“Last class we discussed how heat energy from the sunlight is used in making solar cookers and water heaters. Sunlight is focused to a smaller area to achieve a good heating effect. But as in the case of the solar-powered car that Raju was talking about, sunlight is converted into electricity that drives the motor. Like Raju said, the moment you block the light falling on the panel the motor stops working. This indicates that light energy is converted into electricity. So class, what is special about this panel?” said the teacher.
Meera raised her hand to ask a question. “Teacher, we know that the electricity is the flow of charge by electrons or ions. How is this flow achieved through a panel?”
Raju chimed in, “The hydropower and windmills both use generators to generate electricity, however, solar panels do not have any visible generators.”
The class was surprised. Teacher continued, “Do you now understand why solar power is promoted as a clean and cheap renewable source of energy worldwide. Our own government is also promoting the use of solar energy use. We keep hearing about roof top panels being used on buildings, houses and stadiums to supply the required electrical power. The panels you see are the solar panels which are made of photoelectric cells. These cells convert the light into electricity. These are basically made from silicon which is abundantly available. Photoelectrons start flowing when the sunlight hits it. This is known as a photovoltaic cell. The satellites also use solar panels to get their required energy. The technology to make efficient solar panels is developing. In a country like ours where sunlight is available throughout the year – sunlight forms a very good source of energy to be converted into electricity. There are many solar power generating centres being developed currently. Some industrial units install these panels on their roofs. Thus solar power generation is growing in India at a fast pace. Karnataka, Telangana, Tamil Nadu , Rajasthan, Gujarat are major solar power generating states in India.”
“Apart from the different types of power generating methods we have seen, another highly potential method of energy the tidal power, wherein tidal currents run turbines to generate electricity. Tides are more predictable than the wind. So this method may see more applications in the future. Another clean type of energy generation is through nuclear power plants which are basically thermal power plants. The heat produced during nuclear fission in the nuclear reactor is used to boil water into steam, which turns the blades of a steam turbine, which in turn drives generators that produce electricity.
(Writer is a mechanical engineer and runs a hands-on science activity centre at Margao)