Green Power Generation

1
Green Power Generation Lecture 5

Hydroelectric Power
2

• 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
• Once a hydroelectric complex is constructed, the
  project produces no direct waste, and has a
  considerably lower output level of the greenhouse
  gas carbon dioxide (CO2) than fossil fuel powered
  energy plants
• Worldwide, an installed capacity of 777 GWe
  supplied 2998 TWh of hydroelectricity in 2006
• This was approximately 20 of the world's
  electricity, and accounted for about 88 of
  electricity from renewable sources

3

• History
• Hydropower has been used since ancient times to
  grind flour and perform other tasks. In the
  mid-1770s, French engineer Bernard Forest de
  Belidor published Architecture Hydraulique which
  described vertical- and horizontal-axis hydraulic
  machines
• By the late 19th century, the electrical
  generator was developed and could now be coupled
  with hydraulics
• The growing demand for the Industrial Revolution
  would drive development as well
• In 1878 the world's first hydroelectric power
  scheme was developed at Cragside in
  Northumberland, England by William George
  Armstrong
• It was used to power a single light bulb in his
  art gallery.
• The old Schoelkopf Power Station No. 1 near
  Niagara Falls in the U.S. side began to produce
  electricity in 1881
• The first Edison hydroelectric power plant, the
  Vulcan Street Plant, began operating September
  30, 1882, in Appleton, Wisconsin, with an output
  of about 12.5 kilowatts
• By 1886 there were 45 hydroelectric power plants
  in the U.S. and Canada. By 1889 there were 200 in
  the U.S. alone

4

• At the beginning of the 20th century, many small
  hydroelectric power plants were being constructed
  by commercial companies in mountains near
  metropolitan areas
• Grenoble, France held the International
  Exhibition of Hydropower and Tourism with over
  one million visitors
• By 1920 as 40 of the power produced in the
  United States was hydroelectric, the Federal
  Power Act was enacted into law
• The Act created the Federal Power Commission to
  regulate hydroelectric power plants on federal
  land and water
• As the power plants became larger, their
  associated dams developed additional purposes to
  include flood control, irrigation and navigation
• Federal funding became necessary for large-scale
  development and federally owned corporations,
  such as the Tennessee Valley Authority (1933) and
  the Bonneville Power Administration (1937) were
  created
• Additionally, the Bureau of Reclamation which had
  began a series of western U.S. irrigation
  projects in the early 20th century was now
  constructing large hydroelectric projects such as
  the 1928 Hoover Dam

5

• The U.S. Army Corps of Engineers was also
  involved in hydroelectric development, completing
  the Bonneville Dam in 1937 and being recognized
  by the Flood Control Act of 1936 as the premier
  federal flood control agency
• Hydroelectric power plants continued to become
  larger throughout the 20th century
• Hydropower was referred to as white coal for its
  power and plenty
• Hoover Dam's initial 1,345 MW power plant was the
  world's largest hydroelectric power plant in
  1936 it was eclipsed by the 6809 MW Grand Coulee
  Dam in 1942
• The Itaipu Dam opened in 1984 in South America as
  the largest, producing 14,000 MW but was
  surpassed in 2008 by the Three Gorges Dam in
  China at 22,500 MW
• Hydroelectricity would eventually supply some
  countries, including Norway, Democratic Republic
  of the Congo, Paraguay and Brazil, with over 85
  of their electricity
• The United States currently has over 2,000
  hydroelectric power plants which supply 49 of
  its renewable electricity

6

•  
• Cross section of a conventional hydroelectric dam

7

•  
• A typical turbine and generator

8

• Conventional (dams)
• Most hydroelectric power comes from the potential
  energy of dammed water driving a water turbine
  and generator
• The power extracted from the water depends on the
  volume and on the difference in height between
  the source and the water's outflow
• This height difference is called the head
• The amount of potential energy in water is
  proportional to the head
• A large pipe (the "penstock") delivers water to
  the turbine

9

• Pumped-storage
• This method produces electricity to supply high
  peak demands by moving water between reservoirs
  at different elevations
• At times of low electrical demand, excess
  generation capacity is used to pump water into
  the higher reservoir
• When there is higher demand, water is released
  back into the lower reservoir through a turbine
• Pumped-storage schemes currently provide the most
  commercially important means of large-scale grid
  energy storage and improve the daily capacity
  factor of the generation system

10

• Run-of-the-river
• Run-of-the-river hydroelectric stations are those
  with small or no reservoir capacity, so that the
  water coming from upstream must be used for
  generation at that moment, or must be allowed to
  bypass the dam.

11

• Tide
• A tidal power plant makes use of the daily rise
  and fall of ocean water due to tides such
  sources are highly predictable, and if conditions
  permit construction of reservoirs, can also be
  dispatchable to generate power during high demand
  periods
• Less common types of hydro schemes use water's
  kinetic energy or undammed sources such as
  undershot waterwheels.

