Hello,
I have seen several threads on building a rocket mass heater within a greenhouse. However, I'd like help brainstorming on how to build one within a covered raised growbed.
Please know I have an adequate understanding of growing but have no firsthand knowledge of RMHs.
I'm considering modifying a keyhole garden. These are typically round raised beds with a pie-shaped wedge cut from the edge to the near center, allowing easy access to the center which has been reserved for compost and watering.
I'd like to place the burn barrel in the center with the heated exhaust running under the bed. I would like, as much as is possible, for the majority of the energy to radiate up through the grow medium and not escape from the barrel.
Although the total height of the cover had not yet been determined, I don't have the luxury of a full height greenhouse. I fear heat from the barrel melting the cover. The obvious solution is to have a shorter stack within the barrel. (It seems a cooler barrel would improve draft.) Another option would be to install a thermal mass (such as a cylinder of gravel) enclosed in a wire mesh surrounding the barrel. The third option would be to install some form of heat deflector over the barrel to dissipate the heat.
I invision a round (or octagon?) bed with a 55-gallon barrel in it's center. A diameter of around seven feet should allow me to reach most of the growspace. A wedge from the circumference up to the barrel would allow access the stove. The stove would vent under the growled ideally into an exhaust with a thermal mass such as cinder blocks or clay pipe. Gravel could be placed over this to increase thermal mass as well as improve drainage. Grow media would be placed over this. In summer months the bed would remain open. In colder weather either a dome- or cylinder-shaped cover could trap both solar and radiant heat.
1) Are there any resources online where people document similar projects?
2) Is this project even feasible?
3) What improvements can be made?
Thank you.