Chapter 16 Energy Efficiency and
Renewable Energy
• Improving energy efficiency can save the world at least a third of the energy it uses, and it can save the United States up to 43% of the energy it uses.
We Waste Huge Amounts of Energy
• Advantages of reducing energy waste: – Quick and clean – Usually the cheapest to provide more energy – Reduce pollution and degradation – Slow global warming – Increase economic and national security
• Four widely used devices that waste energy 1. Incandescent light bulb 2. Motor vehicle with internal combustion engine 3. Nuclear power plant 4. Coal-fired power plant
Flow of Commercial Energy through the U.S. Economy
Fig. 16-2, p. 399
Fig. 16-3, p. 399
Solutions
Reducing Energy Waste
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
How Can We Cut Energy Waste?
• We have a variety of technologies for sharply increasing the energy efficiency of industrial operations, motor vehicles, and buildings.
We Can Save Energy and Money in Industry and Utilities
• Cogeneration or combined heat and power (CHP) – Two forms of energy from same fuel source
• Replace energy-wasting electric motors
• Utility companies switching from promote use of energy to promoting energy efficiency
• Switch from low-efficiency incandescent lighting to higher-efficiency fluorescent and LED lighting
LEDs
Fig. 16-4, p. 401
Saving Energy and Money with a Smarter Electrical Grid
• Smart grid – Ultra-high-voltage – Super-efficient transmission lines – Digitally controlled – Responds to local changes in demand and supply – Two-way flow of energy and information – Smart meters show consumers how much energy
each appliance uses
• U.S cost -- $200-$800 billion; save $100 billion/year
Proposed U.S. Smart Grid
Figure 20, Supplement 8
We Can Save Energy and Money in Transportation
• Corporate average fuel standards (CAFE) standards
– Fuel economy standards lower in the U.S. countries
– Fuel-efficient cars are on the market
• Hidden prices in gasoline: $12/gallon
– Car manufacturers and oil companies lobby to prevent laws to raise fuel taxes
Average Fuel Economy of New Vehicles Sold in the U.S. and Other Countries
Fig. 16-5, p. 402
More Energy-Efficient Vehicles Are on the Way
• Superefficient and ultralight cars
• Gasoline-electric hybrid car
• Plug-in hybrid electric vehicle
• Energy-efficient diesel car
• Electric vehicle with a fuel cell
Solutions: A Hybrid-Gasoline-Electric Engine Car and a Plug-in Hybrid Car
Fig. 16-6, p. 403
The Search for Better Batteries
• Current obstacles – Storage capacity – Overheating – Flammability – Cost
• In the future – Lithium-ion battery – Viral battery – Ultracapacitor
We Can Design Buildings That Save Energy and Money
• Green architecture
• Living or green roofs
• Superinsulation
• U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED)
A Green Roof in Chicago
Fig. 16-8, p. 405
We Can Save Money and Energy in Existing Buildings
• Conduct an energy survey
• Insulate and plug leaks • Use energy-efficient windows
• Stop other heating and cooling losses
• Heat houses more efficiently • Heat water more efficiently
• Use energy-efficient appliances
• Use energy-efficient lighting
A Thermogram Shows Heat Loss
Fig. 16-9, p. 406
Individuals Matter: Ways in Which You Can Save Money Where You Live
Fig. 16-10, p. 407
Why Are We Still Wasting So Much Energy?
• Energy remains artificially cheap – Government subsidies
– Tax breaks
– Prices don’t include true cost
• Few large and long-lasting incentives – Tax breaks
– Rebates
– Low-interest loans
We Can Use Renewable Energy to Provide Heat and Electricity
• Renewable energy – Solar energy: direct or indirect
– Geothermal energy
• Benefits of shifting toward renewable energy
• Renewable energy cheaper if we eliminate – Inequitable subsidies
– Inaccurate prices
– Artificially low pricing of nonrenewable energy
What Are the Advantages and Disadvantages of Solar Energy?
