What is Solar Power ? - Working Principle, Advantages & Disadvantages

Solar Radiation on Earth :

     Sun is a huge nuclear reactor ( 7  x l0^5 km radius ) emitting a great amount of radiant energy ( 3.8 x l0^23 KW, 5800°K ), which can be easily converted into thermal energy.

    Among this suns total radiations only 1.7 x 10^14 kW ( 10 days = known fossil fuels resources ) of energy will get to the sun. The solar radiance outside the atmosphere is almost constant ( its value is called "Solar Constant", 1367 W/m² ) Solar radiation at ground level has two components: Direct Radiation and Diffuse Radiation. Only Direct Solar Radiation can be concentrated.

    The energy produced by the sun is constant. At the surface of the Sun the intensity of the solar radiation is about 6.33 x l0^7 W/m². As the sun's rays spread into the space the intensity of the sun rays will go on decreasing and at the time when rays reach the edge of the earth's atmosphere they are considered to be parallel.

Solar Power :

     A number of solar cells electrically connected to each other and mounted in a support structure or frame is called a photo-voltaic module. Modules are designed to supply electricity accordingly to the required voltage, such as a common 12 volt system. The current produced will dependent on amount of light strikes the module.

     Modules can be wired together to form an solar array. In general, the larger the area of a module of array, the more electricity that will be produced. Photo-voltaic modules and arrays produce direct current ( dc ) electricity. Modules are connected either in series and parallel or both to produce any required voltage and current requirement.

Power generation

Energy Conversion of Solar Cell :

     Solar cell operation is based on the photo-voltaic effect. The generation of a voltage at the junction of two different materials in response to visible or other radiation.

1. Absorption of light - generation of charges ( positive and negative ).

2. Separation of charges ( positive and negative ).

3. Collection of electrons ( passage of current ) at the electrodes.

     The figure shows the operation of a basic photo-voltaic cell, also called a solar cell. Solar cells are made-up of of semiconductor materials, such as silicon, used in the microelectronics industry. On the solar cells, a thin layer of semiconductor is kept to form an electric field, positive on one side and negative on the other. When light energy ( solar rays ) strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. When an electrical conductors is connected to the positive and negative sides and then to any load, forming an electrical closed circuit, the electrons will pass through the conductor in the form of an electric current which is known as electricity. This electricity can then be used to power anytype of load, such as a light or fan.

Power generation

Working Principle of Solar Power :

     The P-n junction is usually obtained by putting a P - type base material into a diffusion furnace containing a gaseous n - type dopant such as phosphorous and allowing then n - dopant to diffuse into the surface about 0.2 MM thick. The junction is thus formed slightly below the planar surface of the cell and the sun light impinges perpendicular to the junction. The positive and negative charges formed by the absorption of photons are thus encouraged to drift to the front and back of the solar cell. The back is completely covered by a metallic contact to remove to charges to the electric load.

Advantages of Solar Power :

1. Abundance Solar energy is available at free of cost.

2. Fabrication of PV cells is easy.

3. Bulky mechanical generator, turbines are not  necessary.

4. Photo-voltaic arrays an be installed quickly and in any size required.

5. The environmental impact is minimal.

6. No fuel, cooling system is required.

7. No bye-products are produced.

8. Very little maintenance is required.

9. Can be readily adopted for varying power requirements.

10. No moving parts in the system.

11. Well suited for remote places.

12. Some times Government provides subsidy.

Disadvantages of Solar Power :

1. High initial investment for panels arrays.

2. Sunlight that arrives the earth's surface is not constant.

3. The output varies with time of day, weather and place.

4. Large surface area is required to collect the energy at a useful rate. 

5. Only D.C is generated and needs inverter.

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