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Chapter 18 Renewable Energy
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Renewable Energy Today
Section 18-1 Renewable Energy Today
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Discussion Prompt List 3 reasons you think we have not completely switched over to renewable energy to meet our energy needs.
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Renewable Energy Renewable energy: energy from sources that are constantly being formed Solar Wind Moving water Geothermal (Earth’s heat)
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Solar Energy Sun: medium-sized star that radiates energy from nuclear fusion reactions in its core. Only a small fraction of this energy reaches the Earth yet it is enough to power the wind, plant growth, and the water cycle. Already commonly used Water cycle Photosynthesis Wind Sunshine warming a room Solar cells
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Passive Solar Heating Passive solar heating: Use sun to heat something directly Example: Northern hemisphere homes Large, south facing windows absorb heat in winter Overhangs block sunlight in the summer Helps save money on energy bills Insulation is important also
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Active Solar Heating Active Solar Heating: Sun’s energy is gathered by collectors to heat a building or water A liquid is heated by the sun and flows through solar collectors Solar water heaters Water heated on roof Hot water used to heat water supply
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Active Solar Heating, cont.
Photovoltaic cells: convert the sun’s energy into electricity No moving parts, no pollution Need many cells to produce decent yields Great potential in developing countries which have lesser energy demands Store energy in batteries
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Wind Power Air is heated unevenly by the sun, creating wind
Wind power is the fastest growing source of energy Quadrupled between 1985 and 2000 Cost effective to build wind turbines Cost of wind power has declined
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Wind Farms See Figure 7 on p. 495 280,000 homes in CA powered by wind
Take up little space Farmers add windmills to farm Sell power to cities
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Currently Underused Windiest areas on earth could generate 10 times the energy used worldwide. Difficult to transport the energy Wind farms may make hydrogen from water in the future. Hydrogen could be used as fuel.
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Biomass Biomass Fuel: Plant material, manure, other organic matter used as fuel Different than fossil fuels which are nonrenewable Ex: wood and dung Half of wood cut down is used for heating and cooking (developing countries) Challenges Trees – renewable, but must be managed Burning wood or manure – air pollution
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Methane Methane (CH4) is created when bacteria decompose organic wastes Can be burned for heat or electricity China – 6 million homes use methane for heating and cooking England – Methane from cow manure as fuel for electricity USA – electricity from methane generated by landfills
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Alcohol Ethanol: made by fermenting fruit or agricultural waste
Corn is a major source in the US Gasohol mix of gasoline and ethanol Produces less pollution when burned Some states require (including GA)
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Hydroelectricity Hydroelectricity: Energy produced from moving water
20% of world’s electricity How it works (see p. 497) Reservoir behind a dam holds water Flowing water turns turbines Turbines’ energy transferred to generator Generator turns movement into electricity
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Benefits of Hydroelectricity
Expensive to build but cheap to operate No air pollution Last longer Flood control Water for drinking, agriculture, industry, and recreation
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Disadvantages of Hydroelectricity
Disrupts river flow Ecosystems flooded behind dam River flow diminished below dam Displaces people Farmland downstream less productive Decay in reservoir releases greenhouse gases
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Modern Hydroelectricity
No new dams in the USA Brazil, India, and China still building large dams (developing countries) Micro-hydropower: small streams are used to move turbines without building dams Cheaper Can provide energy to remote areas
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Geothermal Energy Geothermal Energy: Energy from the heat in Earth’s crust How it works (see p. 498) Steam rises to turn turbines through a well Steam drives turbines, generating electricity Leftover liquid water pumped back into hot rock The Geysers in CA powers 1.7 million homes (US uses more than any country) Philippines, Iceland, New Zealand, Japan, Mexico, and Italy Renewable, but must be managed
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Geothermal Heat Pumps See Figure 12 on p. 499
Temperature underground is constant Pumps use stable underground temperatures to warm and cool homes Loop of fluid in a pipe underground and into house In summer, the fluid in the loop is cooler, so it cools the home In winter, the fluid in the loop is warmer, so it warms the home
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Section 18-2: Alternative Energy and Conservation
Discussion Prompt: Contrast alternative energy, renewable energy, and nonrenewable energy.
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Alternative energy Alternative Energy: Still in development
Some renewable energy was once alternative energy (Ex: geothermal). Government investments are vital to development. Need to research
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Tidal Power Tides are the movement of water caused by the gravitational attraction between the Earth, sun, and moon Currently used in France, Russia, and China Benefits Tides happen 2 times a day Generates electricity like hydroelectric dams Drawbacks Expensive Few suitable locations
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Ocean Thermal Energy Conversion (OTEC)
Energy is created from the difference in temp. of the surface of ocean water and deep ocean water Benefits Cold water boils at low temp in vacuum chamber Steam can turn a turbine Drawbacks Not cost effective Uses 1/3 of the energy it produces to pump the cold water up to the surface to be boiled Environmental effects unknown
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Hydrogen Can be burned as fuel Benefits Drawbacks
The most abundant element in the universe No air pollutants when burned Obtain by running electricity through water or from plants (more cost effective) Drawbacks Generating it uses energy, money, and makes pollution Takes a lot of hydrogen to create as much energy as gasoline so it must be compressed dangerous Explosive and dangerous
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Fuel Cells See Figure 16 on p. 502 Produce electricity chemically
Combine H2 and O2 and electricity is produced. Water is only byproduct Space shuttles use
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Energy Efficiency Energy Efficiency: percentage of energy put into a system that does useful work What you get out vs. what you put in %Energy efficiency = Read p. 502 to 503 and summarize energy efficiency today Useful energy out x 100 Energy in
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Efficient Transportation
Read p. 503. Describe how transportation could be made more efficient.
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Cogeneration Production of 2 useful forms of energy from 1 fuel source
Example: use waste heat from a furnace to turn a turbine
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Energy Conservation Energy Conservation: saving energy
Use energy efficient devices Wasting less energy Read about on p. 504 and 505
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Cities and Towns Osage, IA 3,600 people saved $1 million/year
Sealed doors and windows New efficient furnaces Insulated water heaters Businesses moved to the area Unemployment is down
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Around the Home Spend $1,500/year on energy costs Much is wasted
Insulation Efficient windows Weather stripping Wash clothes in cold water
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