Thermal power plants converts the heat energy of primary fuels such as coal, to the electric power. In most of the thermal power stations, combustion of primary fuels heats the water and transforms it to steam. The steam drives steam turbines, which eventually generates electricity. Subsequently, the steam is condensed and recycled back into the system. The thermal power stations may use several different types of heat sources, including fossil fuels, nuclear energy, biomass and waste.
Types of thermal power plants (Wikipedia):
Subcritical: Operate at critical point of water with temperature of 374 °C and pressure 22.12 MPa.
Supercritical: Operate at 500-600°C temperature and 24-26 Mpa Pressure.
Ultra Supercritical: Operate at 760°C temperature and 34 Mpa Pressure.
Supercritical coal-fired power plants have higher thermal efficiency than subcritical power plants due to their higher operation temperature (500-600°C) and pressure (24-26 MPa) (Li & Wang, 2018). The 1980 MW Koradi Thermal Power Station in Maharashtra is a Super-critical coal-fired power plant (Illustration 1). The 420 MW Chandrapur Thermal Power Station in Maharashtra is a Sub-critical power plant (Illustration 2).
Illustration 1: 1980 MW Koradi Thermal Power Station, Maharashtra
Illustration 2: 420 MW Chandapur Thermal Power Station, Maharashtra
The thermal power plants using coal, lignite, diesel, and natural gas, accounted for 69.25% (276,293 MW) share of total installed capacity of conventional power plants in India (MOSPI, 2019). The total installed capacity of coal and lignite based thermal power plants is 171,239 MW. The Vindhyachal Thermal Power Station in Madhya Pradesh, operated by NTPC, is the largest coal-fired power plant in India with an installed capacity of 4,760 MW, followed by the Mudra Thermal Power Plant in Gujarat operated by Adani Power Ltd. with an installed capacity of 4,620 MW.
In a Combined Cycle Gas Turbines (CCGT) power plant, the hot exhaust gas from a gas turbine is used for generating steam in a waste heat steam generator, which is then used in a steam turbine for generating additional electricity (Czisch, 2011). Natural gas based power plants are comparatively less polluting and more efficient than other fossil fuel based power plants in general, and the coal power plants in particular. The Pragati Combined Cycle Gas Turbine (CCGT) – III, located in Delhi state, is the largest gas based power plant in India with an installed capacity of 1,500 MW. Illustration 3 shows 538 MW Kawas CCGT located in Surat district of Gujarat, operated by NTPC.
Illustration 3: 538 MW Kavas CCGT, Gujarat
Diesel-based power plants may use Diesel, Furnace Oil, Heavy Fuel Oil (HFO), Low Sulfur Fuel Oil (LSFO) or Low Sulfur Heavy Stock (LSHS). The Basin Bridge Diesel Generator Power Plant (DGPP) in Tamil Nadu is the largest diesel power plant in India with an installed capacity of 200 MW.
The installed capacity of nuclear power plants in India is 6,780 MW with Kudankulam Nuclear Power Plant in Tamil Nadu being the largest nuclear power plant with an installed capacity of 2,000 MW. All nuclear power plants in India are operated by Nuclear Power Corporation of India Ltd. (NPCIL).
In addition to the conventional thermal power plants, biomass and waste-to-energy (WTE) power plants are also being promoted in India. The installed capacity of biomass-based power plants, including bagasse (waste from distilleries) is 2,941 MW, while that of WTE power plants is 272 MW.
Czisch, G., 2011, Scenarios for a Future Electricity Supply, The Institution of Engineering and Technology, London, United Kingdom.
Li, D. and Wang, J., 2018, Study of supercritical power plant integration with high temperature thermal energy storage for flexible operation, Journal of Energy Storage, 20, pp. 140-152.
MOSPI. (2019). Energy Statistics 2019. New Delhi: Ministry of Statistics and Programme Implementation (MOSPI).
Wikipedia, Thermal power station, URL https://en.wikipedia.org/wiki/Thermal_power_station, Accessed: July 2020.