hydro electricpowerplant

1. Hydro-Electric Power Plant
Dr.NPS
Dr.NPS/EEE 1

2. Introduction:
One of the most widely used renewable source of energy for generating
electricity on large scale basis is hydropower
The power obtained from river or ocean water is called as hydropower.
Hydropower is the renewable source of energy since water is available
in large quantities from rain, rivers, and oceans and this is will be
available for unlimited time to come.
30% of total power of the world is met by hydro-electric power.
Total hydro-potential of the world id 5000 GW.
Dr.NPS/EEE 2

3. Dr.NPS/EEE 3

4. Essential features of Hydro-Electric Power
Plant:
Theessential features of awater power plant are asbelow:
1. Catchment area.
2. Reservoir.
3. Damand intake house.
4. water way.
5. Power house.
6. Tailrace or outlet waterway.
1.CatchmentArea.
Thecatchment area of ahydro plant is thewhole area behind the
dam, draining into astream or river acrosswhich the dam has
been built at asuitableplace.
Dr.NPS/EEE 4

5. 2- Water reservoir:
 In a reservoir the water collected
from the catchment area is stored
behind a dam.
 Catchment area gets its water from
rain and streams.
 The level of water surface in the
reservoir is called Head water level.
Note : Continuous availability of
water is a basic necessity for a
hydro-electric power plant.
3- Dam :
 The purpose of the dam is to store
the water and to regulate the out
going flow of water.
 The dam helps to store all the
incoming water. It also helps to
increase the head of the water. In
order to generate a required quantity
of power it is necessary that a
sufficient head is available. Dr.NPS/EEE 5

6. • Damare classified based on following factors:
a) Function
b) Shape
c) Construction material
d) Design
a) Basedon function the dam may be called asstoragedam,
diversion dam or detentiondam.
c)
b) Basedon the shape the dam may of trapezoidal section&
arch type.
Thematerials used for constructing dams are earth,rock
pieces, stone masonry.
d) According to structural design thedam maybe classified as:
i. Gravity dam
ii. Arch dam
iii. Buttress dam
Dr.NPS/EEE 6

7. Typesof Dam:
es:
1. Masonry Dams.
2. Earth Dams.
Themasonry dams are of three majorclass
a) Gravity dam.
b) Buttress dam.
c) Arched dam.
d) Gravity dam:
Resistthe pressure of water by itsweight.
Construction ofmaterial used for his dam, is solid masonry or
concrete.
Dr.NPS/EEE 7

8. b) Arch dam:
It resist the pressure of water partly due to its
weight and partly due to archaction.
c) Buttress dam:
• Buttress supporting aflat slab.
• When cost of reinforced concrete is highsuch
type of dam isselected.
Dr.NPS/EEE 8

9. Spillway:
 Excess accumulation of water endangers
the stability of dam construction. Also in
order to avoid the over flow of water out
of the dam especially during rainy
seasons spillways are provided. This
prevents the rise of water level in the
dam.
 Spillways are passages which allows the
excess water to flow to a storage area
away from the dam.
Gate:
 A gate is used to regulate or control the
flow of water from the dam.
Pressure tunnel:
 It is a passage that carries water from the
reservoir to the surge tank.
9
Dr.NPS/EEE 9

10. Surge tank:
 A Surge tank is a small reservoir or tank in which the water level rises or
falls due to sudden changes in pressure.
Purpose of surge tank:
 To serve as a supply tank to the turbine when the water in the pipe is
accelerated during increased load conditions and as a storage tank when the
water is decelerating during reduced load conditions.
 To reduce the distance between the free water surface in the dam and the
turbine, thereby reducing the water-hammer effect on penstock and also
protect the upstream tunnel from high pressurerise.
Water-hammer effect :
o The water hammer is defined as the change in pressure rapidly above or below normal
pressure caused by sudden change in the rate of water flow through the pipe, according
to the demand of prime mover i.e. turbine
10
Dr.NPS/EEE 10

11. 4- WaterWays.
Water waysare the passages,through which the water is
conveyed to the turbines from the dam. Thesemay include
tunnels, canals, flumes, forebays and penstocks and also
surge tanks.
Aforebay is an enlarged passagefor drawing the water
from the reservoir or the river and giving it to the pipe lines
or canals.
11
Dr.NPS/EEE 11

12. Number of penstock
Ahydro Power Plant usesanumber of turbine which are tobe
supplied water through penstock.
• T
ouseasingle penstock for the whole aplant.
• T
ouseon penstock for each turbineseparately.
• T
oprovide multiple penstock but each penstock supplyingwater
to at least twoturbine.
Factors for Selecting number of penstocks:
• Economy.
• Operational safety.
• Transportation facilities.
Dr.NPS/EEE 12

