In energy producing plants, turbines are fixed to convert mechanical energy into electrical energy. In a variety of hydroelectric power plants usage of reversible turbines is common which in simple terms can be explained as a turbine that serves the function of either a pump or turbine to operate the electrical generator depending upon the direction of the rotation.
Characteristics of Reversible Turbine
The reversible turbine has some characteristics that distinguish it from the normal turbine which are mentioned as follows:
- It usually comprises motor generators along with an idealistic reversible pump.
- The pump turbines are fixated at the plants having a unit capacity of 10 to 500 MW.
- The speed of the rotating turbine can vary according to the type of motor used such as the synchronous or the asynchronous.
- The efficiency of the grids can be maintained by effectively adjusting the pump capacity based on the amount of energy that is available.
Technology of Reversible Turbine
The energy produced in a power plant needs to be stored in a pumped storage which is an advanced method of storing the energy. There are 2 major components of such power stations i.e., the hydro turbine and pump, which usually adopt the form of bladed hydraulic machinery.
The mechanical energy of both the water and runner are interconvertible where the interaction between motor and energy alters the mechanical energy of the runner.
During the daytime, energy consumption is highest and at night it is lowest. In the former case, water flows from the lower reservoir to the reservoir where it is used to generate electricity whereas in the latter case, the water pumped from the lower reservoir is stored for future use.
Also See: What is Water Turbine?
Reversible Hydro Pumps
As the cost of using the pumps as turbines is low for electricity generation in a hydropower plant, its utilization has increased. The hydraulic machines are found to be used in combination with the motor or the centrifugal pump system which are termed as the reversible hydro pumps. It provides torque to the generator as well as the motor to initiate the pumping function which can be operated using a switch.
Reversible Gas Turbine
A reversible gas turbine is an idealized turbine working in the reversible cycle of thermodynamics. In general, a gas turbine uses the elements in the gaseous state to generate mechanical power which in turn is used for multiple purposes from as simple as electricity generation to launching off a jet.
The working of the gas turbine is based on the Brayton cycle also known as the joule cycle which consists of the following procedural steps:
- Constant pressure combustion: The next step includes compressed air to go through constant pressure in a chamber.
- Isentropic expansion: The high temperature and pressure results in the expansion of gases resulting in the production of mechanical power.
- Isentropic compression: In this process, air is compressed without increasing the entropy of the compressor.
- Constant pressure heat rejection: The remaining hot air is cooled off by a heat rejection process.
The concepts of reversible gas turbines can be used for analyzing and improving the efficiency of the gas turbine by limiting the irreversible losses and ultimately improving the working or the performance of the gas turbine.
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