Esa Unit5

Alternative Energy Sources

RenewableSustainable

Non-polluting

Hydroelectric Power

• Power of Fallingwater

• Used for thousands of

years

Potential to Kinetic Energy

Potential Energy

Kinetic Energy

Hydroelectric Power & Dams

• Three Gorges

Hydroelectric Power Use

US Hydroelectric Power

• 7% total energy use

Nuclear Energy

• Large Reserves

• Currently in use

17% World’s Electricity

• No greenhouse gases

• Safety?

Nuclear Fission Plants

Fission

Fissionable Nuclei

• 235U, 239Pu (but not 238U)

Radioactivity

• All elements with atomic number > 84

What is Radioactivity

Becquerel

• 1897

Radiation Hazards

Radioactive Decay

• Half Life = time until ½ original amount remains

Half Lives

Uranium-238 4 x 109 years

Thorium - 234 24 days

Carbon - 14 5730 years

Polonium-214 1.6 x 10-4 sec

Plutonium-239 24,100 years

Safety Concerns

• Three Mile Island (1979)

Chernobyl

• 1986

Santa Susana

• 1959

US Fission Reactors

Chain Reaction

Controlling the Chain Reaction

Moderators

• Absorb excess neutrons

• Usually Carbon (boron or cadmium)

• Concentrated U (“yellow cake”to 3% enrichment

Disposal

Yucca Mountain

Nuclear Fusion

€

4 11H - - - -- > 2

4He + 2 10p

Requires very high temperturesAnd high pressures

Cold Fusion

Tokamak

The Other Solar Energy

Availability

• Daytime

• Climate

• Elevation

• Latitude

Earth’s Revolution

Solar Angle

Solar Radiation

Passive Solar Energy

• Socrates

“In houses that look toward the south, the sun penetrates the portico in winter.”

Archimedes

• Burning Mirror

Passive Solar Energy

• Anasazi

• deSaussure

Active Solar Energy

Photovoltaic Cells

The Cost of Solar Cells

Efficiency

Concentrating Solar Energy

• DOE Solar Two project (Nevada)

Solar Energy

Pros Cons

+Renewable -low efficiency+Nonpolluting -availability ≠ needs+Si abundance -insolation variability+Becoming - photodegradation

economical

The Other Solar Energy

Windmills

• Grinding grain, Dredging Marshes

Wind Energy Origins

• Warm air rises(less dense)

• Cool air sinks

Convection

currents

Air Pressure Variation

• High pressure clockwise• Low pressure counterclockwise

Extreme Pressure Variation

Where is the Wind?

Installed Wind Capacity

Offshore Wind Farms

• Ireland

• Denmark

Offshore Wind Capacity

Transmission Troubles

• Danger:high voltage

• Ice storms

• Discharge

The Electricity Grid

Bird Hazard?

• Mainly large birds:

golden eagle

Kestrels

red-tailed hawks

Wind Energy

Pros Cons• Cheap --Variable

•easy to install•easy to maintain -- Not where

needed• Nonpolluting -- bird hazard

• Non-carbon --need many turbines

Geothermal Energy

• Geyser power

• Ultimately nuclearfission

Heat from the Earth’s Interior

Earth’s crust

Boundaries and Hot Spots

Island Formation

Harnessing Steam

California’s Resources

Disadvantages

• Sulfurous gases

• Corrosion

• CO2 emission

Iceland

Iceland