A year ago, after we had just completed a prototype of a stove design we liked (it was literally made from an old metal trash can!) we decided to try adding a “pot skirt” to see how much it would improve our stove’s efficiency. We had read about these heat shields in other stoves before; the basic idea is to surround the pot on all sides with a thin metal shield that creates about an inch-gap for hot air to pass through. The pot skirt thus prevents heat from the stove from escaping to its surroundings, keeping it close to the walls of the pot and increasing the heating surface.

The idea sounded interesting, so we set to work building a prototype and testing it out! (My next post, “Frustrated by Frustums” will explain why our prototype is the shape it is-most pot skirts are actually just cylindrical.) The result was… WOW.

Adding the pot skirt cut down our rocket stove’s boiling time almost in half. The rocket stove itself was already able to boil water in maybe half the time it took an open flame, but with the pot skirt, we were boiling water at incredible speeds: up to a third of the time it takes to boil water on an open flame. Whatever we expected, I don’t think it was as drastic as this.

As great as it may sound though, our pot skirt idea still needs a lot of work. Adding that much material to our stove makes it more expensive and difficult to manufacture, not to mention clunky looking. Because it traps hot air, the skirt metal gets really hot too, posing a potential burn hazard to our customers. Our first prototype didn’t allow the cook to see the flame very well either (we fixed that issue by cutting out holes into the skirt).

Right now, we’re starting to explore new skirt designs, as well as some completely new concepts. One of the things we’d like to try is something similar to a “heat exchanger” which traps hot convective air at the bottom of the pot. The Jet Boil camping stove uses a mechanism like this. Such a design wouldn’t increase our heating surface area, but it will at least increase the concentration of hot air, which may be enough.

If you have any ideas about this engineering challenge, we’d love to hear them!

We’ve been talking a lot about our philosophy approaching this project, but I think it’s time to explain a little bit more about our actual stove technology. The stove prototype we’ve built for women in Myanmar is based on the Rocket Stove created by Dr. Larry Winiarski at the Aprovecho Research Center. Many such stoves have been modeled after Dr. Winiarski’s design, including the Berkeley Darfur Stove as well as other home-made versions (there are tons of videos online for how to make your own).

We chose to adapt the rocket stove design because its use of low mass insulation is very effective at keeping the fire hot and transferring most of the heat to the pot.  In my next couple of posts, I’ll explain how a hot fire and a design that channels heat to the pot are both important for improving the overall efficiency of the stove (I’m trying to keep my posts shorter :p).

If you’re wondering why we chose to design our own version of the rocket stove rather than partner with one of the other organizations that are building them,  please read our post about the importance of tailoring the stove to the local culture.  We aren’t seeking to compete with other groups; instead, we learn from them and share our own ideas. Building on someone else’s great technology also gives us time to focus on equally important issues of manufacturing, marketing, distribution, and education, all of which are crucial in getting our stove into the hands of women.

In my last post, I talked about how introducing new technology to developing countries is often not enough, regardless of how great it is. There are many cook stove technologies being developed, but how many, really, have made a significant impact? How many have been embraced by women as the norm, and not as something foisted on them by an aid agency? I think that seeking to understand culture and how it changes over time is what differentiates our cook stove project from many others that have gone before it.

Culture explains why we chose some of the paths we took, such as deciding to make a wood-burning stove rather than choosing “greener” (or even free) sources of heat. It explains how low the stove is because the women we designed it for are used to squatting on the ground, and how wide the opening for the firebox is because they like to regulate the strength of the flame by the amount of wood they add to the fire.

Unexpectedly, culture also explained why women were so excited that the box design of the stove and the flame it produced made it look just like a gas stove; our design made them feel rich.

Don’t get me wrong, having a robust technology is still important to us. We’ve made some improvements to existing stove designs to minimize fuel consumption and to protect women from the heat of the fire because we know those are important considerations for them as well. But besides implementing the technology well, we hope to create a product that provides meaning in our customers’ lives. We’re creating a stove that enhances their culture, not rejecting it as “primitive” or “backward”, which some stove projects have a tendency to convey.

And yes, culture does change. People in this country didn’t use microwave ovens from day one—that technology had to be introduced. Perhaps there was a large resistance to change then, with women complaining that using a microwave wasn’t “real” cooking. As a team, we’re not averse to introducing new technologies as long as it seems to fit with where the culture of cooking is going. In fact, enclosing an open flame is still a pretty revolutionary idea in some parts of the world. And the microwave, though it was a radical departure from the cooking technologies before it, was part of a greater shift towards time-saving devices and a growing culture of convenience; it still made sense.

For me, the most satisfying compliment about our stove is not, “wow, it saves THAT much wood?!” It is in the stories we hear back from our partners saying that the stove has a prominent place in the home, is considered a pet by the women, and has become the focus of the family’s conversation at the dinner table. That’s when I know we have a shot at lasting impact.

Before we started this project, I had no idea that there was such a big stover community out in the world. Go on the web, type “cook stove”. You’ll be amazed at how many hits you’ll get: clay, metal, ceramic, wood-burning, charcoal, solar, new biofuel… you name it, someone’s tried it out. Heck, I would meet random people in Stanford, tell them I was working on a cook stove project and strangely enough, odds were, they were too.

To make my point, the technology we’re using is nothing new. Many people have seen the scarcity of fuel and smokiness of cooking on an open fire and have thought of creating a stove that would change that. But too many of these stoves are all about the technology—how efficient, how cheap, how easy it is to make; not enough are about the customers.

I’m not just talking about the need for a user-friendly stove; many stoves that are sold in developing countries are already easy to use and have addressed issues of safety to some extent. What I’m concerned about is that few stoves are designed with the area’s culture of cooking in mind.

Take a solar oven, for example. It uses zero fuel, can be made out of cheap materials, and has virtually no moving parts. As a technology for extremely affordable cooking, it’s pretty compelling. But will a woman used to seeing a large flame while cooking on an open fire trust that putting her pot into a black box (literally) will cook her food? Will she endure the passive wait time of what is closer to a baking process, or will she miss stirring her pot and checking to see that the food is cooked just right? If she has an indoor cooking hut, is she willing to cook outside, and only when the sun is out? What will the rest of her family think of a wife that lets the solar oven do all the work for her?

What will the food taste like?

What kinds of food will she be unable to cook?

Will she still enjoy cooking?

Expecting customers to use technology that is such a radical departure to their culture of cooking is asking them to turn their backs on traditions that have been passed down from generation to generation. It’s like telling an Italian to make his risotto in the microwave. It just doesn’t work.

Don’t get me wrong, I have nothing against solar ovens, and new technology. Maybe a solar cooker would be perfect for a culture where women are used to baking their foods in the hot sun for long periods of time. But technology itself isn’t going to have a lasting impact if none of the women really want to use it. In my next post, I’m going to explain how respecting culture has affected some of the design decisions we’ve made on our stove that make it a compelling product, not just another technology.