A big component of our stove is its insulation.  Between the inner chamber (where combustion happens) and the outer walls is a lot of space.  If we simply left it empty, then hot air would move around and carry heat from the inside to the outer walls in much the same way your oven cooks food.

The obvious answer is to use insulation.  But what kind?  Often ceramics, sand, and earth come up.  It’s true that these would slow down the transfer of heat from the inner wall to the outer wall, but they do it by absorbing energy.  In scientific terms, they have a higher specific heat capacity than air which means that, for every degree they change, they absorb more energy.  This is helpful for safety, but it can actually decrease the efficiency of a stove.

In order to have an efficient stove, you need materials that don’t transfer heat very well–or, in other words, materials that are not very thermally conductive.  Air is actually pretty good with respect to this, but it’s a problem when it moves around freely.  Many of the best insulators simply work by trapping air in small pockets.  This is how down blankets work.

Our initial prototype used perlite, but it’s not readily available in Myanmar, so we’ve been exploring the possibility of importing it and other materials.  Ash is readily available and a pretty good insulator.  We’ve also been looking at special clay mixtures which are much lighter (and thus have a lower specific heat capacity) than normal ceramics.

As always, we’d love to hear from anyone with thoughts/advice on the manner!

Tags: clay, design, insulation, optimization, perlite

This entry was posted on Tuesday, May 19th, 2009 at 8:23 pm and is filed under Stove Design. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.