I am looking to tap into the knowledge of the brilliant people on this forum. I would like to heat my greenhouse with thermal mass via water in 55 gallon drums. The passive solar will not be enough here in Zone 5 so I am thinking of heating the water with a rocket stove and maintaining with dc water heater directly tied to solar panels. I am stuck between two ideas for the rocket stove water heating portion. Idea number 1: a standard K style rocket stove with a 3/8th inch thick steel water box on top with an input and output. Idea number 2: A poured refractory cement rocket stove with a copper coil around the chimney of the rocket stove. Each idea has some highlights and drawbacks. Looking for input or even other suggestions.
Okay, maybe someone familiar with that stove design else can chime in. I have a similar challenge to keep a poorly insulated Motorhome from freezing. If I use water as thermal mass I can drain it when time to travel. Ive been thinking of something similar to a rocket stove with a pellet hopper that is attached to the side of a water tank.
There really isn't a "standard K-style" RMH here on Permies. From my perspective, that is a You Tube pop culture invention often made of steel which is not what we often promote here on Permies for various reasons. 1) If your using cordwood to burn, the angle at which the feed tube is at doesn't easily allow the wood to slide down and self feed into the burn area reliably enough. This can cause the flames to either creep up the logs or smoke back into the room (both not good). It is a step up from an L tube rocket stove in terms of self feeding, but without being there constantly to monitor it, I wouldn't trust its reliability to operate safety.
2) The high temperatures needed for clean combustion in a RMH needed to have an insulated firebox. If steel was insulated from the outside, it would quickly degrade.
I would start out with a simple 6" J tube core made out of firebrick. Insulated brick would be preferable (for best performance) but regular will work as well, especially around the feed tube area for abrasion resistance.
If you prefer, there are commercial units out there as well like the Gamera , Liberator and Dragonheater rocket stoves that also can be hooked up to a mass. Plans by Matt Walker Walkerstoves are also available if you want a lot more of the details pointed out but still want to build your own.
Have you read the RMH builders guide by the Wisners or Ianto Evans book? Both are excellent resources for systems proven to work and get you well on your way to becoming a rocket scientist.