The free online document linked below has several interesting low tech/low cost stove designs from around the world, including some commercial scale stoves for feeding lots of people.
“In some parts of Indonesia a unique type of cooking stove is made of a mixture of mud and rice husks [hulls] and has the following advantages.
1. It can be made from locally available resources in rice-growing areas.
2. A knife is the only tool needed for construction.
3. The stoves can be built in the kitchen or at a workshop and then transported.
4. The stoves last up to five years before they disintegrate, and can be moved around the kitchen even after a few years use.
5. The material is strong enough so that it could be adapted to a wide variety of stove designs.
Case study of rice hull stove: “In one area of south Sumatra a family from central Java brought their stove building skills with them and set up a small family industry to supply the mud-rice husk stoves to other migrants. They produce about 150 stoves every month throughout the dry season which amounts to nearly one thousand stoves per year. Without any outside assistance this family has been able to sell thousands of these stoves which are an improvement over the traditional stove since people are buying them. A traditional technology transferred via skilled craftsmen is proving to be a more efficient method of diffusion than most centrally controlled attempts at improved stove dissemination.”
More at the source: Boiling Point Stoves