Botkin, Daniel B. Environmental Science: Earth as a Living Planet, 9th Edition. Wiley, 2013-12-23. VitalBook file.
Every other October since 1987, solar-powered cars have raced from Darwin to Adelaide, Australia, in the World Solar Challenge, an 2,900 km (1,800 mi) route that puts the latest alternative-energy technology to the test. The cars can run only on sunlight that their solar cells capture and convert to electricity. Electric motors that are at least 90% efficient are necessary. Racing teams are usually comprised of college students, and teams are backed by major aerospace and high-tech corporations. The eleventh race, held in 2011, was won by a Japanese team; a Netherlands team finished second, and the fast- est U.S. team, from the University of Michigan, finished third. Drivers had to avoid a bushfire, wallabies, cattle, sheep, lizards, and strong winds.1 Top speeds ranged from 143–154 km/hr (89–95 mph), and the average speed of the winning car was about 70 mph.
Suppose you decided to organize a team from your university, design and build a solar-powered car, and enter the race. Here’s the challenge: The roof of an automobile is just barely large enough to hold a solar panel that can gather enough energy to drive a car. It can’t power a regular sedan or SUV, and it can just barely power any car at all. How would you win? Should you build a car that, under the race rules, has the largest solar-powered area and tries to gather as much sunlight as possible, making the car as heavy as you can? Or would you opt for energy efficiency and build the lightest car, trading off a larger energy in- put for greater energy efficiency? Would you spend money and add weight to make the car’s shape as aerodynamic as possible, so that it would have the least resistance from the wind? And how about reliability? Would you build a stronger, therefore heavier car, or would you place your bet on the sleekest, lightest, car?
The car built by the Netherlands Nuon team, the Luna 6, had three wheels, a body made of carbon fiber, and solar panels covering nearly every inch of its top surface. The students who designed it tested a model in a wind tunnel
14.1 Outlook for energy
Energy Today and Tomorrow
The decisions we make today will affect energy use for generations. Should we choose complex, centralized en- ergy production methods, or simpler and widely dispersed
by covering it with oil; the oil activated an ultraviolet light used to highlight any impediments to its aerodynamic de- sign. The Luna 6 was 140 kg (308 lb), 20 kg (44 lb) lighter than the Luna 5 designed two years before.
The Tokai Challenger 2, also a three-wheeler, featured carbon monocoque construction on its top surface that incorporated a 6-m square array of silicon solar cells.
The Netherlands team lost out to the Tokai Challeng- er 2 largely because of the gains the Japanese team made on Day 3 of the four-and-a-half-day race, wrote British Diederik Kinds in The Register.2 He analyzed the race and found that very small measures of efficiency combined to put the Japanese car over the top. The Tokai team was able to draw about 7% more from the car’s battery; the Japanese car weighed 10 kg (22 lb) less than the Luna 6 and had 5% better aerodynamics; its solar panel was able to power the equivalent of two small light bulbs more than the Luna 6. The end result, according to Diederik, was that the Japanese car had available about 10% more energy than its closest competition, which it used to increase its lead by 30 minutes on Day 3 and ultimately win the race.
A few months after the race, the University of Michigan team merged with the Nuon team, forming the Nuum team, and agreed to work together to create a $3 million solar car for the next World Solar Challenge in 2013.3 Part of the impetus for all teams is to be part of an effort to develop zero emission vehicles that can be mass- produced, a goal of international importance as we look to decrease dependence on fossil fuels for transportation.
In deciding how to design and build a winning solar- powered car, the teams needed to understand the fun- damental laws of physics as well as the basic concepts of energy and how to apply them. That understanding is also important to our ability to decide what kinds of en- ergy sources are best for people and for the environment. In this first chapter on energy we introduce those basic concepts.
methods, or a combination of the two? Which energy sources should be emphasized? Which uses of energy should be explored for increased efficiency? How can we develop a sustainable energy policy? There are no easy answers.
The use of fossil fuels, especially oil, has improved sanitation, medicine, and agriculture and is helping to make possible the global human population increase that we have discussed in other chapters. Many of us are liv- ing longer, with a higher standard of living, than people before us. However, burning fossil fuels imposes growing environmental costs, ranging from urban pollution to a change in the global climate.
