Chapter 17

Chapter 17Chapter 17

Energy Efficiency and Energy Efficiency and Renewable EnergyRenewable Energy

REDUCING ENERGY WASTE AND REDUCING ENERGY WASTE AND IMPROVING ENERGY EFFICIENCYIMPROVING ENERGY EFFICIENCY

Energy conservationEnergy conservation – the – the reduction or elimination of reduction or elimination of unnecessary waste unnecessary waste energy.energy.

Flow of commercial Flow of commercial energy through the U.S. energy through the U.S. economy.economy.

84% of all commercial 84% of all commercial energy used in the U.S. is energy used in the U.S. is wasted wasted

41% wasted due to 241% wasted due to 2ndnd law law of thermodynamics.of thermodynamics.

Figure 17-2Figure 17-2

REDUCING ENERGY WASTE AND REDUCING ENERGY WASTE AND IMPROVING ENERGY EFFICIENCYIMPROVING ENERGY EFFICIENCY

Four widely used devices waste large amounts of energy:Four widely used devices waste large amounts of energy: Incandescent light bulbIncandescent light bulb: 95% is lost as heat.: 95% is lost as heat. Internal combustion engineInternal combustion engine: 94% of the energy in its fuel is wasted.: 94% of the energy in its fuel is wasted. Nuclear power plantNuclear power plant: 92% of energy is wasted through nuclear fuel : 92% of energy is wasted through nuclear fuel

and energy needed for waste management.and energy needed for waste management. Coal-burning power plantCoal-burning power plant: 66% of the energy released by burning : 66% of the energy released by burning

coal is lost.coal is lost.

Why do we waste so much energy?Why do we waste so much energy?

Low-priced fossil fuels and few government tax breaks or other Low-priced fossil fuels and few government tax breaks or other financial incentives for saving energy promote energy waste.financial incentives for saving energy promote energy waste.

Fig. 17-3, p. 386

Solutions

Reducing Energy Waste

Prolongs fossil fuel supplies

Reduces oil imports

Very high net energy

Low cost

Reduces pollution and environmental degradation

Buys time to phase in renewable energy

Less need for military protection of Middle East oil resources

Creates local jobs

Net Energy Efficiency: Net Energy Efficiency: Honest AccountingHonest Accounting

Comparison of net energy Comparison of net energy efficiency for two types of efficiency for two types of space heating.space heating.


WAYS TO IMPROVE ENERGY EFFICIENCYWAYS TO IMPROVE ENERGY EFFICIENCY

We can save energy in…We can save energy in… Industry Industry

Produce both heat and electricity from one energy source Produce both heat and electricity from one energy source Use more energy-efficient electric motors and lighting.Use more energy-efficient electric motors and lighting.

TransportationTransportation Increase fuel efficiency Increase fuel efficiency Make vehicles from lighter and stronger materials.Make vehicles from lighter and stronger materials.

Construction/BuildingsConstruction/Buildings Get heat from the sun, Get heat from the sun, Super-insulate buildingsSuper-insulate buildings Use plant covered green roofs.Use plant covered green roofs. Plug leaksPlug leaks Use energy efficient heating and cooling systems, appliances, and lightingUse energy efficient heating and cooling systems, appliances, and lighting

Passive Solar HousePassive Solar House

The heating bill for this energy-efficient passive solar radiation office in The heating bill for this energy-efficient passive solar radiation office in Colorado is $50 a year.Colorado is $50 a year.


Strawbale HouseStrawbale House

Strawbale is a superinsulator that is made from bales of low-Strawbale is a superinsulator that is made from bales of low-cost straw covered with plaster or adobe. Depending on the cost straw covered with plaster or adobe. Depending on the thickness of the bales, its strength exceeds standard thickness of the bales, its strength exceeds standard construction.construction.


Living RoofsLiving Roofs

Roofs covered with plants Roofs covered with plants have been used for have been used for decades in Europe and decades in Europe and Iceland.Iceland.

