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© Cengage Learning 2015
LIVING IN THE ENVIRONMENT, 18e G. TYLER MILLER • SCOTT E. SPOOLMAN
© Cengage Learning 2015
16 Energy Efficiency and Renewable Energy
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• Wind energy – wind farms convert to electrical energy
• Wind power is inexhaustible • Could meet electricity needs of the lower
48 states – Texas and California are top producers
Core Case Study: The Astounding Potential for Wind Power in the U.S.
Fig. 16-1a, p. 402
Gearbox
Electrical generator
Power cable
Wind turbine
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Fig. 16-1b, p. 402
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• Improvements in energy efficiency could save at least a third of the energy used in the world and up to 43% of the energy used in the United States
• We have a variety of technologies for sharply increasing the energy efficiency of industrial operations, motor vehicles, appliances, and buildings
16-1 Why Is Energy Efficiency an Important Energy Resource?
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• Energy efficiency – How much useful work we get from each unit
energy • Advantages of reducing energy waste
– Usually the cheapest way to provide more energy
– Reduces pollution and degradation – Slows global warming – Increases economic and national security
We Use Energy Inefficiently
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• Four widely used devices that waste energy – Incandescent light bulb – Motor vehicle with internal combustion engine – Nuclear power plant – Coal-fired power plant
We Use Energy Inefficiently (cont’d.)
Fig. 16-2, p. 403
Energy Inputs System Outputs 9%
7%
41% 85%
U. S. economy
43%
8%
Nonrenewable fossil fuels Useful energy
Renewable (hydropower, geothermal, wind, solar, biomass) Energy waste
3%
Petrochemicals Unavoidable energy loss
Nonrenewable nuclear
Fig. 16-4, p. 404
Solutions
Improving Energy Efficiency
Prolongs fossil fuel supplies
Reduces oil imports and improves energy security
Very high net energy yield
Low cost
Reduces pollution and environmental degradation
Buys time to phase in renewable energy
Creates local jobs
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• Cogeneration – Combined heat and power (CHP) – Two forms of energy from same fuel source
• Replace energy-wasting electric motors • Recycle materials • Switch from low-efficiency incandescent
lighting to higher-efficiency fluorescent and LED lighting
We Can Improve Energy Efficiency in Industry and Utilities
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• Current electrical grid system – outdated and wasteful
• Smart grid – Ultra-high-voltage – Super-efficient transmission lines – Digitally controlled – Responds to local changes in demand and
supply – Easier to buy renewable energy
Case Study: Saving Energy and Money with a Smarter Electrical Grid
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• Hidden prices in gasoline – Should be $12/gallon – Car manufacturers and oil companies lobby to
prevent laws to raise fuel taxes • Build or expand mass transit and high
speed rail • Encourage biking
We Can Improve Energy Efficiency and Save Money in Transportation
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• Superefficient and ultralight cars • Gasoline-electric hybrid car • Plug-in hybrid electric vehicle • Energy-efficient diesel car • Electric vehicle with a fuel cell
More Energy-Efficient Vehicles Are on the Way
Stepped Art
Conventional hybrid Fuel tank
Battery
Internal combustion engine Transmission Electric motor
Plug-in hybrid Fuel tank
Battery
Internal combustion engine
Transmission Electric motor
Fig 16-6, p. 406
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• Green architecture • Living or green roofs
– With specially designed soil and vegetation • Superinsulation
– No need for heating system • U.S. Green Building Council’s Leadership
in Energy and Environmental Design (LEED)
We Can Design Buildings That Save Energy and Money
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Fig. 16-7, p. 408
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• Conduct an energy audit: – Insulate and plug leaks – Use energy-efficient windows – Stop other heating and cooling losses – Heat houses more efficiently – Use energy-efficient appliances – Use energy-efficient lighting – Use motion sensors to turn lights on and off
We Can Save Money and Energy in Existing Buildings
Fig. 16-9, p. 410
Outside Plant deciduous trees to block summer sun and let in winter sunlight.
Other rooms • Use compact fluorescent lightbulbs or LEDs and avoid using incandescent bulbs wherever possible. • Turn off lights, computers, TV, and other electronic devices when they are not in use. • Use high efficiency windows; use insulating window covers and close them at night and on sunny, hot days. • Set thermostat as low as you can in winter and as high as you can in summer. • Weather-strip and caulk doors, windows, light fixtures, and wall sockets. • Keep heating and cooling vents free of obstructions. • Keep fireplace damper closed when not in use. • Use fans instead of, or along with, air conditioning.
Bathroom • Install water-saving toilets, faucets, and shower heads. • Repair water leaks promptly.
