CHAPTER 16



Chapter 16

Energy Efficiency and Renewable Energy

Summary

1. The advantages of improving energy efficiency include benefits to the environment, people, and the economy through prolonged fossil fuel supplies, reduced oil imports, very high net energy yield, low cost reduction of pollution, and improved local economies.

2. The advantages of solar energy include reduction of air pollution, reduction of dependence on oil, and low land use. Disadvantages include production of photocells results in release of toxic chemicals, life of systems is short, need backup systems, and high cost.

3. The advantages of hydropower include high net energy yield, low cost electricity, long life span, no carbon dioxide emissions during operation, flood control below dam, water for irrigation, and reservoir development. Disadvantages include high construction cost, high environmental impact, high carbon dioxide emissions from biomass decay, flooding of natural areas, conversion of land habitats to lake habitats, danger of dam collapsing, people relocation, limits fish populations below dam, and decrease flow of silt.

4. The advantages of wind power include high net energy yield and efficiency, low cost and environmental impact, no carbon dioxide emissions, and quick construction. Disadvantages include need for winds and backup systems, high land use, visual and noise pollution, interfering with bird migrations.

5. The advantages of biomass include large potential supplies, moderate costs, no net carbon increase, and use of agricultural, timber, and urban wastes. Disadvantages include nonrenewable resource if not harvested sustainably, moderate to high environmental impact, low photosynthetic efficiency, soil erosion, water pollution, and loss of wildlife.

6. The advantages of geothermal energy include very high efficiency, low carbon dioxide emissions, low cost and land use, low land disturbance, and moderate environmental impact. Disadvantages include scarcity of suitable sites, potential depletion, moderate to high air pollution, noise and odor, and high cost.

7. The advantages of hydrogen gas include the fact that it can be produced from water, the low environmental impact, no carbon dioxide emission, competitive price, ease of storage, safety, and high efficiency. Disadvantages include energy needed to produce the fuel, negative energy yield, nonrenewable, high cost, and no fuel distribution system exists.

8. The advantages of using smaller, decentralized micropower sources include size, fast production and installation, high energy efficiency, low or no CO2 emissions, low air pollution, easy repair, reliable, increased national security, and easily financed.

9. We can improve energy efficiency by increasing fuel efficiency standards, large tax credits for purchasing energy efficient cars, houses, and appliances, encouraging independent energy production, and increasing research and development.

Key Questions and Concepts

16-1 Why Is Energy Efficiency an Important Energy Resource?

CORE CASE STUDY: Amory Lovins founded the Rocky Mountain Institute to consult on issues of energy and resource efficiency. The headquarters is located in an ultra-efficient building in Snowmass, Colorado that requires very little energy beyond what is derived from the sun. Lovins is a leader in the transition to a more energy efficient world.

A. Energy saved through efficiency reduces the need for the production of energy from another source. Energy efficiency is a measure of the useful energy produced compared to the energy that is converted to low-quality heat energy. About 84% of all commercial energy used in the U.S. is wasted. About 41% is wasted because of the degradation of energy quality imposed by the second law of thermodynamics. About 43% of the energy used in the United States is unnecessarily wasted by such things as motor vehicles, furnaces, and living and working in leaky, poorly designed buildings. Since the 1980s the U.S. has reduced the amount of energy used per person, but unnecessary energy waste still costs the U.S. about $570,000 per minute.

B. Much energy is wasted because of widespread reliance on incandescent light bulbs, internal combustion engines, nuclear power plants, and coal-fired power plants. .

16-2 How Can We Cut Energy Waste?

A. Industry accounts for 30% of global energy consumption.

B. Ways to save money and energy in industry include:

1. Cogeneration using a combined heat and power system.

2. Replacing energy wasting electric motors.

3. Recycling materials

4. Replacing low-efficiency incandescent lighting.

CASE STUDY: A smart grid is an energy efficient, high-voltage power grid with very efficient transmission lines that is responsive to changes in supply and demand. China is investing heavily in the technology and may become the leader. Energy experts place high priority o converting outdated grids to smart grids.

C. Transportation accounts for 28% of energy consumption in the United States.

1. Between 1973 and 1985, fuel efficiency increased because of government-mandated corporate average fuel economy standards. Since 1985 fuel economy has gone down.

2. Ways to save energy in transportation include offering incentives to purchase more efficient vehicles, shifting to electric rail systems, and encouraging bicycle use.

D. More energy efficient vehicles are now being produced and more are planned.

1. These include hybrids, plug-in hybrids, energy efficient diesels, fuel cell technology, and vehicles made of ultra-light and ultra-strong composite materials.

SCIENCE FOCUS: Lithium-ion batteries, commonly found in cell phones and laptops, are the most promising for electric vehicles. However, there are drawbacks, such as possible risk of fire, and cost. Modern research is bringing about promising alternatives.

E. We can save energy in buildings by getting heat from the sun, super insulating them, and using plant-covered green roofs. We can save energy in existing buildings by insulating them, plugging leaks, and using energy-efficient heating and cooling systems, appliances, and lighting.

F. There are three reasons renewable energy is not more widespread:

1. Since 1950, tax breaks, subsidies, and research funding have been much lower for renewable energy than for fossil fuels.

2. Subsidies and tax breaks are virtually guaranteed for fossil fuels and nuclear power, but must be renewed by Congress every few years for renewable energy.

3. The prices we pay for fossil fuels do not include their detrimental effects on the environment.

16-3 What Are the Advantages and Disadvantages of Using Solar Energy?

A. Solar has two forms for heating, passive and active. We can heat buildings by orienting them toward the sun (passive solar heating) or by pumping a liquid such as water through rooftop collectors (active solar heating). Tradeoffs are listed in figure 16-14.

