How Hydro Power Plant Work

 In hydroelectric power plants the potential energy of water due to its high location is converted into electrical energy. The total power generation capacity of the hydroelectric power plants depends on the head of water and volume of water flowing towards the water turbine

  See also :- Impulse Water turbine

Hydro Power Plants  :-

The hydroelectric power plant, also called as dam or hydro power plant, is used for generation of electricity from water on large scale basis. The dam is built across the large river that has sufficient quantity of water throughout the river. In certain cases where the river is very large, more than one dam can built across the river at different locations.

 Working Principle of Hydroelectric Power plant

The water flowing in the river possesses two type of energy:

(1)the kinetic energy due to flow of water and 

(2)potential energy due to the height of water.

In hydroelectric power and potential energy of water is utilized to generate electricity.

The formula for total power that can be generated from water in hydroelectric power plant due to its height is given

                                                             P=r h g


where “p” is the power produced in "watt"

"r" is the rate of flow of water which in cubic meter/second"J

“h”= height of water which is measured in "meter"

It’s also head of water .

The difference between source of water (from where water is taken) and the water’s outflow (where the water is used to generate electricity, it is the place near the turbines).
“g” is the gravity constant 9.81 m/second square

The formula clearly shows that the total power that can be generated from the hydroelectric power plants depends on two major factors
The flow rate of water or volume of flow of water and


Height or head of water.
More the volume of water and

More the head of water more is the power produced in the hydroelectric power plant.

To obtain the high head of water the reservoir of water should as high as possible and power generation unit should be as low as possible.

 See Also:-Hydro Turbine Operation

The maximum height of reservoir of water is fixed by natural factors like the height of river bed, the amount of water and other environmental factors. 

The location of the power generation unit can be adjusted as per the total amount of power that is to be generated.

Usually the power generation unit is constructed at levels lower than ground level so as to get the maximum head of water.

The total flow rate of water can be adjusted through the pen stock as per the requirements. If more power is to be generated more water can be allowed to flow through it.

Calculation of Hydro Power plants:-

These calculation are concern with river or stream flow and available head through which water  falss to generate the electric power.

water in motion posseses three form of energy 

Kinetic enegry :- Due to its velocity 

potential enegry :- due to its height 

Kinetic enegry := v square /2 Nm per kg of water

Pressure energy :- p/P Nm per kg of water 

Potential energy :- gH Nm per kg of water

V = velocity of flow

p = density of water kg/m3

P = Pressure in N/M2

H= height of level of the water above som datum level .

Theoretical power available from water is = WQH wats

Q= Water flow in cumecs

H = net head available in m = Total head - the friction loss

If the efficiency of turbine is "nt"

The Power at turbine shaft = WQH.nt

if the efficiency of electric generator is "ng"

The effective power at swicth baord is := WQH nt.ng

In the above calculation , the follwoing relation can be used to calculate the dischage

1 cusecs = 1.3 sq mile ft per year 

that is one foot water over an area of 1.2 sq mile will give a discharge of one cusses throughout the year. assuming the run off as 100%

See also :-Features of Water Power plants

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