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Other renewable energy sources Hydropower Wind energy Ocean Thermal Biomass Geothermal Tidal – PowerPoint PPT presentation

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Title: Other%20renewable%20energy%20sources


1
Other renewable energy sources
  • Hydropower
  • Wind energy
  • Ocean Thermal
  • Biomass
  • Geothermal
  • Tidal

2
Hydropower
  • Well established electrical generation
    technology, about 100 years old
  • Known for over 2000 years that the force of
    moving water on a water wheel could save human
    labor
  • 13th century-hammers in iron works in Europe were
    operated with waterwheels.
  • 16th century primary source of industrial power
    in Europe
  • In the US, mills were established at sites with
    reliable water flow and dams were constructed to
    regulate water flow.
  • Cave mill here in BG. Several hydro powered mills
    for corn, flour and sawing in the 19th century
    existed on this site at different times.
  • With the advent of electricity, water wheels were
    used to drive electricity generation.
  • About 7 of US energy generation is from
    hydroelectric plants

3
The physics of Hydropower
  • Gravitational potential energy in the water at a
    height h above the wheel is converted to kinetic
    energy of the wheel which drives a turbine and
    generates electricity.
  • So each mass element of water, m, falls a
    distance h and attain a velocity v. So its
    initial potential energy is mgh, where g is the
    acceleration due to gravity (9.8m/s2) and the
    kinetic energy is 1/2mv2.
  • This tells us the amount of potential energy
    available to be converted to kinetic energy is
    9.8 joules per kilogram of water per meter of
    height above the wheel.
  • h is often called the head.
  • Efficiencies of 80-90 can be achieved.
  • Power (Height of Dam (distance the water
    falls)) x (River Flow) x (Efficiency) / 11.8
  • where the height is in feet, river flow is
    in cubic feet per second , efficiency is what
    you expect and 11.8 converts from feet and
    seconds to killowatts

4
Plant operation
5
Hydro Turbine
6
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7
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8
Net exploitable hydropower resources
9
Advantages
  • No Pollution
  • No waste heat
  • High efficiency
  • Plants have decades long lifetimes and low
    maintenance costs
  • Good response to changing electricity demands
  • Damming of rivers can serve other purposes flood
    control, irrigation, drinking water supply

10
Limitations
  • About 50 of the US capacity for Hydro is
    developed
  • Limited lifetimes for certain reservoirs-as the
    fill with silt, they become less useful for water
    storage. But the dam must be maintained long
    term, if it fails, communities downstream are in
    danger from the tremendous volume of silt that
    would be released.
  • Loss of free flowing streams due to damming and
    the loss of the lands flooded by damming a
    river-environmental impacts
  • Salmon population in the Nothwest has been
    impacted
  • Flood risk due to dam failures
  • Currently hundreds thousands of people in danger
    if dam failures occur

11
Fish Ladders
  • Solution to the salmon problem - have not been
    very effective

12
Wind power
  • Not subject to day night cycles
  • Direct result of solar heating of the Earths
    atmosphere
  • Use of wind for energy first noticed by sailors -
    the old sailing ships could extract the
    equivalent of 10,000 hp from the wind!
  • Windmills were prevalent in Europe in the 19th
    century
  • Several million were pumping water in the US in
    the early 1900s

13
WHAT YOURE PROBABLY THINKING OF.
14
Power in a windmill
  • The power in the wind can be calculated by
    P/m2 6.1 X 10-4v3
  • This gives the power in kilowatts per meter
    squared, where the cross sectional area is
    oriented perpendicular to the wind direction.
  • This is the total power, of course not all of it
    can be extracted. According to Betzs Law,
    developed in 1919 by German physicist Albert
    Betz, no turbine can capture more than 59.3
    percent of the potential energy in wind.
  • However, the total amount of economically
    extractable power available from the wind is
    considerably more than present human power use
    from all sources!

15
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16
Extracting the energy The turbine
  • The world's first automatically operated wind
    turbine was built in Cleveland in 1888 by Charles
    F. Brush. It was 60 feet tall, weighed four tons
    and had 12kW turbine.

17
Turbine types
  • 2 types, based on the direction of the axis that
    the turbine rotates about.
  • Horizontal axis wind turbines (HAWT) -the turbine
    rotates around an axis that is horizontal.
  • Vertical Axis Wind Turbines (VAWT) the turbine
    rotates around a vertical axis

18
HAWT
  • Horizontal Axis Wind Turbines
  • main rotor shaft and electrical generator are
    locate at at the top of a tower, and must be
    pointed into the wind.
  • Small turbines are pointed by a simple wind
    vane, while large turbines generally use a wind
    sensor coupled with a servo motor.
  • Most have a gearbox, which turns the slow
    rotation of the blades into a quicker rotation
    that is more suitable to drive an electrical
    generator.

19
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20
HAWT
  • the turbine is usually pointed upwind of the
    tower since it creates turbulence behind it.
  • Turbine blades are made stiff to prevent the
    blades from being pushed into the tower by high
    winds.
  • The blades are placed a considerable distance in
    front of the tower and are sometimes tilted up a
    small amount.

21
HAWT Advantages
  • Variable blade pitch so the turbine collects the
    maximum amount of wind energy for the time of day
    and season.
  • The tall tower base allows access to stronger
    wind in sites with wind shear. In some wind shear
    sites, every ten meters up, the wind speed can
    increase by 20 and the power output by 34.
  • High efficiency, since the blades always move
    perpendicularly to the wind, receiving power
    through the whole rotation.

22
HAWT Disadvantages
  • The tall towers and blades up to 90 meters long
    are difficult to transport. Transportation can be
    20 of equipment costs.
  • Tall HAWTs are difficult to install, needing very
    tall and expensive cranes and skilled operators.
  • Massive tower construction is required to support
    the heavy blades, gearbox, and generator.
  • Reflections from tall HAWTs may affect side lobes
    of radar installations creating signal clutter,
    although filtering can suppress it.
  • Their height makes them obtrusively visible
    across large areas, disrupting the appearance of
    the landscape and sometimes creating local
    opposition.
  • Downwind variants suffer from fatigue and
    structural failure caused by turbulence when a
    blade passes through the tower's wind shadow (for
    this reason, the majority of HAWTs use an upwind
    design, with the rotor facing the wind in front
    of the tower).
  • HAWTs require an additional yaw control mechanism
    to turn the blades toward the wind.
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