B. Indirect solar energy (wind) and other natural services can be used to help cool buildings.

C. Large arrays of solar collectors in sunny deserts can produce high-temperature heat to spin turbines and produce electricity, but costs are high. Solar thermal systems can collect and transform radiant energy to high-temperature thermal energy (heat), which can be used directly or converted to electricity.

D. Solar can be used to provide electricity. Solar cells convert sunlight to electricity. The primary barrier to use is the high initial cost (though rapidly falling). Photovoltaic (PV) cells/solar cells convert solar energy directly into electrical energy. The solar cell is a transparent wafer that is energized by sunlight, which causes electrons in the semiconductor to flow, creating an electrical current.

16-4 What Are the Advantages and Disadvantages of Using Hydropower?

A. Water flowing in rivers and streams can be trapped in reservoirs behind dams and released as needed to spin turbines and produce electricity. Hydropower is an indirect form of renewable solar energy. Hydropower supplied 20% of the world’s electricity in 2007.

B. Pros and cons are given in Figure 16-22. Some expect that the use of large-scale dams will fall over the next several decades as reservoirs fill with silt and concerns over methane emissions grow. Small-scale projects eliminate most of the harmful environmental effects of large-scale projects.

C. Ocean tides and waves can also be used to generate electricity. However, the costs are high and there are few favorable locations for this technology.

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

A. Wind power is an indirect form of solar energy.

1. Wind farms are large groups of wind turbines clustered together.

2. Wind is the world’s second fastest growing source of energy, behind solar cells.

3. The world’s largest wind producers are china, USA, Germany, Spain and India.

4. Winds are stronger and steadier over water than land, making offshore wind farms a promising option.

5. Wind power is widely distributed, inexhaustible, carbon-free and pollution-free.

6. Some drawbacks include the remoteness of some of the best wind sites, winds can die down and necessitate a backup supply of power, and many people complain that wind farms are unsightly and noisy.

CASE STUDY: The DOE estimates that the Great Plains states could generate the electricity needs of the lower 48 states with wind power. Offshore wind farms could also supply all of the nation’s electricity. With expanded and sustained subsidies, wind farms could replace all of the coal-fired plants in the US.

16-6 What Are the Advantages and Disadvantages of Using Biomass as an Energy Source?

A. Plant materials and animal wastes can be burned to provide heat or electricity, or can be converted into gaseous or liquid biofuels. Most biomass is burned directly for heating and cooking and this comprises up to 95% of the energy used in the poorest developing countries. The general advantages and disadvantages of burning solid biomass are listed in figure 16-26.

B. Motor vehicles can run on ethanol, biodiesel, and methanol produced from plants and plant wastes. The biggest producers (Brazil, the U.S., the European Union, and China) plan to double their production of biofuels by 2020. Biofuels have advantages over gasoline and diesel fuel. Crops that are used to produce biofuels can be grown almost anywhere. The plants must be produced and harvested sustainably, resulting in no net increase in carbon dioxide. Biofuels are available now and are easy to store and transport. Rapid expansion of biofuels may (or may already) reduce the food available for consumption resulting in higher prices. Extensive use of biofuels could have dramatic impacts on the use of agricultural land.

CASE STUDY: Biodiesel is produced from vegetable oils. Production is growing rapidly in the United States. Some drawbacks include the large areas of land required to grow the crops, loss of topsoil, runoff, and the large energy requirements which reduce the overall net energy yield.

CASE STUDY: Ethanol can be made from crops as well as wastes from agriculture, forestry, and municipalities. Brazil and the United States are the largest producers of ethanol. Brazil produces enough to power 45% of its motor vehicles. Drawbacks to ethanol production include habitat destruction, high energy input requirements, soil erosion, runoff, and stresses on water supplies. Ethanol demand is also tied to food prices. An alternative is cellulosic ethanol, made from inedible parts of plants. Switchgrass is one promising plant for cellulosic ethanol production. However, it is difficult and costly to break down cellulose.

CASE STUDY: Scientists are attempting to use existing or genetically engineered oil-rich algae to produce biofuels. This requires much less land, water and other resources than other biofuel production methods. Research is ongoing.

16-7 What Are the Advantages and Disadvantages of Using Geothermal Energy?

A. We can use geothermal energy stored in the earth’s mantle to heat and cool buildings and to produce electricity. Geothermal heat pumps use a pipe and duct system to bring heat stored in underground rocks and fluids. The earth is used as a heat source in winter and a heat sink in summer. A closed loop of buried pipes filled with fluid to move heat in or out of the ground for heating/cooling needs. The EPA declared this the most energy-efficient, cost-effective, and environmentally clean way to heat or cool a building.

B. Hydrothermal reservoirs can be tapped into to extract steam or hot water.

C. The US is the world’s largest producer of geothermal energy.

D. Hot, dry rock found about 3 miles underground can also be used to generate electricity.

1. Digging into the earth’s crust is costly, and may trigger small earthquakes.

16-8 What Are the Advantages and Disadvantages of Using Hydrogen as an Energy Resource?

A. Hydrogen gas can be produced from water and organic molecules and produces nonpolluting water vapor when burned. Widespread use of hydrogen as a fuel would eliminate most of the air pollution problems we face today, but it takes energy and money to produce hydrogen from water and organic compounds. It is not a source of energy, it is a fuel produced by using energy.

B. Current versions of fuel cells are expensive, but are the best way to use hydrogen to produce electricity. Whether a hydrogen-based energy system produces less carbon dioxide than a fossil fuel depends on how the hydrogen is produced. H fuel could be produced by electricity from coal-burning power plants, from coal itself, or strip it from organic compounds, but this could add more carbon dioxide to the atmosphere.

16-9 How Can We Make the Transition to a More Sustainable Energy Future?

A. Decisions about energy futures require consideration of long periods of time (decades) and considerable investment in infrastructure.