One thing certain about the energy picture for to- morrow is that it will involve living with uncertainty when it comes to energy availability and cost. The sources of energy and the patterns of energy use will undoubtedly change. It is clear that we need to examine our entire en- ergy policy in terms of sources, supply, consumption, and environmental concerns. Meanwhile, let’s take a moment to consider a key energy question of the 21st century.
Can the United States Achieve Energy Independence? When? How?
Until recently, the idea of the United States becoming independent with respect to energy seemed a far-fetched idea. A prevailing idea, based on rates of discovery and production of oil, was that oil would become increasingly scarce. After all, until just a few years ago, we were import- ing about two-thirds of the oil we used annually, and, in many years, some of the countries that supplied the oil were not particularly friendly to the United States. During the last several years, we have begun to import less oil and from countries that are friendlier with us. But that is not why we may begin to ask the question: not if, but when will we reach energy independence?
FIGURe 14.1 Map of the United States showing current locations of shale oil and/or natural gas resources.
One idea advanced by many in the early part of this century was that the world would soon reach the time when approximately one-half of the available, conven- tional oil resource, defined as relatively light oil, will have been pumped and burned to fuel society. This is known as the concept of peak oil. With respect to conventional oil from most oil fields around the world, this concept is es- sentially correct; as such, it would indicate a major supply crisis looming.4
The concept of peak oil was labeled a myth by some and a red flag to others in the oil industry.5 Neither posi- tion was entirely correct, but production of conventional oil, according to the International Energy Agency, did likely peak in 2006. Other studies suggest that the peak has not arrived and might not occur for decades.6-8 Total production from all sources today is about 85 million barrels per day (mbd).
So, if oil production has peaked, why is there not a serious gap between nearly constant production and in- creasing world demand for oil? The answer is that the gap (the difference between production and demand) in oil is being filled by new sources of oil (and natural gas) now being developed and produced in ever growing amounts. One example is oil in tight shale rocks in the Bakken for- mation in North Dakota.7,8 The shale is dense, and the oil and gas are tightly held in the fine-grained rock. Oil and natural gas in shale is abundant in the contiguous United States (Figure 14.1) as well as in other locations such as eastern Europe. Significantly, these sources of the shale oil and natural gas are the fastest growing energy resources in the United States today. Many in the industry are touting the projected increase in domestic oil and gas as the major path to U.S. energy independence. In the short term, this is a valid point.
However, there are particular problems associated with these sources: They are more difficult to obtain and more expensive, and likely have higher environmental costs than do conventional methods from standard wells because they require special drilling techniques (these problems are discussed in Chapter 15).
Most environmentalists do not consider reaching en- ergy independence through drilling and burning more and more oil or natural gas as an acceptable long-term energy strategy, especially when environmental costs are factored in, which include the possibility of water, soil, and air pollution. Environmentalists prefer pursuing a sustainable energy policy that can endure for generations and not harm the environment. The emerging use of more alternative energy, particularly wind and solar energy, is the preferred path if sustainable energy is the objective. Our continued dependence on fossil fuels (even our own) will mean we will be destined to endure: air pollution with adverse health effects; damage to ecosystems through dis- turbance of the land and the oceans caused by occasional serious accidents (oil spills); and climate change due to increasing carbon dioxide emissions in the atmosphere as fossil fuels are burned.
Even with increased production in the United States, achieving energy independence will not happen in the next year or two and probably not for several decades or longer. We will continue to be dependent on oil, which is used for most of our transportation, primarily our auto- mobiles and trucks. But where we get that oil is changing.
An important objective of the United States’ energy policy is to promote both sustainable energy and energy independence. We have a long way to go, but we are mov- ing in the right direction. In this chapter we present general principles of energy, sources and use of energy, conserva- tion of energy, and energy planning.