12

• Underground
• An underground power station makes use of a large
  natural height difference between two waterways,
  such as a waterfall or mountain lake
• An underground tunnel is constructed to take
  water from the high reservoir to the generating
  hall built in an underground cavern near the
  lowest point of the water tunnel and a horizontal
  tailrace taking water away to the lower outlet
  waterway

13
Sizes and capacities of hydroelectric facilities

• The Three Gorges Dam in China is the largest
  operating hydroelectric power station, at 22,500
  MW

14

• Although no official definition exists for the
  capacity range of large hydroelectric power
  stations, facilities from over a few hundred
  megawatts to more than 10 GW are generally
  considered large hydroelectric facilities
• Currently, only three facilities over 10 GW
  (10,000 MW) are in operation worldwide Three
  Gorges Dam at 22.5 GW, Itaipu Dam in South
  America at 14 GW, and Guri Dam in Venezuela at
  10.2 GW
• Large-scale hydroelectric power stations are more
  commonly seen as the largest power producing
  facilities in the world, with some hydroelectric
  facilities capable of generating more than double
  the installed capacities of the current largest
  nuclear power stations
• While many hydroelectric projects supply public
  electricity networks, some are created to serve
  specific industrial enterprises

15

• Dedicated hydroelectric projects are often built
  to provide the substantial amounts of electricity
  needed for aluminum electrolytic plants, for
  example. the Grand Coulee Dam switched to support
  Alcoa aluminium in Bellingham, Washington, United
  States for American World War II airplanes before
  it was allowed to provide irrigation and power to
  citizens (in addition to aluminum power) after
  the war
• In Suriname, the Brokopondo Reservoir was
  constructed to provide electricity for the Alcoa
  aluminium industry
• New Zealand's Manapouri Power Station was
  constructed to supply electricity to the aluminum
  smelter at Tiwai Point.

16

• The construction of these large hydroelectric
  facilities, and their changes on the environment,
  are also often on grand scales, creating as much
  damage to the environment as at helps it by being
  a renewable resource
• Many specialized organizations, such as the
  International Hydropower Association, look into
  these matters on a global scale.

17

• Small
• Small hydro is the development of hydroelectric
  power on a scale serving a small community or
  industrial plant
• The definition of a small hydro project varies
  but a generating capacity of up to 10 megawatts
  (MW) is generally accepted as the upper limit of
  what can be termed small hydro
• This may be stretched to 25 MW and 30 MW in
  Canada and the United States
• Small-scale hydroelectricity production grew by
  28 during 2008 from 2005, raising the total
  world small-hydro capacity to 85 GW
• Over 70 of this was in China (65 GW), followed
  by Japan (3.5 GW), the United States (3 GW), and
  India (2 GW)

18

• Small hydro plants may be connected to
  conventional electrical distribution networks as
  a source of low-cost renewable energy
• Alternatively, small hydro projects may be built
  in isolated areas that would be uneconomic to
  serve from a network, or in areas where there is
  no national electrical distribution network
• Since small hydro projects usually have minimal
  reservoirs and civil construction work, they are
  seen as having a relatively low environmental
  impact compared to large hydro
• This decreased environmental impact depends
  strongly on the balance between stream flow and
  power production.

19

• Micro
• Micro hydro is a term used for hydroelectric
  power installations that typically produce up to
  100 KW of power
• These installations can provide power to an
  isolated home or small community, or are
  sometimes connected to electric power networks
• There are many of these installations around the
  world, particularly in developing nations as they
  can provide an economical source of energy
  without purchase of fuel
• Micro hydro systems complement photovoltaic solar
  energy systems because in many areas, water flow,
  and thus available hydro power, is highest in the
  winter when solar energy is at a minimum.

20

• A micro-hydro facility in Vietnam

21
Pico

• Pico hydro is a term used for hydroelectric power
  generation of under 5 KW
• It is useful in small, remote communities that
  require only a small amount of electricity
• For example, to power one or two fluorescent
  light bulbs and a TV or radio for a few homes
• Even smaller turbines of 200-300W may power a
  single home in a developing country with a drop
  of only 1 m (3 ft)
• Pico-hydro setups typically are run-of-the-river,
  meaning that dams are not used, but rather pipes
  divert some of the flow, drop this down a
  gradient, and through the turbine before
  returning it to the stream

22

•  
• Pico hydroelectricity in Mondulkiri, Cambodia

23

• Calculating the amount of available power
• A simple formula for approximating electric power
  production at a hydroelectric plant is P
  ?hrgk, where
• P is Power in watts,
• ? is the density of water (1000 kg/m3),
• h is height in meters,
• r is flow rate in cubic meters per second,
• g is acceleration due to gravity of 9.8 m/s2,
• k is a coefficient of efficiency ranging from 0
  to 1.
• Efficiency is often higher (that is, closer to 1)
  with larger and more modern turbines
• Annual electric energy production depends on the
  available water supply. In some installations the
  water flow rate can vary by a factor of 101 over
  the course of a year.

24

• Advantages and disadvantages of hydroelectricity
• Advantages

• Economics
• The major advantage of hydroelectricity is
  elimination of the cost of fuel
• The cost of operating a hydroelectric plant is
  nearly immune to increases in the cost of fossil
  fuels such as oil, natural gas or coal, and no
  imports are needed
• Hydroelectric plants have long economic lives,
  with some plants still in service after 50100
  years
• Operating labor cost is also usually low, as
  plants are automated and have few personnel on
  site during normal operation.