B. There are three general conclusions about energy transformations.

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

2. The best alternatives combine improved energy efficiency and the use of natural gas and sustainably produced biofuels to make the transition to a diverse mix of locally available renewable-energy resources.

3. Because of their abundance and price, fossil fuels will continue to be used in large quantities, which means there will remain a need to find ways to reduce the environmental impacts of these fuels.

C. Governments can use a combination of subsidies, tax breaks, rebates, taxes, and public education to promote or discourage use of various energy alternatives. Economics and politics are the basic strategies to help stimulate or dampen the short-term and long-term use of a particular energy resource.

Key Terms

active solar heating system

cogeneration

combined heat and power systems (CHP)

energy efficiency

geothermal energy

passive solar heating system

photovoltaic (PV) cells

solar cells

Teaching Tips:

Large Lecture Courses:

Start the lecture with a chart showing the price of oil over the last decade and a comparison of total miles driven in the U.S. First drop since 1979 occurred in 2008. Compare this graph to graphs of the use of wind power, solar power, and biofuel use. All these graphs will show dramatic recent changes. Now contrast these graphs with a map of fossil fuel reserves and particularly unconventional and coal reserves in the U.S. This contrast can be used to set up the basic decision faced by the U.S. in particular in the coming years—to develop national fossil fuel supplies or to follow a renewable path.

Smaller Lecture Courses:

Have students read a selection of articles from the NY Times series on Chinese growth and pollution (). Structure a class around a discussion of the choices China is facing today compared to the history of U.S. development. Ask questions about the tradeoffs between economic development and environmental protection (and human health).

Term Paper Research Topics

1. Improving energy efficiency: energy-efficient office buildings; earth-sheltered houses; retrofitting energy-wasting houses; superinsulation; earth tubes; evaporative coolers; energy-efficient appliances; compact fluorescent light bulbs; "smart" windows; superinsulated windows; roof-attachable solar cell rolls; the Albers Technologies air conditioner.

2. Solar technologies: the solar power tower; the Odeillo furnace; solar power satellites; photovoltaics; active solar systems; passive solar heating; microprocessors to control house temperatures.

3. Biomass: modern wood stoves; bagasse as a biomass fuel; biomass use in the developing countries; gasohol; methanol; Cellulosic ethanol.

4. Wind: wind farming in California; wind turbine designs.

5. Water power: large-scale hydropower projects in developing countries; rehabilitating small-scale hydroelectric plants in New England; wave power devices—a comparison of various approaches; ocean thermal energy conversion; the Bay of Fundy tidal power project.

6. Hydrogen gas: a versatile fuel of the future.

7. Balancing environment and clean energy generation in hydroelectric installations.

8. The role of a decentralized energy supply in the future.

9. Regulation as a tool for energy efficiency. How much should federal, state, and local governments do?

10. Renewable energy potential in the U.S.—what are the limitations to full scale use of renewable energy?

11. Nuclear energy—pros and cons.

Discussion Topics

1. What to do with high level nuclear waste.

2. Restricting energy use in the developing world versus the developed world. What is fair?

3. Who should pay for the use of cleaner energy technologies?

4. Should energy decisions in the U.S. be made at the local, state, or federal level?

5. Should inefficient cars and trucks be banned?

6. LEED building certification—what’s involved and how much does it cost?

7. Should we invest in infrastructure for a hydrogen-based economy?

Activities and Projects

1. Ask an architect or contractor with experience in decentralized use of perpetual and renewable resources to visit the class and discuss the practical aspects of designing, financing, and installing small-scale solar, wind, and biogas systems for individual residences, farms, businesses, or factories.

2. Find out if representatives from your local electrical utility offer customers energy audits of their homes. If so, ask them to come to your class and tell what they look for in homes and what seem to be the most common ways customers can increase their energy efficiency.

3. Have your students find out if your institution's electrical utility has a conservation program. Does it have policies that encourage customers to purchase energy-efficient appliances and use energy-efficient light bulbs?

4. Organize a class field trip featuring guided tours of homes and/or other buildings that have solar heating systems. If possible, include examples of both passive and active systems and an earth-sheltered house.

5. See if there are LEED certified buildings on campus. Have students survey a LEED certified building and compare it to an older, more inefficient building.

6. Have a class debate on fossil fuel versus renewable sources of future energy.

7. Have a class debate/vote on the use of nuclear power (with a power plant located a thousand miles away and one located five miles away).

8. Ask students to survey newspapers for one week for articles on energy use and report back to the class about what they read.

9. Have your students audit energy use and waste on your campus and in activities (such as commuting) associated with the operation of your campus. Are opportunities to conserve significant amounts of energy going unrecognized or ignored?

10. As a class project, conduct a survey of students at your school to determine what beliefs and attitudes they have regarding sustainable-earth energy alternatives that entail a loss of convenience or additional expenditures of time and money on the part of energy users. Are young people today willing to significantly alter their lifestyles to use and waste less energy?

News Videos

End for Selling Traditional Bulbs; The Brooks/Cole Environmental Science Video Library, 2009; DVD 0538733551

Finding Alternatives to Oil; The Brooks/Cole Environmental Science Video Library, 2009; DVD 0538733551

Miles Per Gallon, Requirements for Automakers; Environmental Science in the Headlines, 2007; DVD; ISBN

0495385433

Philadelphia Eagles Playing for Planet’s Victory; Environmental Science in the Headlines, 2008; DVD; ISBN

0495561908

Planet Earth 2007; Environmental Science in the Headlines, 2007; DVD; ISBN 0495385433

Additional Video Resources

Conservation & Energy Alternatives (Documentary, 2001)

Trouble in the Middle East and growing concerns over global warming cause concern about how America is going to get powering the future.

E2 Energy (Documentary, 2007)

This PBS series includes 30-minute segments on the people, places and innovations relevant to our energy future.

