ENVIRONMENTAL SCIENCE

ENVIRONMENTAL SCIENCE

13e 14e 15e

CHAPTER 13:

Energy

13-4 Why Is Energy Efficiency an Important Energy Source?

We waste huge

amounts of energy.

Ex. inefficiency of incandescent lights, furnaces, industrial

motors, coal and nuclear power plants, motor vehicles, other devices and badly designed buildings.

13-4 Why Is Energy Efficiency an Important Energy Source?

• Concept 13-4

The U.S. could save as much as 43% of all the energy it uses by

improving the energy efficiency of industrial operations, motor

vehicles, and buildings.

Fig. 13-19, p. 319 Outputs

System Energy Inputs

43%

7%

9%

3%

4%

41%

85%

8%

U.S.

economy

Nonrenewable fossil fuels Nonrenewable nuclear Hydropower, geothermal, Wind, solar

Biomasss

Useful energy Petrochemicals

Unavoidable energy waste Unnecessary energy

Improving Energy Efficiency

• Energy efficiency

– How much work we get from each unit of energy we use

• Reducing energy waste

– 41% of all commercial energy in U.S. is wasted unnecessarily

• Numerous economic and

environmental advantages

Examples of Energy-Wasting Devices

• Incandescent light bulb ^(90–

95% is wasted as heat)

• Internal combustion engine

(wastes about 94% of the energy in its fuel)

• Nuclear power plants

• Coal-burning power plants wastes (66% of the energy

released by burning coal to produce electricity)

Saving Energy and Money in Industry

• Cogeneration/Combined Heat and Power (CHP) systems

• Recycling

• Energy-saving electric motors

• Fluorescent lighting

• Smart grid electricity

(the steam produced in generating electricity in a CHP system can be used to heat the plant or other nearby buildings, rather than released into the environment and wasted.)

Saving Energy and Money in Transportation

• 2/3 of U.S. oil consumption

• Low fuel-efficiency standards for vehicles compare to other country

• Hidden costs: $12/gallon of gas

• Raise gasoline taxes/cut payroll and income taxes

• Tax breaks for fuel-efficient vehicles

Stepped Art Fig. 13-21, p. 320

25 Cars

20 Cars, trucks, and SUVs

Trucks and SUVs 15

Average fuel economy (miles per gallon)

10

1975 1980 1985 1990 1995 2000 2005 Year

50

45 Europe

40 Japan

35 China

Miles per gallon (mpg) (converted to U.S. test equivalents)

30 Canada

25

United States 20

2002 2004 2006 2008

Year

Hybrid and Fuel-Cell Cars

• Super-efficient and ultralight cars

• Gasoline-electric hybrid car

• Plug-in hybrid electric car

• Hydrogen fuel cells

• Accessible mass-transit systems as

alternative

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. 13-22, p. 321

Saving Energy and Money in New Buildings

• Green architecture

• Solar cells, fuel cells, eco-roofs, recycled materials

• Super insulation

• Straw bale houses

Saving Energy in Existing Buildings

• Insulate and plug leaks

• Use energy-efficient windows

• Heat houses more efficiently

• Heat water more efficiently

• Use energy-efficient appliances

• Use energy-efficient lighting

Fig. 13-24, p. 324 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.

Why Are We Still Wasting So Much Energy?

• Energy costs relatively little

• Lack of government support and economic incentives

• Inadequate building codes

• Inadequate appliance standards

• Lack of information about saving

energy

13-5 What Are Advantages/Disadvantages of Renewable Energy Resources?

• Concept 13-5 Using a mix of renewable energy sources –

especially sunlight, wind, flowing water, sustainable biomass, and

geothermal energy – can drastically reduce pollution, greenhouse gas

emissions, and biodiversity losses.

Renewable Energy

• Sustainability mostly depends on solar energy

– Direct form: from the sun

• Indirect forms

– Wind

– Moving water – Biomass

– Geothermal

Benefits of Shifting to Renewable Energy Resources (1)

• More decentralized, less vulnerable

• Improve national security

• Reduce trade deficits

• Reduce air pollution

Benefits of Shifting to Renewable Energy Resources (2)

