Hydropower

Energy Conversion

  • Solar radiation evaporates water
  • Wind currents from solar air heating move evaporated water to locations where it falls as rain
  • Gravity carries water down hill
  • Hydropower uses this gravitational potential energy and kinetic energy of the water to spin a turbine
  • The turbine is connected to a generator, creating electricity

Ancient Power Technology

  • Waterwheels have been used for centuries
  • Modern hydropower technology has added large scale dams

Energy basics

  • We use the simplest model for the water as a mass at a height or elevation
  • A mass m lifted to a high h has a stored gravitational potential energy of PE = mgh
  • PE is in joules if mass is in kilograms, g = 9.8 m/s2 and the height is in meters

Power

  • How do we convert this to a power? energy = mgh \frac{energy}{time} = \frac{mgh}{time} power = \frac{m}{time} gh power = flow \cdot gh
  • To get flow in mass per time we convert from volume per time

Types

  • Run of river
  • Dams

Hydropower is significant world wide

  • http://wdi.worldbank.org/table/3.7
  • 2010 Hydropower 15.9% of world wide electricity
  • Coal 40.5%, Nuclear 12.8%
  • Largest power station in the world is hydroelectric

Three Gorges

  • Largest power plant in the world
  • Displaced millions of people
  • 22 GW power continuous
  • NYC - 10 GW

Three Gorges

Three Gorges

Three Gorges Satellite

Grand Coulee

  • Largest hydroelectric installation in US
  • 6.8 GW capacity
  • 21 Billion kWh annual energy delivered

Building a dam

  • What is the effect of a dam?
  • How does the dam affect the overall flow of water?

Advantages

  • Once built, very cheap power
  • Reliable technology
  • Can be used as storage

Disadvantages

  • Fish migration
  • Environmental impacts
  • Seasonal variation affects electricity supply
  • Water flow
  • Sedimentation
  • Increased seismic activity
  • Risk of dam failure
  • Methane production from vegetation decomposition
    • Methane is a potent GHG

Carbon Intensity of Electricity

Methane generation has a large effect on the greenhouse gas intensity of hydropower electricity.

  • Run of river 0.01 – 0.03 lb CO2/kWh
  • Dam, Arid region 0.06 lb CO2/kWh
  • Dam, Tropical region 0.5 lb CO2/kWh

Source: IPCC 2011 Report, Chapter 5 and 9

Hydropower

Hydropower

Hydropower

Hydropower

Hydropower similarities to fossil generation

  • Uses spinning generators just like combustion plant
  • Doesn’t use heat, unlike combustion plant

Hydropower turbines

Hoover Dam

Hoover Dam

Scalability

  • Hydropower can be produced at small scale

Hydropower

Hydropower

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