The End of Suburbia: Oil Depletion and the Collapse of The American Dream (Documentary, 2004)



NOVA: Saved by the Sun (Online)

Main Website:

Teacher’s Guide:

Oil on Ice (Documentary, 2004)

Arctic National Wildlife Refuge and drilling for oil.



Who Killed The Electric Car (Documentary, 2006)

Documentary that investigates the birth and death of the electric car, as well as the role of renewable energy and sustainable living in the future.



Attitudes and Values

1. What obligation do you have to use renewable, sustainable energy? Why?

2. Is energy a right for all people? Should it be available to only those who can pay?

3. How should we balance cost and environmental impact in choosing energy sources?

4. Who should bear the cost of cleaner energy, the developed or developing world? Does it matter who uses the most energy now?

5. How much would you personally pay for cleaner energy?

Web Resources

Energy Information Administration

Energy statistics from the US government.



Fuel Cells 2000

Fuel cell information from multiple sources.



National Renewable Energy Laboratory in Golden Colorado

Links to information on multiple forms of renewable energy.



American Wind Energy Association

Trade group for wind power providers.



Suggested Responses to End of Chapter Questions

Review Questions

1. Review the Key Questions and Concepts for this chapter on p. 398. Describe the work of Amory Lovins at the Rocky Mountain Institute.

• Amory Lovins established a non-partisan, nonprofit group that does research and consulting on energy and efficiency. He and the staff at the Rocky Mountain Institute have consulted for more than 80 corporations and 50 countries to help save energy and money.

2. What is energy efficiency? Explain why we can think of energy efficiency as an energy resource. What percentage of the energy used in the United States is unnecessarily wasted? List four widely used energy-wasting technologies. What are the major advantages of reducing energy waste? List three reasons why this source of energy has been neglected?

• The best way to conserve energy is to improve energy efficiency— the measure of how much work we can get from each unit of energy we use.

• To most energy analysts, reducing energy waste is the quickest, cleanest, and usually the cheapest, way to provide for our energy future.

• Forty three percent of all commercial energy used in the United States is wasted unnecessarily, mostly due to the inefficiency of incandescent lights, furnaces, industrial motors, coal and nuclear power plants, most motor vehicles, and other devices.

• Four energy-wasting technologies:

• Incandescent light bulbs

• Internal combustion engines

• Nuclear power-plants

• Coal-fired power plants

• Major advantages of reducing energy waste include prolonging fossil fuel supplies, reducing oil imports and energy security, getting a very high net energy yield, low cost, reducing pollution and environmental degradation, buying time to phase in renewable energy, and creating local jobs.

• One reason improving energy efficiency is neglected is a glut of relatively low- cost fossil fuels. As long as energy remains artificially cheap, people are more likely to waste it and less likely to invest in improving energy efficiency. Another reason is that there are few large and long-lasting governmental tax breaks, rebates, low- interest, long- term loans, and other economic incentives for consumers and businesses to invest in improving energy efficiency. Also, the U. S. federal government has done a poor job of encouraging fuel efficiency in motor.

3. Describe three ways to save energy and money in (a) industry, (b) transportation, (c) new buildings and (d) existing buildings. What is cogeneration (combined heat and power or CHP)? How could we encourage electric utility companies to reduce their energy waste? What is a smart grid and why is it important?

• Ways to save energy and money include:

o In industry: cogeneration, replace energy-wasting electric motors and recycle materials.

o In transportation: increase public transportation, increase mileage standards and more energy-efficient vehicles.

o In new buildings: orient the structure toward the sun, using living roofs and superinsulating.

o In existing buildings: improve insulation, use energy efficient appliances, and use energy efficient windows.

• In cogeneration, two useful forms of energy (such as steam and electricity) are produced from the same fuel source.

• Utility companies could reduce their energy waste by requiring that industries use cogeneration, replace energy-wasting electric motors, recycling materials, and switch from incandescent lighting.

• A smart grid is an energy-efficient, digitally controlled, ultra-high-voltage grid with superefficient transmission lines that is responsive to local and regional changes in demand and supply. It is important because it can help to conserve vast amounts of energy.

4. Describe the trends in fuel efficiency in the United States since the 1970s. Explain why the price of gasoline is much higher than what consumers pay at the pump. What is a feebate? Distinguish among hybrid, plug-in hybrid, and fuel- cell motor vehicles. Describe the possible connection between wind farms and plug-in hybrid cars. Summarize the search for better batteries and describe two promising new developments. What is a living roof? What is the importance of a white or light-colored roof? What is a superinsulated house? Compare the efficiency of incandescent, compact fluorescent, and LED light bulbs. Explain how using compact fluorescent light bulbs can reduce overall air pollution from toxic mercury. What are green buildings and why are they important? List six ways you can save energy where you live. Give three reasons why we waste so much energy.

• The price of gasoline does not include hidden costs such as government subsidies and tax breaks for oil companies, car manufacturers and road builders; costs of pollution control and cleanup; costs of military protection of oil supplies in the Middle East (not including the two Iraq wars); time wasted in traffic jams; and costs of illness from air and water pollution in the form of higher medical bills and health insurance premiums.

• The price of gasoline does not include hidden costs such as government subsidies and tax breaks for oil companies, car manufacturers and road builders; costs of pollution control and cleanup; costs of military protection of oil supplies in the Middle East (not including the two Iraq wars); time wasted in traffic jams; and costs of illness from air and water pollution in the form of higher medical bills and health insurance premiums.

• Feebate is a combination of a fee and a rebate, such as a program in which buyers of fuel-inefficient vehicles pay a high fee, and the resulting revenues are given to buyers of efficient vehicles as rebates.

• Hybrids use more than one form of power. A plug-in hybrid electric vehicle is a hybrid with a second and more powerful battery that can be plugged into a conventional electrical outlet and recharged.

• Fuel-cell motor vehicles use hydrogen gas as fuel to produce electricity.

