See also: Solar food processing
A study in Gujarat State of India among box solar cooker owners showed that a good part of the box solar cooker owners use their cookers for non-cooking purposes. By non-cooking uses I mean uses other than everyday meal cooking. Some examples of non-cooking uses are vegetable drying or baking, which will be discussed later. I observed that due to certain reasons, some families could not use their solar cooker for everyday meals such as lunch or dinner, but they used it mainly for non-cooking purposes. Some other families used their solar cookers for both cooking and non-cooking purposes.
Below are a few of the less obvious uses of a solar cooker, demonstrating it's versatility. Even if a solar cooker is used regularly for everyday cooking, these special purposes may only increase its value. In several cases, a solar oven demonstrates distinct advantages over conventional ovens/cooktops in that a solar oven will not typically reach temperatures that burn.
Jam making/pickle making/ketchup making
During the summer many kinds of vegetables and fruits are available at cheap prices in the market. In many places some of these vegetables and fruits are not available in the cold seasons of fall and winter. For example ketchup or chutney (chatni) can be prepared from tomato in the solar cooker for consumption later in the year. Another example is to make jam or pickle out of certain fruits and/or vegetables for example mango, carrot, cauliflower etc. in the summer time for later consumption. Solar box cooker due to its proper range of temperature for simmering of vegetables and fruits can be used for preparation of jam, pickle and ketchup making.
- (Note that only fruits can be canned safely without the use of pressure.)
Drying of vegetables and fruits
Drying vegetables and fruits for later use (for example ginger) is another special use of a solar oven. This is desired when there is plenty of cheap vegetables or fruits available. In some food cultures people dry onion, aubergine (eggplants), ladyfingers (okra), ginger, tomato etc. for consumption later in the year when they are scarce and also expensive.
Making of Ghee
A solar oven is ideal for the making of clarified butter, known as ghee. Ghee is a very popular food in India, particularly useful because it does not need refrigeration as does butter. Ghee is made by heating butter in the solar oven over about an hour or so. It should have a very low simmering, because over 80°C the butter will burn. After some time an opaque residue will separate from the melted butter leaving a transparent liquid which is the ghee. The residue is discarded. How to ensure the solar oven does not overheat is discussed at the bottom of this page.
A box solar cooker is ideal for heating milk for drinking, cream making or other purposes, because the temperature range a solar cooker reaches will not burn the milk. Milk is sensitive to temperature over ca. 96 °C, it will simply burn and stick and an unpleasant odor will remain in the boiled milk. Here again the temperature range of the solar oven is the advantage.
Candle-making (melting wax)
Leftover wax candle stubs can be saved and melted down in a solar cooker, poured into a mold (paper cup, plastic bottle, coconut, etc.) to make a new candle. The wick: somehow fasten an organic-source string going from the bottom to the top of the mold.
Traditional irons did not use electricity, but had compartments where hot coals would be placed. They are still in use today. A suggestion that arrived from AlSol, is to take two irons and alternate between having one heated by a parabolic solar cooker, and one being used. Adding stones or clay into the compartment will add to the ironing time. A parabolic style cooker is best suited to provide the focused heat required for ironing.
Solar cooking advocate Pat McArdle has produced a short you tube video which demonstrates the ability of a parabolic solar cooker to heat water for tea in the snow when the outside temperature is below 30 degrees F or 0 degrees C. In the summer the same parabolic solar cooker is used to heat a traditional iron to press a linen table cloth. http://www.youtube.com/watch?v=1yOOxCnM6Ns
Insect killing of grains
In some areas and in some seasons, the grain storage of the family may be exposed to development of small insects in the grain. These insects might be mixed with grain! Getting these insects away from the grain may usually be a difficult task to be done manually. In Gujarat I saw that some families put their insect-exposed grain, bean, peas etc. in the solar cooker a few hours during a day or two, in this way the insects are killed due the heat of the oven while the grain, beans, peas etc. was not damaged. Afterwards the family could easily get rid of the dead insects by blowing them or using sieve.
Make water safe to drink
Heating water for household uses
During the study in Gujarat I observed that some families decreased the temperature and moisture developed in their solar cookers, by slightly opening the top glass lid of their cooker by temporarily creating a gap for the oven. This is indeed an easy and effective way to control the temperature/moisture within the oven. One can for example place a coin or a small glass ball to keep the top sash open. This is necessary specially when the sun is high and one should avoid high temperatures for some of the above-mentioned special uses for example when one is heating milk.
I built a solar cooker to heat rocks for keeping our feet warm at night. Adding a little water to the remaining rocks adds nice warm humidity to our dry winter air.
- Solar food processing