clearly identify the definition of hydro power,components of hydro power

1. University of Gondar
Institute of Technology
Design and construction of Water work assignment
Section 2
Prepared by
1. birtukan zeleke
2. eden bekele
3. kidst agegn
4. Kibir molla
5. mahlet asefa
6. Mekdelawit merso
7. Wintana Getahun
Submission date 27/11/2014 E.
Submitted to:

2. Acknowledgement
We would like to thank our teacher Instructor. who gave us this opportunity to work on this
project. We have got to learn a lot from this project .
We would also like to extend our heartfelt thanks to our seniors because without their help this
project would not have been successful. Finally, we would like to thank our dear friends who
have been with us all the time.

3. Definition of hydropower
The hydropower plant or hydroelectric power plant is used to convert the kinetic
energy of water into electric energy. The kinetic energy developed in the water
flow due to the gravity of falling water from higher to lower head.
The kinetic energy is used to rotate the turbine and the turbine is connected with
an alternator to generate electrical energy. A hydroelectric power plant is a non-
convention power plant and widely used to generate electricity from a renewable
source of energy.
To achieve kinetic energy from water, the reservoir or dam is constructed at a
high head from the ground level. The initial cost of a hydroelectric power plant is
very high. But the running cost is very low. In the world, 16% of total power is
generated from the hydroelectric power plant.
Components of hydropower plant
The major components of the hydroelectric power plant are listed below.
 Dam
 Forebay
 Intake structure
 Penstock
 Surge tank
 Turbines
 Powerhouse
 Draft tube
 Tailrace

4. Dam
The dam is the most important component of hydroelectric power plant. The dam
is built on a large river that has abundant quantity of water through out the year. I
should be built at a location where the height of the river is sufficient to get the
maximum possible potential energy from water.
Forebay
The forebay is used to store water temporarily before passes to the intake
structure. The forebay is an optional component of a hydroelectric power plant.
The reservoir is used to store water across the river. In some hydroelectric power
plants, the reservoir behaves as a forebay. And the water from the reservoir leads
to the turbine.
The amount of water stored in the forebay is decided based on the demand of
required water and load in that area.
Intake Structure
The intake structure is a chain between the penstock and forebay. It collects water
from the forebay and passes to the penstock.
It plays an important role in power plants. The water comes in reservoir or forebay
from the river. Therefore, the water contains much trash like trees and debris. The
intake structure contains trash racks and placed trash racks at the entrance of the
penstock.
The trash racks are made of steel rods. It prevents severe damage to the turbine
blades and nozzle. In trash racks, steel rods are placed with a gap of 10 to 30 cm
apart.

5. Trash racks are heated in cols season to avoid ice rocks collision with turbine
blade. Due to heat in trash racks, the ice rocks melted at the entrance of the
penstock. The trash racks must be clean after a regular time period. And racks and
trolly arrangements are used to clean the trash racks.
Penstock
Penstocks are used to increase the velocity of the water. It is large pipes laid on
the slope. It carries water from the reservoir or intake structure to the turbine.
The penstocks are open and close with the gate. So, at the time of opening and
closing of gates, the pressure of water is very high. Therefore, the penstocks are
designed to sustain the hammer of water.
Short length penstock has heavy wall and long length penstock has surge tank is
used to overcome the pressure of water. The penstock is made of steel and
reinforced concrete.
If the length of penstock is small, separate penstock is used for the turbine. If the
length of penstock is large, a single penstock is used and at the end, it divides into
branches.
Surge tank
A surge tank is a cylindrical tank or chamber placed near the powerhouse and it is
connected with the penstock. The surge tank is also known as the surge chamber. It
is used to control the pressure of water in the penstock.
The water level of the surge tank increases when the powerhouse rejects the water
due to low power demand. So, the surge tank controls the pressure in the penstock.
When the power demand is high, a surge tank is used to accelerate the water flow.
And in this condition, the water level of the surge tank is reduced. During steady
load conditions, the water level becomes constant.
Turbine

6. The turbine is used to convert the kinetic energy of water into mechanical energy.
When the high-pressure water coming from the penstock strikes the turbine blade,
the turbine starts rotating.
The shaft is placed at the center of the turbine. And a generator is also connected
with the same shaft and it further converts the mechanical energy into electrical
energy.
There are mail two types of the turbine;
 Impulse turbine
 Reaction turbine
The impulse turbine is also known as a velocity turbine and the reaction turbine is
also known as a pressure turbine.
Powerhouse
The powerhouse is used to provide support and housing to the hydraulic and
electrical equipment. It is divided into two parts; substructure and superstructure.
The substructure can be an integral part of the hydraulic system or it can be placed
away from the hydraulic system. It is used to provide support to the equipment and
provide necessary ways to the water.
The superstructure contains the main unit and electrical accessories. The
generators are placed on the ground floor with the turbine. Generally, for better
visibility, the control room is placed on the first or second floor.
Draft tube
A draft tube connects the turbine outlet (turbine discharge) to the tailrace. To
decrease the velocity of water, the width of the draft tube is gradually increased.
The gates are provided at the end of a draft tube which is closed at the time of

