Hydro-Electric Power Plant

HYDRO-ELECTRIC POWER PLANTS
Prepared by,
Prof. Afaqahmed M J
Prof. Afaqahmed M J , AIKTC, Navi Mumbai

Current Scenario in India
• Annual Flow 1675 Million m3.
• 60 % from Ganga, Bhramaputra, Indus
• 16 % from Narmada,Tapi, Mahanadi

How Hydropower Works!

The Indian Scenario
 The potential is about 84000 MW at 60% load factor spread across
six major basins in the country.
 Pumped storage sites have been found recently which leads to a
further addition of a maximum of 94000 MW.
 Annual yield is assessed to about 420 billion units per year though
with seasonal energy the value crosses 600 billion mark.
 The possible installed capacity is around 150000 MW (Based on the
report submitted by CEA (Central Electricity Authority) to the
Ministry of Power
 The proportion of hydro power increased from 35% from the first
five year plan to 46% in the third five year plan but has since then
decreased continuously to 25% in 2001.
 The theoretical potential of small hydro power is 10071 MW.
 Currently about 17% of the potential is being harnessed
About 6.3% is still under construction.

Site Selection 
1. Preliminary Investigations  Information about
Practicability and Alternatives
2. Final Investigations: 
 Hydrological 
a) Water Availability – Runoff Data over large
catchment area and according Rainfall,
Intensity of flood from hydrograph
b) Water Storage – Storage Capacity, Types i)
For one year ii) For worst dry periods
c) Water Head – Depends on Topology
d) Ground Water Data – Underground movement
for Stability also prevent leakage

TOPOGRAPHY OF THE LAND

MORPHOLOGY OF THE LAND

Topographical Investigation: Aerial
Photographs and Ground Surface
Geological Investigations : Factors affecting
 Tight Basin of ample size
 Narrow outlet
 Strong foundation
 Space for Spillways
 Confiscate water should not submerge valuable
minerals and Agricultural Land
 Availability of Raw mtl. for Dam construction.

Consideration of Water Pollution Effect :
• Causes –
 Submerged underwater deposit of Minerals, Sulphate
causes H2S,
 Presence of Alkaline and Acidic deposits,
 Considerable amount of twigs, leaves, logs
 Wind Velocity - Depletion of oxygen, Thermal
Stratification @ lower strata produce CO2, H2S and
CH4
• Adverse Effects -- CO2, H2S and CH4 is highly corrosive
to dams, its concrete structure, Electrical Machinery
Health hazards – Headache, Dizziness, Dryness of
Nose, Throat and Chest pains due to H2S.
 Sedimentation Effect :-- Causes Erosion of Turbine,
Sedimentation defines life of plant also define capacity
of plant reduced / year.Prof. Afaqahmed M J , AIKTC, Navi Mumbai

 Environmental Aspects : 
Base for design
 Minimize the impact
 To enhance local environment
 Be in the best public interest
Requirements –
• To assure safe, healthful, productive and culturally
pleasing surroundings
• Avoid health Hazards
• To preserve important Historic, Cultural and Natural
aspect of site.
Evaporation Effects :
10 mm per hector during Summer , Maharashtra covers
35000 Hector area and evaporation is 28*10^6 m3 / day

Construction & Operation of components of Hydel Power
Plant

1.Reservoirs :
Functions :
a) Storage
b) Satisfy customer demand

TYPES :
 Reservoirs in valleys - The valley sides act as natural walls

Bank-side reservoir : 
 Bank-side reservoirs may be built to store the water.
 The water stored in such reservoirs may stay there for several months,
during which time normal biological processes may substantially
reduce many contaminants.
 The London water supply system is one example of the use of bank-
side storage: the water is taken from the River Thames and River Lee.

 Service reservoir 
 Service reservoirs store fully treated potable water close to the point of
distribution.
 Many service reservoirs are constructed as water towers, often as
elevated structures on concrete pillars where the landscape is relatively
flat.
 Other service reservoirs are entirely underground, especially in more
hilly or mountainous country.

