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Green Power Generation

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Title: 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
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