The Basics of Cooking | Concerning the Solar Cooker
There are two options for cooking: baking with oil or boiling in water. The first one takes place at about 180 degrees, the second one at 100 degrees. Every 10 degrees the temperature rises, the reaction of cooking goes twice as fast. This is why stir-fried vegetables are ready more quickly than vegetables that are boiled in water.
With solar energy it is possible to heat a baking tray up to 150 degrees, but when vegetables and meat are placed on it, the temperature drops sufficiently. For this reason, a Solar Cooker is unsuitable for baking. On the contrary, it ís possible to bake a fillet of chicken (see Youtube Solar cooking in the snow of Maarten Romijn). It is juicy and ready, but the crispy crust is missing, because this chemical reaction takes place at a higher temperature.
Some dishes, such as dried legumes, leathery meat and attracting broth, need a considerable longer boiling time than others. A pressure cooker boils at 120 degrees so the boiling time becomes roughly a quarter of the original time. This partly explains the use of the pressure cooker in Morocco.
The poorer part of the Moroccan population uses dried legumes, vegetables, couscous, sugar, flour, oil, beans, potatoes and water as main ingredients of their dishes (Vorst, van der, N., 2015).
The sun provides approximately 1000 W/m2 power. The bigger the effective surface of the Solar Cooker, the higher the power. However, the product should also be usable. A Solar Cooker with an effective surface of 0,24 square meters is considered usable. This type has a power of 240 Watt, with which it takes relatively long to heat something. Take for an example one liter water which temperature has to go from 20 degrees to 100 degrees. This takes 4200 J/kg/K * 1 kg * 80 C = 336 kJ. Then it takes 336 kJ/240s = 23 minutes to get the water boiling. In practice it will even take longer, because the process is influenced by heat losses and the fact that there’s isn’t always maximal sunpower due to clouds. Secondly, the vegetables and meat also contain water, so the process will be slower.
Conclusion
When someone has enough time, one could cook with the use of solar energy. In the west we already know such thing as ‘slow cooking’. One should place the pan in the Cooker around 10 o’clock and the food will be ready around 5 o’clock in the evening. The food won’t burn. However, the Solar Cooker should be turned to the direction of the sun every twenty minutes. This act could be automatized.
Product proposition
The cooking process, based on the chemical reaction, starts at 80-90 degrees. It is preferable to achieve this temperature within a short period of time, so the cooking process can begin. With a woodfire or gas flame about 1000 Watt of extra energy can be added. The same liter water then boils within six minutes. When an efficient Wood Gas Stove is used, circa 60 gram wood is needed. When the water has the right temperature, only the heat losses to the surroundings should be compensated. This could be done with the use of solar energy. Compared to conventional ways of cooking on woodfires, the wood consumption can be reduced with 75 percent, without any loss of speed.