Dam
Dam is a solid barrier constructed at a suitable location
across a river valley to store flowing water.
Storage of water is utilized for following objectives:
 Hydropower
 Irrigation
 Water for domestic consumption
 Drought and flood control
 For navigational facilities
 Other additional utilization is to develop fisheries

A typical dam has following parts – Terminology
 Crest – The top of dam. In some cases, this provides a roadway or walk
way.
 Parapet walls – Low protective walls on the either side of the road way on
the crest.
 Abutments – The valley slopes on the either side of dam wall to which it
is keyed.
 Free board – The space between the highest level of water in the reservoir
and crest of the dam.
 Dead storage level – Level of permanent storage below which water will
not be withdrawn.
 Heel – The upstream portion of the dam in contact with the river bed or
foundations.
 Toe – The downstream portion of the dam wall for the discharge of
surplus water from the reservoir.
 Spillway – The passage in the dam wall for the discharge of surplus of
water from the reservoir.
 Gallery – Level or gently sloping tunnel like passage transverse or
longitudinal within the dam. Provided for inspection & behavior of dam

Types of Dam
 Based on Purpose : 
 Storage dam or impounding dam
o High Flow  Low Flow
o It is used for irrigation, power generation, water
supply etc.
o By suitable operation, it can also serve as a
detention dam.

 Detention dam
oIt is primarily constructed to temporarily
detain all or part of the flood water in a river
oTo gradually release the stored water later at
controlled rates so that the entire region on the
downstream side of the dam is protected from
possible damage due to floods.
o It may also be used as a storage dam.

 DIVERSION DAM
o It is constructed to divert part of or all the water
from a river into a conduit or a channel.
o Diverting water from a river into an irrigation
canal, mostly a diversion dam is constructed across
the river.
 COFFER DAM
 It is a temporary dam constructed to exclude
water from a specific area.
 DEBRIS DAM
It is constructed to catch and retain debris flowing
in a river. Prof. Afaqahmed M J , AIKTC, Navi Mumbai

BASED ON MATERIAL OF CONSTRUCTION
 Rigid dam
o It is constructed with rigid material such as stone,
masonry, concrete, steel, or timber.
o Steel dams (steel plates supported on inclined
struts) and timber dams (wooden planks supported
on a wooden framework) are constructed only for
small heights (rarely).

 NON-RIGID DAM (EMBANKMENT DAMS)
It is constructed with non-rigid material such as earth,
tailings, rock-fill etc.
o Earthen dam – gravel/rock fragments, sand, silt/
clay/mud etc. Earthen dams are provided with a
stone masonry or concrete overflow (spillway)
section. Such dams are called composite dams.
o Tailings dam – waste or refuse obtained from mines
o Rockfill dam – rock material supporting a water
tight material on the upper surface
o Rockfill composite dam – Rockfill on the downside
and earth fill on the upperside

BASED ON STRUCTURAL BEHAVIOUR
I. GRAVITY DAM
II. ARCH DAM
III. BUTTRESS DAM
IV. EMBANKMENT DAM

I. GRAVITY DAM

 Built of Masonry (Stone + Brick), Mortar, Concrete
 the whole weight acts vertically downwards
 Height is limited by strength of available foundation
 Simplest but carries massive materials
 Constructed across narrow river valleys
 Bhakra Dam is the highest Concrete Gravity dam in Asia and the
second highest in the world.
 Bhakra Dam is across river Sutlej in Himachal Pradesh
 The construction of this project was started in the year 1948 and was
completed in 1963 .
 It is 740 ft. high above the deepest foundation as straight concrete
dam being more than three times the height of Qutab Minar.