13. 5- PowerHouse.
Thepower house is abuilding in which the turbines,alternators
and the auxiliary plant are housed. Someimportant items of
equipment provided in the power house areasfollows:
i. Turbines
ii. Generators
iii. Governors
iv. Relief valve for penstocksetting
v. Gate valve
vi. Transformer
vii. Switch board equipment andinstruments
viii. Oil circuit breaker
ix. Storage batteries
x. Outgoing connections
xi. Cranes
xii. Shops& offices
Dr.NPS/EEE 13

14. Thesurface power house hasbeen broadly divided into three
subdivisions which isseparated
from the intake asmentioned below:
(a) Substructure ;
(b) Intermediate structure ;
(c) Super-structure.
Dr.NPS/EEE 14

15. Draft tube:
 It is connected to the outlet of the turbine.
 It allows the turbine to be placed above the tail water level.
6- Tail water level or Tail race:
o Tail water level is the water level after the discharge from the
turbine. The discharged water is sent to the river, thus the level of
the river is the tail water level.
Electric generator, Step-up transformer and Pylon :
 As the water rushes through the turbine, it spins the turbine shaft,
which is coupled to the electric generator. The generator has a
rotating electromagnet called a rotor and a stationary part called a
stator. The rotor creates a magnetic field that produces an electric
charge in the stator. The charge is transmitted as electricity. The
step-up transformer increases the voltage of the current coming
from the stator. The electricity is distributed through power lines
also called as pylon. Dr.NPS/EEE 15

16. Classification of hydro-Electric powerplant
The classification of hydro electric power plant depend on the following
factors:
1) Quantity ofwater:
It is followingtypes.
i. Runof river plant.
ii. Storage plant.
iii. Pumped storage.
2) Availability of Head ofWater:
a) Low head plant. Operating head <15m.
b) Medium headplant. Operating head 15 to 50m.
c) High head plants Operating head >50m.
Dr.NPS/EEE 16

17. a) Low headplant
• Operating head is lessthan 15m.
• Vertical shaft Francisturbine or Kaplanturbine.
• Smalldam is required.
Dr.NPS/EEE 17

18. a) Medium headplant
• Operating head is lessthan 15 to 50m.
• Francisturbines.
• Forebayis provided at the beginning of the penstock.
Dr.NPS/EEE 18

19. a) High headplant
• Operating head exceed 50m.
• Pelton turbines.
• surge tank is attached to the penstock to reduce water hammer effect on the
penstock.
Dr.NPS/EEE 19

20. Advantages of hydel power plant :
 Water is a renewable energy source.
 Maintenance and operation charges are very low.
 The efficiency of the plant does not change with age.
 In addition to power generation, hydro-electric power
plants are also useful for flood control, irrigation
purposes, fishery and recreation.
 Have a longer life(100 to 125 years) as they operate at
atmospheric temperature.
 Water stored in the hydro-electric power plants can also
be used for domestic water supply.
 Since hydro-electric power plants run at low speeds(300
to 400 rpm) there is no requirement of special alloy steel
construction materials or specialised mechanical
maintenance.
Dr.NPS/EEE 20

21. Disadvantages of hydel power plant :
 The initial cost of the plant is very high.
 Since they are located far away from the load centre, cost of
transmission lines and transmission losses will be more.
 During drought season the power production may be reduced
or even stopped due to insufficient water in the reservoir.
 Water in the reservoir is lost by evaporation.
Dr.NPS/EEE 21

22. DraftTube:
Reaction turbines must be completely enclosed becausea
pressure difference exists between the working fluid (water) in
the turbine and atmosphere. Therefore, it is necessary to
connect the turbine outlet by means of apipe known asdraft
tube upto tailracelevel.
Types of DraftTubes
(1) Conical DraftTube.
Thisis known astapered draft tube and used in all reaction
turbines where conditions permit. It is preferred for low specific
speed and vertical shaft Francis turbine. Themaximum cone
angle of this draft tube is limited to 8° (a =4°). Thehydraulic
efficiency of such type of draft tube is 90%.
Dr.NPS/EEE 22

23. 2- Elbow TypeDraftTube.
The elbow type draft tube is often preferred in most of the power
plants, where the setting of vertical draft tube does not permit
enough room without excessivecost ofexcavation.
3- Moody DraftTube.
This draft tube has an advantage that its conical portion at the
centerreducesthe whirl action of water moving with high velocity
centre reduces.
Dr.NPS/EEE 23

