets with a horizontal loading front door instead of the downdraft. We have developed a simple plan using firebrick with a masonry arch that creates a nice oven for use after the fire is out and it equalizes similar to a traditional black oven. This way it is not something extra, just a side benefit to the design for more approachable batch load burning. Now after a full season of use with several of these we are refining the design, doing some flue analyzing and we're looking forward to leaning on some of the more experienced rocketeers in the PNW for more testing/input/refinement next month while on tour. We have a goal to make this "kit" or plans available as an affordable option for the do it yourselfers after we are ready in a few months, so stay tuned. I have also played around with the idea of a cob oven downstream from the heatriser and still hold this to be a viable option. In fact, our ash fall out areas right after the barrel have essentially been cob "bell" ovens (we have even bisqued some clay sculptures in them) but they lack the larger door to load with bread etc. Adding an oven door and shaping/adding more mass with the intention of baking would be another great way to go. There are a lot of approaches possible in this oven quest! I look forward to others sharing their experience! Canyon
Although I am not Ernie or Erica I'll share my experience. It works on my stove, I have a bypass(straight to the exit stack) to light when cold, an option for the bench, and an option for the tube/shell hot water heat exchanger. All ultimately share the same exit stack but don't need to. You should have some way of priming the various exit options to ensure draft when switching. Canyon
A good hard plaster coat is what is needed. That can be as simple as sharp sand and clay slip (try a bunch of tests and find the sweet mix that has the minimum of slip to stay tough) or you can get into other plasters (lime) or ammendments. Get ahold of the Natural Plaster book by Cedar Rose Guelberth/Dan Chiras or find someone to show you.
I have learned from others that for general efficient burning conditions w/ avg wood that under around 140 F is the point which condensation is a concern. I try and get a fine tuned rmh to run an exit temp from 160 to 200 F to avoid the issue. There is not a great amount of btu's easily available below that to warrant dealing with the condensate in my and many other masonry stove builders opinions. Perhaps there is someone with more detailed info?
Some people (and governments) get really emotional about this subject. There is a great fear of people having a means to isolate flow through their mass stoves in case they choose to do this when there is a fire producing CO that will back up and sneakily poison the occupants. Certainly a justified concern, but IMHO not a reason to outlaw it for everyone. In my experience it is very easy to guage when it is appropriate to shut off the flow through the mass when one is burning hot "episodic" fires. I am grateful for my homebuilt bypass damper (diverter) that allows me to divert flow from the mass but after building and using a "guillitine" for another rocket that actually positively shuts the flow (except a very small 5/8"hole for residual co) , I will be adding one to mine and others. IF there happens to be a few very small coals left in the ash of the unit, the small amount of co can make it up the 5/8" hole. Plus, with good wood and hot turbulent fire, there is not much left to pollute in the residuals. I have tested with the Testo for ambient CO after corking off the flow for some time and not seen anything coming back out of the unit. If someone did shut the thing too early, smoke becomes visible coming back out. I do realize that there is that period where smoke would not be present and CO is (CO is clear, odorless), my experience has shown me that it is not hard to have a feel for how long that period is. While it is very important for stove operators to be aware of what is going on and the potential dangers and such, it can save a lot of heat with educated use of flue isolation devices and they should at least be allowed! There is a good look at this subject in David Lyle's masonry stove book worth reading. Canyon
Hi Daniel, photos of your build continue to amaze me, nice work! What are the mid run tee (cleanouts?) about? If they are in fact just for cleanouts, it looks like you have it all covered with the cleanouts at the ends and more is not necessarily better as it offers more places to leak and a surface break in your bench right in the middle where you want to be laying down. Just thought I better ask and see what that is about? Canyon
If your needs are such then it might be reasonable. Hopefully you'd be able to use some of that initial hot radiant heat to do something other than heat the outdoor air! If you can pipe the exhaust directly without a "barrel" through the wall and into mass inside it will be a significant amount of heat kept inside although you will need a high temperature capable wall pass through scene (like excell) and the first bit of mass will be subject to high stresses. Perhaps you might enlighten us as to why you have such needs? canyon
I have not buiilt a rocket for coal but I burned coal for my primary heat for the first 5 years that I lived here in Kachemak Bay Alaska as coal washes up on the beach with winter storms. It is nasty stuff but sure does have a bunch of btu's/volume vs. wood and burns for a long time. Bottom air is crucial with a grate and ash pan as the amount of ash is phenomenal (daily emptying a must). If you get into rocket style gas flows, I imagine you will need extra large ashpit fall out after the heat riser too. Figure out what kind of grate material is available because the temps get so hot that they don't last and will need replacing. Firebrick splits that are cut in half lengthwise might be a possible solution. Anyway, sounds like a fun project in a wild scene! canyon
So I just wanted to chime in on this condensate topic as I was alarmed at first. On my first RMH I was shocked by the condensate that ran out my cleanouts at the end of the horizontal flue run (which I pitched to the cleanouts so I saw it all). After a few weeks of firing it stopped. I was only burning very dry wood and it concerned me but I let it go when it stopped. Then, three years later I decided it was time to really ream the flues with a stack brush and low and behold the condensate happened again! I theorize that there is something about the buildup in the flues that helps to mitigate the condensate issue. I have a few thoughts but it is just guesses, the bottom line is that there is some kind of "seasoning" of the bowels that needs to happen to releive the RMH of condensate running. I have since seen this happen on all the other ones and it is a mess that one should expect and plan for dealing with the juices with catchment of some sort that can be easily removed & emptied without spilling the black staining stuff. Canyon
brett watson wrote:Hi Josh, I would like to piggyback onto your questions if I can because your system sounds extremely similar to the one I want to build in my shop. I have Evan's and Jackson's book, I have listened to ALL of the podcasts ernestly, and I have read through most of the posts here that I thought might be relevant to my questions.
I want to build a heater inside the bottom 1/3 of a 55gal drum. I DON'T want to run it through a thermal mass right now.
I have some insulated pipe I want to use for the heat riser; it came out of my attic when we replaced pipe in our house years ago. I believe it is 8". That seems big to me. Is it?
And, is it insulated enough as it is, or does it require more?
And, I am planning on using a 35gal drum for the heat exchanger. Is that too small for that 8" pipe?
I have done a test run with the brick stove built inside the 1/3 drum and it fired great.
I know my questions are somewhat elementary, but that's where I am right now.
Without thermal mass you need to have a major amount of heat exchange to air to get what you so efficiently burned in the rocket. Mass is a key part of using these for heating but people frequently don't understand that until they live with it. Hot air is fleeting but if that is what you want, I do recommend sizing down the 8" riser to 6" (or smaller) and playing with your heat exchanger (you need much more than a 35 gal drum) until your exit flue temp is down around 180 F to avoid condensation but get all you can. This is tricky and can be dangerous because all of your fittings etc. need to be gas tight to avoid CO leakage. TEst Test TEST outside first!
Somehow I have been in a bubble over at Donkey's rocket mass heater forum and missed out on all the fun over here! I didn't realize that there was this much rocket activity! Are there any other people on this forum from Alaska who are or are wanting to be playing with rockets? Anyone else in AK who is heating with a RMH? I am in Homer and am on season three on mine and have been building them/ teaching workshops for the last two years (along with other natural building techniques) and I would love to connect with other people in AK. Not that I don't want to connect with the rest of ya'll, just thought I'd see if there were any others in my region.