Chapter 11 Section 2: Renewable sources of energy• Key Concepts:• What forms of energy does the sun

provide?• What are some renewable sources of

energy?• Key terms:• Solar energy, hydroelectric power, biomass

fuel, gasohol, geothermal energy

Renewable sources

• Solar• Water• Wind• Biomass• Geothermal• Hydrogen

Sun’s energy• Solar energy – energy from the sun• The sun constantly gives off energy in the forms of heat and light• It’s hard to use the sun’s energy because:• Only useful when it’s shining• Widespread, so hard to harness a lot of it within a small area

Solar stuff• Solar Power Plants – use giant mirrors to heat

water to steam• Solar cells – like a battery. Light hits it and

electric current is produced. Takes a lot of them.• Passive Solar Heating – converts sunlight into

thermal energy• Active Solar Heating – captures energy on a

dark metal surface of a solar collector, converts it to thermal energy

Hydroelectric power• Hydroelectric power is electricity

produced by flowing water• Flowing water can move turbines, just

like steam or wind, and create an electric current

• Hydroelectric is the most widely used form of renewable energy• Requires a dam, which can affect

ecosystems• Inexpensive and no air pollution, once

dam is built

Capturing Wind• Wind energy is an indirect form of solar energy• Wind is caused by uneven heating of the earth by the sun• Wind can be used to turn a turbine• Does not cause air pollution, but can be noisy and ineffective. AND

the metal to make the turbine has to be mined and then processed into steel. Very few people mention that the MAKING of “green energy” materials are very un-green.

Biomass fuels• Biomass fuels are made from living things• The best example is wood• Leaves, food wastes, manure• Can be burned or converted to other fuels• For example, corn, sugar cane, and other crops can be used to make alcohol• Adding alcohol to gasoline makes gasohol, which can be used as car fuel

• Bacteria produce methane when they decompose biomass, and the methane can also be captured and used as fuel• Biodiesel fuel – oil produced by some crops• Drawbacks: takes time, expensive

Tapping Earth’s Energy

• Intense heat from Earth’s interior is called geothermal energy• In CERTAIN (not everywhere!) areas, like Iceland and New Zealand,

magma heats underground water to boiling. Hot water and steam can be valuable energy sources. • Disadvantages: doesn’t work everywhere, requires deep drilling

Promise of hydrogen power

• Pure hydrogen can be obtained by passing electricity through water• Takes more energy to obtain the hydrogen than it produces