BHAKRA – NANGAL DAM

II. ARCH DAM :
Solid Concrete Structure
Arch dams are built across narrow, deep river gorges,
but now in recent years they have been considered even
for little wider valleys.
Curved Upstream in Plan
Economy in construction cost
Not only cheaper but also stronger than gravity dams.
Safety factor greater than other types in case of
earthquake if it is Full.
Idikki(Kerala) hydel plant is India’s largest PP of height
168 and 20m wide.
 The safety of an arch dam is dependent on the
strength of the side wall abutments

III. Buttress:
 More Popular by economy
Suitable for weaker foundation
Buttress – a support that transmits a force from a
roof or wall to another supporting structure
Safe for earthquake effects.
Built in large number in Italy and Japan in spite
of high seismic activity

III Earth- Fill / Embankment 
More popular in recent years
They are trapezoidal in shape.
Built by Sand, Soil and Rock
More economical for sites where excavation of foundation soil is
considerable.
Earthen dams are relatively smaller in height and broad at the base
It can built at such situation where other type would be impracticable.

Generating Technology
Water wheels have been used for hundreds of years for industrial
power.
Their main shortcoming is size, which limits the flow rate
and head that can be harnessed.
The migration from water wheels to modern turbines took about one
hundred years.
Development occurred during the Industrial revolution, using scientific
principles and methods.
They also made extensive use of new materials and manufacturing
methods developed at the time.
The first hydroelectric power plant was constructed in 1882 in Appleton,
Wisconsin. It produced 12.5 kilowatts of electricity which was used to
light two paper mills and one home.

Types of Hydro Turbines:
 Impulse turbines
 Pelton Wheel
 Cross Flow Turbines
 Reaction turbines
 Propeller Turbines : Bulb turbine, Straflo, Tube
Turbine, Kaplan Turbine
 Francis Turbines

According to no of stages
1. Single Stage
2. Multi Stage
According to the direction of flow
1. Radial Flow
2. Axial Flow
According to rotational speed
1. Regular speed
2. Low speed
3. High speed
According to inlet steam pressure
1. high pressure (p>6,5MPa)
2. Intermediate pressure(2,5MPa <p<6,5MPa)
3. low-pressure (p<2,5MPa)

 IMPULSE TURBINE Vertical Inlet
Operates on High Velocity
1. CROSS FLOW
Horizontal Inlet

Drum-shaped
Elongated, rectangular-section nozzle directed against
curved vanes on a cylindrically shaped runner
Water flows through the blades twice
First pass : water flows from the outside of the blades to the
inside
Second pass : from the back side.
Larger water flows and lower heads than the Pelton.

2. PELTON TURBINE

In 1880 Pelton was granted a patent with the following text.
"Pelton water turbine or wheel is a rotor driven by the impulse of a jet
of water upon curved buckets fixed to its periphery; each bucket is
divided in half by a splitter edge that divides the water into two streams”.
The buckets have a two-curved section which completely reverses the
direction of the water jet striking them.“
It is an efficient machine particularly suited to high heads.
The nozzles are mounted so that each directs a jet along a tangent to
the circle through the centres of the buckets
Down the centre of each bucket, there is a splitter ridge which divides
the jet into two equal streams which flow round the smooth inner surface
of the bucket and leaves the bucket with a relative velocity almost
opposite in direction to the original jet.

REACTION TURBINE – Pressure & Velocity
1. FRANCIS TURBINE

FRANCIS TURBINE
It is a reaction turbine developed by an English born
American Engineer, Sir J.B. Francis.
The water enters the turbine through the outer periphery of
the runner in the radial direction and leaves the runner in the
axial direction, and hence it is called ‘mixed flow turbine’.
It is a reaction turbine and therefore only a part of the
available head is converted into the velocity head before water
enters the runner.
The pressure head goes on decreasing as the water flows
over the runner blades.
The static pressure at the runner exit may be less than the
atmospheric pressure and as such, water fills all the passages
of the runner blades.
The change in pressure while water is gliding over the
blades is called ‘reaction pressure’ and is partly responsible for
the rotation of the runner.
A Francis turbine is suitable for medium heads (45 to 400
m) and requires a relatively large quantity of water.