• Wind can be used to generate electricity for charging plug-in hybrids, thus generating a carbon neutral, zero-emissions form of transportation.

• The major obstacle standing in the way of mass-market, plug-in, hybrid electric vehicles is the difficulty in making an affordable battery that can store enough energy to power a vehicle over long distances without overheating. Two promising developments are new type of lithium battery that charges more rapidly, is less likely to heat up to dangerous levels, and is cheaper than the batteries used to power today’s hybrid vehicles; and using nanotechnology to make electrodes out of a nanophosphate material that will lengthen battery life and will not heat up and release flammable oxygen.

• Living roofs are covered with soil and vegetation.

• Light colored roofs help reduce cooling costs by reflecting incoming solar radiation especially in hotter climates.

• Superinsulation allows a house to be so heavily insulated and airtight that heat from direct sunlight, appliances, and human bodies can warm it with little or no need for a backup heating system, even in extremely cold climates.

• A compact fluorescent bulb uses one-fourth as much electricity as an incandescent bulb. LEDs use about one-seventh of the electricity required by an incandescent bulb.

• The total amount of mercury in all of the country’s CFLs is a tiny fraction of the amount of mercury released every year by coal-fired power plants that produce the electricity that lights many energy-wasting incandescent bulbs.

• Green buildings incorporate many energy-efficient and money-saving designs, make use of natural lighting, passive solar heating, solar cells, solar hot water heaters, recycled wastewater, and energy-efficient appliances and lighting. They are important in increasing our overall energy efficiency.

• Six ways to save energy are:

o Plant trees to block summer sun.

o Use compact fluorescent light bulbs.

o Turn off lights and electronics when not in use,

o Use high-efficiency windows.

o Weather strip and caulk doors.

o Use fans instead of air conditioning.

• Three reasons we waste energy are:

o Fossil fuels and nuclear power are artificially cheap.

o There are few government incentives to invest in energy efficiency.

o People tend to resist change.

5. List five advantages of relying more on a variety of renewable energy sources and describe two factors holding back such a transition. Distinguish between a passive solar heating system and an active solar heating system and discuss the major advantages and disadvantages of such systems for heating buildings. What are three ways to cool houses naturally? Discuss the major advantages and disadvantages of concentrating solar energy to generate high-temperature heat and electricity. What is a solar cell (photovoltaic or PV cell) and what are the major advantages and disadvantages of using such devices to produce electricity?

• Making a major shift toward a variety of locally available renewable energy resources over the next few decades would

o Result in a more decentralized and efficient energy economy that is less vulnerable to supply cutoffs from terrorist attacks and natural disasters such as hurricanes.

o Improve national security for many countries by reducing their need to import oil from the Middle East.

o Reduce trade deficits that grow when a country imports oil.

o Greatly reduce emissions of climate-changing greenhouse gases and other air pollutants.

o Create large numbers of jobs, including high- paying jobs for skilled workers.

o Save consumers money.

• A passive solar heating system absorbs and stores heat from the sun directly within a well-insulated structure without the need for pumps or fans to distribute the heat. An active solar heating system uses energy from the sun by pumping a heat-absorbing fluid through special collectors usually mounted on a roof or on special racks to face the sun.

• Advantages of heating a house with passive or active solar energy include: energy is free, net energy is moderate (active) to high (passive), quick installation, and no CO2 emissions. Disadvantages include: 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, very low air and water pollution, very low land disturbance (built into roof or windows), and moderate cost (passive).

• Three ways to keep cool:

o Block the high summer sun with window overhangs or awnings.

o Use a light-colored roof to reflect as much as 80% of the sun’s heat (compared to only 8% for a dark colored roof).

o Use geothermal heat pumps for cooling (and heating in winter).

• Advantages of using solar energy to generate high-temperature heat and electricity include: moderate environmental impact, no CO2 emissions, fast construction (1–2 years), and costs reduced with natural gas turbine backup. Disadvantages include: 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, and may disturb desert areas.

• Solar energy can be converted directly into electrical energy by photovoltaic (PV) cells, commonly called solar cells. Most solar cells are thin wafers of purified silicon with trace amounts of metals that allow them to function as semiconductors to produce electricity.

• Advantages of using solar cells to produce electricity include: fairly high net energy yield, work on cloudy days, quick installation, easily expanded or moved, no CO2 emissions, low environmental impact, last 20–40 years, low land use (if on roof or built into walls or windows), and reduces dependence on fossil fuels. Disadvantages include: 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, and DC current must be converted to AC.

6. What are the major advantages and disadvantages of using hydropower? What is the potential for using tides and waves to produce electricity?

• Advantages of using large dams and reservoirs to produce electricity include: 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, and reservoir useful for fishing and recreation. Disadvantages include: high construction costs, high environmental impact from flooding land to form a reservoir, environmental costs not included in market price, high CH4 emissions from rapid biomass decay in shallow tropical reservoirs, danger of collapse, uproots people, decreases fish harvest below dam, and decreases flow of natural fertilizer (silt) to land below dam.

• In some coastal bays and estuaries, water levels can rise or fall by 6 meters or more between daily high and low tides. Dams have been built across the mouths of some bays and estuaries to capture the energy in these flows for hydropower. However, globally, sites with large enough daily tidal flows are limited.

• One way to produce electricity is by tapping wave energy along seacoasts where there are almost continuous waves. Off the coast of Portugal, large chains of floating steel tubes move up and down with the wave action and generate electricity. However, most analysts expect tidal and wave power sources to make only a small contribution to world electricity supplies, primarily because there are few suitable sites, the costs are high, and the equipment is vulnerable to corrosion and storm damage. Improved technology could greatly increase the production of electricity from waves sometime during this century.