You apply a force against gravity, which would otherwise cause the car to roll downhill. If the brake is on, the brakes, tires, and bearings may heat up from friction. The longer the distance over which you exert force in pushing the car, the greater the change in the car’s position and the greater the amount of heat from friction in the brakes, tires, and bearings. In physicists’ terms, exerting the force over the distance moved is work. That is, work is the product of a force times a distance. Conversely, energy is the ability to do work. Thus, if you push hard, but the car doesn’t move, you have exerted a force but have not done any work (according to the definition), even if you feel very tired and sweaty.9
In pushing your stalled car, you have moved it against gravity and caused some of its parts (brakes, tires, bear- ings) to become heated. These effects have something in common: They are forms of energy. You have converted chemical energy in your body to the energy of motion of the car (kinetic energy). When the car is higher on the hill, the potential energy of the car has been increased, and friction produces heat energy.
Energy is often converted or transformed from one kind to another, but the total energy is always conserved. The principle that energy cannot be created or destroyed but is always conserved is known as the first law of ther- modynamics. Thermodynamics is the science that keeps track of energy as it undergoes various transformations from one type to another. We use the first law to keep track of the quantity of energy.10
To illustrate the conservation and conversion of en- ergy, think about a tire swing over a creek (Figure 14.3). When the tire swing is held in its highest position, it is not moving. It does contain stored energy, however, owing to its position. We refer to the stored energy as potential energy. Other examples of potential energy are the gravita- tional energy in water behind a dam; the chemical energy in coal, fuel oil, and gasoline, as well as in the fat in your body; and nuclear energy, which is related to the forces binding the nuclei of atoms.9
14.2 energy Basics
The concept of energy is somewhat ab- stract: You cannot see it or feel it, even though you have to pay for it.9 To un- derstand energy, it is easiest to begin with the idea of a force. We all have had the experience of exerting force by pushing or pulling. The strength of a force can be measured by how much it accelerates an object.
What if your car stalls going up a hill and you get out to push it uphill to the side of the road (Figure 14.2)the tire swing, would you expect the swing to start again? The answer is no! What, then, is used up? It is not energy because energy is always conserved. What is used up is the energy quality—the availability of the energy to perform work. The higher the quality of the energy, the more easily it can be converted to work; the lower the energy quality, the more difficult it is to convert it to work.
This example illustrates another fundamental prop- erty of energy: Energy always tends to go from a more us- able (higher-quality) form to a less usable (lower-quality) form. This is the second law of thermodynamics, and it means that when you use energy, you lower its quality.
Let’s return to the example of the stalled car, which you have now pushed to the side of the road. Having pushed the car a little way uphill, you have increased its potential energy. You can convert this to kinetic energy by letting it roll back downhill. You engage the gears to restart the car. As the car idles, the potential chemical en- ergy (from the gasoline) is converted to waste heat energy and other energy forms, including electricity to charge the battery and play the radio.
Why can’t we collect the wasted heat and use it to run the engine? Again, as the second law of thermodynamics tells us, once energy is degraded to low-quality heat, it can never regain its original availability or energy grade. When we refer to low-grade heat energy, we mean that relatively little of it is available to do useful work. High-grade en- ergy, such as that of gasoline, coal, or natural gas, has high potential to do useful work. The biosphere continuously receives high-grade energy from the sun and radiates low- grade heat to the depths of space.9,10
14.3 energy efficiency
Two fundamental types of energy efficiencies are de- rived from the first and second laws of thermodynamics: first-law efficiency and second-law efficiency. First-law efficiency deals with the amount of energy without any consideration of the quality or availability of the energy. It is calculated as the ratio of the actual amount of energy delivered where it is needed to the amount of energy sup- plied to meet that need. Expressions for efficiencies are given as fractions; multiplying the fraction by 100 con- verts it to a percentage. As an example, consider a furnace system that keeps a home at a desired temperature of 18°C (65°F) when the outside temperature is 0°C (32°F). The furnace, which burns natural gas, delivers 1 unit of heat energy to the house for every 1.5 units of energy extracted from burning the fuel. That means it has a first-law ef- ficiency of 1 divided by 1.5, or 67% (see Table 14.1 for other examples).10 The “unit” of energy for our furnace is arbitrary for the purpose of discussion; we also could use the British thermal unit (Btu) or some other units (see A Closer Look 14.1).
