APES

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Ch. 15 Energy Efficiency and Renewable Energy
Resources

• APES Mrs. Sealy

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A. What is Energy Efficiency?

• 84 of all commercial energy in used in the US
  is wasted
• Energy efficiency- the percentage of total energy
  input that does useful work
• Life cycle cost- the initial cost plus lifetime
  operating costs
• The net efficiency of the entire energy delivery
  process is determined by the efficiency of each
  step in the energy conversion process.
• The three least energy efficient using devices
  are incandescent light bulbs, vehicles with
  internal combustion engines, and nuclear power
  plants producing electricity for space heating.

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B. Why it is important to reduce energy waste?

• 1. make nonrenewable fossil fuels last longer
• 2. gives us more time to phase in renewable
  energy resources
• 3. decreases dependence on oil imports
• 4. lessens the need for military intervention in
  the oil-rich and politically unstable Middle East
• 5. Reduces local and global environmental damage
• 6. Is the cheapest and quickest way to slow
  projected global climate change
• 7. Saves more money, provides more jobs, improves
  productivity and promotes more economic growth
  per unit of energy than other alternatives.
• 8. Improves competitiveness in the international
  marketplace

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B. Why it is important to reduce energy waste?

• The reason there is not more emphasis on
  improving energy efficiency is the glut of
  low-cost underpriced fossil fuels.
• A second cause is huge government subsidies

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II. Ways to Improve Energy Efficiency

• A. How can we use waste heat?
• Energy cannot be recycled (2nd law of
  thermodynamics)
• For a house insulate it, eliminate air leaks and
  equip it with an air-to-air heat exchanger

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B. How can we save energy in industry?

• Cogeneration- production of two useful forms of
  energy from the same fuel source. (Efficiency can
  be increased to approx. 90)
• Replacing energy-wasting electric motors use
  adjustable-speed drives
• switch to high efficiency lighting

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C. How can we save energy in producing
electricity? The Negawatt Revolution

• The negawatt revolution is known as demand-side
  management - reducing demand for electricity

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D. How can we save energy in Transportation?

• 1. Increase the fuel efficiency of motor vehicles
• There is little interest in fuel-efficient
  vehicles when gasoline is so cheap
• 2. Electric cars - pollution to recharge
  batteries is produced elsewhere
• Electric cars are not very efficient
• 3. Hybrid cars run on both internal combustion
  engines and electric motors with batteries
  charged by the internal combustion engine
• 4.Hydrogen fuel cell car run on electric motors
  with electricity (produced with hydrogen) from a
  fuel cell
• 5. Shift to more energy efficient way to move
• people and freight

http//www.topgear.com/uk/videos/electric-shocker
http//auto.howstuffworks.com/engine3.htm
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E. How can we save energy in buildings?

• Superinsulated houses air-to-air heat exchangers
• Use the most energy-efficient ways to heat
  houses passive solar heating and high-efficiency
  natural gas furnaces. electric resistance
  heating is the most wasteful
• Heat Pumps work in warm climates        For
  existing homes add insulation, plug leaks and
  install energy saving windows
• Use the most energy-efficient ways to heat water
  (using electricity is the least efficient)
• Use the most energy-efficient appliances and
  lights
• Rebates or tax credits for building
  energy-efficient buildings, etc.

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III. Solar Energy

• Pros
• Save money
• Create jobs
• Less pollution
• Increase national security
• Cheaper than nuclear

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III. Solar Energy

• Cons
• Initial cash investment

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A. Using Solar Energy to Heat Houses and Water

• Passive Solar Heating - captures sunlight
  directly within a structure and converts it into
  low-temperature heat for space heating
• a. Thermal mass stores collected energy as heat
  and releases it day and night

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A. Using Solar Energy to Heat Houses and Water

• Active Solar Heating - special collectors absorb
  solar energy a fan or pump is used to circulate
  the hot water
• a. Net energy yield is moderate CO2 not emitted
  land disturbance is minimal
• b. Owners need solar legal rights

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B. How Can Solar Energy Be Used to Generate
High-Temperature Heat and Electricity?

• Central Receiver System (Power Tower)
• Heliostats - computer controlled mirrors
• Solar Thermal Plant (distributed receiver system)
  
• Parabolic dish collectors
• Non-imaging optical solar concentrator
• Solar cookers
• Central Receiver System (Power Tower)

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Solar Power Tower
Fig. 15.21a, p. 374
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Solar Thermal Plant
Fig. 15.21b, p. 374
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Nonimaging Optical Solar Concentrator
Fig. 15.21c, p. 374
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Solar Cooker
Fig. 15.21d, p. 374
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C. Producing Electricity from Solar Cells - The
PV Revolution Pros

• Reliable, quiet, No moving parts, Lasts 20-30
  years, Produce no_____________,
• Can be on individual homes or power plants, All
  US power needs could be met if 6 of land is
  covered by them, Low pollution to _____________,
  Ideal for isolated homes and villages, Can be
  attached to a ___________Cons
• .30 Kw/hour, expensive to put in about
  15,000 to outfit a home, battery storage for
  night is large and _____________________       

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• Photovoltaic Cells (Solar Cells) - Sunlight
  falling on a wafer thin silicon sheet releases a
  flow of electrons creating an electric current.
• a. High net energy yield works in __________
• b. Cost of PVs is high, but going down
• C. Storage of electricity produced is a problem
• . Batteries are expensive
• . Flywheels are promising