7. What is a wind turbine? What is a wind farm? What are the major advantages and disadvantages of using wind to produce electricity? Explain why the United States is the “Saudi Arabia of wind energy.” What are the major advantages and disadvantages of burning wood to provide heat and electricity? What are biofuels and what are the major advantages and disadvantages of using biodiesel and ethanol to power motor vehicles? Evaluate the use of corn, sugarcane, and cellulose plants to produce ethanol. Describe the potential for using algae and bacteria to produce gasoline and diesel fuel.

1. A wind turbine is driven by flows of air, or wind, and converts wind energy into electrical energy. Wind farms have interconnected arrays of ten to hundreds of turbines.

• Advantages of wind power include: moderate to high net energy yield, high efficiency, moderate capital cost, low electricity cost, very low environmental impact, no CO2 emissions, quick construction, easily expanded, can be located at sea, and land below turbines can be used to grow crops or graze livestock. Disadvantages include: 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, and can kill birds and interfere with flights of migratory birds if not sited properly.

• Wind farms in the Great Plains states have the potential to generate more then enough power for the lower 48 states, and have been dubbed the Saudi Arabia of wind energy.

• Using wood to provide heat and electricity has advantages that include: potentially renewable forest and can be local, and disadvantages that include increased deforestation, not enough, and air pollution.

• Plant materials and animal wastes can be converted into gaseous or liquid biofuels.

• Advantages of using biodiesel as a vehicle fuel include: reduced CO emissions, reduced CO2 emissions (78%), high net energy yield for oil palm crops, moderate net energy yield for grape seed crops, reduced hydrocarbon emissions, better gas mileage (40%), and potentially renewable. Disadvantages include: increased NOx 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, and can make engines hard to start in cold weather.

• Advantages of using ethanol as a vehicle fuel include: 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, and potentially renewable. Disadvantages include: 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 NOx emissions and more smog, and corrosives can make engines hard to start in cold weather.

• Ethanol can be made through the fermentation and distillation of sugars in plants such as sugarcane, corn, and switchgrass. Running motor vehicles run on ethanol or ethanol- gasoline mixtures can save huge amounts of money in imported oil costs. Brazil and the United States are the largest ethanol producers. In Brazil, ethanol production has created about 1 million rural jobs. Brazil plans to greatly expand its production of sugarcane to produce ethanol and to grow more soybeans to produce biodiesel. However, this could threaten some of the country’s biodiversity. In the United States, most ethanol is made from corn. A growing number of analysts warn that producing ethanol from corn will not significantly reduce the country’s oil imports or help to slow global warming.

• Biofuels can potentially be made from various types of existing or genetically engineered oil-rich algae and bacteria. However, there is much research still to be done in this area.

8. What is geothermal energy and what are three sources of such energy? What are the major advantages and disadvantages of using geothermal energy as a source of heat and to produce electricity? What are the major advantages and disadvantages of using hydrogen as a fuel and to produce electricity and to power motor vehicles?

• Geothermal energy is heat stored in soil, underground rocks, and fluids in the earth’s mantle that can be tapped into to store energy to heat and cool buildings and to produce electricity.

• Advantages of geothermal energy for space heating and for producing electricity or high-temperature heat for industrial processes include: very high efficiency, moderate net energy at accessible sites, lower CO2 emissions than fossil fuels, low cost at favorable sites, low land use and disturbance, and moderate environmental impact. Disadvantages include: 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), and high cost except at the most concentrated and accessible sources.

• Advantages of hydrogen:

o Can be produced from plentiful water.

o Low environmental impact.

o Renewable if produced from renewable energy resources.

o No CO2 emissions if produced from water.

o Good substitute for oil.

o Competitive price if environmental and social costs are included in cost comparisons.

o Easier to store than electricity.

o Safer than gasoline and natural gas.

o Nontoxic.

o High efficiency (45–65%) in fuel cells.

• Disadvantages of hydrogen:

o Not found as H2 in nature.

o Energy is needed to produce fuel.

o Negative net energy.

o CO2 emissions if produced from carbon-containing compounds.

o Environmental costs not included in market price.

o Nonrenewable if generated by fossil fuels or nuclear power.

o High costs (that may eventually come down).

o Will take 25 to 50 years to phase in.

o Short driving range for current fuel-cell cars.

o No fuel distribution system in place.

o Excessive H2 leaks may deplete ozone in the atmosphere.

9. List three general conclusions of energy experts about possible future energy paths for the world. List five major strategies for making the transition to a more sustainable energy future. Describe three roles that governments play in determining which energy resources we use.

• There will be a gradual shift from large, centralized macropower systems to smaller, decentralized micropower systems such as wind turbines, household solar-cell panels, rooftop solar water heaters, small natural gas turbines, and fuel cells for cars, houses, and commercial buildings.

• A combination of greatly improved energy efficiency and the temporary use of a natural gas will best help us to make the transition to a diverse mix of locally available renewable energy resources over the next several decades.

• Because of their supplies and artificially low prices, fossil fuels will continue to be used in large quantities.

• See Figure 16-33 for major strategies for making the transition to a more sustainable energy future.

• Three roles government plays:

o Keeps the prices of selected energy resources artificially low to encourage use of those resources.

o Keeps the prices of selected energy resources artificially high to discourage their use.

o Emphasizes consumer education.

10. What are this chapter’s three big ideas? Describe how the Rocky Mountain Institute applies the three principles of sustainability to evaluating and using energy resources.

• This chapter’s big ideas are:

o 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.

o 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.

o 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.

• The Rocky Mountain Institute seeks solutions that maximize solar energy use, are live sustaining, and non-polluting.

Critical Thinking

The following are examples of the material that should be contained in possible student answers to the end of chapter Critical Thinking questions. They represent only a summary overview and serve to highlight the core concepts that are addressed in the text. It should be anticipated that the students will provide more in-depth and detailed responses to the questions depending on an individual instructor’s stated expectations.