Diagram of a tire swing, illustrating the relation between potential and kinetic energy.
The tire swing, when released from its highest posi- tion, moves downward. At the bottom (straight down), the speed of the tire swing is greatest, and no potential energy remains. At this point, all the swing’s energy is the energy of motion, called kinetic energy. As the tire swings back and forth, the energy continuously changes between the two forms, potential and kinetic. However, with each swing, the tire slows down a little more and goes a little less high because of friction created by the movement of the tire and rope through air and friction at the pivot where the rope is tied to the tree. The friction slows the swing, generating heat energy, which is energy from random motion of atoms and molecules. Eventually, all the energy is converted to heat and emitted to the environment, and the swing stops.9
The example of the swing illustrates the tendency of energy to dissipate and end up as heat. Indeed, physicists have found that it is possible to change all the gravita- tional energy in a tire swing (a type of pendulum) to heat. However, it is impossible to change all the heat en- ergy thus generated back into potential energy. Energy is conserved in the tire swing. When the tire swing finally stops, all the initial gravitational potential energy has been transformed by way of friction to heat energy. If the same amount of energy, in the form of heat, were returned toenergy Units
When we buy electricity by the kilowatt-hour, what are we buying? We say we are buying energy, but what does that mean? Before we go deeper into the concepts of energy and its uses, we need to define some basic units.
The fundamental energy unit in the metric system is the joule; 1 joule is defined as a force of 1 newton* applied over a distance of 1 meter. To work with large quantities, such as the amount of energy used in the United States in a given year, we use the unit exajoule, which is equivalent to 1018 (a billion billion) joules, roughly equivalent to 1 quadrillion, or 1015, Btu, referred to as a quad. To put these big numbers in per- spective, the United States today consumes approximately 100 exajoules (or quads) of energy per year, and world consump- tion is about 500 exajoules (quads) annually.
In many instances, we are particularly interested in the rate of energy use, or power, which is energy divided by time. In the metric system, power may be expressed as joules per second, or watts (W); 1 joule per second is equal to 1 watt. When larger power units are required, we can use multipliers, such as kilo-(thousand), mega-(million), and giga-(billion). For example, a modern nuclear power plant’s electricity production rate is 1,000 megawatts (MW) or 1 gigawatt (GW).
Sometimes, it is useful to use a hybrid energy unit, such as the watt-hour (Wh); remember, energy is power multi- plied by time. Electrical energy is usually expressed and sold in kilowatt-hours (kWh, or 1,000 Wh). This unit of energy is 1,000 W applied for 1 hour (3,600 seconds), the equivalent energy of 3,600,000 J (3.6 MJ).
The average estimated electrical energy in kilowatt-hours used by various household appliances over a period of a year is shown in Table 14.2. The total energy used annually is the power rating of the appliance multiplied by the time the appliance was actually used. The appliances that use most of the electrical energy are water heaters, refrigerators, clothes driers, and washing machines. A list of common household appliances and the amounts of energy they consume is useful in identifying the ones that might help save energy through conservation or improved efficiency.
First-law efficiencies are misleading because a high value suggests (often incorrectly) that little can be done to save energy through additional improvements in efficien- cy. This problem is addressed by the use of second-law effi- ciency. Second-law efficiency refers to how well matched the energy end use is with the quality of the energy source. For our home-heating example, the second-law efficiency would compare the minimum energy necessary to heat the home to the energy actually used by the gas furnace. If we calculated the second-law efficiency (which is beyond the scope of this discussion), the result might be 6%— much lower than the first-law efficiency of 65%.10 (We will see why later.) Table 14.1 also lists some second-law efficiencies for common uses of energy.
Values of second-law efficiency are important be- cause low values indicate where improvements in energy technology and planning may save significant amounts of high-quality energy. Second-law efficiency tells us whether the energy quality is appropriate to the task. For example, you could use a welder’s acetylene blowtorch to light a can- dle, but a match is much more efficient (and safer as well).