Stepped Art
Attic • Hang reflective foil near roof to reflect heat. • Use house fan. • Be sure attic insulation is at least 30 centimeters (12 inches).
Kitchen • Use microwave rather than stove or oven as much as possible. • Run only full loads in dishwasher and use low- or no-heat drying. • Clean refrigerator coils regularly.
Basement or utility room • Use front-loading clothes washer. If possible run only full loads with warm or cold water.
• Hang clothes on racks for drying. • Run only full loads in clothes dryer and use lower heat setting. • Set water heater at 140° if dishwasher is used and 120° or lower if no dishwasher is used.
• Use water heater thermal blanket. • Insulate exposed hot water pipes. • Regularly clean or replace furnace filters.
Fig. 16-10, p. 411
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• Energy remains artificially cheap – Government subsidies – Tax breaks – Prices don’t include true cost
• Few large and long-lasting incentives – Government rebates – Low-interest loans
• Lack of education
Why Are We Still Wasting So Much Energy and Money?
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• Renewable energy – Solar energy – Geothermal energy
• Renewable energy will be cheaper if we eliminate: – Inequitable subsidies – Inaccurate prices – Artificially low pricing of nonrenewable energy
We Can Use Renewable Energy to Provide Heat and Electricity
Fig. 16-11, p. 412
Available Energy Flow (exajoules per year)
World energy use (2010)
Direct solar
Wind
Geothermal
Biomass
Hydropower
Ocean <1
500
600
527
>1,000
50
<250
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• Passive and active solar heating systems can heat water and buildings effectively
• The costs of using direct sunlight to produce high-temperature heat and electricity are coming down
16-3 What Are the Advantages and Disadvantages of Solar Energy?
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• Passive solar heating system – Absorbs and stores heat from the sun directly
within a well-insulated structure • Active solar heating system
– Captures energy from the sun in a heat-absorbing fluid
We Can Heat Buildings and Water with Solar Energy
Fig. 16-14, p. 415
Trade-Offs
Passive or Active Solar Heating
Advantages Disadvantages Net energy is moderate (active) to high (passive)
Need access to sun 60% of time during daylight
Very low emissions of CO2 and other air pollutants
Sun can be blocked by trees and other structures
High installation and maintenance costs for active systems
Very low land disturbance
Moderate cost (passive)
Need backup system for cloudy days
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• Technologies available – Open windows when cooler outside – Use fans – Superinsulation and high-efficiency windows – Overhangs or awnings on windows – Light-colored roof – Geothermal pumps
We Can Cool Buildings Naturally
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• Solar thermal systems – Collect sunlight to boil water, generate
electricity – 1% of world deserts could supply all the
world’s electricity – Require large amounts of water
• Wet cooling • Dry cooling
• Low net energy yields
We Can Concentrate Sunlight to Produce High-Temperature Heat and Electricity
Fig. 16-15, p. 416
Fig. 16-16, p. 416
Solar Thermal Systems
High potential for growth
Low net energy and high costs
Advantages Disadvantages
No direct emissions of CO2 and other air pollutants Needs backup or
storage system on cloudy days
Source of new jobs
Can disrupt desert ecosystems
Trade-Offs
Lower costs with natural gas turbine backup
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• Photovoltaic (PV) cells – Convert solar energy to electric energy
• Design of solar cells – Sunlight hits cells and releases electrons into
wires • What are the benefits of using solar cells?
We Can Use Solar Cells to Produce Electricity
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• Key problems – High cost of producing electricity – Need to be located in sunny desert areas – Fossil fuels used in production – Solar cells contain toxic materials
• Cost could drop with: – Mass production and new designs – Government subsidies and tax breaks
We Can Use Solar Cells to Produce Electricity (cont’d.)