• Passive and active solar heating systems can heat water and buildings effectively, and the costs of using direct sunlight to produce high-temperature heat and electricity are coming down.
Solutions: Passive and Active Solar Heating for a Home
Fig. 16-11, p. 409
Passive Solar Home in Colorado
Fig. 16-12, p. 410
Rooftop Solar Hot Water on Apartment Buildings in Kunming, China
Fig. 16-13, p. 410
Fig. 16-14, p. 411
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
World Availability of Direct Solar Energy
Figure 22, Supplement 8
U.S. Availability of Direct Solar Energy
Figure 23, Supplement 8
We Can Cool Buildings Naturally
• 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 Use Sunlight to Produce High-Temperature Heat and Electricity
• Solar thermal systems
– Central receiver system
– Collect sunlight to boil water, generate electricity
– 1% of world deserts could supply all the world’s electricity
– Require large amounts of water – could limit
• Wet cooling
• Dry cooling
• Low net energy yields
Solar Thermal Power in California Desert
Fig. 16-15, p. 411
Fig. 16-16, p. 412
Solar Energy for High-Temperature Heat and Electricity
Moderate environmental impact
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
Lower costs with natural gas turbine backup
High water use for cooling
Trade-Offs
Solutions: Solar Cooker in India
Fig. 16-17, p. 412
We Can Use Sunlight to Produce Electricity
• Photovoltaic (PV) cells (solar cells)
– Convert solar energy to electric energy
• Design of solar cells
– Sunlight hits cells and releases electrons into wires
Solutions: Solar Cells on Rooftop and for Many Purposes
Fig. 16-18, p. 413
Solar Cell Array in Niger, West Africa
Fig. 16-19, p. 413
Solar-Cell Power Plant in Arizona
Fig. 16-20, p. 414
We Can Use Sunlight to Produce Electricity
• 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
• Will the cost drop with – Mass production
– New designs
– Government subsidies and tax breaks
Global Production of Solar Electricity
Figure 11, Supplement 9
Fig. 16-21, p. 414
Solar Cells
Advantages Disadvantages
Moderate 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
High costs for older systems but decreasing rapidly
Solar-cell power plants could disrupt desert ecosystems
Competitive cost for newer cells
Trade-Offs
16-4 What Are the Advantages and Disadvantages of Using Hydropower
• Concept 16-4 We can use water flowing over dams, tidal flows, and ocean waves to generate electricity, but environmental concerns and limited availability of suitable sites may limit the use of these energy resources.
We Can Produce Electricity from Falling and Flowing Water
• Hydropower
– Uses kinetic energy of moving water
– Indirect form of solar energy
– World’s leading renewable energy source used to produce electricity
Tradeoffs: Dams and Reservoirs
Fig. 13-13, p. 328
Fig. 13-13b, p. 328
Powerlines
Reservoir
Dam
Intake Powerhouse
Turbine
Fig. 16-22, p. 415
Large-Scale Hydropower
Advantages Disadvantages
Moderate to high net energy
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
Tides and Waves Can Be Used to Produce Electricity
• Produce electricity from flowing water – Ocean tides and waves
• So far, power systems are limited
• Disadvantages – Few suitable sites
– High costs
– Equipment damaged by storms and corrosion
What Are the Advantages and Disadvantages of Using Wind Power?
• When we include the environmental costs of using energy resources in the market prices of energy, wind power is the least expensive and least polluting way to produce electricity.
Using Wind to Produce Electricity Is an Important Step toward Sustainability
• Wind: indirect form of solar energy – Captured by turbines
– Converted into electrical energy
• Second fastest-growing source of energy
• What is the global potential for wind energy?