We are now in a position to understand why the second-law efficiency is so low (6%) for the house-heating example discussed earlier. This low efficiency implies that the furnace is consuming too much high-quality energy in car- rying out the task of heating the house. In other words, the task of heating the house requires heat at a relatively low tem- perature, near 18°C (65°F), not heat with temperatures in ex- cess of 1,000°C (1,832°F), such as is generated inside the gas furnace. Lower-quality energy, such as solar energy, could do the task and yield higher second-law efficiency because there is a better match between the required energy quality and the house-heating end use. Through better energy planning, such as matching the quality of energy supplies to the end use, higher second-law efficiencies can be achieved, resulting in substantial savings of high-quality energy.
Examination of Table 14.1 indicates that electric- ity-generating plants have nearly the same first-law and second-law efficiencies. These generating plants are exam- ples of heat engines. A heat engine produces work from heat. Most of the electricity generated in the world today comes from heat engines that use nuclear fuel, coal, gas, or other fuels. Our own bodies are examples of heat engines, operating with a capacity (power) of about 100 watts and fueled indirectly by solar energy. (See A Closer Look 14.1 for an explanation of watts and other units of energy.) The internal combustion engine (used in automobiles) and the steam engine are additional examples of heat engines. A great deal of the world’s energy is used in heat engines, with profound environmental effects, such as thermal pol- lution, urban smog, acid rain, and global warming.
The maximum possible efficiency of a heat engine, known as thermal efficiency, was discovered by the French engineer Sadi Carnot in 1824, before the first law of ther- modynamics was formulated.11 Modern heat engines have
thermal efficiencies that range between 60 and 80% of their ideal Carnot efficiencies. Modern 1,000-megawatt (MW) electrical generating plants have thermal efficiencies ranging between 30 and 40%; that means at least 60 to 70% of the energy input to the plant is rejected as waste heat. For ex- ample, assume that the electric power output from a large generating plant is 1 unit of power (typically 1,000 MW). Producing that 1 unit of power requires 3 units of input (such as burning coal) at the power plant, and the entire pro- cess produces 2 units of waste heat, for a thermal efficiency of 33%. The significant number here is the waste heat, 2 units, which amounts to twice the actual electric power produced.
Electricity may be produced by large power plants that burn coal or natural gas, by plants that use nuclear fuel, or by smaller producers, such as geothermal, solar, or wind sources (see Chapters 15, 16, and 17). Once produced, the electricity is fed into the grid, which is the network of power lines or the distribution system. Eventually, it reaches homes, shops, farms, and factories, where it provides light and heat and also drives motors and other machinery used by society. As electricity moves through the grid, losses take place. The wires that transport electricity (power lines) have a natural resistance to electrical flow. Known as electrical resistivity, this resistance converts some of the electric energy in the transmission lines to heat energy, which is radiated into the environment surrounding the lines.
14.4 energy Sources and Consumption
People living in industrialized countries make up a rela- tively small percentage of the world’s population but consume a disproportionate share of the total energy con- sumed in the world. There is a direct relationship between a country’s standard of living (as measured by gross na- tional product) and energy consumption per capita.
When petroleum production eventually declines near the end of the 21st century, oil and gasoline will be in short- er supply and more expensive. Before then, use of these fuels may be curtailed in an effort to lessen global climate change. As a result, within the next 30 years, both developed and developing countries will need to find innovative ways to obtain energy. In the future, affluence may be related as closely to more efficient use of a wider variety of energy sources as it is now to total energy consumption.
Fossil Fuels and Alternative Energy Sources
Today, approximately 85% of the energy consumed in the United States is derived from petroleum, natural gas, and coal. Because they originated from plant and animal material that existed millions of years ago, they are called fossil fuels. They are forms of stored solar energy that are part of our geologic resource base, and they are essentially onrenewable. Other sources of energy—geothermal, nu- clear, hydropower, and solar, among others—are referred to as alternative energy sources because they may serve as alternatives to fossil fuels in the future. Some of them, such as solar and wind, are not depleted by consumption and are known as renewable energy sources.
