1. Chapter 16 Energy Efficiency and Renewable Energy

2. 16-4 What Are the Advantages and Disadvantages of Using Hydropower
Concept 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.

3. 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
Advantages and disadvantages
Micro-hydropower generators

4. Tradeoffs: Dams and Reservoirs
Figure 13.13: Trade-offs.
Large dams and reservoirs have advantages (green) and disadvantages (orange) (Concept 13-3). The world’s 45,000 large dams (15 meters (49 feet) or higher) capture and store about 14% of the world’s surface runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used in 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. Question: Which single advantage and which single disadvantage do you think are the most important?
Fig , p. 328

5. Provides irrigation water above and below dam
Flooded land destroys forests or cropland and displaces people
Large losses of water through evaporation
Provides water for drinking
Deprives downstream cropland and estuaries of nutrient-rich silt
Reservoir useful for recreation and fishing
Risk of failure and devastating downstream flooding
Can produce cheap electricity (hydropower)
Figure 13.13: Trade-offs.
Large dams and reservoirs have advantages (green) and disadvantages (orange) (Concept 13-3). The world’s 45,000 large dams (15 meters (49 feet) or higher) capture and store about 14% of the world’s surface runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used in 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. Question: Which single advantage and which single disadvantage do you think are the most important?
Reduces down-stream flooding of cities and farms
Disrupts migration and spawning of some fish
Fig a, p. 328

6. Powerlines Reservoir Dam Powerhouse Intake Turbine
Figure 13.13: Trade-offs.
Large dams and reservoirs have advantages (green) and disadvantages (orange) (Concept 13-3). The world’s 45,000 large dams (15 meters (49 feet) or higher) capture and store about 14% of the world’s surface runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used in 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. Question: Which single advantage and which single disadvantage do you think are the most important?
Fig b, p. 328

7. Trade-Offs: Large-Scale Hydropower, Advantages and Disadvantages
Figure 16.22: Using large dams and reservoirs to produce electricity has advantages and disadvantages (Concept 16-4). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Fig , p. 415

8. Large-Scale Hydropower
Trade-Offs
Large-Scale Hydropower
Advantages
Disadvantages
Moderate to high net energy
Large land disturbance and displacement of people
Large untapped potential
High CH4 emissions from rapid biomass decay in shallow tropical reservoirs
Low-cost electricity
Figure 16.22: Using large dams and reservoirs to produce electricity has advantages and disadvantages (Concept 16-4). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Low emissions of CO2 and other air pollutants in temperate areas
Disrupts downstream aquatic ecosystems
Fig , p. 415

9. 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

10. 16-5 What Are the Advantages and Disadvantages of Using Wind Power?
Concept 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.

11. Using Wind to Produce Electricity Is an Important Step toward Sustainability (1)
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

12. World Electricity from Wind Energy
Figure 12, Supplement 9

13. Solutions: Wind Turbine and Wind Farms on Land and Offshore
Figure 16.23: Solutions.
A single wind turbine (left) can produce electricity. Increasingly, they are interconnected in arrays of tens to hundreds of turbines. These wind farms or wind parks can be located on land (middle) or offshore (right). The land beneath these turbines can still be used to grow crops or to raise cattle. Questions: Would you object to having a wind farm located near where you live? Why or why not?
Fig , p. 417

14. Gearbox Electrical generator Power cable Wind turbine
Figure 16.23: Solutions.
A single wind turbine (left) can produce electricity. Increasingly, they are interconnected in arrays of tens to hundreds of turbines. These wind farms or wind parks can be located on land (middle) or offshore (right). The land beneath these turbines can still be used to grow crops or to raise cattle. Questions: Would you object to having a wind farm located near where you live? Why or why not?
Wind turbine
Fig a, p. 417

15. Wind farm Figure 16.23: Solutions.
A single wind turbine (left) can produce electricity. Increasingly, they are interconnected in arrays of tens to hundreds of turbines. These wind farms or wind parks can be located on land (middle) or offshore (right). The land beneath these turbines can still be used to grow crops or to raise cattle. Questions: Would you object to having a wind farm located near where you live? Why or why not?
Wind farm
Fig b, p. 417

16. Wind farm (offshore) Figure 16.23: Solutions.
A single wind turbine (left) can produce electricity. Increasingly, they are interconnected in arrays of tens to hundreds of turbines. These wind farms or wind parks can be located on land (middle) or offshore (right). The land beneath these turbines can still be used to grow crops or to raise cattle. Questions: Would you object to having a wind farm located near where you live? Why or why not?
Wind farm (offshore)
Fig c, p. 417

