Lecture No.

14
 The energy of water is utilized for hydro-power
generation.

 The energy of water may be kinetic or potential.

 Kinetic energy of water is its energy in motion and

is a function of mass and velocity.

 Potential energy is a function of the difference in

water in between two points.
 Life of hydropower plant is higher than thermal and
nuclear power plants.

 However capital cost for the construction and

commissioning is more than TPP and NPP.

 It requires less man-power and offers less

pollution.

 Unit cost of production of energy is low, because

main fuel is water which is renewable.
 Availability of Water
Run-off data for many years should be available to know
the maximum, minimum, average annual and seasonal
flows.

 Water Storage
Sufficient Water Storage should be present for water
availability throughout the year.

 Head of Water:
Most economic head is calculated or there should be the
possibility of constructing a dam to get required head.
 Geological Investigations
Strong foundation should be available and those sites are
considered where earthquake frequency is less.

 Water Pollution
Water should be free of pollution otherwise it can cause
excessive corrosion and damage to metallic structures.

 Social and Environmental Effects

Hydropower scheme may cause submergence of areas which
may result is loss of sites of cultural and historic aspects.
 Access to Site
Easy access to site should be available for transportation of
construction material and heavy machinery. New railway lines or
roads may be needed.

 Multipurpose
Multipurpose reservoirs are selected for power
generation, irrigation, flood control, navigation,
recreation; because initial cost of power plant is high
because of civil engineering construction work.
Hydro power plants are classified Based upon:

(1) Quantity of water available

(2) Available Head

(3) Nature of load

1. Run-off river plants without pondage

 It doesn’t store water.

 It uses water as it comes.

 It uses water only when available.

 Generating capacity primarily depending on the

rate of flow of water.
 During rainy season some quantity of water
wasted without using for the generation of
power.

 During low run-off periods due to low flow

rates , the generating capacity of plant is low.
2. Run-off river plants with pondage

 Usefulness of a run-off river plant is increased by

pondage.

 Pondage permits storage of water during the off-

peak periods and use of this water during peak
periods.

 It is cope up by the size of the pondage.

 This plant can be used on parts of the load curve
requirement, within certain limitations.

 It is more useful than a plant without pondage or

storage.
3. RESERVOIR PLANTS

 Majority of the plants are this type.

 It permit carrying over storage from wet season to

the next dry season.

 Water is stored behind the Dam and is available to

plant with proper control.

 It has better capacity and can be used through out

year.
 It can be used as a base-load plant or peak load
plant as required.

 It can also be used on any portion of the load curve

as required
1. LOW HEAD PLANTS
 Small dam is built across the river to provide the
necessary head (up to 30m).

 The excess water is allowed to flow over the dam

itself.

 Used turbines: Francis, Propeller or Kaplan turbine.

 No surge tank is required

2. MEDIUM HEAD PLANTS
 Forebay is provided at the beginning of penstock.

 Forebay serves as water reservoir for such plants.

 Generally in these plants water carried in open canals from

main reservoir to the forebay and then to the power house
through penstock.

 The forebay itselfs works as a surge tank.

 Prime mover or Turbines: Francis, Propeller and Kaplan

3. HIGH HEAD PLANTS

 All water is carried from the main reservoir by a

tunnel up to the surge tank and then from surge tank
to the power house through pen stock.

 Heads more than 300m Pelton wheel turbine is

preferred.
1. BASE LOAD PLANTS
 Such loads can take up the load on base portion of the
load curve.

 In this type plant load is almost constant.

 Load factor is high.

 Run-off power plants without pondage can be used as

base load plant.

 Similarly the plants which has storage also work as base

load plants.
2. PEAK-LOAD PLANTS

 Plants used to supply the peak load of the system

corresponding to the load at the top portion of the
load curve are known as peak-load plants.

 Run-off river plants with pondage can be used as

peak- load plants.

 Reservoir plants with water storage back side dam

may be used as either base-load plant or peak load
plant as required.
3. PUMPED STORAGE PLANTS
 They are built for peak-load.

 Water after passing through the turbine stores in tail-

race pond.

 It may fed back to the head water pond.

 Water is fed back from tail-race pond to Head water

pond during off-peak period.

 During peak load period water passes from Head water

pond to the penstock to operate the turbines.
 It can recover 70% of the power by using pumping
water.

 By using reversible-turbine-pump unit a turbine can

generate power and a pump while pumping water to
storage.

 The generator is worked as a motor during reverse

operation so that efficiency is high. The cost of
reversible-turbine-pump sets increases.

 It meets peak loads.

 The various components of HP are as follows:

1. Reservoir
2. Trash Racks and Sand Traps
3. Spillways
4. Intakes or Control Gates
5. Conduits
6. Penstocks
7. Surge tanks
8. Forebay
9. Draft tubes
10. Tail Race
11. Turbines
12. Power house Switchyard for power evacuation
13. Power house
1. Reservoir

 Dam Develops a reservoir to store water.

 It also builds up head for power generation.

2. Trash Rack and Sand Traps

 Trash Rack is placed across the intake to stop the entry of

debris.

 They might damage the turbine runners or choking of

nozzles of the impulse turbines.

 Sand Traps are the long passages where small rocks and
sands are trapped to avoid damages to the turbines.

