Hydro electric power plant, the energy of water utilized may be potential or kinetic.
The potential energy of water is used to run water turbine to that the electric generator is coupled.
The mechanical energy available at the turbine shaft is converted into electrical energy by generator.
Water reservoir
The very basic requirement of this plant is that the availability of water. In the catchment area the water is collected and stored in reservoir.
Head race term is defined as the water surfaces in the reservoir.
Dam
Dam’s main function is to increase the water level height
It is also helps to increase the working heat of the hydro power plant.
Spillway
Water after a certain level in the reservoir overflows through spillway while not permitting the rise in water level in the reservoir.
Penstock
Penstock is used to transfer the water from surge tank to turbine.
Penstocks is made up of steel or reinforced concrete pipes.
Surge tank
The surge tank is introduced between the dam and the power house to keep in reducing the sudden rise of pressure in the penstock.
There is sudden increase of pressure in the penstock due to sudden backflow of water as load on the turbine is reduced. The sudden rise of pressure in the penstock is known as water hammer.
Water turbine
Water enters into the turbine through inlet valve from penstock.
Prime movers which are in common use are Pelton turbine, Francis turbine and Kaplan turbine.
The potential energy of water entering the turbine is converted into mechanical energy.
The mechanical energy available at the turbine shaft is used to run the electric generator. The water is then discharged through the draft tube.
Draft tube
It is connected to the outlet of the turbine. It allows the turbine to be placed over tail race level.
Tail race
Tail race may be a water way to lead the water discharged from the turbine to the river.
The water held in the tail race is called tail race water level.
Step-up transformer
Its function is to raise the voltage generated at the generator terminating before transmitting the power to consumers.
Advantages:
Water is renewable source of energy.
Water is the cheapest source of energy. The Fuels needed for the thermal, diesel and nuclear plants are expensive.
There is no ash disposal problem.
Hydro-plant does not pose the problem.
Variable loads doesn’t affect the efficiency.
Disadvantages:
Hydro-plants are generally situated away from the load centres. Hence long transmission lines are required for delivery of power. This increases the cost of transmission lines.
The power produced by hydro-plant depends upon the quantity of water which in turn is dependent upon the rainfall.
Initial cost of the plant is high.
Erection of hydro-plant takes long period of time.
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