Hydroelectric Power Plants

Hydroelectric Power Plants

What is hydro-electric power plant?

The hydro-electric power plants produces electric energy using the potential and kinetic energy of water to move the hydraulic turbines which are coupled with electric generators.

Classification of hydroelectric power plants-

1)    Based on Availability of head

a)     Low head plants ( Head less than 30 meters)

b)    Medium head plants (head between 30 to 100 meters)

c)     High head plants ( Head more than 100 meters)

2)    Based on Nature of load

a)     Base load plants

b)    Peak load plants

3)    Based on Availability of quantity of water

a)     Run-off river plants without pondage

b)    Run-off plants with pondage

c)     Storage type plants

d)    Pumped storage peak load plants

e)     Mini and micro-hydrel plants

Site Selection for Hydro-electric Power Plants-

The following factors should be consider during selection of site for hydro-electric power plant-

1)    The site should have large catchment area and high average rainfall.

2)    It should have high storage capacity.

3)    Power demand centres should located near to power station.

4)    There should be less economical disturbance.

5)    Availability of construction material.

6)    Availability of manpower. 

7)    Availability of transportation facilities for access of mans and material.

8)    Capital/Total cost of project and time required for completion.

9)    Free from mineral deposits.

10)  Free from earthquake damage.

Principle of operation of Hydro-electric power plant-

In Hydroelectric power plants the energy of water is used to move the hydraulic turbine which rotates the electrical generator to convert mechanical energy of turbine to electrical energy. 

The power developed by hydraulic turbines depends on head of water and quantity of water.

Fig. General layout of hydro-electric power plant

The main components of hydroelectric power plant and their functions are as follows:

1)    Reservoir- It store the water during rainy season and that water is supplied during  other seasons. Also this water is used to rotate hydraulic turbine.

2)    Dam- It is structure constructed on river to increase storage capacity of reservoir and to provide working head for power plants.

3)    Gate- It is provided to control flow of water from reservoir to hydraulic turbine.

4)    Penstock- It is the pipeline which supply water from reservoir to hydraulic turbine/powerhouse.

5)    Anchors-These are concrete structure which supports the penstock as water flows at high pressure from penstock.

6)    Surge tank-It is used to control the water hammering/sudden pressure change in the pipeline.

7)    Hydraulic turbines-These are used to convert kinetic energy of water to mechanical energy.

8)    Power house-It consist of hydraulic turbine and electric generator which convert mechanical energy produced by turbine to electrical energy.

9)    Tail race-In tail race water is discharged from the turbine to river.

Working of hydro-electric power plant-

The water stored in the reservoir has high P.E. (Potential Energy) ,when water flows from penstock(Pipeline) then the P.E. gets converted into K.E.(Kinetic Energy) and that water flows through the hydraulic turbine so that K.E. is converted to M.E.(Mechanical Energy).

Electrical generator is coupled to the hydraulic turbine which rotates with hydraulic turbine and M.E. is converted to E.E.(Electrical Energy).In this way hydro-electric power plant works.

Advantages of hydropower plants

1)    The operational cost is less.

2)    There is no problem of ash or waste disposal.

3)    The life of plant is higher about 50 years.

4)    These plants require less supervising staff.

5)    It does not require fuel for power generation.

6)    These plants are more reliable.

7)    These plants have high efficiency.

Disadvantages of hydropower plants

1)    The capital cost is high.

2)    These plants are totally depends on the quantity of water.

3)    More time require to construct plants.

4)    Ecological disturbance take place during construction of the plants.