1. Imagine that you live in the Rocky Mountain Institute’s building (Figure 16-1), powered mostly by the sun (Core Case Study). Do you think that you would have to give up any of the conveniences you now enjoy? If so, what are they? Describe any adjustments you might have to make in your way of living.

Student responses may vary. The designs advocated by the Rocky Mountain Institute do not necessarily prohibit modern conveniences, but rather focus on efficiency, which may require certain behavioral modifications.

2. List five ways in which you unnecessarily waste energy during a typical day, and explain how these actions violate any of the four scientific principles of sustainability (see back cover).

People unnecessarily waste energy by having too many lights on in the home at night. Also, people use air conditioners when it is not absolutely necessary; try opening a window! This applies in the winter, too. People should wear more clothes instead of wasting energy by having their heaters turned on high. People should not leave computers on at night when they go to bed and are not using them. When using a dish washer you should make sure it has a full load in it. These are examples of things that I used to do, but after realizing that I am going against the principles of sustainability, I no longer do them, particularly not relying on the sun for energy.

3. Congratulations! You have won $500,000 to build a more sustainable house of your choice. With the goal of maximizing energy efficiency, what type of house would you build? How large would it be? Where would you locate it? What types of materials would you use? What types of materials would you not use? How would you heat and cool the house? How would you heat water? What types of lighting, stove, refrigerator, washer, and dryer would you use? Which, if any, of these appliances could you do without?

Student answers will vary but $500,000 would allow considerable innovation in home design. Student answers may include alternative energy supplies including geothermal, solar (active or passive). Locations will vary with student choices. Materials could include reclaimed building materials, sustainably harvested materials or renewable materials such as strawbales. Heavy use of metals and non-sustainably produced woods would be discouraged. Lighting, heating and appliances can be highly energy efficient (e.g. CFL or LED lighting). Options for doing without will vary by student.

4. A homebuilder installs electric baseboard heat and claims, “It is the cheapest and cleanest way to go.” Apply your understanding of the second law of thermodynamics (see Chapter 2, p. 47) and net energy (see Figure 15-3) to evaluate this claim.

The second law of thermodynamics states that when energy changes from one form to another, some of the useful energy is always degraded to lower-quality, more dispersed, less useful energy. If the electricity came from a nuclear plant then it could be argued that this is cleaner than generating it from coal. However, the net energy efficiency in either case is very low (@14%) when compared to other methods, such as passive solar that has a much higher net energy efficiency (@90%). His claim is very flawed.

5. Should buyers of energy-efficient motor vehicles receive large rebates funded by fees levied on gas-guzzlers? Explain.

An argument in favor of this proposal is that buyers of energy efficient vehicles are helping the environment and should be rewarded in some way. If this is a monetary reward then the funds could be raised by taxing those less-responsible people that drive the gas-guzzlers. We need to introduce more incentives for purchasing hybrids and more disincentives for buying low-mpg vehicles.

6. Explain why you agree or disagree with the following proposals made by various energy analysts:

a. We should eliminate government subsidies for all energy alternatives so that all energy providers can compete in a true free-market system. b. We should phase out all government tax breaks and other subsidies for conventional fossil fuels (oil, natural gas, and coal), synthetic natural gas and oil, and nuclear power (fission and fusion). We should replace them with subsidies and tax breaks for improving energy efficiency and developing solar, wind, geothermal, hydrogen, and biomass energy alternatives. c. We should leave development of solar, wind, and hydrogen energy to private enterprise and it should receive little or no help from the federal government, but nuclear energy and fossil fuels should continue to receive large federal government subsidies.

(a) I agree that government subsidies for all energy alternatives should be eliminated so all energy choices can compete in a true free-market system. A counter argument is that government should try to steer energy development toward renewable technologies and this may require subsides.

(b) I agree that all government subsidies or tax breaks for conventional fuels should be replaced with subsidies and tax breaks for improving energy efficiency and developing solar, wind, geothermal, hydrogen, and biomass energy alternatives.

(c) The government should not leave development of alternative energies in the hands of the private sector so long as other energy sources receive large government subsidies.

7. Imagine that you are in charge of the U.S. Department of Energy (or the energy agency in the country where you live). What percentages of your research and development budget will you devote to fossil fuels, nuclear power, renewable energy, and improving energy efficiency? How would you distribute your funds among the various types of renewable energy? Explain your thinking.

I would devote 15 percent of the R&D budget to fossil fuels. This would be in order to develop cleaner coal burning technology and methods to reduce carbon dioxide and nitrogen oxide emissions. Fifteen percent of the budget would go to nuclear, which would be focused on dealing with the radioactive waste that is produced so it can be transformed into less dangerous forms. We will still need to rely on these “old” methods to supply our energy needs until we can replace them with other forms of “newer” energy sources. That is why I would allocate 50 percent toward R&D in the arena of renewable/alternative energy sources. These cannot be developed overnight, and it will take time to get the ones that work out the best into widespread use. We can also reduce the amount of energy right now by being more energy efficient and improving energy conservation in all areas of our energy use, which is why I would set aside 20 percent of the budget for R&D in this area.

8. China is investing 10 times as much as the United States is spending (as a percentage of its gross domestic product) in new, cleaner energy technologies such as electric cars, wind power, and solar energy. Chinese leaders understand that these technologies represent one of the biggest money-making opportunities of this century, and they plan to sell these technologies to the world. Energy analysts and economists call for the United States to launch a massive research and development program to join China in becoming a technological and economic leader in the area of clean energy. Do you agree with this proposal? Explain.

Absolutely. The United States has a wonderful opportunity to contribute to the development of new technologies and to bolster its economy by positioning itself as a global leader in the clean energy movement.

