Rocket Mass Heater submerged in a water tank

Not sure if there is any merit in this but maybe some of the RMH specialists can have a quick read.

I'm located off-grid in a remote area, no clay for cob and bringing anything else in for the thermal mass is a giant headache, even if I could get components down here my wife would have a hernia if I built it inside. What I do have a lot of is wood, water and space.

Would it be possible to build a RMH outside where the burn chamber, riser, barrel and exhaust pipe is submerged in an insulated low pressure water tank. The normal design of the RMH will remain unchanged in any way, only the thermal mass substituted. Pipes would then be used to thermo siphon the heated water under my living area direct from the tank. The intention is to dispense with any wetback copper tubing normally used for the siphon and keep the system as simple as possible. The cavity under the living space is insulated to the ground and sides so I'm hoping to have the heat rise through the un-insulated floor to heat the space above.

Will the RMH suspended in the tank surrounded by water run at overall lower temperatures as the heat is continuously conducted away, thinking about this being similar to boiling water in a plastic bottle on an open fire...

As I understand it, other than the intake and exhaust, the system should be relatively airtight and therefore also watertight so submerging the whole unit should not pose a problem ?

I only need to increase inside temperature by 20 degrees C, average outside ambient is around -1 to 5 for 6 months of the year, I have considered alternatives however none seem to be right for my situation.

What do you think, is this doable ?

Ken Diver : Sorry no ! Because you will never get heater temps above 212 degreesF, you will never have a Rocket Mass Heater RMH,
that will reach the maximum operating temperatures needed to have an efficient RMH,the best that you could hope for would be one
more stinking creosote loaded outdoor wood boiler !

But, keep looking, there are a few RMH videos of very attractive builds that might pass muster with your wife, Remember ''Happy
wife, happy life !''

Do however take anything you see on U-tube with a ton of salt, there is a lot of crap out there CALLED Rocket Mass Heaters, >>>
that should be called 'Units of Flaming Death' . Again sorry I couldn't be more helpful keep coming back here and read the forums and
ask questions, if there is a RMH in your future we will help you find it ! Big AL

Thank you Allen !

So what if I move the main components out of the tank and ensure the critical burn temp is still achieved by only running the exhaust through the water tank, is water a workable substitute for cob as a storage medium ?

Happy wife is the way to go

Ken - that sounds a more reasonable approach, and probably easier to engineer as well. I'd consider a lightweight traditional bench design with some thermosyphoning pipes embeded into it. Keep as much of the design as standard as possible. Extracting heat in the exhaust will give both a cleaner and (with some careful thought) a safer design taking heat from the lower temperature portion of the system. If you want to test it out you could put your thermosyphon pipes a layer of sand so you can easily rip it appart and try different configurations.

I think this might warant a diagram.

Mike

Ken Diver : Michael Cox very likely has special insight here be cause almost no one in the British Isles has Fossil Fuel Fired Forced-air Furnaces, mostly it is
boilers of one sort or another, I believe I understand that most of them are solid fuel Fired, and all are vented to the atmosphere a pressurized system solid fueled
system being illegal in the Brit isles !

Due to the nature of This Beast, it is a common occurrence for the water pipes to start banging in the middle of the night, and the head of the house deals
with this by getting up, drawing off a bathtub full and going back to bed ! These Units are mostly fed with an Auger-feed of some sort controlled primarily with a
thermostat and then the owner !

Which brings us back to who will be feeding your Rocket Mass Heater, so that starting about 4 P.M. there is hot water for dishes, cooking, and cleaning, Have you
got your Help-mate to buy into the toting and tending related to any type of wood stove? Are You prepared to give up a 1/2 hours sleep in the morning to start
the mornings fires before being at a remote location and unable to tend fires, and is that an acceptable deal for your partner?

I personally don't like or endorse a Rocket Mass Heater at a remote location, The best that you can hope to run would be to add on a mudroom/wood shed onto
an entrance to your house, that is barely separated from the house, The only clues you will have to check for the Rockets functioning is being able to see an
indicator needle (tiny) on a 2'' thermostat disc, and the ever popular listening to the roaring sound that the rocket makes!

When It comes to toilet training young children, we say '' First you train the parents, and then you train the child, obviously the child can not and should not be in a
remote location, and nether should your RMH. I do promise however that with proper attention smell should never be an issue, and cleanup is a much more
pleasant and smaller job!

Has this been done, likely, can it be done, surely, the question comes down to the extra effort and time and resources needed to make this work, especially as you
attempt to place this system farther and farther away in a different location !

There are no absolutes, but before I said that there was no good clay in your area I would check with The local highway depts., they know where the earthslides
happen in a Road cut after heavy rains requiring they to send a crew and X hours worth of crew to clear road lanes and unplug road side culverts !

Oh, Yes! Water is a fantastic heat storage medium, and do send Pictures and Sketches, if there is a RMH in your future we will help you find it ! Big Al