very interactive explanation of the course within the slides

2. What is Hydroelectric Power?
 Hydroelectricity is a term referring to the electricity
generated by hydro power
 A hydropower development is essentially to utilize the
hydraulic power possessed by the water flowing in a
stream and to develop from it electric power through
hydraulic turbines coupled to electric generators
 The total amount of hydroelectric power that would be
made available from a stream depends on continuous
flow rate of the stream and the head possessed by the
flowing water

5. Lay out of typical hydroelectric power scheme

6. Comparison of Hydroelectric and Thermal Power Plants
Criterion Hydroelectric Power Plant Thermal Power Plant
1. Initial cost and life
expectancy
Higher initial cost due to costly
infrastructure such as dam,
spillway, et., and its location at
a place far off from the
consumer or load centre
Lower initial cost due to its
proximity to consumer or load
centre
Higher life expectancy, may be
about 50 years
Lower life expectancy
2. operation, maintenance and
repair (OMR) cost
Low OMR cost due to no fuel
cost
High OMR cost due to costly
fuel and the cost of fuel
transport
Less maintenance and repair
cost and staff needed for
operation is less
High maintenance and repair
cost and staff needed for
operation is more
Water is replenished every year
an put to non-consumable use.
However, supply of water may
be erratic year after year
Non-replenishable source
Low taxes due to its location in
remote areas
High taxes due to its location
near cities

7. Criterion Hydroelectric power plant Thermal power plant
3. Transmission losses
More due to long transmission
lines
Less due to short transmission
lines
4. Pollution
No problem of pollution or
ecological unbalance later
Causes air pollution as well as
stream pollution resulting in
ecological imbalance unless
cooling towers or cooling ponds
are provided
No waste product and hence no
problem of its disposal
Problem of haulage and disposal
of waste product viz., smoke,
ash etc.
5. Actuating time
A few seconds to 3 to 4 minutes
depending on the length of
conduit
About 30 minutes
Quite suitable to take up peak
load
Not suitable for use as peak
load plants

8. Selection of Suitable Types of Turbines
S.No Head in meters Type of turbine Specific speed
1 300 or more
Pelton wheel,
single or
multiple jet
8.5 to 47
2 150 to 300
Pelton or
Francis
30 to 85
3 60 to 150
Francis or
Deriaz
85 to 188
4 Less than 60
Kaplan or
Deriaz
188 to 860

9. Advantages of Hydroelectric Power
Fuel is not burned so there is minimal pollution
Water to run the power plant is provided free by
nature
Hydropower plays a major role in reducing
greenhouse gas emissions
Relatively low operations and maintenance costs
The technology is reliable and proven over time
It's renewable - rainfall renews the water in the
reservoir, so the fuel is almost always there

10. Disadvantages of Hydroelectric Power
High investment costs
Hydrology dependent (precipitation)
In some cases, inundation of land and wildlife
habitat
In some cases, loss or modification of fish habitat
Fish entrainment or passage restriction
In some cases, changes in reservoir and stream
water quality
In some cases, displacement of local populations

11. Classification of Hydel Plants
1. Classification based on storage characteristics
 Run-off river plants
- Utilize the minimum flow of a river
- Do not have appreciable storage on the u/s side
- Suitable only on perennial rivers

12.  Storage plants
- It has an upstream storage reservoir
- Continuous firm power generation is possible
 Pumped storage plants
- Power is generated during peak hours, but during off-peak hours water is
pumped back from the tail water pool to head water pool for future use
- Primarily meant for assisting an existing thermal or other hydel plant

13.  Tidal plants
- Works on the principle that there is a rise in sea water
during high tide period and fall during the low ebb
period
- The tidal range, i.e. the difference between high and
low tide levels is utilized to generate power

14. 2. Classification according to functional basis
 Base load plants
- These are the plants which are capable of substantially
continuous operation in the base of the load curve throughout
the year
 Peak load plants
- It is a hydel plant designed and constructed primarily for taking
care of the peak load of a power system
3. Classification based on the basis of head
 Micro head plants – H = 10 m to 20 m
 Low head plants – H <= 30 m
 Medium head plants – H = 30 m to 250 m
 High head plants – H > 250 m

15. Important Terms Connected With Hydropower
 Water Power Potential
- It is the amount of power generated when Q cumecs of water
is allowed to fall through a head difference of H meters and is
given by:
P = η γ Q H
 Normal Water Level (NWL)
- It is the highest elevation of water level that can be
maintained in the reservoir without any spillway discharge
 Minimum Water Level (MWL)
- It is the elevation of the water level which produces minimum
net head on the power units (i.e. 60% of the design head)

