Ways of Harnessing Solar Energy

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Solar energy is generally referred to energy generated by sun. It’s renewable and clean source of energy thus does not produce any harmful pollutants. Daily earth receives 174 peta watts of solar energy at upper atmosphere out of which 30 % is reflected back to space. This energy is absorbed by earth in the form of heat and light that broadly contains infrared, visible and UV regions of electromagnetic spectrum.

Infrared waves are responsible for keeping earth warm and making life possible on our planet by the process of green house effect. Solar energy is also responsible for supporting life cycle for various organisms on earth, for example plants absorb the sunlight and produce nutrients to support their life through photosynthesis process. It helps in formation of clouds for rain by evaporation and condensation process, makes the wind blow, the ocean currents flow, drying our clothes, lighting and heating homes, etc. These are natural ways of harnessing solar energy but there are also some technological or man-made methods that are used to harness solar energy.

Solar cell: Solar cell is a device that converts solar energy into electrical energy through photovoltaic effect, which was discovered by French physicist Alexandre-Edmond Becquerel. Solar cell generally contains a semiconductor, usually made of silicon. The semiconductors have ability to absorb sunlight, which in turn excites the electron from lower to higher energy level. Due to this voltage is generated and causes flow of electrons that produces electricity. Today, Si solar cells produce maximum power efficiency of 22-23 %.

In India, the Indian Renewable Energy Development Agency and the Ministry of Non-Conventional Energy Sources are devising technical schemes to empower solar energy in the next few years. As a part of it, a Mega Solar Park of 7500 MW capacity is going to develop in the rocky mountainous region of Ladakh.

Solar heaters: Solar heater is a device, which converts solar energy into heat energy using a solar thermal collector. A solar thermal collector captures heat by absorbing sunlight that is generally embedded in a thermally insulated box with a transparent cover to minimize thermal loss. When water is heated by the solar energy, the hot water with lower density moves upwards and cold water with higher density moves down from the tank due to gravity. This hot water is collected and supplied to homes, offices, etc. Typically, an insulated tank of 100 litres capacity having a collector area of 2 m2 can supply water of temperature ≈ 60 - 80°C.

Solar cooker: Solar cooker is a simple device that is used to utilize solar energy directly to heat or cook food. In a solar cooker, a mirror surface with high reflectivity is used for concentrating the sunlight to small cooking area where cooking pan is kept. This setup is then isolated using a glass lid that increases light absorption and provides a greenhouse effect that improves heat retention and minimizes convection loss. Such devices can produce temperature ranging from 65 to 400 °C.

Author: Dr Alka Pareek, National-Postdoctoral Fellow, Bioengineering and Environmental Science Lab, EEFF Department, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad.

Posted By : ScienceIndia Administrator
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