Anyone with rocket mass heater in a greenhouse?

Hi,
please do anyone have a rocket mass heater in greenhouse, please?
i have built a geodesic greenhouse (R2.75m) with the base set aprox 50cm below the ground level. Im starting seeds now and later put them into Bato buckets based hydroponics inside the dome.
for next winter i want to have a rocket mass heater built already so i can warm the dome and warm one cubim meter of water (ibc container) to act as a additional heating mass.
im playing with the idea to set the fireplace outside if the dome, just because it can be feed without entering the dome and my main idea is to have greenhouse in safe if/when back smoke might accur. One accident it all in the greenhouse can be dead
what do you think? Is there any big forum to ask the same, also, please?

thank you

Here you go
https://permies.com/t/19178/rocket-stoves/Rocket-stoves-Greenhouses-forum-topic


Smokeback is best prevented with a good tall chimney which is well insulated, and located away from taller buildings. If you really want to keep the RMH feed away from the plants, a vestibule where you can store firewood, feed the fire, and go in and out without letting cold air into the plant area, makes sense.

Thais is what i have
https://permies.com/t/48139/greenhouses/Geodesic-greenhouse-questions

here are some more pics with IBC water mass and entrance.

To place a RMH i selected this spot, near the IBC


Question, how big RHM should be to heat 40m3 of space?
Ground of my greenhouse is -46cm below the ground, RMH will be sitting there.

Where to better make a feeding place? Anyone with external feeding experience? Would you build RMH with external feed again?

For safety, the barrel of a RMH needs to be at least one meter more or less from anything plastic or wood. The burn tunnel cannot be too long or it will reduce the draft, so this means that the feed tube opening is going to have to be about 1/2m inside the dome wall. The curved surface makes effective placement much more difficult. The only practical ways you can feed it from outside are to build a metal tunnel going in from the nearest triangle to reach and enclose the feed, or to build a vertical-walled divider and a vestibule of some sort.

You will also need a mass for ducting to pass through to transfer heat. An 8" system, the most common size for something like this, can generally support up to 50'/15m of duct, minus 5' per 90 degree elbow. I would run the duct first under the water tank... all sorts of possible routes depending on your desires.

Thanks a lot
My english is not perfect, so i might better draw and explain it differently.
First, how do you rate the heat output? I dont want to build a rmh that will give me a looot of heat, because it will be waisted via opened windows or ventilation.

What size should i build?

Let say the fireplace will be inside, and to not draw too much oxygen from the greenhouse i would add external oxygen input, from the ouside. Is it ok?

Please check pictures, if it can be in this way?

Thank you

If you build a larger RMH than you actually need, you just burn it less often or for shorter times. If you build one that is too small, you will have to burn it all day and all night in cold spells. The costs for an 8" system are not significantly greater than for a 6" system, so unless you have a mild climate or don't want to do more than keep it from freezing, I would advise the larger size.

To best avoid smokeback, I would put the chimney in the middle of the greenhouse. The exhaust will be cool enough when you have the right mass to not be hazardous to the plastic and wood, and you will get better draft especially at startup, and more reliable draft in windy conditions.

What does it mean a 8" system?
Thank you

Rocket mass heaters are described by the diameter of their ducting and flue channels. 8" diameter is a common size for heating an average house in a colder climate, while 6" diameter will heat a small house or a large room, or a whole house in a milder climate.

So 20cm pipe, ok.. Can it be galvanized or better heavywall one? I also want to substitute a drum, i would build all out of firebricks. Please why the double pipe inside the drum should be insulated?

If by double pipe you mean the heat riser, that needs to be kept as hot as possible so the fuel can burn completely. If it cools too fast by not being insulated, you will have smoke, creosote (dangerous), and lower efficiency (more wood burned). Also you will get less draft-push and may have problems avoiding smokeback.

Yeah, this is it
Thank you

What si the usual cost of the rmh?

That's impossible to say. It can range from almost free if you are good at scrounging scraps and used materials and not fussy about appearances, to several thousand dollars if you buy all new, high quality materials and nice finishes.