Hydropower

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/s^2^ 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

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

Hydropower turbines

Hoover Dam

Hoover Dam

Scalability

• Hydropower can be produced at small scale

Hydropower

Hydropower