The shift to alternative energy sources may be gradu- al as fossil fuels continue to be used, or it could be accel- erated by concern about potential environmental effects of burning fossil fuels. Regardless of which path we take, one thing is certain: Fossil fuels are finite. It took millions of years to form them, but they will be depleted in only a few hundred years of human history. Using even the most optimistic predictions, the fossil fuel epoch that started with the Industrial Revolution will represent only about 500 years of human history. Therefore, although fossil fuels have been extremely significant in the development of modern civilization, their use will be a brief event in the span of human history.
Energy Consumption in the United States
Energy consumption in the United States from 1980 and projected to 2035 is shown in Figure 14.4a. World energy consumption (for comparison) is shown in Figure 14.5. The United States, with about 5% of the world’s population, uses about 20% of the world’s energy. These figures dramatically illustrate the ongoing dependence on the three major fossil fuels (coal, natural gas, and petroleum) in the United States and the world. From approximately 1950 through the late 1970s, ener- gy consumption in the United States soared from about 30 exajoules to 75 exajoules annually. (Energy units are defined in A Closer Look 14.1.) Since about 1980, en- ergy consumption in the United States has risen by only about 25 exajoules (Figure 14.4b). This is encouraging because it suggests that policies promoting energy-effi- ciency improvements (such as requiring new automo- biles to be more fuel efficient and buildings to be better insulated) have been at least partially successful.
What is not shown in Figure 14.4a, however, is the huge energy loss. For example, energy consumption in the United States in 1965 was approxi- mately 50 exajoules, of which only about half was used effectively. Energy losses were about 50% (the number shown earlier in Table 14.1 for all en- ergy). In 2011, energy consumption in the United States was about 100 exa- joules, and, again, about 50% was lost in conversion processes. Energy losses in 2011 were about equal to total U.S. energy consumption in 1965! The larg- est energy losses are associated with the production of electricity and with transportation, mostly through the use of heat engines, which produce waste heat that is lost to the environment.
Another way to examine energy use is to look at the generalized energy flow of the United States by end use for a particular year. In 2008, we imported considerably more oil than we produced (we imported about 60% of the oil we used), and our energy consumption was fairly evenly distributed in three sectors: residential/commercial, industrial, and transportation. In 2010, our imports or other parts of the environment as a thermal pollutant. In other words, we design energy systems and power plants to provide en- ergy more than once14—that is, to use it a second time, at a lower temperature, and, possibly, to use it in more than one way as well.
An example of cogeneration is the natural gas combined cycle power plant that produces elec- tricity in two ways: gas cycle and steam cycle. In the gas cycle, the natural gas fuel is burned in a gas turbine to produce electricity. In
FIGURe 14.5 world energy consumption 1986-2011.
had been reduced to about 49% and are expected to drop to 36% by 2035 as we produce more domestic oil (Figure 14.4b). However, it is clear that we remain dangerously vulnerable to changing world conditions affecting the pro- duction and delivery of crude oil. We need to evaluate the entire spectrum of potential energy sources to ensure that sufficient energy will be available in the future, while sus- taining environmental quality.
14.5 energy Conservation, Increased efficiency, and Cogeneration
We have come to realize that there are two ways to meet our growing demand for electricity—building more power plants or implementing energy efficiency programs at the customer level (homes, businesses, and industries). Util- ity companies have evidence to support the concept that energy conservation programs are a significant energy re- source. It is far cheaper to reduce demand through effi- ciency programs than to build power plants. As a result, utility companies in the past decade have increased spend- ing on energy efficiency programs by several billion dollars per year. Efficiency saves money, adds jobs to the economy, and reduces emissions of greenhouse gasses.12
Conservation of energy refers simply to using less ener- gy and adjusting our energy needs and uses to minimize the amount of high-quality energy necessary for a given task.13 Increased energy efficiency involves designing equip- ment to yield more energy output from a given amount of energy input (first-law efficiency) or better matches be- tween energy source and end use (second-law efficiency). Another concept is cogeneration, which includes a num- ber of processes designed to capture and use waste heat, rather than simply releasing it into the atmosphere, water, the steam cycle, hot exhaust from the gas turbine is used to create steam that is fed into a steam generator to produce additional electricity. The combined cycles capture waste heat from the gas cycle, nearly doubling the efficiency of the power plant from about 30% to 50–60%. Energy con- servation is particularly attractive because it provides more than a one-to-one savings. Remember that it takes 3 units of fuel such as coal to produce 1 unit of power such as elec- tricity (two-thirds is waste heat). Therefore, not using (con- serving) 1 unit of power saves 3 units of fuel!