25

• CO2 emissions
• Since hydroelectric dams do not burn fossil
  fuels, they do not directly produce carbon
  dioxide
• While some carbon dioxide is produced during
  manufacture and construction of the project, this
  is a tiny fraction of the operating emissions of
  equivalent fossil-fuel electricity generation
• Hydroelectricity produces the least amount of
  greenhouse gases and externality of any energy
  source
• Coming in second place was wind, third was
  nuclear energy, and fourth was solar photovoltaic
• The extremely positive greenhouse gas impact of
  hydroelectricity is found especially in temperate
  climates
• The above study was for local energy in Europe
  presumably similar conditions prevail in North
  America and Northern Asia, which all see a
  regular, natural freeze/thaw cycle (with
  associated seasonal plant decay and regrowth).

26

• Other uses of the reservoir
• Reservoirs created by hydroelectric schemes often
  provide facilities for water sports, and become
  tourist attractions themselves
• In some countries, aquaculture in reservoirs is
  common
• Multi-use dams installed for irrigation support
  agriculture with a relatively constant water
  supply
• Large hydro dams can control floods, which would
  otherwise affect people living downstream of the
  project

27

• Disadvantages
• Ecosystem damage and loss of land

28

• Large reservoirs required for the operation of
  hydroelectric power stations result in submersion
  of extensive areas upstream of the dams,
  destroying biologically rich and productive
  lowland and riverine valley forests, marshland
  and grasslands
• The loss of land is often exacerbated by the fact
  that reservoirs cause habitat fragmentation of
  surrounding areas
• Hydroelectric projects can be disruptive to
  surrounding aquatic ecosystems both upstream and
  downstream of the plant site
• For instance, studies have shown that dams along
  the Atlantic and Pacific coasts of North America
  have reduced salmon populations by preventing
  access to spawning grounds upstream, even though
  most dams in salmon habitat have fish ladders
  installed.

29

• Salmon spawn are also harmed on their migration
  to sea when they must pass through turbines
• This has led to some areas transporting smolt
  downstream by barge during parts of the year
• In some cases dams, such as the Marmot Dam in
  Oregon, have been demolished due to the high
  impact on fish.
• Turbine and power-plant designs that are easier
  on aquatic life are an active area of research
• Mitigation measures such as fish ladders may be
  required at new projects or as a condition of
  re-licensing of existing projects

30

• Generation of hydroelectric power changes the
  downstream river environment
• Water exiting a turbine usually contains very
  little suspended sediment, which can lead to
  scouring of river beds and loss of riverbanks
• Since turbine gates are often opened
  intermittently, rapid or even daily fluctuations
  in river flow are observed
• For example, in the Grand Canyon, the daily
  cyclic flow variation caused by Glen Canyon Dam
  was found to be contributing to erosion of sand
  bars
• Dissolved oxygen content of the water may change
  from pre-construction conditions.

31

• Depending on the location, water exiting from
  turbines is typically much warmer than the
  pre-dam water, which can change aquatic faunal
  populations, including endangered species, and
  prevent natural freezing processes from occurring
• Some hydroelectric projects also use canals to
  divert a river at a shallower gradient to
  increase the head of the scheme
• In some cases, the entire river may be diverted
  leaving a dry riverbed
• Examples include the Tekapo and Pukaki Rivers in
  New Zealand

32

• Siltation
• When water flows it has the ability to transport
  particles heavier than itself downstream
• This has a negative effect on dams and
  subsequently their power stations, particularly
  those on rivers or within catchment areas with
  high siltation
• Siltation can fill a reservoir and reduce its
  capacity to control floods along with causing
  additional horizontal pressure on the upstream
  portion of the dam
• Eventually, some reservoirs can become completely
  full of sediment and useless or over-top during a
  flood and fail

33

• Flow shortage
• Changes in the amount of river flow will
  correlate with the amount of energy produced by a
  dam
• Lower river flows because of drought, climate
  change or upstream dams and diversions will
  reduce the amount of live storage in a reservoir
  therefore reducing the amount of water that can
  be used for hydroelectricity
• The result of diminished river flow can be power
  shortages in areas that depend heavily on
  hydroelectric power
• The risk of flow shortage may increase as a
  result of climate change
• Studies from the Colorado River in the United
  States suggest that modest climate changes, such
  as an increase in temperature in 2 degree Celsius
  resulting in a 10 decline in precipitation,
  might reduce river run-o? by up to 40
• Brazil in particular is vulnerable due to its
  heaving reliance on hydroelectricity, as
  increasing temperatures, lower water ?ow and
  alterations in the rainfall regime, could reduce
  total energy production by 7 annually by the end
  of the century

34
The Hoover Dam in the United States is a large
conventional dammed-hydro facility, with an
installed capacity of 2,080 MW
35

• Methane emissions (from reservoirs)
• Lower positive impacts are found in the tropical
  regions, as it has been noted that the reservoirs
  of power plants in tropical regions may produce
  substantial amounts of methane
• This is due to plant material in flooded areas
  decaying in an anaerobic environment, and forming
  methane, a potent greenhouse gas

36

• According to the World Commission on Dams report,
  where the reservoir is large compared to the
  generating capacity (less than 100 watts per
  square metre of surface area) and no clearing of
  the forests in the area was undertaken prior to
  impoundment of the reservoir, greenhouse gas
  emissions from the reservoir may be higher than
  those of a conventional oil-fired thermal
  generation plant
• Although these emissions represent carbon already
  in the biosphere, not fossil deposits that had
  been sequestered from the carbon cycle, there is
  a greater amount of methane due to anaerobic
  decay, causing greater damage than would
  otherwise have occurred had the forest decayed
  naturally.

