My question is: Could one build a rocket mass heater in an outside building that is block 8'X10, six feet high with roof and run the pipes around the building and then fill with sand half way. Then loop 1500 feet of Pex pipe in the sand and fill the rest up with sand. Run water thru the pex pipe and use for radiant heat in a house? The water temp. does not have to be very high maybe 110 degrees.
Also how big can you build a rocket mass heater? I am new to this idea but it sounds grand. And I know there are a lot of pro's out there that have a lot of knowledge on this subject and I look forward to learning all I can about these mass storage devices. I would like to go off grid in time and wonder if my idea would work.
I thank all of you in advance in helping me with this question!
"If you learn nothing else in life remember people like to be treated with respect."
Ken Jackson : I feel like a dummy, but I did a Due-diligence Google Search, ( English only ) before I came here and am still no wiser! What is a HAHAS?
Anyway, welcome to permies.com ( and our sister site richsoil.com ) and a Warm Welcome to the Rocket Stoves and Wood Heater Forum Threads ! This is exactly the kind of out
of the box thinking that we really need to grow ! There are a few problems with your build but many people would like a simple outside building to contain their wood stove so we
all look at new ideas carefully for adaptation, someone may see something I don't!
The newest innovations of the Rocket Mass Heater R.M.H. burn freaky hot giving them their Great Efficiency, after the combustion chamber the hot Exhaust gases must travel up
the very well insulated Internal Chimney/ Heat Riser where the gases slam into the inside top of the 55 gal metal drum. Seen from the side the swirling gases would look like
Rams Horns. Seen from on top looking down if you could - the gases flow in a toroid or doughnut shape, here they start radiating off large amounts of heat energy, cooling and
falling down the outside of the internal chimney / Heat Riser, still inside the skin of the barrel, and still radiating Gobs of heat !
It is important that there is a great difference in temperatures between the inside of the Heat Riser and the outside of the Heat Riser, this is only possible because of the insulation
and special positioning of the heat riser and the tremendous amount of heat that radiates off of the 55 gal drum / Heat Exchanger !
Because your building is so small, eventually your interior space will warm up to the point that the rooms temperature would equalize with the temperature of the skin of the Drum,
and No more heat could be radiated off of its skin ! At this point your R.M.H. will backdraft, filling your outside building with smoke !
It is interesting to note that as air is such a poor carrier of heat thru conduction or convection, that it would be the warming of the room through the re-radiation of heat energy off
of the interior walls that would mostly cause the Temperatures to Equalize !
However that being said, I have to admit that I don't know exactly what would happen if the R.M.H. had its own air supply and the room was a perfect vacuum ! as heat would still
radiate both ways I expect an equilibrium would be reached !
Even if you had an all metal outside building that would quickly radiate much of the Heat Energy through its exterior walls, I Think that sand, even wet sand would have problems
taking up the heat before your R.M.H. and its room reach Equalization !
It has been estimated that world wide there have been approximately 100,000 R.M.H.s built, almost all of them in the 6'', 7'', 8'', range, due to Friction loses and problems connected
to laminar Flow, for every working unit smaller than that, there are probably thousands of failed/abandoned builds, I would personally build a second R.M.H. before I would go big !
This is where I recommend going to rocketstoves.com to pick up your PDF Copy $15.oo of Evans' and Jackson's great book Rocket Mass Heaters, there is STILL No other book
in any language with as much Rocket Mass Heater Information ! (and I don't make a nickel! )
Keep coming back to talk with your fellow members, with over 18,000 members you will always find someone that wants to talk about what you want to talk about ! Good Luck !
For the Good of the Craft, as always comments and questions are Solicited and Welcome! Think like fire, flow like gas, Don't be the Marshmallow ! PYRO - Magically Big AL !
Success has a Thousand Fathers , Failure is an Orphan
Hahas is an Acronym, Definition. HAHSA, Heating and Heat Storage Apparatus. It is a block building with foam along the walls with a heater built into the front and filled with sand it hat a shingle roof and is used to store heat mostly for radiant heat projects.
I thought that you could build a rocket heater into the front of the unit and it would heat the sand and keep it warm for some time after the fire goes out. With the pipe from the rocket running thru the sand and out the far wall it would heat the sand and then in turn heat the pex pipe with water in it That you could use to run your radiant heat system. Maybe I am thinking to far out of the box. But for some reason in theory it sound like it might work.
The sand would replace the cob as a heat storage device. As I have read the cob benches and beds can be upwards of 115degrees. and have been told you can cover the barrel all the way with cob. So why not sand?
All that have more knowledge please chime in and tell me where I am going wrong with this idea.
