A steam turbine is a prime mover that converts mechanical energy from heat energy. Water is used as the working fluid in a conventional steam turbine cycle. Water is heated in a boiler by the combustion of fuel. It evaporates into steam, which is expanded in a turbine to generate mechanical power. The steam produced has a high temperature and pressure. The temperature is usually between 450 and 540 degrees Celsius. Pressures range from 60 to 120 bar. Nozzles and blades are essential components of all steam turbines.
What is a steam turbine?
A steam turbine is a device that converts the thermal energy of steam pressure into mechanical energy by expanding the steam in stages in the turbine to perform the required work. Steam turbine engines are used all over the world to power countless electric motors (such as the master switch for pumps, compressors, and other equipment used on the shaft). A turbine’s capacity can range from a few kilowatts to several hundred megawatts. In 1884, Sir Charles Parsons built the first modern steam turbine.
What is the operation of a steam turbine?
In other words, the principle of a steam turbine is to use a heat source (gas, coal, nuclear energy, or solar energy) to heat water to extremely high temperatures until it converts to steam. The steam expands and cools as it passes through the turbine blades.
As a result, the potential energy of the steam is converted into driving force in the turbine’s rotating blades. Because turbines generate circular motion, they are ideal for moving generators that generate electricity. The turbine is connected to the generator via a shaft, and the generator generates energy via a magnetic field that generates electricity. A turbine generates energy by varying the speed of a high-speed jet of steam striking free-spinning curved blades.
As the steam passes through the turbine, both temperature and pressure fall. The greater the pressure drop, the greater the amount of energy that can be extracted from the steam. At the end of the turbine, more efficient power plants condense the steam back to water.
Efficiency of Steam Turbine.
The theoretical maximum efficiency of a steam turbine-based power plant is determined by the temperature difference between when the steam enters the high pressure turbine and when it exits the low pressure turbine. The greater the temperature difference, the greater the amount of energy that can be extracted.
It is increasingly being used in process industries (such as steel and chemicals) that generate large amounts of waste heat. The waste heat generated can be used to generate both steam and electricity. The capital cost of such plants may be slightly higher, but power generation is a useful byproduct when waste must be burned in any case.
Steam turbines can also be used effectively in industries with high demands for both steam and power. They are used in cogeneration or combined heat and power applications where process steam is also used to generate electricity in the turbine. This also leads to significant improvements in overall process efficiency.
How to increase efficiency?
More efforts are being made to improve the efficiency. The areas are as follows:
- Critical technological advances aiming for 50% efficiency.
- Renovating and upgrading for better value.
- Combined heat and power for lower costs and increased flexibility.
- A new market for combined-cycle steam turbines.
- Clean coal technologies such as FBC, PFBC, and IGCC to improve overall efficiency and reduce pollution levels.