X blade runnerTraditional runner
The Francis Runner

2. KAPLAN TURBINE

Superior Hydrodynamic Features
Section of Guide Wheel Runner
Essential for High Efficiency at low Heads

The kaplan turbine is a great development of early 20th century.
Invented by Prof. Viktor Kaplan of Austria during 1913 – 1922.
The Kaplan is of the propeller type, similar to an airplane propeller.
The difference between the Propeller and Kaplan turbines is that the Propeller
turbine has fixed runner blades while the Kaplan turbine has adjustable runner
blades.
It is a pure axial flow turbine uses basic airfoil / hydrofoil theory.
The kaplan's blades are adjustable for pitch and will handle a great variation of
flow very efficiently.
They are 90% or better in efficiency and are used in place some of the old
(but great) Francis types is good in many of installations.
They are very expensive.
The kaplan turbine, unlike all other turbines, the runner's blades are movable.
The application of Kaplan turbines are from a head of 2m to 40m.

SPILL WAYS
I. When the water in the reservoir increases, the large accumulation of water
endangers the stability of the dam structure. To avoid this a structure is
provided in the body of a dam or near the dam or periphery of the
reservoir. This structure is called as spillway.
II. Mainly used to discharge water during flood period.
III. One of the most important structural component of a dam.
IV. Spillway evacuates the flood wave from reservoir to river at the
downstream. „
Requirements:
 Provide structural stability to the dam under all condition
 Should able to pass the designed flood without raising the reservoir level
above H.F.L.
 Should have an efficient operation
 Should be economical

Spillway
It is normally composed of three major
components:
„ The approach facility admits flow to the
spillway. „
The discharging conduit evacuates the flow
from the approach facility to an outlet structure. „
 The outlet structure (tail water channel)
dissipates the excessive energy of the flow from
the discharging conduits and conveys tranquil
flow to the downstream.

TYPES OF SPILLWAYS
 Over-fall spillway
 Chute spillway
 Saddle spillway
 Shaft spillway
 Side channel spillway
 Emergency spillway
 Siphon spillway

LOCATION OF SPILLWAY
 Generally, the spillways are provided at the
following places
 Spillways may be provided within the body of the
dam.
 Spillways may sometimes be provided at one side
or both sides of the dam.
 Sometimes by-pass spillway is provided which is
completely separate from the dam.

Over-fall spillway:
• That allows water to pass over its crest widely used
on gravity, arch, & buttress dam
• This is a simplest type
• Overflow spillways also called ogee-shaped (S-
shaped) spillways.
• „Widely used on : Gravity dams, „Arch dams, and „
Buttress dams

Chute Spillway
 Chute spill ways are common and basic in design as
they transfer excess water from behind the dam
down a smooth decline into the river below.
 The spillway‟s slope and it‟s sides are lined with
concrete.
 In case of having sufficient stiff foundation conditions
at the spillway location, a chute spillway may be
used in stead of overflow spillway due to economic
consideration.
 Chute spillway scan being rained with a baffle of
concrete blocks but usually have a 'fliplip„ and/or
dissipater basin which creates hydraulic jump,
protecting the toe of the dam from erosion.

SADDLE SPILLWAYS
This type is mainly used when other types are not
favourable.
In some basins formed by a dam, there may be one or
more natural depressions or saddles in the rim of the
basin, which can be used as spillway.
It is essential that the bottom of the depression should
be at full reservoir level.
 It is usually necessary for the saddle to be on firm
rock.

