This document summarizes different types of dams and how hydroelectricity works. It describes the main types of dams as arch dams, gravity dams, arch-gravity dams, and embankment dams. It then explains how hydroelectricity is produced by building a dam to store water in a reservoir, which is then released through a turbine to generate electricity. The document also notes some advantages and disadvantages of large hydroelectric plants.

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Hydroelectric Dam
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CHARACTERISTICS OF
VARIOUS TYPES OF DAMS
AND THEIR
SELECTION PROCEDURE

2.  A dam is a hydraulic structure of impervious
material built across a river or stream to
create a reservoir on its upstream side for
storing water for various purposes.
 These purposes may be irrigation, hydro-
power, water-supply, flood control,
navigation, fishing and recreation.

4. Dams are classified on the basis of following
types:
 By structure
 By material

5.  Arch dams
 Gravity dams
 Arch – Gravity dams
 Embankment dams

6.  Situated at narrow
canyon with steep side
walls
 Constant angle dams are
more common than
constant radius
 Double curvature
 Require good rock
foundation

7.  Force that holds dam is
earth’s gravity pulling
down on mass of dam
 Well suited for blocking
rivers in wide valleys
 Dam is made from
concrete or masonry or
both
 Foundation must have
high bearing strength

8.  It has characteristics of
arch dam and gravity
dam
 They are made up of
conventional concrete
or RCC or masonry
 It is thinner than pure
gravity dams and
require less internal fill

9.  Special kind of dam
which consist of a line
of large gates that can
be opened or closed to
control the amount of
water
 Built at mouth of rivers
and often used to
control water flow for
irrigation system

10.  These are embankments
of compact granular soil
in combination with
impervious areas
 If clay is used then it is
composite dam
 These dams are resistant
to damage from
earthquakes

11.  They are generally made
up of one type of
material
 Earthen dams can be
constructed from
materials found on site
or nearby
 They are cost effective

12.  STEEL DAMS
 TIMBER DAMS

13. •Steel dam is a type of dam that is
made of steel, rather than common
masonry ,earthworks , concrete or
construction material
•Steel dams - an experiment which
failed
•Maintenance cost is high due to rust
and corrosion

14.  Advantages and Disadvantages

15.  Timber dams were
widely used in early
part of industrial
revolution and rarely
used now
 Suitable location for
construction
 In order to maintain
water retension
property they must be
kept wet

16.  Cofferdam : a barrier usually temporary,
constructed to exclude water from area that
is normally submerged
 Natural dams : created by natural geological
forces. Volcanic dams are formed when
erupted lava intercept path of a stream.
Natural disasters like earthquake and
landslides frequently create landslide dams in
mountainous region. Eg. Usoi dam in
Tajikistan

17. Hydroelectricity
• Hydroelectricity is the term referring to
electricity generated by hydropower; the
production of electrical power through the
use of the gravitational force of falling or
flowing water.
• It is the most widely used form of renewable
energy, accounting for 16 percent of global
electricity generation 3,427 terawatt-hours
of electricity production in 2010.
• Hydropower is produced in 150 countries,
with the Asia-Pacific region generating 32
percent of global hydropower in 2010. China
is the largest hydroelectricity producer.

18. • The theory is to build a dam on a large river that has a
large drop in elevation .
• The dam stores lots of water behind it in the reservoir.
• Near the bottom of the dam wall there is the water intake.
Gravity causes it to fall through the penstock inside the
dam.
• At the end of the penstock
there is a turbine propeller,
which is turned by the
moving water.
• The shaft from the turbine
goes up into the generator,
which produces the power.
Power lines are connected
to the generator that carry
electricity to user .
WORKING PRINCIPLE

19. Pumped storage: Reusing
water for peak electricity
demand
 Pumped storage is a method
of keeping water in
reserve for peak period
power demands by pumping
water that has already
flowed through the turbines
back up at storage pool
above the powerplant.
 An advantage of pumped
storage is that hydroelectric
generating units are able to
start up quickly and make
rapid adjustments in output.

20. Disadvantages of big Hydroelectricity
plant
• Ecosystem damage and
loss of land
• Siltation and flow shortage
• Relocation of local people
• Failure risks

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