37

• In boreal reservoirs of Canada and Northern
  Europe, however, greenhouse gas emissions are
  typically only 2 to 8 of any kind of
  conventional fossil-fuel thermal generation
• A new class of underwater logging operation that
  targets drowned forests can mitigate the effect
  of forest decay
• In 2007, International Rivers accused hydropower
  firms of cheating with fake carbon credits under
  the Clean Development Mechanism, for hydropower
  projects already finished or under construction
  at the moment they applied to join the CDM. These
  carbon credits of hydropower projects under the
  CDM in developing countries can be sold to
  companies and governments in rich countries, in
  order to comply with the Kyoto protocol

38

• Relocation
• Another disadvantage of hydroelectric dams is the
  need to relocate the people living where the
  reservoirs are planned
• In February 2008 it was estimated that 40-80
  million people worldwide had been physically
  displaced as a direct result of dam construction
• In many cases, no amount of compensation can
  replace ancestral and cultural attachments to
  places that have spiritual value to the displaced
  population
• Additionally, historically and culturally
  important sites can be flooded and lost
• Such problems have arisen at the Aswan Dam in
  Egypt between 1960 and 1980, the Three Gorges Dam
  in China, the Clyde Dam in New Zealand, and the
  Ilisu Dam in Turkey.

39

• Failure hazard
• Because large conventional dammed-hydro
  facilities hold back large volumes of water, a
  failure due to poor construction, terrorism, or
  other cause can be catastrophic to downriver
  settlements and infrastructure
• Dam failures have been some of the largest
  man-made disasters in history
• Also, good design and construction are not an
  adequate guarantee of safety
• Dams are tempting industrial targets for wartime
  attack, sabotage and terrorism, such as Operation
  Chastise in World War II

40

• The Banquio Damfailure in Southern China directly
  resulted in the deaths of 26,000 people, and
  another 145,000 from epidemics
• Millions were left homeless
• Also, the creation of a dam in a geologically
  inappropriate location may cause disasters such
  as 1963 disaster at Vajont Dam in Italy, where
  almost 2000 people died
• Smaller dams and micro hydro facilities create
  less risk, but can form continuing hazards even
  after being decommissioned
• For example, the small Kelly Barnes Dam in
  Georgia failed in 1967, causing 39 deaths with
  the Toccoa Flood, ten years after its power plant
  was decommissioned

41

• Comparison with other methods of power generation
• Hydroelectricity eliminates the flue gas
  emissions from fossil fuel combustion, including
  pollutants such as sulfur dioxide, nitric oxide,
  carbon monoxide, dust, and mercury in the coal
• Hydroelectricity also avoids the hazards of coal
  mining and the indirect health effects of coal
  emissions
• Compared to nuclear power, hydroelectricity
  generates no nuclear waste, has none of the
  dangers associated with uranium mining, nor
  nuclear leaks
• Unlike uranium, hydroelectricity is also a
  renewable energy source
• Compared to wind farms, hydroelectricity power
  plants have a more predictable load factor
• If the project has a storage reservoir, it can
  generate power when needed, Hydroelectric plants
  can be easily regulated to follow variations in
  power demand.

42

• Unlike fossil-fuelled combustion turbines,
  construction of a hydroelectric plant requires a
  long lead-time for site studies, hydrological
  studies, and environmental impact assessment
• Hydrological data up to 50 years or more is
  usually required to determine the best sites and
  operating regimes for a large hydroelectric plant
• Unlike plants operated by fuel, such as fossil or
  nuclear energy, the number of sites that can be
  economically developed for hydroelectric
  production is limited in many areas the most
  cost-effective sites have already been exploited
• New hydro sites tend to be far from population
  centers and require extensive transmission lines
• Hydroelectric generation depends on rainfall in
  the watershed, and may be significantly reduced
  in years of low rainfall or snowmelt
• Long-term energy yield may be affected by climate
  change
• Utilities that primarily use hydroelectric power
  may spend additional capital to build extra
  capacity to ensure sufficient power is available
  in low water years

43

• World hydroelectric capacity

• World renewable energy share (2008), with
  hydroelectricity more than 50 of all renewable
  energy sources

44

• The ranking of hydro-electric capacity is either
  by actual annual energy production or by
  installed capacity power rating
• A hydro-electric plant rarely operates at its
  full power rating over a full year the ratio
  between annual average power and installed
  capacity rating is the capacity factor
• The installed capacity is the sum of all
  generator nameplate power ratings. Sources came
  from BP Statistical Review - Full Report 2009
• Brazil, Canada, New Zealand, Norway, Paraguay,
  Switzerland, and Venezuela are the only countries
  in the world where the majority of the internal
  electric energy production is from hydroelectric
  power
• Paraguay produces 100 of its electricity from
  hydroelectric dams, and exports 90 of its
  production to Brazil and to Argentina
• Norway produces 9899 of its electricity from
  hydroelectric sources.