17. Wind Turbine
Figure 16.24: Maintenance workers get a long-distance view from atop a wind turbine, somewhere in North America, built by Suzlon Energy, a company established in India in 1995.
Fig , p. 417

18. Using Wind to Produce Electricity Is an Important Step toward Sustainability (2)
Countries with the highest total installed wind power capacity
Germany
United States
Spain
India
Denmark
Installation is increasing in several other countries

19. 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”

20. Trade-Offs: Wind Power
Figure 16.25: Using wind to produce electricity has advantages and disadvantages (Concept 16-5). With sufficient and consistent government incentives, wind power could supply more than 10% of the world’s electricity and 20% of the electricity used in the United States by Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Fig , p. 418

21. Moderate to high net energy yield
Trade-Offs
Wind Power
Advantages
Disadvantages
Moderate to high net energy yield
Needs backup or storage system when winds die down
Widely available
Visual pollution for some people
Low electricity cost
Figure 16.25: Using wind to produce electricity has advantages and disadvantages (Concept 16-5). With sufficient and consistent government incentives, wind power could supply more than 10% of the world’s electricity and 20% of the electricity used in the United States by Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Little or no direct emissions of CO2 and other air pollutants
Low-level noise bothers some people
Can kill birds if not properly designed and located
Easy to build and expand
Fig , p. 418

22. Case Study: 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

23. United States Wind Power Potential
Figure 24, Supplement 8

24. 16-6 Advantages and Disadvantages of Using Biomass as an Energy Source
Concept 16-6A 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.
Concept 16-6B 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.

25. We Can Get Energy by Burning Solid 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
Advantages and disadvantages

26. Trade-Offs: Solid Biomass
Figure 16.26: Burning solid biomass as a fuel has advantages and disadvantages (Concept 16-6a). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Fig , p. 420

27. Widely available in some areas Moderate to high environmental impact
Trade-Offs
Solid Biomass
Advantages
Disadvantages
Widely available in some areas
Moderate to high environmental impact
Moderate costs
Increases CO2 emissions if harvested and burned unsustainably
No net CO2 increase if harvested, burned, and replanted sustainably
Clear cutting can cause soil erosion, water pollution, and loss of wildlife habitat
Figure 16.26: Burning solid biomass as a fuel has advantages and disadvantages (Concept 16-6a). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Often burned in inefficient and polluting open fires and stoves
Plantations can help restore degraded lands
Fig , p. 420

28. We Can Convert Plants and Plant Wastes to Liquid Biofuels (1)
Biodiesel
Ethanol
Biggest producers of biofuel
The United States
Brazil
The European Union
China

29. We Can Convert Plants and Plant Wastes to Liquid Biofuels (2)
Major advantages over gasoline and diesel fuel produced from oil
Biofuel crops can be grown almost anywhere
No net increase in CO2 emissions if managed properly
Available now

30. We Can Convert Plants and Plant Wastes to Liquid Biofuels (3)
Studies warn of problems:
Decrease biodiversity
Increase soil degrading, erosion, and nutrient leaching
Push farmers off their land
Raise food prices
Reduce water supplies, especially for corn and soy

31. Case Study: 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
Advantages and disadvantages

32. Trade-Offs: Biodiesel
Figure 16.27: Using biodiesel as a vehicle fuel has advantages and disadvantages compared to gasoline. Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of biodiesel fuel outweigh its disadvantages?
Fig , p. 421

33. Reduced CO and CO2 emissions Increased NOx emissions and smog
Trade-Offs
Biodiesel
Advantages
Disadvantages
Reduced CO and CO2 emissions
Increased NOx emissions and smog
Low net energy yield for soybean crops
High net energy yield for oil palm crops
Competes with food for cropland
Figure 16.27: Using biodiesel as a vehicle fuel has advantages and disadvantages compared to gasoline. Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of biodiesel fuel outweigh its disadvantages?
Reduced hydrocarbon emissions
Clearing natural areas for plantations reduces biodiversity and increases atmospheric CO2 levels
Better mileage (up to 40%)
Fig , p. 421

34. Case Study: Is Ethanol the Answer? (1)
Ethanol from plants and plant wastes
Brazil produces ethanol from sugarcane
Environmental consequences
United States: ethanol from corn
Low net energy yield
Reduce the need for oil imports?
Harm food supply
Air pollution and climate change?