 Trapped sand and rocks are washed away back in to the

main stream after certain accumulation.
3. Spillway
 Spillways are safeguards of the dam when water level in the
reservoir rises.
4. INTAKE OR CONTROL GATES

 These are the gates built on the inside of the dam.

 The water from reservoir is released and controlled through

these gates.

 These are called inlet gates because water enters the power
generation unit through these gates.

 When the control gates are opened the water flows due to
gravity through the penstock and towards the turbines.

 The water flowing through the gates possesses potential as

well as kinetic energy.
5. Conduits/Channels

a. Headrace
 It is a channel which lead the water to the turbine.

b. Tailrace
 It is a channel which carries water from the turbine.

c. Power canal
 It is an open waterway excavated in natural ground following
its contour. (Ghazi-Brotha Canal)
5. Conduits/Channels

d. Tunnel
 It is a closed channel excavated through an obstruction.

e. Pipeline
 It is a closed conduit supported on the ground.
6. The Penstock
 The penstock is the long pipe or the shaft that carries the
water flowing from the reservoir towards the power
generation unit.

 The water in the penstock possesses kinetic energy due to its

motion and potential energy due to its height.

 The total amount of power generated in the hydroelectric

power plant depends on the height of the water reservoir and
the amount of water flowing through the penstock.

 The amount of water flowing through the penstock is

controlled by the control gates.
7. SURGE TANK

 A surge tank is a small reservoir in which the water level rises

or falls to reduce the pressure swings so that they are not
transmitted to the penstock.
a. Water Hammer

 When Load on the turbine is suddenly reduced, Governor closes

turbine gates.

 This causes sudden increase of pressure in the penstock which is

Negative Pressure.

 When Load on the generator is suddenly increased, Governor

opens the turbine gates which Tends to cause a vacuum in the
penstock.

 When the gates are closed, water level rises in the surge tank and
when the gates are suddenly opened, surge tank provides the
initial water supply.
8. Forebay
 Enlarged body of water just above the intake or at the
beginning of penstock.

 Forebay serves as water reservoir for Medium head plants.

 Generally in this plants water carried in open canals from

main reservoir to the forebay and then to the power house
through penstock.

 The forebay itselfs works as a surge tank.

9. Draft Tubes

 The function of the draft tube is to reduce the velocity head

losses of the water.

 To allow the turbine to be set above the tailrace to facilitate

inspection and maintenance.
10. Tailrace

 A tailrace is required to discharge the water leaving

the turbine into the river.

 The design of the tail race should be such that water

has a free exit.
11. TYPES OF HYDRAULIC TURBINES

1. According to the head and quantity of water available

a. a. Low head (2-30m)
b. b. Medium head (31-300m)

c. c. High head (>300m)

d. d. Very high head (>500m)
11. TYPES OF HYDRAULIC TURBINES

2. According to the name of the originator

a. Francis
b. Kaplan
c. Pelton
11. TYPES OF HYDRAULIC TURBINES

3. According to the nature of working of water on blades

a. Impulse Turbines (Pelton Wheel)

b. Reaction Turbines (Francis, Kaplan)
11. TYPES OF HYDRAULIC TURBINES

4. According to the direction of flow of water

a. Radial
b. Axial
c. Tangential (Deriaz)

5. According to the axis of the turbine shaft:

a. vertical
b. horizontal
12. SWITCHYARD
An electrical substation of an electricity generation,
transmission and distribution system where voltage is
transformed from high to low or the reverse using
transformers.
a. Transformers
1. Step up transformers 2. Step Down transformers
A transformer that increases voltage from primary to secondary
(more secondary winding turns than primary winding turns) is
called a step-up transformer. Conversely,
a transformer designed to do just the opposite is called a step-
down transformer.
b. Transmission lines
13. POWER HOUSE
1. Hydraulic turbines
 Consists of Blades which move with the water energy.

2. Electric generators
 They convert the mechanical energy in to Electric Energy.

3. Governors
 They control the flow of water in sudden rejection or need of
load.

4. Gate valves
 They control the entrance of water.
13. POWER HOUSE

5. Relief valves
 The pressure is relieved by allowing the pressurized
fluid to flow from an auxiliary passage out of the
system.

 The relief valve is designed or set to open at a

predetermined set pressure to protect pressure vessels
and other equipment from being subjected to pressures
that exceed their design limits.
13. POWER HOUSE

6. Water circulation pumps

 These pumps provide the cooling of the system.

7. Air ducts
 To provide ventilation of air around the system.
13. POWER HOUSE

8. Switch board and instruments

 They Control the whole electric power house electricity
system generation.

9. Storage batteries
 They provide backup system for Instrumentation.

10. Cranes
 They are made to lift the loads like turbines, shafts etc for
installation and removing for repair.
1. It is a non-polluting source of energy.

2. It has lower operational cost compared to fossil fuel-based

generation plants.

3. Can be easily transmitted through wires to long distances.

4. Dams made for generation of Hydroelectricity also help in

irrigation projects.
1. It can be generated only in areas with heavy rainfall and
sufficient supply of water.

2. Hydel power generation stations are to be located in hilly

mountainous terrains where ideal sites for dams are
located.

3. Losses during transmission is very high, sometimes up to

30%.
4) Hydropower is an expensive scheme.

5) Building a dam for hydropower affects the environment and

wildlife of adjoining areas.

6) Nearby low-lying areas are always under the threat of floods.

7) If precipitation is scarce, there might not be enough water to

turn turbines.
Thanks