RENEWABLE SOURCES OF ENERGY
The devices which convert solar energy directly into electricity are called solar cells. Solar cells are made from thin layers of semi-conductor materials such as silicon and gallium. Semiconductors are those substances which have electrical conductivity more than insulators but less than conductors. When sun rays fall on a thin sheet of selenium, electricity is produced.
Solar Cell Efficiency
The efficiency of first solar cell (to convert solar energy into solar power) made in 1954 was about 1%. This efficiency of solar cell was so small that it could not be used for practical purposes. But, the modern solar cells have efficiencies of about 25% which is very high. Now days the semiconductor materials used for fabrication of solar cells are available in abundance and on cheap rates. The solar cells are also environment friendly as they cause no pollution. Due to all these reasons the use of solar cells has increased considerably in last few decades. The solar cells are used extensively as a main source of solar power in artificial satellites, water pumps, street lighting, traffic signals, research centers located in remote areas, toys, electronic instruments such as calculators and watches etc. the solar cells are also used by scientists to run cars on experimental basis.
Solar Cell Panel
A single solar cell can generate about 60 milliamperes of current which is quite low for working of various devices. So, in order to generate required amount of current a large number of solar cells are joined together in a definite manner. This group of large number of solar cells joined together in a definite manner to produce required amount of electric current is called solar cell panel. Solar cell panels are used in those areas which receive a lot of sunshine. The schematic arrangement of use of solar cell panel to provide electricity of a street light is shown in diagram.
Diagram Of Solar Panel Providing Electricity To A Street Light
During day the solar power (electric current) produced by a solar cell panel from solar energy is stored in a storage battery. The electric current stored in the battery can be used to run various devices whenever required.
In spite of various benefits of solar cells, it is not possible to make use of solar cells to meet all our energy needs. The main reason for this are:
- The solar cells cannot be used during night and rainy days when the sky is covered with clouds.
- The fabrication and installation of solar cells is still quite expensive.
- The efficiency of solar cells is still low.
Test Your Understanding and Answer These Questions:
- What is a solar cell?
- What is a solar panel?
- What is a semiconductor?
- How do solar panels work?
- What are drawbacks in solar cells?
- What is efficiency of a solar panel?
- Give two examples of semiconductors.