• Create jobs

• Save money

• Renewable energy handicapped by

– Unbalanced, intermittent subsidies – Inaccurate pricing

Using Solar Energy to Heat Buildings and Water

• Passive solar heating system

• Active solar heating system

Using Solar Energy to Heat Buildings and Water

• Passive solar heating system

• Active solar heating system

PASSIVE

Summer sun

Winter sun

Vent allows hot air to escape in summer

Superwindow

Superwindow

Stone floor and wall for heat storage Heavy insulation

Fig. 13-25, p. 325

Fig. 13-26, p. 326

Passive or Active Solar Heating

Need access to sun 60%

of time

Sun can be blocked by trees and other structures Environmental costs not included in market price Need heat storage system High cost (active)

Active system needs maintenance and repair Active collectors

unattractive Energy is free

Net energy is moderate (active) to high (passive) Quick installation

No CO₂ emissions

Very low air and water pollution

Very low land disturbance (built into roof or windows) Moderate cost (passive)

Advantages Disadvantages

Trade-Offs

Solar Energy for High-

Temperature Heat and Electricity

• Solar thermal systems

• Solar thermal plant

• Solar cookers

• Photovoltaic (solar) cells

Solar thermal systems Solar thermal plant

Solar cookers

Boron- enriched silicon

Phosphorus- enriched silicon Junction

Single solar cell

Solar-cell roof

Roof options

Fig. 13-29, p. 328

Panels of solar cells

Solar shingles

Fig. 13-27, p. 326

Trade-Offs

Low efficiency Low net energy High costs

Environmental costs not included in market price Needs backup or storage system

Needs access to sun most of the time

May disturb desert areas Costs reduced with

natural gas turbine backup

No CO₂ emissions

Fast construction (1–2 years)

Moderate environmental impact

Advantages Disadvantages

Solar Energy for High-Temperature Heat and Electricity

Fig. 13-31, p. 328

Solar Cells

Need access to sun

Low efficiency

Need electricity storage system or backup

Environmental costs not included in market price

High costs (but should be competitive in 5–15 years)

High land use (solar-cell power plants) could disrupt desert areas

DC current must be converted to AC Reduces dependence on

fossil fuels

Low land use (if on roof or built into walls or windows) Last 20–40 years

Low environmental impact No CO₂emissions

Easily expanded or moved Quick installation

Work on cloudy days

Fairly high net energy yield

Trade-Offs

Disadvantages Advantages

Producing Electricity from Flowing Water

• Hydropower

– Leading renewable energy source – Much unused capacity

• Dams and reservoirs

– Turbines generate electricity – Eventually fill with silt

• Micro-hydro generators

Fig. 13-32, p. 329

Large-Scale Hydropower

High construction costs High environmental

impact from flooding land to form a reservoir

Environmental costs not included in market price High CH₄emissions from rapid biomass decay in shallow tropical reservoirs

Danger of collapse Uproots people

Decreases fish harvest below dam

Decreases flow of natural fertilizer (silt) to land below dam

Moderate to high net energy

High efficiency (80%)

Large untapped potential

Low-cost electricity

Long life span

No CO₂ emissions during operation in temperate areas Can provide flood control below dam

Provides irrigation water Reservoir useful for fishing and recreation

Disadvantages Advantages

Trade-Offs

Producing Electricity from Wind

• Indirect form of solar energy

• World’s second fastest-growing source of energy

• Vast potential

– Land

– Offshore

Fig. 13-34, p. 331

Trade-Offs

Steady winds needed

Backup systems needed when winds are low

Plastic components produced from oil

Environmental costs not included in market price

High land use for wind farm

Visual pollution

Noise when located near populated areas

Can kill birds and interfere with flights of migratory birds if not sited properly

Moderate to high net energy yield

High efficiency

Moderate capital cost Low electricity cost (and falling)

Very low environmental impact

No CO₂emissions Quick construction Easily expanded

Can be located at sea Land below turbines can be used to grow crops or graze livestock

Advantages Disadvantages

Wind Power

Energy from Burning Biomass

• Biomass

– Wood

– Agricultural waste – Plantations

– Charcoal

– Animal manure

• Common in developing countries

• Carbon dioxide increase in atmosphere

Converting Plant Matter to Liquid Biofuel

• Biofuels

– Ethanol and biodiesel

– Crops can be grown in most countries – No net increase in carbon dioxide

emissions

– Available now

• Sustainability

The cellulose in this rapidly growing switch grass can be converted into ethanol.