These roofs are built from a These roofs are built from a blend of light-weight blend of light-weight compost, mulch and compost, mulch and sponge-like materials that sponge-like materials that hold water.hold water.


Saving Energy in Existing BuildingsSaving Energy in Existing Buildings

About one-third of the heated air in typical U.S. homes and About one-third of the heated air in typical U.S. homes and buildings escapes through closed windows and holes and buildings escapes through closed windows and holes and cracks.cracks.


USING RENEWABLE SOLAR ENERGY TO USING RENEWABLE SOLAR ENERGY TO PROVIDE HEAT AND ELECTRICITYPROVIDE HEAT AND ELECTRICITY

A variety of renewable-energy resources are available but A variety of renewable-energy resources are available but their use has been hindered by a lack of government support their use has been hindered by a lack of government support compared to nonrenewable fossil fuels and nuclear power.compared to nonrenewable fossil fuels and nuclear power.

Direct solar Direct solar Moving water Moving water Wind Wind GeothermalGeothermal

Solar CellsSolar Cells

It is possible to get electricity from solar cells that convert It is possible to get electricity from solar cells that convert sunlight into electricity.sunlight into electricity.

Can be attached like shingles on a roof.Can be attached like shingles on a roof. Can be applied to window glass as a coating.Can be applied to window glass as a coating. Can be mounted on racks almost anywhere.Can be mounted on racks almost anywhere.

Heating Buildings and Water with Solar EnergyHeating Buildings and Water with Solar Energy

We can heat buildings by orienting them toward the sun or We can heat buildings by orienting them toward the sun or by pumping a liquid such as water through rooftop collectors.by pumping a liquid such as water through rooftop collectors.


Passive Solar HeatingPassive Solar Heating

Passive solar heating system Passive solar heating system absorbs and stores heat from absorbs and stores heat from the sun directly within a the sun directly within a structure without the need for structure without the need for pumps to distribute the heat.pumps to distribute the heat.


Fig. 17-13, p. 396

Direct Gain

Summer sunHot air

Warm air

Super-insulated windows

Winter sun

Cool air

Earth tubes

Ceiling and north wall heavily insulated

Fig. 17-13, p. 396

Greenhouse, Sunspace, or Attached Solarium

Summer cooling vent

Warm air

Insulated windows

Cool air

Fig. 17-13, p. 396

Earth Sheltered

Reinforced concrete, carefully waterproofed walls and roof

Triple-paned or superwindowsEarth

Flagstone floor for heat storage

Fig. 17-14, p. 396

Trade-Offs

Passive or Active Solar Heating

Advantages Disadvantages

Energy is free Need access to sun 60% of time

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

Sun blocked by other structures

Need heat storage system

Quick installation

No CO2 emissions

Very low air and water pollution High cost (active)

Very low land disturbance (built into roof or window)

Active system needs maintenance and repair

Moderate cost (passive)

Active collectors unattractive

Cooling Houses NaturallyCooling Houses Naturally

We can cool houses by:We can cool houses by: Superinsulating them.Superinsulating them. Taking advantages of breezes. Taking advantages of breezes. Shading them.Shading them. Having light colored or green roofs.Having light colored or green roofs. Using geothermal cooling.Using geothermal cooling.

Using Solar Energy to Generate High-Using Solar Energy to Generate High-Temperature Heat and ElectricityTemperature Heat and Electricity

Large arrays of solar Large arrays of solar collectors in sunny collectors in sunny deserts can produce deserts can produce high-temperature heat to high-temperature heat to spin turbines for spin turbines for electricity, but costs are electricity, but costs are high.high.


Producing Electricity with Solar CellsProducing Electricity with Solar Cells

Solar cells convert Solar cells convert sunlight to electricity.sunlight to electricity.

Their costs are high, but Their costs are high, but expected to fall.expected to fall.



Photovoltaic (PV) cells can provide electricity for a house of Photovoltaic (PV) cells can provide electricity for a house of building using solar-cell roof shingles.building using solar-cell roof shingles.



Solar cells can be used in Solar cells can be used in rural villages with ample rural villages with ample sunlight who are not sunlight who are not connected to an electrical connected to an electrical grid.grid.


Fig. 17-19, p. 399

Trade-OffsSolar Cells


Fairly high net energy Need access to sun

Work on cloudy daysLow efficiency

Quick installation

Need electricity storage system or backup

Easily expanded or moved

No CO2 emissions

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

Low environmental impact

Last 20–40 years

Low land use (if on roof or built into walls or windows)

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

Reduces dependence on fossil fuels DC current must be converted

to AC

PRODUCING ELECTRICITY FROM THE PRODUCING ELECTRICITY FROM THE WATER CYCLEWATER CYCLE

Water flowing in rivers and streams can be trapped in Water flowing in rivers and streams can be trapped in reservoirs behind dams and released as needed to spin reservoirs behind dams and released as needed to spin turbines and produce electricity.turbines and produce electricity.

There is little room for expansion in the U.S. – Dams and There is little room for expansion in the U.S. – Dams and reservoirs have been created on 98% of suitable rivers.reservoirs have been created on 98% of suitable rivers.

Fig. 17-20, p. 400

Trade-OffsLarge-Scale Hydropower


Moderate to high net energy High construction costs

Large untapped potential

High environmental impact from flooding land to form a reservoir

High efficiency (80%)

High CO2 emissions from biomass decay in shallow tropical reservoirs

Low-cost electricity

Long life span

No CO2 emissions during operation in temperate areas

Floods natural areas behind dam

May provide flood control below dam

Converts land habitat to lake habitat

Danger of collapse

Provides water for year-round irrigation of cropland

Uproots peopleDecreases fish harvest below dam

Reservoir is useful for fishing and recreation

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

PRODUCING ELECTRICITY FROM THE PRODUCING ELECTRICITY FROM THE WATER CYCLEWATER CYCLE

Ocean tides and waves and temperature differences Ocean tides and waves and temperature differences between surface and bottom waters in tropical waters are between surface and bottom waters in tropical waters are not expected to provide much of the world’s electrical needs.not expected to provide much of the world’s electrical needs.

Only two large tidal energy dams are currently operating: Only two large tidal energy dams are currently operating: one in La Rance, France and Nova Scotia’s bay of Fundy one in La Rance, France and Nova Scotia’s bay of Fundy where the tidal amplitude can be as high as 16 meters (63 where the tidal amplitude can be as high as 16 meters (63 feet).feet).

PRODUCING ELECTRICITY FROM WINDPRODUCING ELECTRICITY FROM WIND Wind power is the world’s most “promising” energy Wind power is the world’s most “promising” energy

resource resource AbundantAbundant InexhaustibleInexhaustible widely distributedwidely distributed ““Cheap”Cheap” CleanClean emits no greenhouse gasesemits no greenhouse gases

Much of the world’s potential for wind power Much of the world’s potential for wind power remains untapped.remains untapped.

Capturing only 20% of the wind energy at the Capturing only 20% of the wind energy at the world’s best energy sites could meet all the world’s world’s best energy sites could meet all the world’s energy demands.energy demands.

PRODUCING ELECTRICITY PRODUCING ELECTRICITY FROM WINDFROM WIND

Wind turbines can be used individually to produce Wind turbines can be used individually to produce electricity. They are also used interconnected in arrays electricity. They are also used interconnected in arrays on wind farms.on wind farms.


WIND POWER VIDEOSWIND POWER VIDEOSWind Power Wind Power

All AlongAll Along

Vertical Axis Windmill

(New Mexico)

Wind PowerWind PowerIssuesIssues

Types of Wind Types of Wind TurbinesTurbines

Windmills in TX

Windmills in CA

VAWT(California)

Helix Wind Turbine

Wind Farm Noise

Wind Turbine Collapse

(Denmark)

Birds & Wind

Turbines

PRODUCING ELECTRICITY FROM WINDPRODUCING ELECTRICITY FROM WIND

The United States once led the wind power industry, but The United States once led the wind power industry, but Europe now leads this rapidly growing business.Europe now leads this rapidly growing business.

The U.S. government lacked subsidies, tax breaks and other The U.S. government lacked subsidies, tax breaks and other financial incentives.financial incentives.

European companies manufacture 80% of the wind turbines European companies manufacture 80% of the wind turbines sold in the global marketsold in the global market

The success has been aided by strong government subsidies.The success has been aided by strong government subsidies.

Fig. 17-22, p. 403

Trade-Offs

Wind Power


Moderate to high net energy Steady winds needed

Backup systems needed when winds are low

High efficiency

Moderate capital cost

Low electricity cost (and falling)High land use for wind farm

Very low environmental impact

No CO2 emissions Visual pollution

Quick constructionNoise when located near populated areasEasily expanded

Can be located at sea

Land below turbines can be used to grow crops or graze livestock

May interfere in flights of migratory birds and kill birds of prey

PRODUCING ENERGY PRODUCING ENERGY FROM BIOMASSFROM BIOMASS

Plant materials and animal Plant materials and animal wastes can be burned to wastes can be burned to provide heat or electricity or provide heat or electricity or converted into gaseous or converted into gaseous or liquid biofuels.liquid biofuels.


PRODUCING ENERGY FROM BIOMASSPRODUCING ENERGY FROM BIOMASS

The scarcity of fuelwood The scarcity of fuelwood causes people to make causes people to make fuel briquettes from cow fuel briquettes from cow dung in India. This dung in India. This deprives soil of plant deprives soil of plant nutrients.nutrients.


Fig. 17-25, p. 405

Trade-OffsSolid Biomass


Large potential supply in some areas

Nonrenewable if harvested unsustainably

Moderate costs Moderate to high environmental impact

No net CO2 increase if harvested and burned sustainably

CO2 emissions if harvested and burned unsustainably

Low photosynthetic efficiencyPlantation can be located on semiarid land not needed for crops

Soil erosion, water pollution, and loss of wildlife habitat

Plantation can help restore degraded lands

Plantations could compete with cropland

Often burned in inefficient and polluting open fires and stoves

Can make use of agricultural, timber, and urban wastes

GEOTHERMAL ENERGYGEOTHERMAL ENERGY

Geothermal energy consists of heat stored in soil, Geothermal energy consists of heat stored in soil, underground rocks, and fluids in the earth’s mantle.underground rocks, and fluids in the earth’s mantle.

We can use geothermal energy stored in the earth’s mantle We can use geothermal energy stored in the earth’s mantle to heat and cool buildings and to produce electricity.to heat and cool buildings and to produce electricity.

A geothermal heat pump (GHP) can heat and cool a house by A geothermal heat pump (GHP) can heat and cool a house by exploiting the difference between the earth’s surface and exploiting the difference between the earth’s surface and underground temperatures.underground temperatures.

Geothermal Heat PumpGeothermal Heat Pump

The house is heated in The house is heated in the winter by transferring the winter by transferring heat from the ground into heat from the ground into the house.the house.

The process is reversed The process is reversed in the summer to cool in the summer to cool the house.the house.


GEOTHERMAL ENERGYGEOTHERMAL ENERGY

Deeper more concentrated hydrothermal reservoirs can be Deeper more concentrated hydrothermal reservoirs can be used to heat homes and buildings and spin turbines:used to heat homes and buildings and spin turbines:

Dry steamDry steam: water vapor with no water droplets.: water vapor with no water droplets. Wet steamWet steam: a mixture of steam and water droplets.: a mixture of steam and water droplets. Hot waterHot water: is trapped in fractured or porous rock.: is trapped in fractured or porous rock.

Fig. 17-32, p. 410

Trade-Offs

Geothermal Energy


Very high efficiency

Scarcity of suitable sites

Moderate net energy at accessible sites

Depleted if used too rapidly

Lower CO2 emissions than fossil fuels Moderate to high

local air pollutionLow cost at favorable sites

CO2 emissions

Noise and odor (H2S)Low land use

Low land disturbance Cost too high

except at the most concentrated and accessible sources

Moderate environmental impact

A SUSTAINABLE ENERGY STRATEGYA SUSTAINABLE ENERGY STRATEGY

Shifts in the use of commercial energy resources in the U.S. Shifts in the use of commercial energy resources in the U.S. since 1800, with projected changes to 2100.since 1800, with projected changes to 2100.


A SUSTAINABLE ENERGY STRATEGYA SUSTAINABLE ENERGY STRATEGY

A more sustainable energy policy would improve energy A more sustainable energy policy would improve energy efficiency, rely more on renewable energy, and reduce the efficiency, rely more on renewable energy, and reduce the harmful effects of using fossil fuels and nuclear energy.harmful effects of using fossil fuels and nuclear energy.

There will be a gradual shift from large, centralized macropower There will be a gradual shift from large, centralized macropower systems to smaller, decentralized micropower systems.systems to smaller, decentralized micropower systems.

Fig. 17-35, p. 414

Small solar-cell power plantsBioenergy power

plantsWind farm

Rooftop solar cell arrays

Fuel cellsSolar-cell

rooftop systems

Transmission and distribution system

CommercialSmall wind

turbineResidential

Industrial Microturbines

Fig. 17-36, p. 415

More Renewable Energy

Increase renewable energy to 20% by 2020 and 50% by 2050

Provide large subsidies and tax credits for renewable energy

Use full-cost accounting and life-cycle cost for comparing all energy alternatives

Encourage government purchase of renewable energy devices

Greatly increase renewable energy R&D

Reduce Pollution and Health Risk

Cut coal use 50% by 2020

Phase out coal subsidies

Levy taxes on coal and oil use

Phase out nuclear power or put it on hold until 2020

Phase out nuclear power subsidies

Improve Energy Efficiency

Increase fuel-efficiency standards for vehicles, buildings, and appliances

Mandate govern-ment purchases of efficient vehicles and other devices

Provide large tax credits for buying efficient cars, houses, and appliances

Offer large tax credits for invest-ments in energy efficiency

Reward utilities for reducing demand for electricity Encourage indepen-dent power producers Greatly increase energyefficiency research and development

Economics, Politics, Education, and Energy Economics, Politics, Education, and Energy ResourcesResources

Governments can use a combination of subsidies, tax Governments can use a combination of subsidies, tax breaks, rebates, taxes and public education to promote or breaks, rebates, taxes and public education to promote or discourage use of various energy alternatives:discourage use of various energy alternatives:

Can keep prices artificially low to encourage selected energy Can keep prices artificially low to encourage selected energy resources.resources.

Can keep prices artificially high to discourage other energy Can keep prices artificially high to discourage other energy resources.resources.

Emphasize consumer education.Emphasize consumer education.

Fig. 17-37, p. 416

What Can You Do?Energy Use and Waste

• Get an energy audit at your house or office.

• Drive a car that gets at least 15 kilometers per liter (35 miles per gallon) and join a carpool.

• Use mass transit, walking, and bicycling.

• Superinsulate your house and plug all air leaks.

• Turn off lights, TV sets, computers, and other electronic equipment when they are not in use.

• Wash laundry in warm or cold water.

• Use passive solar heating.

• For cooling, open windows and use ceiling fans or whole-house attic or window fans.

• Turn thermostats down in winter, up in summer.

• Buy the most energy-efficient homes, lights, cars, and appliances available.

• Turn down the thermostat on water heaters to 43–49°C (110–120°F) and insulate hot water heaters and pipes.

Chapter 17

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