2. Hydro-Electric Power Plant
• The purpose of a hydro-electric plant is to harness
power from water flowing under pressure
• Water flowing under pressure has two forms of
energy:
– Kinetic and,
– Potential
• The kinetic energy depends on the mass of water
flowing and its velocity
• The potential energy exists as a result of the
difference in water level between two points which
is known as ‘head’
3. Hydro-Electric Power Plant
• The water or hydraulic turbine, as it is sometimes
named, converts the kinetic and potential energies
possessed by water into mechanical power
• The hydraulic turbine, is thus, a prime mover
which when coupled to a generator produces
electric power
• The project design to produce electric power from
water are known as hydro-electric projects
• Single purpose projects (power generation) and
multipurpose projects (irrigation, floods etc..)
4. Hydro-Electric Power Plant
• Hydropower is a conventional renewable
source of energy
• Clean,
• Free from pollution and,
• Generally has a good environmental effect
5. Status of Hydropower and its
potential
• Next to thermal power, hydro power is important in
regard to power generation
• Provide 30% of the total power of the world
• Total hydro-potential of the world is about 5 000
GW
• In some countries like Norway almost total power
generation is hydro based
• Nepal:
– Total potential is about 83 000 MW
– Economical & technical feasible potential is about
42 000 MW
– Total installed capacity is about 700 MW
6. Obstacles in the utilization of
hydropower resources
• Large investments
• Long gestation period
• Increases cost of power transmission
• Sediment erosion problem in Himalayan
Rivers
8. Essential Components and Features
• Storage reservoir
• Dam with its control works
• Waterways with their control works
• Power house with turbo and other machinery
• Tail race
• Generation and transmission of electric power
9. Reservoir
• A reservoir is employed to store water available form
catchment area which is further utilized to generate
power by running the hydraulic turbines
• Two types: Natural and Artificial
• An artificial reservoir is built by erecting a dam across
the river
• Water held in upstream reservoir is called storage
whereas water behind the dam at the plant is called
poundage
10. Dam with its Control Works
• Dam is a barrier to confine or raise water for storage or
diversion to create a hydraulic head
• An hydro-electric dam diverts the flow from the river to
the turbines and usually increases the head
• A reservoir dam stores water by raising its level
• Dams are built of concrete or stone masonry, earth or
rock fill, or timber
• A barrage is a diversion dam, especially at a tidal power
project
• A weir is a low overflow dam across a stream for
measuring flow or maintain water level, as at a lake
outlet
12. • Earth Dam
– An earth dam is made of earth (or soil) built up by
compacting successive layers of earth, using the most
impervious materials to form a core and placing more
permeable substances on the upstream and downstream
sides
– Earth dam resists the forces exerted upon it mainly due to
shear strength of the soil
Canyon Dam, an
earthen dam
13. • Rock - fill Dam
– A rock fill dam is built of rock fragments and boulders of
large size
– An impervious membrane is placed on the rock fill on the
upstream side to reduce the seepage through the dam
14. • Gravity Dam
– A gravity dam is a massive sized dam fabricated from
concrete or stone masonry
– The weight of the dam is actually able to resist the
horizontal thrust of water pushing against it
– Gravity essentially holds the dam down to the ground,
stopping water from toppling it over
Grand coulee Dam,
Washington, USA, a
solid gravity dam
15. • Buttress Dam
– It has a watertight upstream side supported by triangular
shaped walls called buttresses
16. • Arc Dam
– An arch dam is curved in plan, with its convexity towards
the upstream side
– An arch dam transfers the water pressure and other forces
mainly to the abutments by arch action
Hoover Dam,
USA; concrete
arch type
gravity dam
17. • Timber Dam
– Main load-carrying structural elements of timber dam are
made of wood
– Timber dams are made for small heads (2-4 m or, rarely, 4-
8 m)
Redridge
Timber Crib
Dam,
Michigan,
USA
18. Dam Contd…
• Principal Elements of Control Works
– Gates and Valves of various types and their operating
mechanisms
– Structures necessary for their operations
– Devices for the protection of gates and hydraulic machines
19. Dam Contd…
• Gates
– Different types of hydraulic gates and hoists, working on
different principles and mechanism are in use for
controlled release of water through spillways, sluices,
intakes, regulators, ducts, tunnels, etc.
– Types of Hoist used
• Mechanical Hoist
– Rope drum Type
– Screw operated
– Chain and sprocket
• Hydraulic Hoist
22. Dam Contd…
• Valves
– Spherical Valves
• Spherical valve mostly applied in front of high head
turbine, covering pressure range of 160 to 1250m water
head
• Consist of valve housing with flanges, valve rotor,
bearing and seals
23. Dam Contd…
• Butterfly Valves
– Butterfly valve normally applied in front of the low and
medium head water turbine with head range up to 200m
– Mainly consist of a ring shaped housing, the valve disc,
operating mechanism and counter weight
25. Dam Contd..
• Devices for protection of gates and hydraulic machines
– Trashracks
• They are made up of a row of rectangular cross sectional structural steel bars
placed across the entire intake opening in an inclined position.
