When I visited Kelly Coyne and Erik Knutzen of Homegrown Evolution last week they showed me the rocket stove they made in their backyard. Theirs is quite fancy because it is made of bricks. They sometimes use their rocket stove to fry a meal in a skillet.
The rocket stove was invented about 10 years ago by Dr. Larry Winiarski at the Aprovecho Research Center in Oregon. It consists of an elbow-shaped combustion chamber (usually made from metal cans) surrounded by insulating material (often a large can filled with sand). It uses twigs for fuel, so it's ideal for areas where the trees have been depleted.
Here's a video from the Aprovecho Research Center that shows how to make a rocket stove.
Here are the first 3 of 10 rocket stove principles, by Larry Winiarski.Illustration from In the Wake, a cool website on various simple off-the-grid tools.
1.) Insulate, particularly the combustion chamber, with low mass, heatresistant materials in order to keep the fire as hot as possible and not toheat the higher mass of the stove body.
2.) Within the stove body, above the combustion chamber, use an insulated,upright chimney of a height that is about two or three times the diameterbefore extracting heat to any surface (griddle, pots, etc.).
3.) Heat only the fuel that is burning (and not too much). Burn the tips ofsticks as they enter the combustion chamber, for example. The object is NOTto produce more gasses or charcoal than can be cleanly burned at the powerlevel desired.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects