How Do Thermal Power Plants Work? the Working Principle

How Do Thermal Power Plants Work? the Working Principle

You can learn more about thermal power plants by reading about their operating principles and gaining a better understanding of them.

The conversion of heat energy to electric power for domestic and industrial uses takes place in a thermal power plant. Steam-driven turbines convert heat into mechanical power, which is then converted into electric power during the production of electricity.

The purpose of this article is to give you a conceptual introduction to the working principle of thermal power plants. Read Advantages and Disadvantages of Thermal Power Plants.

How Does a Thermal Power Plant Work?

The working principle of a thermal power plant is “heat released by burning fuel, which produces (working fluid) (steam) from water.” In thermal power plants, the steam that is produced drives a turbine that, when connected to a generator, generates electricity.

Thermal Power Plant and Steam Turbine

In thermal power plants, water is used as the working fluid. Nuclear and coal-fired power plants fall under this category. How fuel energy is transformed into electricity determines how a power plant operates. In a thermal power plant, high-pressure, high-temperature steam rotates a steam turbine, which then transfers that rotation to a generator to create electricity. The steam turbine is the power plant’s heart.

How Do Thermal Power Plants Work? the Working Principle

Three Stages of Steam Turbine

Steam turbines in their various stages, including high-pressure, intermediate-pressure, and low-pressure turbines, are frequently used in high-capacity power plants.

High-pressure, high-temperature steam loses energy while rotating turbine blades. The turbine’s outlet will consequently have steam that is low in pressure and temperature. Here, steam is increased until saturation is attained. The entropy of the steam should not change because there is no heat being added to or removed from it.

The p-v and T-s diagrams below show how this shift happens. We will be able to continuously produce electricity if we can restore this low-pressure, low-temperature steam to its initial state.

Use of Condenser

A gaseous fluid should first be transformed into a liquid state because compressing a gaseous fluid requires a significant amount of energy. A condenser is used for this purpose, which rejects heat from the environment and converts steam to liquid. Because the fluid in a condenser is free to expand, there should be no pressure change during this heat rejection process.


Because the fluid at the condenser’s exit is liquid, we can use a pump to increase the pressure. The fluid is in a liquid state, so little change occurs in the fluid’s volume or temperature during this process (it rises by 2 to 3 degrees Celsius). The fluid has now returned to its original pressure.

How Do Thermal Power Plants Work? the Working Principle

Heat Addition in Boiler and Rankine Cycle

The fluid is heated from the outside in order to bring it back to its original temperature. A heat exchanger known as a boiler is used to introduce this heat. Because the fluid is free to expand in heat exchanger tubes, the pressure of the fluid remains constant.

The liquid turns into vapor as the temperature rises, then the temperature drops back to where it started. The Rankine Cycle—the thermodynamic cycle of a thermal power plant—is now finished. Continuous power generation is possible thanks to the endless repetition of this cycle.

Condenser Heat Rejection – Cooling Tower

For the condenser to reject heat, a colder liquid needs to come into contact with it. In a thermal power plant, a cooling tower produces an endless supply of cold liquid. The cooling tower’s cold fluid absorbs heat from the condenser and warms up, rejecting this heat to the atmosphere through natural convection.

Boiler Furnace for Heat Addition

To heat up the boiler, a boiler furnace is used. Here, the fuel and air interact to create heat. Coal or nuclear fuel can be used in a thermal power plant. When coal is burned as a fuel, it emits a large amount of pollution, which must be removed before it is released into the environment.

A number of steps are taken to achieve this, the most crucial of which is the use of an electrostatic precipitator (ESP), which removes ash particles from the exhaust. Now, an exhaust stack releases much cleaner exhaust into the atmosphere.

Working Components of Thermal Power Plant

Thermal Power Plant consists of a whole set of steps in series for producing electricity.

How Do Thermal Power Plants Work? the Working Principle
  • Boiler: The furnace is a massive boiler that transfers heat from the burning fuel to countless rows of water tubes that completely encircle the flames. Through the tubes, water is continuously pumped.
  • Drum: It generates a stream for the turbine while containing steam and water under high pressure. Additionally, a boiler-feed pump delivers water to it.
  • High-pressure (HP) Turbine: Steam is allowed to expand as it travels through turbine blades, converting thermal energy into mechanical energy. Next, the steam is passed through a reheater S3, which boosts thermal efficiency and prevents premature condensation.
  • Medium-pressure(MP) turbine: It is comparable to an HP turbine, but because it is bigger, the steam can expand even more. contains high-pressure water and steam and generates a stream for the turbine
  • Low-pressure(LP) Turbine: It is responsible for removing the last of the steam’s usable energy and is divided into two identical sections. It is possible for the steam turbine to be either an impulse, reaction, or a hybrid of the two.
  • Condenser: By letting the steam pass through the cooling pipes S4, it causes the steam to condense. Through pipes from outside sources, cold water dissipates heat. As cooling water flows through the condenser tubes, its temperature rises by 5oC to 10oC. The condensed steam has a temperature range of 27 to 33 degrees Celsius. A pressure of 5kPa is produced when steam condenses. The reheater transfers the lukewarm condensed steam to a feedwater pump before being removed by a condensate pump.
  • Reheater: To raise the temperature of the feedwater, the heat exchanger receives hot steam bled off from the high-pressure turbine. This method of removing some steam boosts overall effectiveness, according to thermodynamic studies.
  • Burner: The burners are in charge of supplying and managing the amount of gas, oil, or coal injected into the boiler. Pulverized coal is prepared for injection. Heavy bunker oil is heated up and injected as an atomized jet to increase surface contact with the air.
  • Forced draft: The enormous amounts of air required for combustion are provided by it.
  • Induced-draft fan: It moves combustion gases and other waste products to the cleaning equipment, where they are then sent to the stack and the outside air.
  • Generator: Connected to three turbines converts mechanical energy into electrical energy.
  • Cooling Towers: When one percent of a body of water evaporates, the remaining water cools to 5.8 degrees Celsius. In order to cool the condenser, the evaporation phenomenon is used.

Conclusion: Working Principle of Thermal Power Plants

In thermal power plants, the heat energy obtained from the combustion of solid fuel (mostly coal) is used to convert water into steam, this steam is at high pressure and temperature. The turbine shaft, which is connected to the generator, rotates the turbine blades using this steam. The generator transforms the turbine impeller’s kinetic energy into electrical energy.

I’m hoping you now understand how thermal power plants work. You can learn more about other types of power plants, such as Nuclear Power PlantsHydroelectric Power PlantsGeothermal Power PlantsSolar Power PlantsWind Power PlantsTidal Power Plants, and Biomass Power Plants.


How is Heat Produced in Thermal Power Plant?

Thermal power generation consists of using steam power created by burning oil, liquid natural gas (LNG), coal, and other substances to rotate generators and create electricity.

How Does a Coal Thermal Power Plant Work?

The process of burning coal in a boiler to create steam is how coal-fired power plants generate electricity. Under extreme pressure, the steam produced enters a turbine, which turns a generator to produce electricity. In order to restart the process, the steam is then cooled, condensed back into the water, and fed back into the boiler.

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