1. The sunlight falling on the earth per day delivers energy which is 50,000 times (fifty thousand times) the total energy used all over the world in one year. Sources of Energy Solar Energy

2. What is meant by solar energy Sun emits visible, infrared and small amount of ultraviolet radiations. Visible radiation gives light energy and the infrared radiation gives heat energy. The light and heat energies of the sunlight are collectively called solar energy. Sources of Energy Solar Energy

3. The amount of solar energy reaching the periphery of the earth’s atmosphere at an average distance between the sun and the earth, per second per square metre area exposed at right angle to the sun rays is called the solar constant. The estimated value of solar constant is 1.4 kilojoules per second per square metre. Thus, one can write, Solar constant = 1.4 kilojoule per second per square metre or, Solar constant = 1.4 kJ s –1 m –2. Sources of Energy Solar Constant

4. Solar energy has been traditionally used for the following purposes: (i)For drying clothes (ii) For making salt from sea water (iii) For reducing the moisture content of food grains (iv) For sun-drying of vegetables, fruits and fish, etc Sources of Energy Traditional applications of Solar energy

5. Some of the most common ways in which the solar energy can be utilised are, (a)For cooking: Solar cookers are used for cooking food by utilising heat energy of solar radiation. (b) For heating water. By using solar heaters, solar energy can be directly used for heating water for domestic / industrial uses. (c) For producing electricity. Light energy of the sun radiation can be used to produce electricity by using solar cells made of silicon (these are called photovoltaic cells). Sources of Energy Utilization of solar energy

6. (i)Solar energy is a renewable and almost inexhaustible source of energy. (ii) Solar energy is cheap and easily available for major part of the year particularly in the tropical countries. (iii) Solar energy does not cause any pollution. Sources of Energy Advantages of solar Energy Using solar energy has the following advantages

7. (i)Solar energy is not available at all the places, all the time. (ii)Solar energy is a diffused (low intensity) source of energy. Therefore, the processes needing more energy cannot be run with the help of solar energy. Such processes require concentrated forms of energy, e.g. coal, diesel, electricity, etc. Solar energy has the following limitations Sources of Energy Limitations of solar Energy

8. A solar cooker is a device that is used to cook food by utilising the energy radiated by the sun. The range of temperature that can be attained in a solar cooker is 100  C - 140  C. Sources of Energy Solar Cooker

9. Sources of Energy A solar panel is a packaged, connected assembly of photovoltaic cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. Solar Cell Panel

10. Sources of Energy Solar Cell Panel Solar panels use light energy (photons) from the sun to generate electricity through the photovoltaic effect. The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon. Cells must also be protected from mechanical damage and moisture. Most solar panels are rigid, but semi-flexible ones are available, based on thin-film cells.