• Wind farms: on land and offshore
World Electricity from Wind Energy
Figure 12, Supplement 9
Solutions: Wind Turbine and Wind Farms on Land and Offshore
Fig. 16-23, p. 417
Fig. 16-23a, p. 417
Gearbox
Electrical generator
Power cable
Wind turbine
Fig. 16-23b, p. 417 Wind farm
Fig. 16-23c, p. 417 Wind farm (offshore)
Wind Turbine
Fig. 16-24, p. 417
Using Wind to Produce Electricity Is an Important Step toward Sustainability
• Countries with the highest total installed wind power capacity
– Germany
– United States
– Spain
– India
– Denmark
• Installation is increasing in several other countries
Using Wind to Produce Electricity Is an Important Step toward Sustainability (3)
• Advantages of wind energy
• Drawbacks – Windy areas may be sparsely populated – need to
develop grid system to transfer electricity
– Winds die down; need back-up energy
– Storage of wind energy
– Kills migratory birds
– “Not in my backyard”
Fig. 16-25, p. 418
Trade-Offs
Wind Power
Advantages Disadvantages
Moderate to 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
The Astounding Potential of Wind Power in the United States
• “Saudi Arabia of wind power” – North Dakota
– South Dakota
– Kansas
– Texas
• How much electricity is possible with wind farms in those states? – Could create up to 500,000 jobs
United States Wind Power Potential
Figure 24, Supplement 8
Advantages and Disadvantages of Using Biomass as an Energy Source
• 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, and creating biomass plantations can degrade soil biodiversity.
• We can use liquid biofuels derived from biomass in place of gasoline and diesel fuels, but creating biofuel plantations can degrade soil and biodiversity and increase food prices and greenhouse gas emissions.
We Can Get Energy by Burning Solid Biomass
• 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
Fig. 16-26, p. 420
Solid Biomass
Advantages Disadvantages
Widely available in some areas
Moderate to high environmental impact
Increases CO2 emissions if harvested and burned unsustainably
No net CO2 increase if harvested, burned, and replanted sustainably
Moderate costs
Plantations can help restore degraded lands
Trade-Offs
Often burned in inefficient and polluting open fires and stoves
Clear cutting can cause soil erosion, water pollution, and loss of wildlife habitat
We Can Convert Plants and Plant Wastes to Liquid Biofuels
• Liquid biofuels – Biodiesel – Ethanol
• Major advantages over gasoline and diesel fuel produced from oil 1. Biofuel crops can be grown almost anywhere 2. No net increase in CO2 emissions if managed properly 3. Available now
• Biggest producers of biofuel – The United States – Brazil – The European Union – China
Is Biodiesel the Answer?
• Biodiesel production from vegetable oil from various sources
• 95% produced by the European Union
• Subsidies promote rapid growth in United States
Fig. 16-27, p. 421
Biodiesel
Advantages Disadvantages
Reduced CO and CO2 emissions
Increased NOx emissions and smog
High net energy yield for oil palm crops
Low net energy yield for soybean crops
Competes with food for cropland
Reduced hydrocarbon emissions
Clearing natural areas for plantations reduces biodiversity and increases atmospheric CO2 levels Better mileage (up
to 40%)
Trade-Offs
Case Study: Is Ethanol the Answer?
• Ethanol from plants and plant wastes • Brazil produces ethanol from sugarcane • United States: ethanol from corn
– Low net energy yield – Reduce the need for oil imports? – Harm food supply – Air pollution and climate change?
• Cellulosic ethanol: alternative to corn ethanol – Switchgrass – Crop residues – Municipal wastes
World Ethanol Production
Figure 13, Supplement 9
Bagasse is Sugarcane Residue
Fig. 16-28, p. 421
Natural Capital: Rapidly Growing Switchgrass
Fig. 16-29, p. 423
Fig. 16-30, p. 423
Ethanol Fuel
Advantages Disadvantages
Some reduction in CO2 emissions (sugarcane bagasse)
Low net energy yield (corn) and higher cost
Higher CO2 emissions (corn)
High net energy yield (bagasse and switchgrass)
Corn ethanol competes with food crops and may raise food prices
Potentially renewable
Trade-Offs
Getting Gasoline and Diesel Fuel from Algae and Bacteria
• Algae remove CO2 and convert it to oil – Not compete for cropland =
not affect food prices – Wastewater/sewage
treatment plants – Could transfer CO2 from
power plants
• Algae challenges 1. Need to lower costs 2. Open ponds vs. bioreactors 3. Affordable ways of extracting
oil 4. Scaling to large production
• Bacteria: synthetic biology – Convert sugarcane juice to
biodiesel – Need large regions growing
sugarcane
• Producing fuels from algae and bacteria can be done almost anywhere
What Are the Advantages and Disadvantages of Geothermal Energy?
