2016 Feb

Electricity: Thermal Power

February 25, 2016

Steam Turbine

Thermal power is one of the oldest ways of generation of electricity. ‘Thermal’, here represents the heat mediation in power generation. In a generic sense, any form of power generation which involves the generation of heat and its subsequent utilisation to run a turbine comes under the category of thermal power generation. But in a conventional sense, and in most of the thermal power plants coal and other fossil fuels are the major source for the generation of this heat. Hence, this article is dedicated to power generation from fossil fuels. The article also deals with the subsequent damage imparted on the environment in comparison with other power sources like solar wind, etc.

A typical thermal power plant needs a source of heat, equipment to handle the water-steam generation cycle, turbines and other periphery tools to handle the power generated. The source of heat is generally fossil fuels like coal and hence most of the thermal power plants are located near the sites rich in these fossil fuels. Combustion of coal in which carbon is converted into carbon dioxide generates large amounts of heat energy( around 30 kilojoules/gram). In this process, carbon reacts with oxygen and forms carbon dioxide; carbon monoxide is formed when the oxygen is present in insufficient quantities. The heat generated is used to increase the temperature of water and convert it into steam. Steam thus generated is used to run the turbines. As we have learnt during our JC Physics tuition classes on Electromagnetic Induction, due to the motion of these turbines, the coils connected to them move in a magnetic field and hence the time varying magnetic field produces current/voltage in coils. The steam is then condensed to water at the cooling towers and this condensed water enters the cycle once again.

The environmental woes of thermal power start with coal mining. Coal mining is an environmentally unfriendly activity. Carbon dioxide and carbon monoxide are harmful beyond certain levels with the former being a green house gas. Depending on the nature of the coal bed, different forms of chemicals arise as by-products are called fly ash and bottom ash based on their nature. Fly ash contains minute particles that can suspended in the air, these particles are generally made of oxides of various materials present in the coal bed. These are collected using electrostatic devices that attract the suspended particles. The tiny amounts of fly ash that escape these devices pose serious environmental threat as it contains heavy metals. Bottom ash is also chemically similar to fly ash but has particles large enough to be collected at the bottom.

In addition to causing air, water and soil pollution, thermal power generation has serious ramifications in the terms of global warming. Hence most of the developed and developing nations across the country, erstwhile dependent on thermal power, are now switching to sustainable, renewable and environmentally viable methods of power generation.

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