Chapter 18 Renewable Energy 18-1 Renewable Energy Today

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Chapter 18 Renewable Energy18-1 Renewable Energy
Today

• Renewable Energy from sources that are
  constantly being formed (ex. solar, wind, moving
  water, Earths heat)

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I. Solar Energy Power from the Sun

• Passive Solar Heating uses the suns energy to
  heat something directly
• Passive Solar Homes
• Large south-facing windows
• Well insulated
• Overhanging roof
• -summer suns path is high in the sky (roof
  provides shade)
• -winter suns path is lower in the sky
  (sunlight can shine into the home)

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Passive Solar Home
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Active Solar Heating energy from the sun is
gathered by collectors and used to heat water or
to heat a building
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Photovoltaic Cells
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Photovoltaic Cells solar cells convert suns
energy into electricity

• Produces a very small electrical current
• A small city would need hundreds of acres of
  solar panels
• Require extended periods of sunshine
• Energy has to be stored in batteries or fed back
  into the grid (net-metering)
• Becoming increasingly efficient less expensive
• Great potential in developed countries, where
  energy consumption is minimal

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Wind Farm
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II. Wind Power Cheap Abundant

• Wind moves a turbine to generate electricity
• Fastest growing energy source in the world
• Wind Turbines are cost effective and can be built
  in 3 months
• Wind Farms large arrays of wind turbines
• Turbines take little space
• Some farmers add wind turbines to their land and
  sell the electricity
• An underdeveloped resource scientists estimate
  that the windiest spots on Earth could generate
  more than 10 times the energy used worldwide
• Problem transporting electricity from rural
  areas where it is generated to urban centers

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III. Biomass power from living things

• Biomass fuel any organic matter that is used as
  an energy source (plant material, manure, etc.)
• Fossil fuels dont count because they are
  nonrenewable
• Wood Dung are major sources of energy in
  developing countries
• Although wood is renewable it can result in
  habitat loss, deforestation, and soil erosion if
  trees are cut down faster than they can grow
• Burning wood dung can release harmful air
  pollution

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Biofuels
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• Methane produced when bacteria decompose organic
  wastes
• Burn it to make heat / electricity
• China ferments manure to make gas for heating
  cooking
• Britain opened a dung-fired power plant in 2002
• Some landfills generate electricity w/ methane
  made from decomposing trash
• Alcohol
• Ethanol made by fermenting fruit or
  agricultural waste
• Corn is a major source in the US
• Gasohol gasoline ethanol
• produces 28 less emissions than fossil fuels,
  but produces 38 less energy

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DAM
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IV. Hydroelectricity Power from Moving Water

• Hydroelectric Energy produced from moving water
• Dam is built across a river to hold back a
  reservoir of water
• Water is released to turn a turbine
• Turbine spins a generator to produce electricity

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DAM
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• Benefits
• Expensive to build, but inexpensive to operate
  last longer than fossil-fuel powered plants
• No air pollutants
• Flood control
• Water for drinking, agriculture, industry,
  recreation
• Disadvantages
• Changes a rivers flow
• Reservoir floods large areas of habitat above the
  dam
• People are often displaced
• Water flow below the dam is reduced disrupting
  ecosystems downstream
• Prevents salmon from swimming upriver to spawn
• As river slows, it deposits sediment behind the
  dam instead of enriching the land farther
  downstream
• Plant matter decaying in reservoirs can release
  large amounts of greenhouse gasses

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• Modern Trends - Micro-hydropower
• Electricity produced in a small stream w/out a
  big dam
• Turbine may even float and not block the river at
  all!

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V. Geothermal Energy Power from the Earth

• Energy from heat in the Earths crust
• In some areas, deposits of water in the Earths
  crust are heated by energy within the Earth
• Geothermal Power Plants pump heated water or
  steam from rock formations and use the water or
  steam to power a turbine the water is usually
  returned to the crust

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• Geothermal Heat Pumps Energy for Homes
• Temp. of the ground is nearly constant year-round
• Geothermal heat pump uses stable underground
  temp. to warm and cool homes
• Simply a loop of piping that circulates a fluid
  underground

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18-2 Alternative Energy and Conservation

• Alternative Energy energy sources that are still
  in development
• Must be
• Cost effective
• Acceptable environmental effects
• Government investment is often the only way to
  research some of these possibilities.

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Tidal Power

• Works like a hydroelectric dam
• Tide rises, water flows behind a dam
• Sea level falls trapping water behind the dam
• Reservoir is released to turn a turbine
• Used in France, Russia, and Canada
• Pros renewable, non-polluting
• Cons high cost of building and maintaining, few
  locations are suitable

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Ocean Thermal Energy Conversion (OTEC)

• Warm surface water used to boil sea water (boils
  at low temp. at low pressure in a vacuum chamber)
• Steam turns turbine
• Deep, cold ocean water cools the steam to make
  reusable water
• not cost effective (so far)
• environmental effects unknown

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Hydrogen A Future Fuel Source?

• The most abundant element in the universe
• Can be burned as a fuel
• Does not release pollutants associated w/ burning
  fossil fuels and biomass
• When hydrogen is burned, it combines with oxygen
  to produce water vapor and small amounts of
  nitrogen oxides
• Can be produced by using electricity to split
  molecules of water
• The Challenge of Hydrogen
• Takes a lot of energy to produce
• 1 alternative use electricity from solar cells
  or wind power to split water molecules to produce
  hydrogen ?then store it in pressurized tanks and
  transport it in pipelines
• Fuel Cells produces electricity chemically (like
  a battery)
• Combines hydrogen fuel w/ oxygen from the air
• Electricity is produced
• Water is the only byproduct
• Can be fueled by anything that contains plenty of
  hydrogen (natural gas, alcohol, gasoline)
• Soon portable electronics (phones, games) may be
  powered by micro-fuel cells (fueled w/ alcohol) ?
  no charging or changing batteries ?

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Energy Efficiency the percentage of energy put
into a system that does useful work

• Energy efficiency (in ) energy out/energy in X
  100

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Efficient Transportation

• Developing efficient engines
• Increasing the use of public transportation
  systems

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Hybrid Cars

• Energy-efficient vehicles currently in use
• Use a small, efficient gasoline engine most of
  the time
• Also use an electric motor when extra power is
  needed (i.e. accelerating)
• Converts some of the energy of braking into
  electricity (stored in battery)
• Sometime shut off the gasoline engine (i.e. when
  stopped at a red light)
• Cost less to refuel
• Produce less harmful
• Emissions

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• Cogeneration the production of 2 useful forms of
  energy from the same fuel source
• i.e. waste heat from an industrial furnace can
  power a steam turbine that produces electricity
• Energy Conservation saving energy
• Using energy-efficient devices, wasting less
  energy
• Using less of any resource usually translates
  into saving energy
• Most of the energy lost from homes is lost
  through poorly insulated windows, doors, walls,
  and the roof
• Replace old windows w/ new high efficiency
  windows
• Seal gaps around doors and windows with caulking
  or weather stripping

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Ways to Save Energy Around The House