Solar Box Cooker Pdf
For most foods, such as rice, the typical person would be unable to tell how it was cooked from looking at the final product. Bread and cakes brown on their tops instead of on the bottom. Crumpled newspaper, wool, rags, dry grass, sheets of cardboard, etc.
Food is prepared as if for an oven or stove top. Wikimedia Commons has media related to Solar cookers. Paraboloidal reflectors that have their centres of mass coincident with their focal points are useful. Solar cookers concentrate sunlight onto a receiver such as a cooking pan. This is the basis for the use of this kind of reflector for solar cooking.
It is important to reduce convection by isolating the air inside the cooker from the air outside the cooker. Cooking containers and the inside bottom of the cooker should be dark-colored or black.
The inside of the tube is lined with copper, stainless steel, and aluminum nitrile to better absorb and conduct heat from the sun's rays. See Liquid mirror telescope. World Health Organization. Frequently, these reflectors are made using many small segments that are all single curves which together approximate compound curves.
Some Gazans have started to make solar cookers made from cement bricks and mud mixed with straw and two sheets of glass. From Wikipedia, the free encyclopedia. On the other hand, there are disadvantages. Therefore, if the reflector were a rigid paraboloid, its focus would not remain stationary at the cooking vessel as the reflector tilts. Simply using a glass lid on your pot enhances light absorption from the top of the pan and provides a greenhouse effect that improves heat retention and minimizes convection loss.
The two troughs are held in a fixed orientation relative to each other by being both fixed to a frame. The second trough intercepts the converging light and focuses it to a point.
Although paraboloidal solar cookers can cook as well as or better than a conventional stove, they are difficult to construct by hand. If the material solidifies while it is rotating, the paraboloidal shape is maintained after the rotation stops, and can be used to make a reflector. More mirror material is needed, increasing the cost, and the light is reflected by two surfaces instead of one, which inevitably increases the amount that is lost.
The cooking vessel is located at the focus which is on the axis of rotation, so the mirror concentrates sunlight onto it all day. It turns out that the depression is an exact paraboloid.
Compared to cooking over a fire, the food does not have a smoky flavor. It is often made up of a large number of small plane sections, such as glass mirrors, joined together by flexible plastic. Some concentrating dishes such as satellite dishes that do not require a precise focus opt for a spherical curvature over a paraboloid.
Also, the light that reaches the targeted cooking pot is directed approximately downward, which reduces the danger of damage to the eyes of anyone nearby. Cooking portal Renewable energy portal. Parabolic solar cookers concentrate sunlight to a single point.
Depending on the size of the solar cooker and the number and quantity of cooked foods, a family may use one or more solar cookers. Panel solar cookers are inexpensive solar cookers that use reflective panels to direct sunlight to a cooking pot that is enclosed in a clear plastic bag. Different kinds of solar cookers use somewhat different methods of cooking, when nothing matters anymore pdf but most follow the same basic principles.
Although paraboloids are difficult to make from flat sheets of solid material, they can be made quite simply by rotating open-topped containers which hold liquids. They can be easily turned to follow the sun's motions in the sky, rotating about any axis that passes through the focus. The interaction between the light energy and the receiver material converts light to heat and this is called conduction. However, because food cooks faster when it is in smaller pieces, food placed inside a solar cooker is usually cut into smaller pieces than it might otherwise be.
The Scheffler reflector is therefore flexible, and can be bent to adjust its shape. The mirror is never exactly paraboloidal, but it is always close enough for cooking purposes. If the axis of symmetry is aimed at the sun, any object that is located at the focus receives highly concentrated sunlight, and therefore becomes very hot. The mirror has to be occasionally tilted about a perpendicular axis to compensate for the seasonal variation in the sun's declination.
Some solar cookers have been built that use them in the same way. This requires the trough to be tilted up and down as the seasons progress. Rice for a mid-day meal might be started early in the morning, with vegetables, cheese, or soup added to the solar cooker in the middle of the morning. Large quantities of food, and food in large pieces, take longer to cook.
Usually, the cooker is used only during this period, so no automatic sun tracking is incorporated into it. The cooking time depends primarily on the equipment being used, the amount of sunlight at the time, and the quantity of food that needs to be cooked. Food cooks faster in the two hours before and after the local solar noon than it does in either the early morning or the late afternoon. Evacuated tube solar cookers are essentially a vacuum sealed between two layers of glass. The central cooking tube is made from borosilicate glass, which is resistant to thermal shock, and has a vacuum beneath the surface to insulate the interior.
If several foods are to be cooked separately, then they are placed in different containers. Spherical reflectors operate much like paraboloidal reflectors, such that the axis of symmetry is pointed towards the sun so that light is concentrated to a focus. Paraboloidal reflectors generate high temperatures and cook quickly, but require frequent adjustment and supervision for safe operation. When this point is focused on the bottom of a pot, it can heat the pot quickly to very high temperatures which can often be comparable with the temperatures achieved in gas and charcoal grills. Several hundred thousand exist, mainly in China.
Air temperature, wind, and latitude also affect performance. Depending on the geometry of the surface, sunlight could be concentrated by several orders of magnitude producing temperatures high enough to melt salt and metal. Parabolic troughs are used to concentrate sunlight for solar-energy purposes. However, depending on local conditions and the solar cooker type, these projects could take half as long, or twice as long.
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