These three concepts—energy conservation, energy efficiency, and cogeneration—are all interlinked. For ex- ample, when big, coal-burning power stations produce electricity, they may release large amounts of heat into the atmosphere. Cogeneration, by using that waste heat, can increase the overall efficiency of a typical power plant from 33% to as much as 75%, effectively reducing losses from 67 to 25%. Cogeneration also involves generating electricity as a by-product of industrial processes that pro- duce steam as part of their regular operations. Optimistic energy forecasters estimate that, eventually, we may meet approximately one-half the electrical power needs of in- dustry through cogeneration.13,14 Another source has esti- mated that cogeneration could provide more than 10% of the power capacity of the United States.
The average first-law efficiency of only 50% (Table 14.1) illustrates that large amounts of energy are cur- rently lost in producing electricity and in transporting people and goods. Innovations in how we produce en- ergy for a particular use can help prevent this loss, raising second-law efficiencies. Of particular importance will be energy uses with applications below 100°C (212°F) because a large portion of U.S. energy consumption for uses below 300°C, or 572°F, is for space heating and water heating.
In considering where to focus our efforts to improve energy efficiency, we need to look at the total energy-use picture. In the United States, space heating and cooling of homes and offices, water heating, industrial processes (to produce steam), and automobiles account for nearly 60% of the total energy use, whereas transportation by train, bus, and airplane accounts for only about 5%. Therefore, the areas we should target for improvement are building design, industrial energy use, and automobile design. We note, however, that debate continues as to how much effi- ciency improvements and conservation can reduce future energy demands and the need for increased energy pro- duction from traditional sources, such as fossil fuel.
Building Design
A spectrum of possibilities exists for increasing energy efficiency and conservation in residential buildings. For new homes, the answer is to design and construct homes that require less energy for comfortable living.15 For ex- ample, we can design buildings to take advantage of pas- sive solar potential, as did the early Greeks and Romans and the Native American cliff dwellers. (Passive solar energy systems collect solar heat without using moving parts.) Windows and overhanging structures can be po- sitioned so that the overhangs shade the windows from solar energy in summer, thereby keeping the house cool, while allowing winter sun to penetrate the windows and warm the house.
The potential for energy savings through architectural design for older buildings is extremely limited. The po- sition of the building on the site is already established, and reconstruction and modifications are often not cost- effective. The best approach to energy conservation for these buildings is insulation, caulking, weather stripping, installation of window coverings and storm windows, and regular maintenance.
Ironically, buildings constructed to conserve energy are more likely to develop indoor air pollution due to re- duced ventilation. In fact, air pollution is emerging as one of our most serious environmental problems. Potential difficulties can be reduced by better designs for air circu- lation systems that purify indoor air and bring in fresh, clean air. Construction that incorporates environmental principles is more expensive, ow- ing to higher fees for architects and engineers, as well as higher initial construction costs. Nevertheless, moving toward improved design of homes and residential buildings to conserve energy remains an impor- tant endeavor.