24. Hydraulic Turbines
Advantages:
Simple in construction.
Easilycontrollable.
Efficient.
Ability towork at peak load.
Work on loadvariation.
Start from cold conditions & pick up load at short time.
Types of turbines:
a) Impulse
b) Reaction
Dr.NPS/EEE 24

25. Impulse Turbine:
Thepassagesare not completely filled, water acting on awheel
buckets is at atmospheric pressure and is supplied at few points atthe
periphery of wheel & kinetic energy is supplied to the wheel.
Casing
Penstock
Nozzle
Runner
Buckets
Needle V
alve
shaft
Dr.NPS/EEE 25

26. ReactionTurbine:
Water passagesare completely filled with water, water acting on
wheel vanes is under pressure greater than atmospheric, waterenter
all around the periphery of wheel and energy is in the form of both
pressure &kinetic energy is utilized by the wheel.
Essential parts:
Spiral casing
Guidewheel
Runner
Draft tube
• Horizontal shaft type or vertical shaft type turbine
• Low & medium headturbines
Dr.NPS/EEE 26

27. Direction of flow ofwater:
I. Tangential flow turbine
II. Radial flow turbine.
III. Axial flow turbine.
IV. Mixed flow turbine.
Types of turbine Flow direction
Kaplan turbine Axial flow
Franics Turbine Radial inward or mixed flow
Pelton wheel Tangential flow
Dr.NPS/EEE 27

28. Position of shaft:
I. Vertical shaftturbine.
II. Horizontal shaftturbine.
Headof water:
I. High head turbines.
II. Medium headturbines.
III. Low head turbines.
Impulse turbines
Reactionturbines
high head.
low & mediumheads.
Dr.NPS/EEE 28

29. Performance of waterturbine:
Important parameter for any particular turbine are:
• Discharge
• Head
• Efficiency
• Speed
• Power
The turbine characteristic like unit power, unit speed & unit discharge
help in studying the performance ofturbines.
Dr.NPS/EEE 29

30. SELECTION OFSITE FOR A HYDRO-ELECTRIC
POWER PLANT
Thefollowing factors should be given carefulconsideration
while selecting asite for ahydro-electric powerplant:
1.Water Available.
Therecorded observation should be taken over anumber of yearsto
know within reasonable, limits the maximum and minimum
variations from the average discharge. the river flow data should be
based on daily, weekly, monthly and yearly flow ever anumber of
years. Then the curves or graphs canbe plotted between tile river
flow and time. Theseare known ashygrographs andflow
duration curves.
Dr.NPS/EEE 30

31. 2.Water-Storage.
Theoutput of ahydropower plant is not uniform due to wide
variations of rain fall. T
ohave auniform power output, awater
storage is needed sothat excessflow at certaintimes may be stored
to make it available at the times of low flow. T
oselect the site of the
Dam, careful study should be made of thegeology and topography of
the catchment area to seeif the natural foundations could be found
and put to thebest use.
3.Head of Water.
The level of water in the reservoir for aproposed plant should always
be within limitsthroughout the year.
Dr.NPS/EEE 31

32. 4.Distance from LoadCenter.
Most of the time the electric power generated in ahydro-electric
power plant hasto be used some considerable distance from the
site of plant. For this reason, to be economical on transmission of
electric power, the routes and the distances should be carefully
considered since the cost of erection of transmission lines and
their maintenance will depend upon the route
selected.
5.Access to Site.
It is always adesirable factor to havea good accessto the site of
the plant. Thisfactor is very important if the electric power
generated is to be utilized at or near the plant site. Thetransport
facilities must also be given dueconsideration.
Dr.NPS/EEE 32

33. Hydrology
• It is natural sciencethat deal with the distribution of water on land
beneath the surface of earth.
• It deal with the solid, liquid & vapour forms of water.
Hydrologic cycle:
The various processes involved in the transfer of moisture from the sea
to the land and back to the seaagain constitute which is called
hydrologic cycle.
Hydrologic eq. is expressed asfollows:
P=R+E
Where,
P=perspiration
R=Run-off
E= Evaporation.
Dr.NPS/EEE 33

34. Perspiration:
It includes all the water that falls from atm. T
othe earth
surface. Mostly perspiration is of twotypes.
(rainfall)
(Snow,Hail storm)
Liquidperspiration
Solid perspiration
Run-off:
It is that portion of the perspiration which makesits way
towards stream, lakesor ocean.
Run-off occur only if the rate of perspiration exceedthe rate
at which water infiltrate into the soil & after depression
small and large on the soil surface get filled in the water.
Evaporation:
Transfer of water from liquid to vapour state
Transpiration:
Processby which water is released to theatmosphere by the
plant.
Dr.NPS/EEE 34

35. Questions?
Dr.NPS/EEE 35