45
Ten of the largest hydroelectric producers as at 2009.3132 Ten of the largest hydroelectric producers as at 2009.3132 Ten of the largest hydroelectric producers as at 2009.3132 Ten of the largest hydroelectric producers as at 2009.3132 Ten of the largest hydroelectric producers as at 2009.3132
Country Annual hydroelectricproduction (TWh) Installedcapacity (GW) Capacityfactor   of totalcapacity
 China 652.05 196.79 0.37 22.25
 Canada 369.5 88.974 0.59 61.12
 Brazil 363.8 69.080 0.56 85.56
 United States 250.6 79.511 0.42 5.74
 Russia 167.0 45.000 0.42 17.64
 Norway 140.5 27.528 0.49 98.25
 India 115.6 33.600 0.43 15.80
 Venezuela 85.96 14.622 0.67 69.20
 Japan 69.2 27.229 0.37 7.21
 Sweden 65.5 16.209 0.46 44.34
46

• Hydropower, hydraulic power or water power is
  power that is derived from the force or energy of
  moving water, which may be harnessed for useful
  purposes
• Prior to the development of electric power,
  hydropower was used for irrigation, and operation
  of various machines, such as watermills, textile
  machines, sawmills, dock cranes, and domestic
  lifts
• Another method used a trompe to produce
  compressed air from falling water, which could
  then be used to power other machinery at a
  distance from the water
• In hydrology, hydropower is manifested in the
  force of the water on the riverbed and banks of a
  river. It is particularly powerful when the river
  is in flood
• The force of the water results in the removal of
  sediment and other materials from the riverbed
  and banks of the river, causing erosion and other
  alterations.

47

• Waterwheels and mills
• Hydropower has been used for hundreds of years.
  In India, water wheels and watermills were built
  in Imperial Rome, water powered mills produced
  flour from grain, and were also used for sawing
  timber and stone in China, watermills were
  widely used since the Han Dynasty
• The power of a wave of water released from a tank
  was used for extraction of metal ores in a method
  known as hushing
• The method was first used at the Dolaucothi Gold
  Minein Wales from 75 AD onwards, but had been
  developed in Spain at such mines as Las Medulas
• Hushing was also widely used in Britain in the
  Medieval and later periods to extract lead and
  tin ores
• It later evolved into hydraulic mining when used
  during the California gold rush

48

• In China and the rest of the Far East,
  hydraulically operated "pot wheel" pumps raised
  water into irrigation canals
• At the beginning of the Industrial revolution in
  Britain, water was the main source of power for
  new inventions such as Richard Arkwright's water
  frame
• Although the use of water power gave way to steam
  power in many of the larger mills and factories,
  it was still used during the 18th and 19th
  centuries for many smaller operations, such as
  driving the bellows in small blast furnaces (e.g.
  the Dyfi Furnace) and gristmills, such as those
  built at Saint Anthony Falls, which uses the
  50-foot (15 m) drop in the Mississippi River
• In the 1830s, at the peak of the canal-building
  era, hydropower was used to transport barge
  traffic up and down steep hills using inclined
  plane railroads.

49

• Hydraulic power pipes
• Hydraulic power networks also existed, using
  pipes carrying pressurized liquid to transmit
  mechanical power from a power source, such as a
  pump, to end users
• These were extensive in Victorian cities in the
  United Kingdom
• A hydraulic power network was also in use in
  Geneva, Switzerland. The world famous Jet d'Eau
  was originally the only over pressure valve of
  this network

50

• Compressed air hydro
• Where there is a plentiful head of water it can
  be made to generate compressed air directly
  without moving parts
• A falling column of water is mixed with air
  bubbles generated through turbulence at the inlet
• This is allowed to fall down a shaft into a
  subterranean chamber where the air separates from
  the water
• The weight of falling water compresses the air in
  the top of the chamber
• A submerged outlet from the chamber allows water
  to flow to the surface at a lower height than the
  intake
• An outlet in the roof of the chamber supplies the
  compressed air to the surface
• A facility on this principal was built on the
  Montreal River at Ragged Shutes near Cobalt,
  Ontario in 1910 and supplied 5,000 horsepower to
  nearby mines. 4

51

• A conventional dammed-hydro facility
  (hydroelectric dam) is the most common type of
  hydroelectric power generation

52

• A Pelamis wave device under test at the European
  Marine Energy Centre (EMEC), Orkney, Scotland

53

• Marine Power
• Marine current power, which captures the kinetic
  energy from marine currents
• Osmotic power, which channels river water into a
  container separated from sea water by a
  semi-permeable membrane
• Ocean thermal energy, which exploits the
  temperature difference between deep and shallow
  waters
• Tidal power, which captures energy from the tides
  in horizontal direction. Also a popular form of
  hydroelectric power generation
• Tidal stream power, usage of stream generators,
  somewhat similar to that of a wind turbine
• Tidal barrage power, usage of a tidal dam
• Dynamic tidal power, utilizing large areas to
  generate head.
• Wave power, the use ocean surface waves to
  generate power.

54

• Calculating the amount of available power
• A hydropower resource can be measured according
  to the amount of available power, or energy per
  unit time. In large reservoirs, the available
  power is generally only a function of the
  hydraulic head and rate of fluid flow. In a
  reservoir, the head is the height of water in the
  reservoir relative to its height after discharge.
  Each unit of water can do an amount of work equal
  to its weight times the head.
• The amount of energy, E, released when an object
  of mass m drops a height h in a gravitational
  field of strength g is given by
• The energy available to hydroelectric dams is the
  energy that can be liberated by lowering water in
  a controlled way
• In these situations, the power is related to the
  mass flow rate.