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Producing Electricity from Moving Water and from
Heat in Stored Water

•    Hydroelectric Power
• a. Large-scale hydroelectric project (large dam)
• b. Small-scale hydroelectric project - a low dam
  with no _______________
• c. Pumped storage hydropower systems - water
  reservoirs at two different levels

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        Hydroelectric Power

• Advantage All have Moderate to high net energy
  yield, downstream flooding is reduced, provides
  year-round irrigation water, cheap, reservoir can
  be used for recreation, produces no
  _______________
• Disadvantage Flood vast areas, destroy wildlife
  habitat, uproots people, loss of water to
  evaporation, mass of water can cause earthquakes,
  expensive to build, fish migration disrupted,
  danger of collapse, downstream deprived of
  nutrient rich silt, no more dam-able rivers left
  ___________________

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Producing electricity from Tides and Waves

• Using the tidal flow energy waves to produce
  electricity
• Pros No polluting
• No carbon dioxide Cons
• Easily damaged
• Few areas with the right conditions
• expensive

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• Producing electricity from heat stored in water
• a. OTEC (Ocean thermal energy conversion)
• b. Saline solar ponds
• c. Freshwater solar ponds

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V. Producing electricity from Wind

• Wind turbines produce ____________
• Currently 25,000 of them in world
• Wind-farms are large groups of them

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V. Producing electricity from Wind

• Pros Cons
• Unlimited source of energy Only
  economical in areas
• Easily built expanded Steady wind
• High net energy Need
  back up power when
• No air pollution wind dies down
• No CO2 Visual noise pollution
• Cheap Interferes with flight of _______
• Farming could take
  Kills birds of prey place underneath

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VI. Producing Energy from Biomass

• Biomass organic matter in plants
• Can be burned directly or
• Converted to bio fuels
• Biogas Digester bacteria digest plant material
  to produce methane fuel ethanol
• Can be used in place
• of gasoline or mixed
• with gasoline (gasohol)

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VI. Producing Energy from Biomass

• Pros
• Can be renewable if not harvested faster than
  they grow back
• No net increase in CO2
• Add less SO2 NO2 than coal
• Cons
• W/out effective land use controls soil
  erosion, flooding, loss of habitat
• Wood is heavy to haul
• Expensive
• Produces air pollution particulates and PAH
  poly aromatic hydrocarbons

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VI. Producing Energy from Biomass

• Biomass Plantation plant large of fast growing
  trees that will be burned directly or converted
  to bio fuels
• Problem requires lots H20 fertilizer, large
  areas of land, reduces
• Using wood in fireplaces 4
• in U.S. get their heat from this problem
  is it results in net energy loss of wildlife
  habitat

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Burning Agriculture Waste

• Bagasse sugarcane residue- low oxygen burning
  produces a gas that can be used for electricity
  and the ash used for fertilizer.
• Organic matter can be burned directly as a solid
  fuel, or converted into gaseous or liquid biogas
• Potentially renewable if managed properly.
• Biogas (60 methane, 40 CO2) liquid methanol
  liquid ethanol
• Biomass Plantations of Btu Bushes burned
  directly or converted to alternative fuels
•         Requires large areas of land
•         Burning Wood
• a. contains pollutants known to cause cancer,
  bronchitis, emphysema
• b. Need efficient wood-burning stoves
• Burning agricultural or urban wastes
•       Bagasse residue left after harvesting and
  processing sugar cane.

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VII. Solar Hydrogen Revolution

• Water can be split by electricity into hydrogen
  and oxygen
• Solar energy can be used to produce this
  electricity
• Hydrogen can be used in fuel cells to produce
  electricty to run cars, cell phones, computers,
  homes

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VII. Solar Hydrogen Revolution

• Cons
• It takes energy to produce it
• To make it you need to react natural gas and
  electricity which makes CO2
• Cost is .65 to .92 a gallon to make
• Requires energy from coal or nuclear power to
  produce, the only way it could be
• Sustainable would be if solar power were used to
  make it
• Requires larger gas tanks in cars

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VII. Solar Hydrogen Revolution

• Pros
• Easy to store
• Doesnt pollute like gasoline
• Will not explode
• Does not produce CO2

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VII. Solar Hydrogen Revolution

• Why havent we done it?
• -economics
• -we need to convince governments and companies to
  make financial investments and phase out fossil
  fuels.
• -politics

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VIII. Geothermal Energy

• Geothermal heat contained in underground rocks
  and fluids
• - dry steam, wet stream, hot h2o is extracted
  and used to turn a turbine
• - 20 countries have geothermal sites

http//www1.eere.energy.gov/geothermal/
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VIII. Geothermal Energy

• Pros Cons
• Vast, reliable - not many available
  sites
• renewable - can be depleted
• moderate net energy - can degrade
  ecosystems
• 96 fewer co2 - causes land to emissions
  sink
• competitive - noise, odor, climate change

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IX. Sustainable Energy Strategy

• improved energy efficiency
• chose projects carefully
• we cannot continue to depend on a single
  nonrenewable energy source.
• What the government can do
• a. increase fuel efficiency standards for motor
  vehicles
• b. establish energy-efficiency standards for
  buildings and appliances
• c. increase government sponsored RD to improve
  energy efficiency
• d. give tax credits and exemptions for purchases
  of energy efficient vehicles, houses, buildings
  and appliances
• e. phase in full-cost pricing to include the
  environmental impact
•