Fig. 13-35, p. 333 Increased NO_x emissions

and more smog Higher cost than regular diesel

Environmental costs not included in market price Low net energy yield for soybean crops

May compete with growing food on

cropland and raise food prices

Loss and degradation of biodiversity from crop plantations

Can make engines hard to start in cold weather Reduced CO

emissions Reduced CO₂ emissions (78%) High net energy yield for oil palm crops

Moderate net energy yield for rapeseed crops Reduced

hydrocarbon emissions Better gas mileage (40%) Potentially renewable

Trade-Offs

Advantages Disadvantages

Biodiesel

Fig. 13-37, p. 335 Lower driving range

Low net energy yield (corn)

Higher CO₂ emissions (corn) Much higher cost

Environmental costs not included in market price May compete with growing food and raise food prices Higher NO_x emissions and more smog

Corrosive

Can make engines hard to start in cold weather

High octane

Some reduction in CO₂ emissions

(sugarcane bagasse)

High net energy yield

(bagasse and switchgrass)

Can be sold as a mixture of gasoline and ethanol or as pure ethanol

Potentially renewable

Trade-Offs

Advantages Disadvantages

Ethanol Fuel

Energy by Tapping the Earth’s Internal Heat

• Geothermal energy

• Geothermal heat pumps

• Hydrothermal reservoirs

– Steam

– Hot water

• Deep geothermal energy

Supplement 9, Fig. 9, p. S43

Fig. 13-38, p. 336

Very high efficiency Scarcity of suitable sites Can be depleted if used too rapidly

Environmental costs not included in market price CO₂ emissions

Moderate to high local air pollution

Noise and odor (H₂S)

High cost except at the most concentrated and accessible sources

Moderate environmental impact

Low land use and disturbance

Low cost at favorable sites Lower CO₂emissions than fossil fuels

Moderate net energy at accessible sites

Trade-Offs

Advantages Disadvantages

Geothermal Energy

Can Hydrogen Replace Oil?

• Hydrogen is environmentally friendly

• Problems

– Most hydrogen is in water – Net energy yield is negative – Fuel is expensive

– Air pollution depends on production method

– Storage

Fig. 13-39, p. 337

Science Focus: The Quest to Make Hydrogen Workable

• Bacteria and Algae

• Electricity from solar, wind, geothermal

• Storage: liquid and solid

• Preventing explosions

13-6 How Can We Make the Transition to a More Sustainable Energy Future?

• Concept 13-6 We can make a transition to a more sustainable energy future by

greatly improving energy efficiency, using a mix of renewable energy resources, and including environmental costs of energy resources in their market prices.

Transition to a More

Sustainable Energy Future (1)

• For each energy alternative:

– How much available next 25-50 years?

– Estimated net energy yield – Total costs

– Necessary subsidies and tax breaks – How affect economic and military

security

– Vulnerability to terrorism – Environmental effects

Transition to a More

Sustainable Energy Future (2)

• Gradual shift from centralized macropower to decentralized micropower

• Greatly improved energy efficiency

• Temporary use of natural gas

• Decrease environmental impact of

fossil fuels

Fig. 13-41, p. 340 Increase fuel-efficiency standards

for vehicles, buildings, and appliances

Mandate government purchases of efficient vehicles and other devices Provide large tax credits or

feebates for buying efficient cars, houses, and appliances

Offer large tax credits for

investments in energy efficiency Reward utilities for reducing demand for electricity

Greatly increase energy efficiency research and development

Improve Energy Efficiency

Making the Transition to a More Sustainable Energy Future

Solutions

Phase out nuclear power subsidies, tax breaks, and loan guarantees

More Renewable Energy

Greatly increase use of renewable energy

Provide large subsidies and tax credits for use of renewable energy

Include environmental costs in prices for all energy resources

Encourage government purchase of renewable energy Greatly increase renewable energy research and development

Reduce Pollution and Health Risk Cut coal use 50% by 2020

Phase out coal subsidies and tax breaks Levy taxes on coal and oil use

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. 13-40, p. 339

Economic, Political, and Educational Strategies to Sustainable Energy

• Requires government strategies

• Keep prices low in selected resource to encourage use

– Same strategy for fossil fuels and nuclear power

• Keep prices high in selected resource to discourage use

• Emphasize consumer education

Three Big Ideas from This Chapter - #1

1. Energy resources should be evaluated on the basis of their potential supplies, net

useful energy, and environmental impact.

2. Using a mix of renewable energy can drastically reduce pollution, GHGs

emissions, and biodiversity losses.

Three Big Ideas from This Chapter

3.

sustainable energy future requires sharply reducing energy waste, using a mix of

environmentally friendly renewable energy resources, and including the harmful

environmental costs of energy resources in their market prices.

THE END