 The shape is just like a funnel .
 If a sufficient space is not available for an overflow
spillway, a shaft spillway may be considered.
 water drops through a vertical shaft in a the foundation
material to a horizontal conduit that conveys the water past
the dam.
 Lower end of shaft is turned at right angle and then water
taken out below the dam horizontally.
 Also called as glory hole spillway.
 In the site of shaft spillway „
1. Seismic action should be small, „
2. Stiff geologic formation should be available and „
3. Possibility of floating debris is relatively small.
SHAFT SPILLWAY

1. Low Level 2. Maximum Level

ii ) Stepped Spillway
Used over 3000 years
 Steps produce energy dissipation

5. POWER HOUSE
Types of Power House
i) SURFACE
 All the components of Hydel Power plant are on
Ground Surface
 Water inlets from Tunnel or Penstock

II) UNDERGROUND
They are not only economical but also
protecting against
air raid / strikes
Large no of installations are in USA, UK,
Russia, Japan
and Canada after World war II
 Mostly used in pumped storage power
stations

6. PENSTOCK and CANAL  It is Sluice / Gate /
Structure
 Maintenance cost is more
in case of pollution
Need to be washed by
Hot Water

6. Surge Tank

7. SURGE TANK
Closed aqueduct to absorb sudden pressure rise and
provide during pressure drop
 It is mostly installed when distance between dam and
power house is large
Functions –
1. When load decreases water moves backwards & get
stored
2. Addition supply of water will be provided, when load
increases
3. Avoid vacuum during water supply closedProf. Afaqahmed M J , AIKTC, Navi Mumbai

RAINFALL MEASUREMENT : 
Rain fall (used in a general sense) or “precipitation” may
be defined as the total condensation of moisture that
reaches the earth in any form. It includes all forms of
rains, ice, snow etc.

CATCHMENT AREA
Area from which Rainfall flows into River, Lake or
Reservoir

NWS- National Weather Service

125mm
Recording Type

Non Recording type

RUN-OFF MEASUREMENT
Depends on Rainfall
Runoff after Evaporation,
Absorption by vegetation &
Crops, Percolation.
Runoff = Precipitation – Loss
Runoff = Rainfall X Runoff Coeff.
Garden- 0.5, Commercial- 0.9, Forest
– 0.5 – 0.1

Factors Affecting Runoff
 Rainfall Pattern – Heavy, Less
Characteristics of catchment area -
Topography
Shape & Size of catchment area
Vegetation – More crops  less
Runoff
Geology Rocky and Sandy
Weather Conditions-
• More Runoff @ Low temp, High
Humidity & low windsProf. Afaqahmed M J , AIKTC, Navi Mumbai

Hydrograph
Hydrograph is defined as a graph showing
discharge (Runoff) of flowing water wrt time.
Time Horizon may be - hr, day, week, month.
Discharge - m3 / sec, km2 -cm/hr.
Each hydrograph represent particular river
Prominently impact during project design

Terminology –
 Rising limb: The rising limb of hydro graph, also known as concentration
curve, reflects a prolonged increase in discharge from a catchment area,
typically in response to a rainfall event
 The recession limb: represents the withdrawal of water from the storage built
up in the basin during the earlier phases of the hydrograph.
 Peak discharge: the highest point on the hydro graph when the rate of
discharge is greatest
 Discharge: the rate of flow (volume per unit time) passing a specific location
in a river or other channel

Hydrograph 
Rate of flow @ any instant
Volume of flow @ any instant
Mean Runoff for Month, Year
Max. Min. Runoff / Month or Yr
Max. rate of runoff during flood
Gives idea about dry period

FLOW DURATION CURVE
Another representation of Runoff data over
the time
It shows Runoff data for given time
Magnitudes of Runoff on ordinate
Taking 100% time on abscissa
Ordinate represent potential power called
Power Duration Curve
Useful in water power development
Most useful for comparisons between streams

Method to draw Hydrograph , Flow Duration
Curve and Mass Curve

MASS CURVE
 Graph of Cumulative values of water quantity
against time
 Express area under hydrograph
 A summation of daily flows, instead of monthly
flow, results in superior exactitude
 If rainfall is uniform throughout, the mass curve
will be straight line

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