9. Congratulations! You are in charge of the world. List the five most important features of your energy policy.

Five important features of my energy policy would be: promote energy conservation and efficiency; phase-out the use of wasteful energy appliances in the home; improve the mpg of all vehicles on the road and encourage more people to drive hybrids and/or similar fuel efficient cars; ensure that all new construction meets sustainable energy standards or are LEED certified, and promote zero population growth strategies immediately.

10. List two questions that you would like to have answered as a result of reading this chapter.

Student answers will vary and provide a good starting point for class discussion.

Ecological Footprint Question

Make calculations to fill in the missing data in this table. Show all calculations. (1 liter = 0.265 gallon; 1 kilogram = 2.20 pounds; 1 hectare = 10,000 square meters = 2.47 acres)

|EPA Size Class |Model |Combined highway and | Liters (gallons) of| Kilograms (pounds) of CO2 |Hectares (acres) of |

| | |city fuel efficiency in |gasoline consumed |produced per year, assuming|tropical rain forest |

| | |kpl (mpg) |per year, assuming |that the combustion of |needed to uptake the |

| | | |an average mileage |gasoline releases 2.3 |CO2 produced per |

| | | |of 19,300 kilometers|kilograms per liter (19 |year, assuming that |

| | | |(12,000 miles) |pounds per gallon) |the uptake of an |

| | | | | |undisturbed forest is|

| | | | | |0.5 kilograms of CO2 |

| | | | | |per square meter |

|Compact |Honda Civic |17.8 (42.0) | | | |

| |Hybrid | | | | |

|Midsize Car |Toyota Camry |14.4 (34.0) | | | |

| |Hybrid | | | | |

|Sports Utility |Hummer H3 |6.40 (15.0) | | | |

|Vehicle (SUV) | | | | | |

Source : : feg/findacar.htm

Answers

|EPA Size Class |Model |Combined highway and |Liters (gallons) of |Kilograms (pounds) of CO2 |Hectares (acres) of |

| | |city fuel efficiency in |gasoline consumed |produced per year, assuming|tropical rain forest |

| | |kpl (mpg) |per year, assuming |that the combustion of |needed to uptake the |

| | | |an average mileage |gasoline releases 2.4 |CO2 produced per |

| | | |of 19,300 kilometers|kilograms per liter (19.6 |year, assuming that |

| | | |(12,000 miles) |pounds per gallon) |the uptake of an |

| | | | | |undisturbed forest is|

| | | | | |0.5 kilograms of CO2 |

| | | | | |per square meter |

|Compact |Honda Civic |17.8 (42.0) |1,084 (286) |2,602 (5,606) |0.5 (1.2) |

| |Hybrid | | | | |

|Midsize Car |Toyota Camry |14.4 (34.0) |1,340 (353) |3,216 (6,919) |0.64 (1.6) |

| |Hybrid | | | | |

|Sports Utility |Hummer H3 |6.40 (15.0) |3,016 (800) |7,238 (15,680) |1.4 (3.6) |

|Vehicle (SUV) | | | | | |

1. About how many times as much CO2 per year is produced by the SUV as is produced by the compact car?

2. About how many times as much CO2 per year is produced by the SUV as is produced by the midsize car?

3. How many hectares (acres) of tropical rain forest are needed to take up the CO2 produced annually by 1 million SUVs?

4. How many hectares (acres) of tropical rain forest are needed to take up the CO2 produced annually by 1 million midsize cars?

5. How many hectares (acres) of tropical rain forest are needed to take up the CO2 produced annually by 1 million compact cars?

Calculations:

Gasoline consumed per year:

Compact:

19,300 kilometers per year/17.8 kilometers per year = 1,084 liters

12,000 miles per year/42.0 miles per gallon = 286 gallons

Midsize:

19,300 kilometers per year/14.4 kilometers per year = 1,340 liters

12,000 miles per year/34.0 miles per gallon = 353 gallons

SUV:

19,300 kilometers per year/6.40 kilometers per year = 3,016 liters

12,000 miles per year/15.0 miles per gallon = 800 gallons

CO2 produced per year

Compact:

1,084 liters gasoline x 2.4 kilograms CO2 per liter = 2,602 kilograms of CO2 per year

286 gallons gasoline x 19.6 pounds CO2 per liter = 5,606 pounds of CO2 per year

Midsize:

1,340 liters gasoline x 2.4 kilograms CO2 per liter = 3,216 kilograms of CO2 per year

353 gallons gasoline x 19.6 pounds CO2 per liter = 6,919 pounds of CO2 per year

SUV:

3,016 liters gasoline x 2.4 kilograms CO2 per liter = 7,238 kilograms of CO2 per year

800 gallons gasoline x 19.6 pounds CO2 per liter = 15,680 pounds of CO2 per year

Tropical forest needed to remove CO2 output per year

Compact:

2,602 kilograms CO2 x 1 square meter forest/0.5 kilograms CO2 x 1 hectare/10,000 square meters = 0.5 hectares of forest

0.5 hectares x 2.47 acres/hectare = 1.2 acres of forest

Midsize:

3,216 kilograms CO2 x 1 square meter forest/0.50 kilograms CO2 x 1 hectare/10,000 square meters = 0.64 hectares of forest

0.62 hectares x 2.47 acres/hectare = 1.6 acres of forest

SUV:

7,238 kilograms CO2 x 1 square meter forest/0.50 kilograms CO2 x 1 hectare/10,000 square meters = 1.4 hectares of forest

1.4 hectares x 2.47 acres/hectare = 3.6 acres of forest

Answers:

1. 15,680 pounds of CO2 per year/5,606 pounds of CO2 per year = 2.8 times

2. 15,680 pounds of CO2 per year/6,919 pounds of CO2 per year = 2.3 times

3. 3.6 acres of forest x 1 million = 3.6 million acres

4. 1.6 acres of forest x 1 million = 1.6 million acres

5. 1.2 acres of forest x 1 million = 1.2 million acres

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