• Geothermal energy has great potential for supplying many areas with heat and electricity, and it has a generally low environmental impact, but sites where it can be used economically are limited.
Getting Energy from the Earth’s Internal Heat
• Geothermal energy: heat 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
Natural Capital: A Geothermal Heat Pump System Can Heat or Cool a House
Fig. 16-31, p. 425
Fig. 16-31a, p. 425
Basement pump
Geothermal heating
Fig. 16-31b, p. 425
Geothermal cooling
Getting Energy from the Earth’s Internal Heat
• Hydrothermal reservoirs – U.S. is the world’s largest producer
• Hot, dry rock
• Geothermal energy problems – High cost of tapping hydrothermal reservoirs – Dry- or wet-steam geothermal reservoirs could be
depleted – Could create earthquakes
Geothermal Sites in the United States
Figure 26, Supplement 8
Geothermal Sites Worldwide
Figure 25, Supplement 8
Geothermal Power Plant in Iceland
Fig. 16-32, p. 425
Fig. 16-33, p. 426
Geothermal Energy
Advantages Disadvantages
Moderate net energy and high efficiency at accessible sites
High cost and low efficiency 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
Using Hydrogen as an Energy Source
• Hydrogen fuel holds great promise for powering cars and generating electricity, but for it to be environmentally beneficial, we would have to produce it without the use of fossil fuels.
Will Hydrogen Save Us?
• Hydrogen as a fuel – Eliminate most of the air pollution problems
– Reduce threats of global warming
• 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
A Fuel Cell Separates the Hydrogen Atoms’ Electrons from Their Protons
Fig. 16-34, p. 427
Fig. 16-34a, p. 427
Electrons
Hydrogen gas (H2) in Polymer electrolyte
membrane
Anode
Cathode
Protons
Water vapor (H2O) out Air (O2) in
Fig. 16-35, p. 428
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 direct CO2 emissions if produced from water
Good substitute for oil
High costs require subsidies
High efficiency (45–65%) in fuel cells
Needs H2 storage and distribution system
Choosing Energy Paths
• General conclusions – Gradual shift to smaller, decentralized micropower
systems
– Transition to a diverse mix of locally available renewable energy resources
– Improved energy efficiency
– Fossil fuels will still be used in large amounts • Natural gas is the best choice
Fig. 16-37, p. 431
Solutions
Making the Transition to a More Sustainable Energy Future
Improve Energy Efficiency More Renewable Energy Increase fuel-efficiency standards for vehicles, buildings, and appliances
Greatly increase use of renewable energy
Provide large subsidies and tax credits for use of renewable energy
Provide large tax credits or feebates for buying efficient cars, houses, and appliances
Greatly increase renewable energy research and development
Reduce Pollution and Health Risk
Reward utilities for reducing demand for electricity
Phase out coal subsidies and tax breaks
Levy taxes on coal and oil use Greatly increase energy efficiency research and development Phase out nuclear power subsidies, tax breaks,
and loan guarantees
What Can you Do? Shifting to More Sustainable Energy Use
Fig. 16-38, p. 432
Three Big Ideas
1. We should evaluate energy resources on the basis of their potential supplies, how much net useful energy they provide, and the environmental impacts of using them.
2. Using a mix of renewable energy sources—especially solar, wind, flowing water, sustainable biofuels, and geothermal energy—can drastically reduce pollution, greenhouse gas emissions, and biodiversity losses.
Three Big Ideas
3. Making the transition to a more sustainable energy future will require 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.
