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| Solar Cooker |
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| A solar heating device is one which allows collection of a large amount of heat from the sunlight in a given region and restrict the loss of heat to the surrounding in the form of radiation. |
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| Solar Cooker |
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| The following facts help us to design an efficient solar cooker. |
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 A black body absorbs maximum heat. |
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 Loss of heat by convection can be restricted in a closed system. |
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 Radiation losses can be avoided by reflecting the rays inside the body with the help of reflection. |
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 Conduction can be reduced by using poor conducting materials. |
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| A solar cooker contains a box made of insulating material, with its inner surfaces blackened. The top is closed by a glass sheet. |
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| The box is closed such that the inner part does not come in contact with the outside air, there by reducing heat loss due to convection currents. The glass top reflects the light back to the box thereby reducing the heat loss due to radiation. The inside surfaces of the box is about 100 - 120o C and emit radiation in the infrared region. The glass top can reflect infrared radiation more effectively than visible light. A phenomenon similar to green house effect happens here. The glass top allows most of sun light (mostly visible range) into the box and does not allow the infrared rays to escape from the box. |
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| The efficiency of this solar cooker can be increased by placing a plane mirror at some inclination with the glass top to enhance more trapping of sunlight. |
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| Solar Furnace |
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| This type can be used for cooking. But the time of cooking depends on the intensity of the sunlight and hence the time taken is shorter in the summer and longer in the winter. Rice, pulses and vegetables can be boiled by keeping them inside the box. Baking and frying can be done in reflector type solar cooker. |
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| In reflector type suitable mirrors are arranged in a particular fashion, to focus the sunlight collected over a larger surface area on to a smaller region. A spherical mirror can help a larger one. In still larger one a number of plane mirrors are arranged side by side with different orientation to focus the light on to a desired area. |
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