From Solar Cooking
Heat-retention cooking (or retained-heat cooking) saves cooking fuel because after food has been heated to cooking temperature, it is placed into an insulated box where it will continue to cook until it is done. Retained-heat cooking is often introduced along with solar cooking since it further reduces the use of traditional fuels such as firewood, and the use of this method allows much more food to be cooked each day in a solar cooker. This method of cooking is also known as fireless cooking, haybox cooking, or wonder box cooking.
Using an solar box cooker as a retained-heat cooker
When combining retained heat and solar cooking, if food has gotten thoroughly hot in an solar box cooker (SBC), but clouds arrive before the food is finished cooking, a switch from solar to retained heat cooking should be made before the oven temperature drops below the boiling point. For large recipes this may be accomplished by simply closing the reflective lid on the pots of cooking foods. For smaller recipes, the solar oven is opened, taking care not to allow steam to escape from under the lids, pots are pushed close together along with any heated additional mass. Insulating pads or soft cushions are tucked closely around the pots and well heated mass. The SBC lid is then closed. This effectively makes the transition from solar to retained heat cooking. The cooker lid remains closed until shortly before serving time, when the food is tested. If not completely done, a very little conventional fuel will usually finish the job.Usually solar/retained heat cooking is done right where the SBC is located. However, a lightweight portable SBC can be moved temporarily indoors for its retained heat cooking time if the sun clouds over or if it rains. It may also be brought inside more or less permanently during the off season or at night and function as an insulated box for retained heat cooking. Used in this way the SBC continues to save fuel rather than simply being stored until conditions are right for solar cooking.
- Haybox how to and description
- A good external resource on this topic is BioEnergy Lists: Haybox, Retained Heat or Fireless Cookers.
- An audio interview with Mike Bridgwater about his work in combining solar cooker and heat-retention cooking in Tanzania.
- Heat Retention Cooking vs. Solar Cooking – Mike Bridgwater
- A Wikipedia article on Vacuum flask cooking
- How to make a cooking basket with banana leaves (and a basket). The top of the webpage is slightly broken, but it has good pictures and instructions and some cooking suggestions.