Fig. 16-18, p. 418
Fig. 16-19, p. 418
Fig. 16-21, p. 419
Solar Cells
Advantages Disadvantages
Medium net energy yield
Need access to sun
Little or no direct emissions of CO2 and other air pollutants
Need electricity storage system or backup
Easy to install, move around, and expand as needed
Costs high for older systems but dropping rapidly
Solar-cell power plants could disrupt desert ecosystems
Competitive cost for newer cells
Trade-Offs
Some designs have low net energy yield
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• We can use water flowing over dams, tidal flows, and ocean waves to generate electricity – However, environmental concerns and limited
availability of suitable sites may limit the use of these energy resources
16-4 What Are the Advantages and Disadvantages of Using Hydropower
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• Hydropower – Uses kinetic energy of moving water – Indirect form of solar energy – World’s leading renewable energy source
used to produce electricity • What are the advantages and
disadvantages? • Micro-hydropower generators: floating
turbines
We Can Produce Electricity from Falling and Flowing Water
Fig. 16-22, p. 420
Large-Scale Hydropower
Advantages Disadvantages
High net energy yield
Large land disturbance and displacement of people
Low-cost electricity
High CH4 emissions from rapid biomass decay in shallow tropical reservoirs
Low emissions of CO2 and other air pollutants in temperate areas
Disrupts downstream aquatic ecosystems
Trade-Offs
Large untapped potential
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• Produce electricity from flowing water – Ocean tides and waves in coastal bays and
estuaries • Power systems are limited
– Few suitable sites – High costs – Equipment damaged by storms and corrosion
We Can Use Tides and Waves to Produce Electricity
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• When we include the environmental costs of using energy resources in their market prices, wind power is the least expensive and least polluting way to produce electricity
16-5 What Are the Advantages and Disadvantages of Using Wind Power?
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• Tall, long-blade turbines can extract more energy from the wind
• Rapidly growing power source – U.S., Europe, and China – Future is offshore wind farms
• Wind power has potential to produce 40 times of the world’s current electricity used
Using Wind to Produce Electricity Is an Important Step toward Sustainability
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• Wind is abundant, widely distributed, and inexhaustible
• High net energy yield • Drawbacks:
– Largest potential areas are usually rural – Winds can die down – need backup power
source
Using Wind to Produce Electricity Is an Important Step (cont’d.)
Fig. 16-25, p. 423
Trade-Offs
Wind Power
Advantages Disadvantages
High net energy yield
Needs backup or storage system when winds die down
Low electricity cost
Visual pollution for some people
Low-level noise bothers some people
Can kill birds if not properly designed and located
Widely available
Easy to build and expand
Little or no direct emissions of CO2 and other air pollutants
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• Solid biomass is a renewable resource for much of the world’s population, but burning it faster than it is replenished produces a net gain in atmospheric greenhouse gases
16-6 Advantages and Disadvantages of Using Biomass as an Energy Source
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• We can use liquid biofuels derived from biomass to lessen our dependence on oil-based fuels, but creating biofuel plantations can: – Degrade soil and biodiversity – Increase greenhouse gas emissions – Lead to higher food prices
16-6 Advantages and Disadvantages of Biomass as an Energy Source (cont’d.)
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• Biomass – Plant materials and animal waste we can burn
or turn into biofuels • Production of solid mass fuel
– Plant fast-growing trees; biomass plantations – Collect crop residues and animal manure
• What are the advantages and disadvantages of biomass energy?
We Can Produce Energy by Burning Solid Biomass
Fig. 16-26, p. 424
Solid Biomass
Advantages Disadvantages Widely available in some areas
Contributes to deforestation
Clear-cutting can cause soil erosion, water pollution, and loss of wildlife habitat
No net CO2 increase if harvested, burned, and replanted sustainably
Medium net energy yield
Plantations can help restore degraded lands
Trade-Offs
Increases CO2 emissions if harvested and burned unsustainably
Can open ecosystems to invasive species
Moderate costs
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• Biodiesel – Produced from vegetable oil – European Union countries produce 95% of
the world’s biodiesel • Crops require large amounts of land • Production requires fossil fuels
Case Study: Is Biodiesel the Answer?
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• Ethanol – Can be made from sugarcane, corn,
switchgrass, and various wastes – United States largest producer
• Made from corn; low net energy yield
– Brazil second • Sugarcane has medium net energy yield
• Cellulosic ethanol – Produced from cellulose
Case Study: Is Ethanol the Answer?
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• Problems with cellulosic ethanol – Chemical processes still being developed – Growing enough switchgrass would require
too much land • Evaluating use of algae and bacteria
Case Study: Is Ethanol the Answer? (cont’d.)
Fig. 16-28, p. 426
Liquid Biofuels
Advantages Disadvantages
Reduced CO2 emissions for some crops
Fuel crops can compete with food crops for land and raise food prices
Medium net energy yield for biodiesel from oil palms
Fuel crops can be invasive species
Low net energy yield for corn ethanol and for biodiesel from soybeans Medium net
energy yield for ethanol from sugarcane
Higher CO2 emissions from corn ethanol
Trade-Offs
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• Geothermal energy has great potential for supplying many areas with heat and electricity, and has a generally low environmental impact – However, the sites where it can be produced
economically are limited
16-7 What Are the Advantages and Disadvantages of Geothermal Energy?