55

• Substituting P for E/t and expressing m/t in
  terms of the volume of liquid moved per unit time
  (the rate of fluid flow, f) and the density of
  water, we arrive at the usual form of this
  expression
• or
• A simple formula for approximating electric power
  production at a hydroelectric plant is
• P hrgk
• where P is Power in kilowatts, h is height in
  meters, r is flow rate in cubic meters per
  second, g is acceleration due to gravity of 9.8
  m/s2, and k is a coefficient of efficiency
  ranging from 0 to 1
• Efficiency is often higher with larger and more
  modern turbines

56

• Some hydropower systems such as water wheels can
  draw power from the flow of a body of water
  without necessarily changing its height. In this
  case, the available power is the kinetic energy
  of the flowing water.
• where v is the speed of the water, or with
• where A is the area through which the water
  passes, also
• Over-shot water wheels can efficiently capture
  both types of energy

57

• Water turbine

• Kaplan turbine and electrical generator cut-away
  view.

58

• The runner of the small water turbine

59

• Swirl
• The word turbine was introduced by the French
  engineer Claude Bourdin in the early 19th century
  and is derived from the Latin word for "whirling"
  or a "vortex
• The main difference between early water turbines
  and water wheels is a swirl component of the
  water which passes energy to a spinning rotor
• This additional component of motion allowed the
  turbine to be smaller than a water wheel of the
  same power
• They could process more water by spinning faster
  and could harness much greater heads
• Later, impulse turbines were developed which
  didn't use swirl

60

• The earliest known water turbines date to the
  Roman Empire
• Two helix-turbine mill sites of almost identical
  design were found at Chemtou and Testier,
  modern-day Tunisia, dating to the late 3rd or
  early 4th century AD
• The horizontal water wheel with angled blades was
  installed at the bottom of a water-filled,
  circular shaft
• The water from the mill-race entered tangentially
  the pit, creating a swirling water column which
  made the fully submerged wheel act like a true
  turbine
• Jan Andrei Segner developed a reactive water
  turbine in the mid-18th century
• It had a horizontal axis and was a precursor to
  modern water turbines. It is a very simple
  machine that is still produced today for use in
  small hydro sites
• Segner worked with Euler on some of the early
  mathematical theories of turbine design.

61

• In 1826, Benoit Fournerior developed an
  outward-flow turbine. This was an efficient
  machine (80) that sent water through a runner
  with blades curved in one dimension. The
  stationary outlet also had curved guides
• In 1844, Uriah A. Boyden developed an outward
  flow turbine that improved on the performance of
  the Fourneyron turbine. Its runner shape was
  similar to that of a Francis turbine
• In 1849, James B. Francis improved the inward
  flow reaction turbine to over 90 efficiency
• He also conducted sophisticated tests and
  developed engineering methods for water turbine
  design
• The Francis turbine, named for him, is the first
  modern water turbine
• It is still the most widely used water turbine in
  the world today
• The Francis turbine is also called a radial flow
  turbine, since water flows from the outer
  circumference towards the centre of runner.

62

• Francis turbine

• The Francis turbine is a type of water turbine
  that was developed by James B. Francis in Lowell,
  Massachusetts
• It is an inward-flow reaction turbine that
  combines radial and axial flow concepts
• Francis turbines are the most common water
  turbine in use today
• They operate in a head range of ten meters to six
  hundred and fifty meters and are primarily used
  for electrical power production
• The power output ranges from 10 to 750MW,
  mini-hydro excluded
• Runner diameters are between 1 and 10 meters
• The speed range of the turbine is from 83 to 1000
  rpm
• Medium size and larger Francis turbines are most
  often arranged with a vertical shaft
• Vertical shaft may also be used for small size
  turbines, but normally they have horizontal shaft

63

•  
• Side-view cutaway of a Francis turbine

64

• Francis Runner, Grand Coulee Dam

65

• Water wheels have been used historically to power
  mills of all types, but they are inefficient.
  Nineteenth-century efficiency improvements of
  water turbines allowed them to compete with steam
  engines (wherever water was available)
• In 1826 Benoit Fourneyron developed a high
  efficiency (80) outward-flow water turbine
• Water was directed tangentially through the
  turbine runner, causing it to spin
• Jean-Victor Poncelet designed an inward-flow
  turbine in about 1820 that used the same
  principles. S. B. Howd obtained a U.S. patent in
  1838 for a similar design
• In 1848 James B. Francis, while working as head
  engineer of the Locks and Canals company in the
  water-powered factory city of Lowell,
  Massachusetts, improved on these designs to
  create a turbine with 90 efficiency
• He applied scientific principles and testing
  methods to produce a very efficient turbine
  design
• More importantly, his mathematical and graphical
  calculation methods improved turbine design and
  engineering
• His analytical methods allowed confident design
  of high efficiency turbines to exactly match a
  site's flow conditions

66

• Three Gorges Dam Francis turbine runner

67

• The Francis turbine is a reaction turbine, which
  means that the working fluid changes pressure as
  it moves through the turbine, giving up its
  energy
• A casement is needed to contain the water flow
• The turbine is located between the high-pressure
  water source and the low-pressure water exit,
  usually at the base of a dam
• The inlet is spiral shaped
• Guide vanes direct the water tangentially to the
  turbine wheel, known as a runner
• This radial flow acts on the runner's vanes,
  causing the runner to spin
• The guide vanes (or wicket gate) may be
  adjustable to allow efficient turbine operation
  for a range of water flow conditions

