A rocket stove is a "rocket" combustion approach to preparing meals, which provides high combustion efficiency and efficient heat transfer to the cooking pot. Research suggests (through practical experience) that by using a rocket stove, you could save at least 50% of fuelwood, which is a significant savings for anyone's financial situation.
Institutional rocket stoves are designed mainly for use in poor countries, like Malawi in Africa, one of the poorest countries in the world. They have a huge problem of de-forestation, somewhat caused by high population density and because of large amounts of land taken by cash crops such as tobacco and tea. For the people of Malawi, fuelwood and charcoal are their main fuels for both home and institutional cooking.
This eight-part video series from Aprovecho Research Center details the steps necessary to build an institutional barrel stove. The exact measurements needed for the construction of the stove will depend on the dimensions of your pot. The barrel rocket stove made in this video is for larger quantities of food for orphanages, schools, hospitals, prisons, etc., and is made from a 200-liter (55 gallon) barrel.
No matter who you are or whether or not you live in a poor country such as Malawi, this fuel efficient stove could save you big money. You can make one from readily available materials. The rocket stove design uses significantly less fuel than an open fire to cook an equivalent amount of food, and it produces significantly less smoke and carbon monoxide. The stove design includes a chimney, so it can be used indoors when properly installed and vented.
PS: Here is the worksheet for computing gaps in the institutional rocket stove.