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Solar Cooker

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Rural Technology

A solar cooker is a device which uses sunlight as its energy source. It requires no other fuel to run. In India we get almost 250 sunny days.

Generally cooking requires a temperature around 1000 C (B.P. of water). From the sun we get the temperature near about 35-400 C. By making proper arrangements for to track sun & trap the heat we can cook very efficiently, saving huge amount of wood, kerosene and other possible fuels. Due to this reason , since a decade the use of solar cooker domestically increased its need.

There are many different types of Solar cookers. All solar cookers use the sun's heat and light to cook food. The basic principles of solar cookers are:

  • Concentrating sunlight: Sun’s rays are scattered from source, need to concentrate for higher temperature & heat. Mirrors or reflective metal is used to concentrate light and heat from the sun into a small cooking area.
  • Converting light to heat: Sunlight heats the pan. A black pan will absorb almost all of the sun's light and turn it into heat. Solar cooker tried to absorb maximum heat from sunrays.
  • Trapping heat: Air flow will cool the surface. Therefore air inside the cooker is isolated from the outside air. For better efficiency the collected hot need to be trapped.

Solar cookers are based on above principles.

1) Box Type Solar Cooker :

The box type solar cooker consists of a rectangular box insulated on the bottom and sides & having two glass covers on the top. A single glass reflector whose inclination can be varied with the attachment to the box. Temperature up to 150 deg C can be reached in the cooker. But food containing water can be heated up to 100 deg C. Since temperature is not increasing beyond particular limit, there is no danger of food getting over cooked.

(1) Outside lid (2) Glass reflector (3) Cooking utensils. (4) Inside cover (5) Double glass cover (6) Box (7) Handle (8) Inclination Adjustment.

Fig. of Box type Solar Cooker

Concentrator Type Solar Cooker :

In this type the radiation is concentrated by a parabolic reflecting surface concentrating the radiation towards the focus. The cooking vessel is hence placed at the focus of the parabolic mirror. These cookers requires system to track sunlight. Temperatures well above 2000C can be achieved in such cookers. The reflecting surface can be glass mirrors, aluminum sheet and aluminium foil. The main limitation with these cookers is that it requires constant attention to track the sun, as a result the operator has to be all the time in sun but can be compensated by automatic tracking system. Another disadvantage is that except for glass , the reflectivity of all other surfaces decreases with the passage of time. The concentrator cookers are useful where large number of meals to be prepared at the same time on daily bases( hostels, hotels, pilgrimage places etc)

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