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• With geothermal energy, heat is stored in: – Soil – Underground rocks – Fluids in the earth’s mantle
• Geothermal heat pump system – Energy efficient and reliable – Environmentally clean – Cost effective to heat or cool a space
We Can Get Energy by Tapping the Earth’s Internal Heat
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• Hydrothermal reservoirs – Drill wells and extract various steams, water – U.S. is the world’s largest producer
• Geothermal energy problems – High cost of tapping hydrothermal reservoirs – Dry- or wet-steam geothermal reservoirs
could be depleted – Could create earthquakes
We Can Get Energy by Tapping the Earth’s Internal Heat (cont’d.)
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Fig. 16-30a, p. 428
Production well
Geothermal reservoir
Injection well
Heat exchanger
Steam turbine
Generator
2. Heat from underground spins a turbine to power a generator and produce electricity
1. Hot water or steam is pumped under pressure to the surface from underground
3. Steam from turbine condenses to water and is pumped back down to geothermal reservoir
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Fig. 16-30b, p. 428
Fig. 16-31, p. 430
Geothermal Energy
Advantages Disadvantages
Medium net energy yield and high efficiency at accessible sites
High cost except at concentrated and accessible sites
Lower CO2 emissions than fossil fuels
Scarcity of suitable sites
Low cost at favorable sites
Noise and some CO2 emissions
Trade-Offs
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• Hydrogen is a clean energy source as long as it is not produced with the use of fossil fuels – However, it has a negative net energy yield
16-8 The Advantages and Disadvantages of Using Hydrogen as an Energy Source
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• Hydrogen as a fuel – Eliminates most of the air pollution problems – Reduces threats of global warming
Will Hydrogen Save Us?
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• Some challenges – Chemically locked in water and organic
compounds – net negative energy yield – Expensive fuel cells are the best way to use
hydrogen – CO2 levels dependent on method of hydrogen
production
Will Hydrogen Save Us?
Fig. 16-32, p. 430
Electrons
Hydrogen gas (H2) in
Polymer electrolyte membrane
Anode
Cathode
Protons
Water vapor (H2O) out
Air (O2) in
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• Production and storage of H2 – Must be produced using other sources of
energy • Hydrogen-powered vehicles – prototypes
available • Can we produce hydrogen on demand? • Larger fuel cells – fuel-cell stacks
Will Hydrogen Save Us? (cont’d.)
Fig. 16-33, p. 432
Trade-Offs
Hydrogen
Advantages Disadvantages Can be produced from plentiful water at some sites
Fuel cell
Negative net energy yield
CO2 emissions if produced from carbon-containing compounds
No CO2 emissions if produced with use of renewables
Good substitute for oil
High costs create need for subsidies
High efficiency in fuel cells
Needs H2 storage and distribution system
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• We can make the transition to a more sustainable energy future by: – Greatly improving energy efficiency – Using a mix of renewable energy resources – Including the environmental and health costs
of energy resources in their market prices
16-9 How Can We Make the Transition to a More Sustainable Energy Future?
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• General conclusions: – Gradual shift to smaller, decentralized
micropower systems – Combination of increased energy efficiency
and regulated use of natural gas will be the best way to transition to renewable energy
– Because fossil fuels are cheap we will continue to use them
Choosing Energy Paths
Bioenergy power plants
Smart electrical and distribution system
Small solar-cell power plants
Solar-cell rooftop systems
Commercial
Fuel cells
Rooftop solar- cell arrays
Residential
Small wind turbine
Stepped Art Industrial Microturbines
Wind farm
Fig. 16-34, p. 433 © Cengage Learning 2015
© Cengage Learning 2015
• Government strategies: – Keep the prices of selected energy resources
artificially low to encourage their use – Keep energy prices artificially high for
selected resources to discourage their use – Consumer education
Economics, Politics, Education, and Sustainable Energy Resources
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Fig. 16-35, p. 434
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• We should evaluate energy resources on the basis of: – Their potential supplies – Their net energy yields – Environmental and health impacts of using
them
Three Big Ideas
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• By using a mix of renewable energy sources we could drastically reduce pollution, greenhouse gas emissions, and biodiversity losses – Solar, wind, flowing water, sustainable
biofuels, and geothermal energy
Three Big Ideas (cont’d.)
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• Making the transition to a more sustainable energy future will require: – Sharply increasing energy efficiency – Using a mix of environmentally friendly
renewable energy resources – Including the harmful environmental and
health costs of energy resources in their market prices
Three Big Ideas (cont’d.)
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• Relying on a diversity of direct and indirect forms of solar energy: – Would implement three principles of
sustainability – Recycle and reuse materials to reduce
consumption of energy – Mimic nature’s reliance on biodiversity by
diversifying energy sources
Tying It All Together: Wind Power and Sustainability
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