Other renewable energy sources

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Other renewable energy sources

• Hydropower
• Wind energy
• Ocean Thermal
• Biomass
• Geothermal
• Tidal

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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

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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
  

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Plant operation
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Hydro Turbine
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Net exploitable hydropower resources
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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

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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

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Fish Ladders

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