7. maintenance. In the case of the reaction turbine, the draft tube is a necessary
component.
Tailrace
The tailrace is a flow of water from the draft tube or turbine outlet. The
powerhouse must be located near to the stream. If the powerhouse is placed far
from the stream, it is compulsory to build a way or channel to flow the water into a
stream.
It will decrease the efficiency, cavitation, damage the turbine by silting caused
unnecessary flow of water. Therefore, while designing a hydroelectric power plant,
place the powerhouse near the stream.
Sources of Energy
Energy can be described as potential for work, which may be withdrawn if needed.
The three most important and common sources, known as CONVENTIONAL are:
 Thermal power,
 Hydropower , and
 Nuclear power.
The other sources of energy are also valuable, but in comparison to the main
three sources, their contribution is limited – UNCONVENTIONAL :
 Tidal power
 Solar power
 Geothermal power
 Wind power , and
 Depression power.

8. Advantages and Disadvantages of Hydropower
Hydropower has the following inherent advantages over other sources
of energy
Hydropower has a ‘perpetual’ source of energy, while thermal power
has a depletable fossil fuel source
Hydropower does not consume water;Running cost of hydropower
plant is very low compared to thermal and nuclear plants
Hydropower plants can be brought into operation in few minutes while
thermal and nuclear power plants lack this capability. Thus, hydropower
plants are particularlyuseful in taking up short period peak loads in a
power grid system
Efficiency of hydropower system is very high (80 – 90%), while thermal
powe plants have low efficiency, as low as 40%;
Hydropower development also provides secondary benefits such as
recreation,fishing, flood control, etc, where storage is contemplated.
Some of the disadvantages of hydropower
development are:
It is capital intensive and therefore rate of return is low;
 The gestation period (about 10 to 15 years between initial idea and final
project inauguration) is long.
 This period is low for thermal power plants;

9.  Hydropower is dependent on natural flow of streams. Since this is very
variable the dependable or firm power is considerably low compared to
total capacity
Classification of hydropower
Types of Hydropower Plant
The hydroelectric power plants are classified into different types as follows.
Based on the availability of water head
 Low head plant
 Medium head plant
 High head plant
Based on the nature of the load
 Base load plant
 Peak load plant
Based on the quantity of water available
 Run-off river plants without pondage
 Run-off river plant with pondage
 Storage type plant
 Pumped storage peak load plant
 Mini and micro hydel plant
Based on the Availability of Water Head
According to the available water head, the power plants classifies into three types,
Low head plants

10. In this type of hydroelectric power plant, the available water head is less than 30m.
In this type of plant, by constructing a dam, the water is stored. And the power
plant is constructed at the base of the dam.
If the excess water is available in the dam, it will flow over the dam itself. In this
type of plant, Francis, propellor, or Kaplan type turbines are used in most of the
cases.
Medium head plant
The hydroelectric power plant which has an available water head of 30m to 100m
is considered a medium head plant. In most cases, the Francis turbine is used in
this type of power plant.
High head plant
The hydroelectric plant having an available water head is more than 100m consider
a high head plant. In this type of plant, a bulk amount of water is available in the
dam from the rain or melting of snow.
These plants are constructed in hilly areas to achieve high water head. In most
cases, these plants are constructed on big rives in which the water is available
throughout the year.
The high head plant uses Francis turbine up to the head of 300m and Pelton
turbine uses if the available water head is more than 300m.
Based on the Nature of the Load
Two types of load can be connected with the power plant. The plant running
continuously throughout the day is said to be a base load plant. And the plant
which is used to meet the peak demand is known as peak load plants.
According to the type of load connected with the plant, the hydroelectric plants are
classified into two types;

11. Base load plant
These plants are used to take a load on the base portion of the load curve of the
power system network. The base load plants are large capacity plants as it is built
to meet the demand of the base load.
The load factor of these plants is very high. In most cases, these plants are runoff
river or storage type plants
Peak load plant
The hydroelectric power plant that was built only to meet the peak portion of the
load curve is known as the peak load hydropower plant.
The capacity of this plant is less than base load plants and these plants are turned
ON only while the peak demand of load and after this plant turned OFF. Therefore,
these plants are used to run for a short duration of time.
In most cases, these plants are runoff river plants with pondage or storage type of
hydel plant
Based on the Quantity of Water Available
According to the quantity of water available to generate electric power, the
hydroelectric power plants are classified into five types;
Run-off river plants without pondage
This type of hydropower plant does not store water. It uses the water directly from
the river. The power output of these plants is not constant. Because there is no
control over the availability of water. Hence, the power output fluctuates and the
utility of this plant is very less compared to other plants.
Run-off river plants with pondage

