This is an April 2016 Blog Post on how we built a Thermal Mass Rocket Stove at Jordan Rubin’s ‘Heal the Planet Farm’.
(We cover the foundations of rocket stove building at every Permaculture Design Certificate (PDC) course we host.) Schedule of Upcoming Courses
We call it the Epic Greenhouse Rocket-Mass Heater because of it’s sheer size and multiple modifications we designed into it. The whole stove is built around an 8″ flue system that exits outside of the greenhouse below floor level, under the greenhouse end-wall, and then turns towards the sky.
Designed by Bill Wilson (MWP) and Kevin Kepplinger (HTP Farm)
Construction and Design Assistance from Heal the Planet Farm Team (All are Midwest Permaculture PDC graduates)
The key modifications we made to this stove that are not usually found on more traditional rocket mass heaters are:
- The feed chamber is very large capable of holding full-sized firewood logs so it can be loaded to burn for up to 4 hours at a time and produce a lot of heat.
- The thermal battery or thermal mass is below grade and insulated so the heat will not wick into the soil surrounding it but instead radiate up to keep fish (aquaponics system) and bedding plants warm even in the dead of winter.
- We installed a multiple-speed flue fan and a flue damper near the end of the exhaust pipe to give ourselves greater control over the speed of the exhaust and even the burn. We can slow the exhaust down to hold the heat in the thermal mass longer when it’s hot or speed it up when we need a stronger pull to get it started. We know this is unorthodox and a bit like cheating, but it’s very helpful and the fan is variable speed using very little electricity.