35. Case Study: Is Ethanol the Answer? (2)
Cellulosic ethanol: alternative to corn ethanol
Switchgrass
Crop residues
Municipal wastes
Advantages and disadvantages

36. World Ethanol Production
Figure 13, Supplement 9

37. Bagasse is Sugarcane Residue
Figure 16.28: Bagasse is a sugarcane residue that can be used to make ethanol.
Fig , p. 421

38. Natural Capital: Rapidly Growing Switchgrass
Figure 16.29: Natural capital.
The cellulose in this rapidly growing switchgrass can be converted into ethanol, but further research is needed to develop affordable production methods. This perennial plant can also help to slow projected climate change by removing carbon dioxide from the atmosphere and storing it as organic compounds in the soil.
Fig , p. 423

39. Trade-Offs: Ethanol Fuel
Figure 16.30: Using ethanol as a vehicle fuel has advantages and disadvantages compared to using gasoline (Concept 16-6b). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Fig , p. 423

40. Some reduction in CO2 emissions (sugarcane bagasse)
Trade-Offs
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)
Figure 16.30: Using ethanol as a vehicle fuel has advantages and disadvantages compared to using gasoline (Concept 16-6b). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Corn ethanol competes with food crops and may raise food prices
Potentially renewable
Fig , p. 423

41. Case Study: Getting Gasoline and Diesel Fuel from Algae and Bacteria (1)
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
Need to lower costs
Open ponds vs. bioreactors
Affordable ways of extracting oil
Scaling to large production

42. Case Study: Getting Gasoline and Diesel Fuel from Algae and Bacteria (2)
Bacteria: synthetic biology
Convert sugarcane juice to biodiesel
Need large regions growing sugarcane
Producing fuels from algae and bacteria can be done almost anywhere

43. 16-7 What Are the Advantages and Disadvantages of Geothermal Energy?
Concept 16-7 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.

44. Getting Energy from the Earth’s Internal Heat (1)
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

45. Natural Capital: A Geothermal Heat Pump System Can Heat or Cool a House
Figure 16.31: Natural capital.
A geothermal heat pump system can heat or cool a house almost anywhere. It heats the house in winter by transferring heat from the ground into the house (shown here). In the summer, it cools the house by transferring heat from the house to the ground.
Fig , p. 425

46. Basement pump Geothermal heating Figure 16.31: Natural capital.
A geothermal heat pump system can heat or cool a house almost anywhere. It heats the house in winter by transferring heat from the ground into the house (shown here). In the summer, it cools the house by transferring heat from the house to the ground.
Geothermal heating
Fig a, p. 425

47. Geothermal cooling Figure 16.31: Natural capital.
A geothermal heat pump system can heat or cool a house almost anywhere. It heats the house in winter by transferring heat from the ground into the house (shown here). In the summer, it cools the house by transferring heat from the house to the ground.
Geothermal cooling
Fig b, p. 425

48. Getting Energy from the Earth’s Internal Heat (2)
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

49. Geothermal Sites in the United States
Figure 26, Supplement 8

50. Geothermal Sites Worldwide
Figure 25, Supplement 8

51. Geothermal Power Plant in Iceland
Figure 16.32: This geothermal power plant in Iceland produces electricity and heats a nearby spa called the Blue Lagoon.
Fig , p. 425

52. Trade Offs: Geothermal Energy
Figure 16.33: Using geothermal energy for space heating and for producing electricity or high-temperature heat for industrial processes has advantages and disadvantages (Concept 16-7). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Fig , p. 426

53. Moderate net energy and high efficiency at accessible sites
Trade-Offs
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
Figure 16.33: Using geothermal energy for space heating and for producing electricity or high-temperature heat for industrial processes has advantages and disadvantages (Concept 16-7). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Low cost at favorable sites
Noise and some CO2 emissions
Fig , p. 426

54. 16-8 The Advantages and Disadvantages of Using Hydrogen as an Energy Source
Concept 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.

55. Will Hydrogen Save Us? (1)
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

56. Will Hydrogen Save Us? (2)
Net negative energy yield
Production and storage of H2
Hydrogen-powered vehicles: prototypes available
Can we produce hydrogen on demand?
Larger fuel cells – fuel-cell stacks

57. A Fuel Cell Separates the Hydrogen Atoms’ Electrons from Their Protons
Figure 16.34: A fuel cell takes in hydrogen gas and separates the hydrogen atoms’ electrons from their protons. The electrons flow through wires to provide electricity, while the protons pass through a membrane and combine with oxygen gas to form water vapor. Note that this process is the reverse of electrolysis, the process of passing electricity through water to produce hydrogen fuel. The photo (right) shows a fuel-cell concept car introduced by Honda Motor Company in 2009 at an international car show in Toronto, Canada. All of the exhaust from this car is water vapor.
Fig , p. 427