68

• Francis Turbine (exterior view) attached to a
  generator

69

• As the water moves through the runner, its
  spinning radius decreases, further acting on the
  runner
• For an analogy, imagine swinging a ball on a
  string around in a circle if the string is
  pulled short, the ball spins faster due to the
  conservation of angular momentum
• This property, in addition to the water's
  pressure, helps Francis and other inward-flow
  turbines harness water energy efficiently
• At the exit, water acts on cup-shaped runner
  features, leaving with no swirl and very little
  kinetic or potential energy
• The turbine's exit tube is shaped to help
  decelerate the water flow and recover the
  pressure

70
Application

• Francis turbines may be designed for a wide range
  of heads and flows
• This, along with their high efficiency, has made
  them the most widely used turbine in the world
• Francis type units cover a head range from 20
  meters to 700 meters, and their output power
  varies from just a few kilowatts up to one
  gigawatt
• Large Francis turbines are individually designed
  for each site to operate at the highest possible
  efficiency, typically over 90
• In addition to electrical production, they may
  also be used for pumped storage, where a
  reservoir is filled by the turbine (acting as a
  pump) during low power demand, and then reversed
  and used to generate power during peak demand

71

• Inward flow water turbines have a better
  mechanical arrangement and all modern reaction
  water turbines are of this design
• As the water swirls inward, it accelerates, and
  transfers energy to the runner. Water pressure
  decreases to atmospheric, or in some cases
  subatmospheric, as the water passes through the
  turbine blades and loses energy
• Around 1890, the modern fluid bearing was
  invented, now universally used to support heavy
  water turbine spindles
• As of 2002, fluid bearings appear to have a mean
  time between failures of more than 1300 years.
• Around 1913, Viktor Kaplan created the Kaplan
  turbine, a propeller-type machine
• It was an evolution of the Francis turbine but
  revolutionized the ability to develop low-head
  hydro sites.

72
A new concept

• Figure from Pelton's original patent (October
  1880)

73

• All common water machines until the late 19th
  century (including water wheels) were basically
  reaction machines water pressure head acted on
  the machine and produced work. A reaction turbine
  needs to fully contain the water during energy
  transfer
• In 1866, California millwright Samuel Knight
  invented a machine that took the impulse system
  to a new level
• Inspired by the high pressure jet systems used in
  hydraulic mining in the gold fields, Knight
  developed a bucketed wheel which captured the
  energy of a free jet, which had converted a high
  head (hundreds of vertical feet in a pipe or
  penstock) of water to kinetic energy
• This is called an impulse or tangential turbine
• The water's velocity, roughly twice the velocity
  of the bucket periphery, does a u-turn in the
  bucket and drops out of the runner at low
  velocity.

74

• In 1879, Lester Pelton (1829-1908), experimenting
  with a Knight Wheel, developed a double bucket
  design, which exhausted the water to the side,
  eliminating some energy loss of the Knight wheel
  which exhausted some water back against the
  center of the wheel
• In about 1895, William Doble improved on Pelton's
  half-cylindrical bucket form with an elliptical
  bucket that included a cut in it to allow the jet
  a cleaner bucket entry
• This is the modern form of the Pelton turbine
  which today achieves up to 92 efficiency
• Pelton had been quite an effective promoter of
  his design and although Doble took over the
  Pelton company he did not change the name to
  Doble because it had brand name recognition
• Turgo and Crossflow Turbineswere later impulse
  designs.

75

• Theory of operation
• Flowing water is directed on to the blades of a
  turbine runner, creating a force on the blades
• Since the runner is spinning, the force acts
  through a distance (force acting through a
  distance is the definition of work)
• In this way, energy is transferred from the water
  flow to the turbine
• Water turbines are divided into two groups
  reaction turbines and impulse turbines
• The precise shape of water turbine blades is a
  function of the supply pressure of water, and the
  type of impeller selected.

76

• Reaction turbines
• Reaction turbines are acted on by water, which
  changes pressure as it moves through the turbine
  and gives up its energy
• They must be encased to contain the water
  pressure (or suction), or they must be fully
  submerged in the water flow
• Newton's third law describes the transfer of
  energy for reaction turbines.
• Most water turbines in use are reaction turbines
  and are used in low (lt30m/98 ft) and medium
  (30-300m/98984 ft)head applications. In reaction
  turbine pressure drop occurs in both fixed and
  moving blades.

77

• Impulse turbines
• Impulse turbines change the velocity of a water
  jet. The jet pushes on the turbine's curved
  blades which changes the direction of the flow
• The resulting change in momentum (impulse) causes
  a force on the turbine blades. Since the turbine
  is spinning, the force acts through a distance
  (work) and the diverted water flow is left with
  diminished energy
• Prior to hitting the turbine blades, the water's
  pressure (potential energy) is converted to
  kinetic energy by a nozzle and focused on the
  turbine
• No pressure change occurs at the turbine blades,
  and the turbine doesn't require a housing for
  operation
• Newton's second law describes the transfer of
  energy for impulse turbines
• Impulse turbines are most often used in very high
  (gt300m/984 ft) head applications

78

• Newtons Laws of Motion

• Newton's First Law of Motion
• I. Every object in a state of uniform motion
  tends to remain in that state of motion unless an
  external force is applied to it.
• Newton's Second Law of Motion
• II. The relationship between an object's mass m,
  its acceleration a, and the applied force F is F
  ma. Acceleration and force are vectors in this
  law the direction of the force vector is the same
  as the direction of the acceleration vector.
• Newton's Third Law of Motion
• III. For every action there is an equal and
  opposite reaction.