• They are used to obstruct debris from going into the intake
– Debris cleaning device fitted to the trash rack
– Heating element against ice troubles
26. Waterways with their Control Works
• Waterway is the passage through which the water is carried
from the storage reservoir to the power house
• It may consist of
– Tunnels
– Canals
– Flumes
– Forebays
– Pipes (Penstock)
27. • Tunnel
– Tunnel is the passage made by cutting mountain to save distance
– In high head power plants it is normally called head race tunnel which
connects the water intake and the pressure shaft
– At the end of the head race tunnel there is a sand trap
– Beside the sump in the tunnel floor the cross section of the tunnel is
gradually increased to reduce the water velocity and allow for a better
sedimentation of suspended particles
28. • Canals
– They serve the same purpose as the tunnels
– Open canals are usually digged in the ground, blasted in
rock or built up as a chute of wood or concrete
29. • Forebay
– It is an enlarged section of a canal spread out to
accommodate the required width of intake
– Its function is to store temporarily, the water rejected by
the plant when its load is reduced and to meet the
instantaneous increased demand of water due to sudden
increase in load
– Usually found in case of medium and low head power
plants where the length of penstock is short
30. • Penstocks
– They are pipes of large diameter carrying water under
pressure from the storage reservoir to the turbine
32. • Surge Tank
– It is a storage reservoir fitted at some opening made on a
long penstock to receive the rejected flow when the
penstock is suddenly closed by a valve fitted at its steep
end
– Functions of surge tank
• Control of pressure variations resulting from rapid
changes of flow in penstock, relieving the line of
excessive pressure, thus eliminating water hammer
effects
• Regulation of flow in power plants by providing
necessary acceleration and retarding head
• Regulation of turbine speed
33.
34. • Power house is a building to house the turbines, generators
and other accessories for operating the machines
• Tail Race is a waterway to conduct the water discharged from
the turbines to a suitable point where it can be safely
disposed of or stored to be pumped back into the original
reservoir
• Generation and Transmission of Electric Power: It consists of
electrical generating machines, transformers, switching
equipment and transmission lines
35. Important Equipment in Power
House
• Hydraulic turbines
• Electric generators
• Governors
• Gate valves
• Relief valves
• Water circulating pumps
• Flow measuring equipment
• Air duct
• Water circulating pumps
• Switch board equipment and instruments
• Oil circuit breakers
• Reactors
• Low tension and high tension bar
• Storage batteries
• Cranes etc…
36. Selection of site for a hydro-
electric plant
• Availability of water
• Water storage
• Water head
• Accessibility of the site
• Distance from load centre
• Type of the land of site
38. Intake gate
Intake trashrack
Headrace tunnel
Anchor block
Surge tank
Penstock inlet
Valve
Tunnel Inlet
trashrack
Tunnel Inlet
Anchor block
Exp. joint
Shaddle
Power house
Tailrace
IV G
SC
DT
R
DT end gate
Desilting basin
gate hoist
IV -inlet valve
R -turbine runner
SC -spiral case
G -generator
Typical Power House with Francis Turbine
39. Hydropower plants
Tail water
Draft tube gate
Draft tube
Turbine
Main valve
Penstock
Air inlet
Inlet gate
Surge shaft
Tunnel
Sand trap
Trash rack
Self closing valve
42. Essential elements of hydro power
plant
• Catchment area
• Reservoir
• Dam
• Spillways
• Conduits
• Intakes, Canals, Tunnels, Fore-bay,
Flumes etc. to control Gates and
Valves
• Surge tanks
• Protection device e.g. Trash racks,
Debris cleaning device and Heating
element
• Prime movers
• Draft tubes
• Power house and equipment
43. Classification of Hydro-electric
plants
• According to availability of head
– High head power plants
– Medium head power plants
– Low head power plants
• According to nature of load
– Base load power plants
– Peak load power plants
• According to quantity of water available
– Run-off-river plant without pondage
– Run-off-river with pondage
– Storage type plants
– Pump storage plants
– Mini and micro-hydel plants
44. Cost of hydro-plant
• Reservoir, dam, intake, tailrace: 35%
• Turbines and generators: 20%
• Land, building and foundations: 30%
• Switching and wiring: 5%
• Switchyard: 5%
• Miscellaneous: 5%
45. Life of hydro plant components
Components Average
life
(years)
Components Average life
(years)
Reservoirs 70-80 Power house and
equipment
Dams: Building 35-50
Earthen,
concrete or
masonry
150 Generators 25
Loose rock 60 Transformers 30
Water ways: Turbines
(hydraulic)
5
Canals, tunnels 50-100 Pumps 20-25
Penstocks:
Steel 40-50 Concrete 25-50