12. In this type of plant, a pond is constructed behind the dam and near the plant. This
pond increases the utility of the power plant.
To meet fluctuating loads, the capacity of the pond decides based on the 24 hours
fluctuation in load demand. This plant can be used as a base load as well as a peak
load plant.
Storage type plant
This type of plant uses a reservoir to store water. In some areas where the water is
available in rainy seasons only. In this area, the storage type of plants is used to
store water in bulk amounts and use in dry seasons.The storage type of plant can be
used as base load and peak load plant. The capacity of the plant decides by the
water storage capacity of the reservoir.
Pumped storage peak load plant
This type of plant is used to meet the peak load demand. It has a reservoir to
store the water. When the load demand is high, it used the water of the reservoir.
And when the load demand is reduced, this plant is designed with a pump that is
used to supply water from tailrace to head race.
The pumped storage plants are used to run along with the steam (thermal) power
plant to improve the overall efficiency of a combined power plant. The pump of
this plant is energized from the secondary power plant like run-off river plant or
nuclear plant.
In this plant, the required water is very less compared to other hydropower plants.
Mini and micro hydel plant
Mini and micro hydropower plants are used to meet the power crises. Mini
power plants work in the range of 5 to 20 m head and micro power plants work in
the range of fewer than 5 m available water head.

13. This plant is a small capacity plant. and the time required and cost to build this
plant are less compared to other hydroelectric plants. The mini-Hydropower Plant
uses a special type of turbine known as bulb type turbine.
Estimating Power Potential
Technique of estimating hydropower potential
Before any power plant is contemplated, it is essential to assess the inherent
power available from the d is char ge of the river and the head available at the
site.
The gross head of any proposed scheme can be assessed by simple surveying
techniques, whereas
Hydrological data on rainfall and runoff are essential in order to assess the
quantity of water available.
The hydrological data necessary for potential assessment are:
The daily, weekly, or monthly flow over a period of several years, to determine
the plant capacity and estimate output,
Low flows, to assess the primary, firm or dependable power.
The potential or theoretical power in any river stretch with a difference in
elevation H is computed from
Pp = γ*Q*H
Where Pp = Potential (theoretical) power of the stream in Kw
H = head in m
Q = stream discharge in m3/s
= unit weight of water, 9.81 KN/m3
The hydraulic power P is given by
P= η*γ*Q*H(KW)
Where η = the total efficiency
 The actual use of the equation for estimating the potential, Pp, however, is
made difficult due to the fact that the discharge of any river varies over a
wide range.
 High discharges are available only for short durations in a year.
 The corresponding available power would be of short duration.

14.  If the discharge rate and the percentage duration of time for which it is
available are plotted, a flow duration curve results.
 Power duration curve can also be plotted since power is directly
proportional to the discharge and available head.
 Dis charge/Power duration curve indicates discharge or power available in
the stream for the given percentage of time.
Flow duration analysis
Flow duration curves
A flow duration curve is a plot of flow versus the percent of time a particular flow
can be expected to be exceeded
A flow duration curve merely reorders the flows in order of magnitude instead
of the true time ordering of flows in a flow versus time plot.
The flow duration curve also allows the characterizing of the flow over long
periods of time to be presented in one compact curve.
Characteristics of Flow Duration Curves
The flow duration curve (FDC) shows how flow is distributed over a period
(usually a year).
A steep flow duration curve implies a flashy catchment – one which is subject to
extreme floods and droughts
Factors which cause a catchment to be flashy are
Rocky, shallow soil
Lack of vegetation cover,
Steep, short streams,
Uneven rainfall (frequent storms, long dry periods).
Such type of FDC (i.e. steep) is bad for hydropower development (especially run-
of-river type).
A flat flow duration curve is good because it means that the total annual flow will
be spread more evenly over the year, giving a useful flow for longer periods, and
less severe floods.
Characteristics of a flat FDC are:
Deep soil, Heavy vegetation (e.g. jungle),
Long gently sloping streams,
Bogs, marshes,
Even rainfall (e.g. temperate climate).

15. Power Duration Curve
Minimum potential power computed from the minimum flow available for 100 %
of the time (365 days or 8760 hours). This is represented as Pp100;
Small potential power computed from the flow available for 95 % of time (flow
available for 8322 hours). This is represented as Pp95;
Average potential power computed from the flow available for 50% of the time
(flow available for 6 months or 4380 hours). This is represented as Pp50;
Mean potential power computed from the average of mean yearly flows for a
period of 10 to 30 years, which is equal to the area of the flow-duration curve
corresponding to this mean year. This is known as ‘ Gross river power potential’
and is represented as Ppm.
It would be more significant to find out the technically available power from the
potential power;