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Chapter 17

Alternative Energy Sources

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Section 17.1 – Solar Energy

Sun = source of all energy on Earth.• Solar energy – energy from the sun

– It is absorbed by plants and used as fuel by virtually all organisms.

• Fossil fuels contain energy from the remains of organisms so they also contain energy originally from the sun

• The sun obtains its energy through thermonuclear fusion.

• High temperatures in the sun’s core cause hydrogen nuclei to fuse, or join, forming helium nuclei. As each helium nucleus forms a loss of mass occurs, this is converted to heat and light energy of the sun.

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Section 17.1 – Solar Energy

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Advantages of Solar Energy• Free• Clean• Non-polluting• Can be collected and stored

Drawbacks of Solar Energy

Section 17.1 – Solar Energy

• Energy source is not constant• Limited sunlight; like cloudy/rainy

days• Devices for storing it are not very

efficient (expensive)

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Passive Solar Energy• Sunlight energy is used directly as a source of light

or heat.• The sun’s energy is collected, stored, and distributed

naturally in an enclosed dwelling.• Greenhouse• Enclosed car with windows up on a hot day• Not used to produce electricity.• Provides an alternative source of heat.• Helps reduce the use of fossil and nuclear fuels.• Building houses where the windows face the majority

of sunlight – dark roof and sides.

Section 17.1 – Solar Energy

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Passive Solar Energy

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Active Solar Energy• Has a greater capacity for storing and distributing

energy.• Devices used to collect, store and circulate heat

produced from solar energy.• Uses tubes, tanks, fluids, pumps, fans to collect and

distribute energy.

Section 17.1 – Solar Energy

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Active Solar Energy

• Use of solar collectors – mounted on roofs• Use water which heats to steam.

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Section 17.1 – Solar Energy

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Photovoltaic Cells (PV cells)• A solar cell that produces electricity.• Use thin wafers of semiconductor material to produce

electricity directly from solar energy.• Sunlight strikes the cell causing electrons to move from one

slice of material to the other.• The movement of electrons results in an electric current.• Includes the use of calculators, satellites, and watches.

Section 17.1 – Solar Energy

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Section 17.2 – Hydroelectric Energy

• Electricity that is produced from the energy of moving water.

• Water power is an indirect use of solar energy.• Construction of dams to control the rate of the

water.

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Section 17.3 – Wind Energy

• Aerogenerators – windmills that are used to generate electricity, also known as wind turbine generators.

• Advantages Disadvantages• Free • Unlimited• Nonpolluting• Saves fuel

• Wind energy can be used to move ships, pump water, generate electricity.

• Not always available• Take up space• Danger to birds• Ugly• Costly

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Section 17.4 – Geothermal Energy

• The heat generated within the Earth.• It does not involve the energy from the sun.• Source is generated by the decay of radioactive

elements deep beneath the ground.• Enough heat is present deep within the Earth to melt

rock.• Magma is molten rock.• Lava is magma that has reached the surface.• Includes geysers, steam vents, hot springs

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Demo

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Disadvantages• Not widely available because costly to extract.• Not always easy to locate.• Gives off toxic hydrogen sulfide (corrosive gas).

Section 17.4 – Geothermal Energy

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• Nuclear fusion – two atomic nuclei fuse to become one larger nucleus.

• Source of energy given off from the sun.• Problem - Not yet learned to control and harness the

energy and use it efficiently.• The fuel for nuclear fusion is Hydrogen and its

isotopes.• H-2 abundant in seawater.

Section 17.4 – Geothermal Energy