Question

Explain the working of solar cooker.

Answer 1

A solar cooker is a type of solar thermal collector. It “gathers” and traps the Sun’s thermal (heat) energy.

Concentrating sunlight:

1. A mirror surface with high specular reflection is used to concentrate and channelize light from the sun into a small cooking space.
2. The sunlight can be concentrated by several orders of magnitude, producing magnitudes high enough to melt salt and metal.
3. For household solar cooking applications, such high temperatures are not required.
4. Solar cookers available in the market are designed to achieve temperatures of $650°Cto4000°C.$

Converting light energy to heat energy:

1. The concentrated sunlight is focused onto a receiver such as a cooking pan.
2. The interaction between the light energy and the receiver material helps to convert light into heat by a process called conduction.
3. The conversion is maximized by making use of materials that conduct and retain heat.
4. Pots and pans used in solar cookers should be matte black in colour to maximise absorption.

Trapping heat energy:

1. The occurrence of convection is reduced by isolating the air inside the cooker from the air outside.
2. Using a glass lid on the pot enhances light absorption from the top of the pan and decreases the convection energy loss along with improving the heat holding capacity of the cooker.
3. The glazing taps the incoming sunlight but is opaque to escape infrared thermal rays.