Solar Energy

Solar Energy

• Solar radiation arriving at earth’s surface, called as ‘insolation’ is in the form of electromagnetic waves, without any mass associated with it. Hence it is the direct and pure form of energy.

• The solar radiations are intercepted by suitable ‘collector system’ (flat plate or parabolic collectors) and heat energy available can be used for heating air, water or liquids as required.

• Density of insolation varies from place to place depending on altitude and metrological conditions.

• A solar thermal device consists of collector, distribution (circulation) system, storage and insulation.

• Solar energy is trapped by collector and by simple heat transfer techniques, heat energy is transferred through water, air or other suitable fluid.

• For more temperature and efficiency, number of collectors and parabolic collectors are designed.

Harvesting / Harnessing Solar Energy

• The techniques for collecting, converting and using solar energy is called as harvesting or harnessing. Some important solar harvesting devices are :

1. Solar cells / photovoltaic cells / PV cells

2. Solar heat collectors

3. Solar water heaters

4. Solar cooker

5. Solar water pumps

Solar cells or PV cells

• Solar cells are actually p-n junction diode working on photovoltaic technology i.e. there is direct conversion of solar radiation into Direct Current (DC) electricity.

• Semiconducting materials are most effective in this process of conversion.

• The light energy is converted into equivalent DC energy by solar cells (PV cells). This energy is then stored in some device (battery); so that it can be used whenever needed.

Uses

1. PV cells are commonly used in calculators and watches.

2. PV cells provide power to satellites.

3. Small electric appliances like - solar lamp, radio, street lighting.

4. Industrial applications - water pumping, wheather stations.

Solar heat collectors

• A solar heat collector is used for heating modern houses in eastern countries. A solar home or building is designed to collect the Sun's heat through South facing glass windows.

• In solar-heated buildings, sunspaces are built as large heat absorbers. The floors are made of tiles or bricks that absorb heat throughout the day, they release the heat at night when weather is cold.

Uses

1. Solar heat collector used in cold countries for making domestic or commercial places hot.

 

1. Use of Solar Energy

• Solar energy can be used for following purposes :

1) Air or water heating for industrial processes, use of solar pumps for water pumping.

2) Distillation and desalination of water (solar still).

3) Hot water for cooking, cleaning and similar uses, (solar water heater).

4) Electricity generation by using photovoltaic cells.

5) Solar drying for food and vegetable products for cottage and small scale industries.

6) Other uses like solar cookers, lamps, lanterns, battery charger, etc. for household purpose.

7) Solar cars/vehicles have been designed.

 

2. Advantages of Solar Energy

1. Solar energy is freely available.

2. It does not produce ash, fumes and noise pollution hence it is clean, noiseless and environment friendly.

3. It saves money in long run.

4. It is renewable form of energy

5. Non polluting. No wastes created by its use.

6. Has lot of domestic applications. Hence advantageous for huge Indian population.

 

3. Disadvantages of Solar Energy

1. Initial cost is very large.

2. Energy should be stored in batteries.

3. Large space is needed for installation.

4. Energy generated is dependent on solar intensity

5. High temperatures cannot be achieved (> 40 °C). Efficiency of collector goes down with increase in temperature.

6. Clouds affect the amount and quality (efficiency). Hence may not be available when required.