58. Polymer electrolyte membrane
Electrons
Hydrogen gas (H2) in
Anode
Polymer electrolyte membrane
Cathode
Figure 16.34: A fuel cell takes in hydrogen gas and separates the hydrogen atoms’ electrons from their protons. The electrons flow through wires to provide electricity, while the protons pass through a membrane and combine with oxygen gas to form water vapor. Note that this process is the reverse of electrolysis, the process of passing electricity through water to produce hydrogen fuel. The photo (right) shows a fuel-cell concept car introduced by Honda Motor Company in 2009 at an international car show in Toronto, Canada. All of the exhaust from this car is water vapor.
Protons
Water vapor (H2O) out
Air (O2) in
Fig a, p. 427

59. Trade-Offs: Hydrogen, Advantages and Disadvantages
Figure 16.35: Using hydrogen as a fuel for vehicles and for providing heat and electricity has advantages and disadvantages (Concept 16-8). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Fig , p. 428

60. Can be produced from plentiful water at some sites
Trade-Offs
Hydrogen
Advantages
Disadvantages
Can be produced from plentiful water at some sites
Negative net energy yield
Fuel cell
CO2 emissions
if produced from carbon-containing compounds
No direct CO2 emissions if produced from water
Figure 16.35: Using hydrogen as a fuel for vehicles and for providing heat and electricity has advantages and disadvantages (Concept 16-8). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Good substitute for oil
High costs require subsidies
High efficiency (45–65%) in fuel cells
Needs H2 storage and distribution system
Fig , p. 428

61. Science Focus: The Quest to Make Hydrogen Workable
Bacteria and algae can produce hydrogen through biodegrading organic material
Use electricity from renewable energy sources to produce hydrogen
Storage options for hydrogen

62. 16-9 How Can We Make the Transition to a More Sustainable Energy Future?
Concept We can make the transition to a more sustainable energy future if we greatly improve energy efficiency, use a mix of renewable energy resources, and include environmental costs in the market prices of all energy resources.

63. Choosing Energy Paths (1)
How will energy policies be created?
Hard energy path
Soft energy path

64. Choosing Energy Paths (2)
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

65. Solutions: Decentralized Power System
Figure 16.36: Solutions.
During the next few decades, we will probably shift from dependence on a centralized macropower system, based on a few hundred large coal-burning and nuclear power plants to a decentralized micropower system, in which electricity is produced by a large number of dispersed, small-scale, local power generating systems. Some of the smaller systems would produce power on site; others would feed the power they produce into a modern electrical distribution system. Over the next few decades, many energy and financial analysts expect a shift to this type of power system, largely based on locally available renewable energy resources. Question: Can you think of any disadvantages of a decentralized power system?
Fig , p. 430

66. Small solar-cell power plants Bioenergy power plants Wind farm
Fuel cells
Rooftop solar- cell arrays
Solar-cell rooftop systems
Smart electrical and distribution system
Figure 16.36: Solutions.
During the next few decades, we will probably shift from dependence on a centralized macropower system, based on a few hundred large coal-burning and nuclear power plants to a decentralized micropower system, in which electricity is produced by a large number of dispersed, small-scale, local power generating systems. Some of the smaller systems would produce power on site; others would feed the power they produce into a modern electrical distribution system. Over the next few decades, many energy and financial analysts expect a shift to this type of power system, largely based on locally available renewable energy resources. Question: Can you think of any disadvantages of a decentralized power system?
Commercial
Small wind turbine
Residential
Industrial
Microturbines
Fig , p. 430

67. Bioenergy power plants Wind farm
Small solar-cell
power plants
Bioenergy power plants
Wind farm
Solar-cell
rooftop
systems
Commercial
Fuel cells
Rooftop solar-
cell arrays
Residential
Small wind
turbine
Smart electrical
and distribution
system
Microturbines
Industrial
Stepped Art
Fig , p. 430

68. Solutions: Making the Transition to a More Sustainable Energy Future
Figure 16.37: Energy analysts have made a number of suggestions for helping us make the transition to a more sustainable energy future (Concept 16-9). Questions: Which five of these solutions do you think are the most important? Why?
Fig , p. 431

69. 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
Figure 16.37: Energy analysts have made a number of suggestions for helping us make the transition to a more sustainable energy future (Concept 16-9). Questions: Which five of these solutions do you think are the most important? Why?
Phase out nuclear power subsidies, tax breaks, and loan guarantees
Fig , p. 431

70. Economics, Politics, Education, and Sustainable Energy Resources
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

71. What Can you Do? Shifting to More Sustainable Energy Use
Figure 16.38: Individuals matter.
You can reduce your use and waste of energy. Questions: Which three of these items do you think are the most important? Why? Which things in this list do you already do or plan to do?
Fig , p. 432

72. Three Big Ideas
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.
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.

73. Three Big Ideas
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.