Write a note on Solar Cells.?
ANS:
* Solar cell is a device that converts solar energy directly into electrical energy.
* Earlier, it was observed that when solar rays fall on a thin wafer of selenium, electricity is generated.
* A solar cell made of selenium wafer converts only 0.7% of solar energy into electrical energy which is a very small output and hence impracticable for generating electricity.
* The first solar cell made in 1954 could convert about 1% of incident solar energy into electricity.
* Modern solar cells most commonly made from semimetal silicon can have efficiency of upto 25%. Silicon is easily available and is eco-friendly.
* A typical solar cell consisting of a 2 x 2 cm square piece of pure silicon can produce about 0.7 watt electricity with about 10% efficiency.
* This electricity is quite small and to get large amount of electricity several solarcells are connected together in series. This arrangement is called Solar Panel.
* ADVANTAGES:
1. Solar cells provide eco-friendly environment.
2. Solar cells can be used anywhere as a self-generating source of electricity.
* LIMITATIONS:
1. The availability of the special grade silicon required for making solar cells is very limited.
2. The cost of connecting material used in solar panels is very high as it is generally silver.
3. The current produced by solar cells is direct current (DC) and it has to be converted to alternating current (AC) for some devices. This involves high cost and loss of efficiency.
4. The conventional method of storing solar energy in storage batteries is not efficient enough.
* USES:
1. In artificial satellites.
2. In radio wireless transmission.
3. In TV transmission.
4. In traffic signals and research centres.
5. In calculators and watches.
6. In solar cars.
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