" If I could do it all over again I would change nothing For I am the sum total of all that I have done"
Ken, I guess the only thing I see as "wrong" with this idea is the inefficiency of multiple heat transfers. I would rather think in terms of using the rocket mass heater directly to heat my living space, than indirectly, as you are suggesting.
Now, the idea of capturing heat by running water through PEX tubing isn't a bad one, at all, but I would want to look for heat sources like a hot compost pile, where the heat is a waste product that you get incidentally in producing something else and that can't be used directly (you really can't just put a hot compost pile in your living room )
So I don't think your idea is "wrong", so much as not being optimal.
And there may be factors that make a less than optimal choice the best choice that's actually available.
Multiple heat transfers may be "inefficient" unless you need to heat multiple locations, or can't put a wood stove in the house for insurance, or need a LITTLE heat in the house only at night, or a number of other reasons.
I think I have seen someone build exactly that on a blog, but not sure where.
Sand may not be the best heat battery for a rocket stove. It still might be, just not sure.
Biggest issue is the constant babysitting a rocket stove usually needs. Most HAHAS systems I have seen have HUGE fireboxes so you load them and let them burn for 12+ hours. Stupid inefficient use of wood, but more efficient use of time.
"You must be the change you want to see in the world." "First they ignore you, then they laugh at you, then they fight you, then you win." --Mahatma Gandhi
"Preach the Gospel always, and if necessary, use words." --Francis of Assisi.
"Family farms work when the whole family works the farm." -- Adam Klaus
Peter: The compost pile is a grand idea. Now all I have to do is buy some beefcattle to create a compost pile. just kidding.
I was just looking at a mass storage that would not take up space in an always to small garage. The bigger I build the garage the smaller it gets. Right now it is 1720SF and don't have room for all the things I have.
I have radiant heat in the garage and thru-out the house but my energy bill is killing me. Right now power and heat cost me around 3900 per year and I use CFL's everywhere I can. I have two air tight wood burners in the house with heat coils in them to help radiant heat system plus 2 air source heat pumps ( I now go thru 5 or six cords of wood a year and still have high energy bills) I am heating around 4600SF and have high ceilings in the house and 11foot in garage.
But I am so impressed with the rocket heater I want to some how incorporate one or two to off set the heating of water for the radiant system. There has to be a way to use a rocket heater to heat enough water to heat my house and garage. By the way I live in northern Minnesota and we can see -25 degree days several times a year. So I am asking those big brain people on this forum with a lot of knowledge to throw there 2 cents into my problem. I am not shy when it comes to research or hand on trial and error. And as a disabled Vet I have more time than money.
And I thank you Peter for your input so far I know taking time to reply to my post takes time out of your day.
My true goal is to go off grid but don't know if it is possible in my life time. But every little bit put me closer to my goal.
Again thank you all for you input, knowledge is best when passed on.
Howdy Ken, welcome to permies.
I think your idea might be worth trying.
Is there a way you could do an experiment using a smaller "mock up" of your idea , just to see how things work?
Many of the folks who have built these systems started out with smaller experimental units.
Ken : Thanks for the clarification, I'm afraid the same problem remains, too small a building and insulation on the walls will cause the temps between the inside of the barrel
and the outside of the barrel to quickly equalize. Then you will have no draft in your system, and your Rocket will turn your feed tube into a chimney with lots of smoke !
In order for the Heat Riser to Be in the center of your 8X10 building, if you cheat just a little, your burn tunnel will need to be about 44" deep and that means your heat riser itself
will need to be a minimum of 88 '' tall, then allow 2'' for air gap in the barrel and at least a 4'' air gap to your reflective foil, a second air gap and regular insulation and rafters - With
a 'Tin roof' we are talking ~ 100'' ~ !
Rocket Mass Heaters, need frequent feeding/attention and deserve pride of place in the very heart of your home, the happy owner going about his home duties tending the R.M.H.
as necessary over 6 - 8 hrs to 'charge' his Thermal battery with 20 - 24 hrs of heat, I see no reason why someone can not combine the Thermal bench with PEX tubing moving the
heat energy to a remote and or supplemental Location.
I have checked my 'but we've always done it THIS way meter!' and outside of a mild bias against wasting heat outdoors, I think this system may be made to work with a more
conventional Wood Heater, though not as efficiently !
Sand just has to many air spaces hidden within a given mass of it sand and clay will have a much higher mass, holding and radiating the heat energy more efficiently ! Wet sand has
storage problems, as water always seeks the lowest level until heated, in ether case it has to be vented to the environment for safety reasons !
For the Craft! As always questions/comments are solicited and welcome Big AL
Success has a Thousand Fathers , Failure is an Orphan
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