16.  Rated Head – The head at which the turbine functioning at
full gate opening will produce a power output, equal to that
specified on the name plate of the turbine.
 Gross Head – It is the difference in water level elevation at the
point of diversion of water for the hydel scheme and the point
of return of water back to the river.
 Operating Head – It is the difference between the elevation of
water surface in the fore-bay and the tailrace after making
due allowance for approach and exit velocity heads
 Net Head or Effective Head – It is the difference of head at the
point of entry and exit of turbine and includes the respective
velocity and pressure heads at both places

17.  Installed Capacity – It is the total capacity in kilowatts or
million kilowatts of all the turbine generator units installed in
a power house.
 Dependable Capacity – It is the load carrying capability of the
power house with respect to the load characteristics during a
specified time interval
 Load Factor (LF) – It is defined as the ratio of the average load
over a certain period of time to the peak load during the same
period
 Utilization Factor (UF) or Plant Use Factor
Average load over a certain period
Peak load during that period
Load Factor 
Water actually utilized for power production
Water available in the river
UF 

18.  Capacity Factor or Plant Factor – It is the ratio of average output
of the plant for a given period of time to the plant capacity or, it
can also be defined as:
 Firm Power – The net amount of power which is continuously
available from a plant without any break on firm or guaranteed
basis.
 Secondary Power – The excess power available over the firm
power during the off peak hours or during monsoon season
 Power Factor – It is the ratio of actual power in kilowatts to the
apparent power in kilo volt amperes (KVA)
Energy actually produced in a given time
Max. energy that can be produced by the plant during the same time
CF 

19. Principal Components of a Hydroelectric
Scheme
 The fore-bay
 Intake structure
 Penstocks
 Surge tank or surge chambers
 Turbines
 Power house
 Draft tube
 The tailrace

20. Components of a Hydroelectric Power Plant

21. 1. Forebay
 An enlarged body of water provided just in front of the penstock
 It is provided in the case of run-of-river plants and storage plants
when the power house is located far away from the dam
 The main function of forebay is to provide a small balancing
storage upstream of the power house
2. Intake structures
 The water from the reservoir or forebay is let into the penstocks
through intake structure
 The main components of an intake structure are trash racks and
gates
 Trash rack is provided to prevent the entry of debris into the water
passage of hydropower plant
 The gates are provided to control the entry of water into the
penstocks

22. 3. Penstocks
 Penstocks are the pipes of large diameter used for conveying
water from the reservoir to the turbines
 A sufficient water depth should be provided above the penstock
entrance to avoid formation of vortices which may carry air into
the penstock and result in lowered turbine efficiency and
undesirable pressure surges
4. Surge tanks
 A surge tank is a cylindrical open-topped storage tank which is
connected to the penstock at a suitable point.
 These are provided to relieve the penstocks of excess pressure
caused by water hammer
 They also provide additional supply of water when the turbines
are in need of more water on account of increased load
 A surge tank should be provided as close to the power house as is
possible

23. 4. Power house
 It is a structure which houses the various hydraulic and electric
equipment
 The various hydraulic equipments are turbines, gates or gate
valves, governors, etc.
 The various electrical equipments are, generators, transformers,
switching equipments, transmission lines and transmission
structures
5. Turbines
 The machine which converts hydraulic energy to mechanical
energy, and finally to electrical energy
6. Tail race
 A channel into which the water is discharged after passing
through the turbines
7. Draft tube: - An elongated pipe connecting turbine to tail race

24. Example Problems
Example 1: Three turbo-generators each of capacity 10000 kW have
been installed at a hydel power station. During a certain period of
load, the load on the plant varies from 12000 kW to 26000 kW.
Calculate (i) total installed capacity, (ii) load factor, (iii) plant factor
and (iv) utilization factor.
Example 2 : During a low water week a river has an average daily
flow of 32 m3/sec with a fluctuation during the day requiring a
pondage capacity of approximately 15% of the daily discharge. a HEP
is to be located on the river which will operate 5 days a week, 24
hours a day, but will supply power at varying rate such that the daily
load factor is 55% corresponding to which the pondage required is
equal to 0.2 times the mean flow to the turbine. On Saturday and
Sunday all the flow is ponded for use on rest of the days.

25. Contd.
If the effective head on the turbines when the pond is full is to be 25
m and the maximum allowable fluctuation in pond level is 1 m find
(a) the surface area of the pond to satisfy all the operating
conditions, (b) the weekly output at the switch board in kwh.
Assume turbine efficiency 55% and generator efficiency 92%