79

• Power
• The power available in a stream of water is
• where
• P power (J/s or watts)
• ? turbine efficiency
• ? density of water (kg/m³)
• g acceleration of gravity (9.81 m/s²)
• h head (m)
• For still water, this is the difference in height
  between the inlet and outlet surfaces
• Moving water has an additional component added to
  account for the kinetic energy of the flow
• The total head equals the
• pressure head plus velocity head. flow rate
  (m³/s)

80

• Pumped storage
• Some water turbines are designed for pumped
  storage hydroelectricity
• They can reverse flow and operate as a pump to
  fill a high reservoir during off-peak electrical
  hours, and then revert to a turbine for power
  generation during peak electrical demand
• This type of turbine is usually a Deriaz or
  Francis in design
• Efficiency
• Large modern water turbines operate at mechanical
  efficiencies greater than 90 (not to be confused
  with thermodynamic efficiency).

81
Types of water turbines

• Various types of water turbine runners. From
  left to right Pelton Wheel, two types of Francis
  Turbine and Kaplan Turbine

82

• Reaction turbines
• Francis
• Kaplan, Propeller, Bulb, Tube, Straflo
• Tyson
• Gorlov
• Impulse turbine
• Waterwheel
• Pelton
• Turgo
• Michell-Banki (also known as the Crossflow or
  Ossberger turbine)
• Jonval turbine
• Reverse overshot water-wheel
• Archimedes' screw turbine

83
Design and application
84

• Turbine selection is based mostly on the
  available water head, and less so on the
  available flow rate
• In general, impulse turbines are used for high
  head sites, and reaction turbines are used for
  low head sites
• Kaplan turbines with adjustable blade pitch are
  well-adapted to wide ranges of flow or head
  conditions, since their peak efficiency can be
  achieved over a wide range of flow conditions.
• Small turbines (mostly under 10 MW) may have
  horizontal shafts, and even fairly large
  bulb-type turbines up to 100 MW or so may be
  horizontal
• Very large Francis and Kaplan machines usually
  have vertical shafts because this makes best use
  of the available head, and makes installation of
  a generator more economical
• Pelton wheels may be either vertical or
  horizontal shaft machines because the size of the
  machine is so much less than the available head
• Some impulse turbines use multiple water jets per
  runner to increase specific speed and balance
  shaft thrust.

85

• Typical range of heads
• Hydraulic wheel turbine
  Archimedes' screw turbine Kaplan______________
  ___
  Francis
  10 lt H lt 350
  Pelton
  50 lt H lt 1300
  Turgo
  50 lt H lt 250

0.2 lt H lt 4   (H head in m)
1 lt H lt 10
2 lt H lt 40
86

• Specific speed
• The specific speed ns of a turbine characterizes
  the turbine's shape in a way that is not related
  to its size
• This allows a new turbine design to be scaled
  from an existing design of known performance
• The specific speed is also the main criteria for
  matching a specific hydro site with the correct
  turbine type
• The specific speed is the speed with which the
  turbine turns for a particular discharge Q, with
  unit head and thereby is able to produce unit
  power.

87

• Affinity laws
• Affinity Laws allow the output of a turbine to be
  predicted based on model tests
• A miniature replica of a proposed design, about
  one foot (0.3 m) in diameter, can be tested and
  the laboratory measurements applied to the final
  application with high confidence
• Affinity laws are derived by requiring similitude
  between the test model and the application
• Flow through the turbine is controlled either by
  a large valve or by wicket gates arranged around
  the outside of the turbine runner
• Differential head and flow can be plotted for a
  number of different values of gate opening,
  producing a hill diagram used to show the
  efficiency of the turbine at varying conditions

88

• Runaway speed
• The runaway speed of a water turbine is its speed
  at full flow, and no shaft load
• The turbine will be designed to survive the
  mechanical forces of this speed
• The manufacturer will supply the runaway speed
  rating.

89

• Environmental impact
• Water turbines are generally considered a clean
  power producer, as the turbine causes essentially
  no change to the water
• They use a renewable energy source and are
  designed to operate for decades
• They produce significant amounts of the world's
  electrical supply
• Historically there have also been negative
  consequences, mostly associated with the dams
  normally required for power production
• Dams alter the natural ecology of rivers,
  potentially killing fish, stopping migrations,
  and disrupting peoples' livelihoods.

90

• For example, American Indian tribes in the
  Pacific Northwest had livelihoods built around
  salmon fishing, but aggressive dam-building
  destroyed their way of life
• Dams also cause less obvious, but potentially
  serious consequences, including increased
  evaporation of water (especially in arid
  regions), build up of silt behind the dam, and
  changes to water temperature and flow patterns
• Some people believe that it is possible to
  construct hydropower systems that divert fish and
  other organisms away from turbine intakes without
  significant damage or loss of power historical
  performance of diversion structures have been
  poor.
• n the United States, it is now illegal to block
  the migration of fish, for example the endangered
  great white sturgeon in North America, so fish
  ladders must be provided by dam builders
• The actual performance of fish ladders is often
  poor