Energy Systems — by Tim Barker October 16, 2012
We’re using this awesome rocket stove powered wall oven for all the catering here at Koanga — it gets daily use and we’re loving it! The amount of wood required is minimal, a tiny fraction of what a regular wood fired stove would use.
by Tim Barker
During our last workshop at the Koanga Institute, we built a rocket stove. Our design brief was very specific in that the stove had to be practical, easy to use and long lasting, whereas what is being built by most backyard experimenters like myself, while being fun to make and muck around with, are more along the lines of ‘camp stoves’ built from tin cans that quickly disintegrate with use. Another consideration which I felt was important was that most rocket stoves are just that – stoves, as in place a pot on top and boil something.
What I envisaged was not a rocket stove but a rocket oven. This is a concept I had originally developed nearly three years ago when living in a small two room shack. It had a camping gas burner but no oven. Missing those things that only an oven can provide is a great motivator. Of course, due to my previous work making rocket stove powered water heaters (a subject we’ll get to at a later date), it was always going to be rocket powered. The hard part, or so I thought, was making an oven chamber that was insulated, had racks and a fitting door. Plus, it had to look good. It was then that I realised I had described an electric or gas oven. From there, the rest was easy. A quick trip to the local scrap merchant secured an old bench top unit where the hot plates are beside the oven. Cost: $20.
After discarding the hot plate section, the next step was to build a rocket stove ‘j’ elbow (see photo), cut a hole in the base of the oven and sit it on top of the rocket stove. The next step was to insulate the rocket stove for maximum combustion efficiency and finally the fun part – light her up!
I can honestly say I’ve never done an experiment that went so smoothly and which easily met and surpassed my expectations. With only slight modifications and tweaks, this oven was in near daily use for approximately two years. The stove at the Koanga Institute is the distillation of everything that I’ve learned since in subsequent builds. Between our internship program and various courses, it is in near constant use and has performed flawlessly.
Finally, I can honestly say that as I pass through the institute kitchen during the day, I can’t help but go over to the oven and peer down into the combustion chamber to see if I can hear the soft rumble of the stove as it goes about its business.
Covering the rocket elbow is a 50/50 mixture of sawdust and clay, which acts as insulation and protects against getting burnt by the extremely hot elbow. Note the chicken wire mesh is used to strengthen and hold the mixture in place till it dries.
Our first rocket oven dinner! It roasts meat and vegetables beautifully… and
bakes excellent bread. We’re using very little wood — just a tiny fraction of
what we’d use in a regular wood fired pizza oven.