production of goods (automobiles, appliances, etc.) continued to grow significantly. Today, U.S. industry consumes about one-third of the energy produced. The reason we have had higher productivity with lower growth of energy use is that more industries are us- ing cogeneration and more energy-efficient machin- ery, such as motors and pumps designed to use less energy.13,15
Automobile Design
The development of fuel-efficient automobiles has steadily improved during the last 30 years. In the early 1970s, the average U.S. automobile burned approximate- ly 1 gallon of gas for every 14 miles traveled. By 1996, the miles per gallon (mpg) had risen to an average of 28 for highway driving and as high as 49 for some automo- biles.16 Fuel consumption rates did not improve much from 1996 to 1999. In 2004, many vehicles sold were SUVs and light trucks with fuel consumption of 10–20 mpg. A loophole in regulations permits these vehicles to have poorer fuel consumption than conventional au- tomobiles.16 As a result of higher gasoline prices, sales of larger SUVs declined in 2006, but smaller SUVs re- main popular as consumers are apparently sacrificing size for economy (up to a point). In 2012, the government (through executive action, without congressional ap- proval) agreed on new Corporate Average Fuel Economy (CAFE) regulations that are visionary in scope. Starting in 2017 and reached by 2025, the new proposed CAFE standard will be 54.5 mpg, a significant increase from the previous standard of 35.5 mpg by 2016. This increased fuel efficiency will be reached with new innovative tech- nology, including cars with lighter diesel engines and transmissions; use of lighter materials and improved tires; hybrid cars, which combine a fuel-burning engine and an electric motor; and all-electric vehicles and vehicles that use natural gas as a fuel. Demand for hybrid vehicles is growing rapidly and will benefit from the development of more advanced rechargeable batteries (plug-in hybrids; see Figure 14.6).
A real change in cars is coming. What it will be and when are not entirely known, but it may be a transforma- tion to all-electric cars. Where and how we produce the electricity to power those cars will be an issue.
Values, Choices, and Energy Conservation
What is the relationship between human development (a measure of life expectancy, education, and wealth) and use of energy per person? The results may surprise you. The United Nations has developed the Index of Human Development (HDI) for many countries. HDI varies from about 0.3 (low) to 0.5 (medium) to 0.9 (high). The HDI and annual electricity use per person can be com- pared for various countries (see Figure 14.7). The graph produced from this comparison shows that the HDI for western European countries such as France, Germany, the U.K., Spain, and Italy is 9—about the same as that for the United States—but per capita use of electricity in these countries (shown on the bottom line of the graph) is one- third to one-half of U.S. consumption. The graph shows that human development, in terms of life expectancy, ed- ucation, and income per person, peaks at an electricity use of about 4,000 kWh (remember that 1 kWh is equivalent to 3.6 Mj; see a Closer Look 14.1). However, U.S. and Canadian usage to achieve this HDI is about 13,000 kWh and 16,000 kWh, respectively. Does this mean that the United States uses too much electricity? The answer is likely yes. With energy conservation, we should be able to reduce our per capita use of electricity to be more in line with other industrial countries such as Germany, the U.K., France, Japan, and South Korea.17
Changing behavior to conserve energy involves our values and the choices we make to act at a local level; these choices, in turn, address global environmental problems,
such as human-induced warming caused by burning fossil fuels. For example, we make choices as to how far we com- mute to school or work and what method of transport we use to get there. Some people commute more than an hour by car to get to work, while others ride a bike, walk, or take a bus or train. Other ways of modifying behavior to conserve energy include the following:
• Using carpools to travel to and from work or school • Purchasing a hybrid or all-electric car • Turning off lights when leaving rooms • Taking shorter showers (conserves hot water)
• Putting on a sweater and turning down the thermostat in winter
• Using energy-efficient compact fluorescent light bulbs or light-emitting diode (LED) lights
• Purchasing energy-efficient appliances • Sealing drafts in buildings with weather stripping and
caulk
• Better insulating your home
• Washing clothes in cold water and hanging them to dry whenever possible
• Purchasing local foods rather than foods that must be brought to market from afar
• Reducing standby power for electronic devices and ap- pliances by using power strips and turning them off when not in use
• Installing solar water heaters or collectors What other ways of modifying your behavior would help
conserve energy?
14.6 Sustainable-energy policy
Presidents of the United States since the mid-1970s have attempted to address energy problems and the question of how to become independent of foreign energy sourc- es. The Energy Policy Act of 2005, passed by Congress and signed into law by then President George W. Bush in the summer of 2005, has been followed by heated de- bate about energy policy in the 21st century. A number of topics related to energy are being discussed, including the American Clean Energy and Security Act of 2009, which took a serious step toward energy self-sufficiency in the United States.
The 2009 act (not yet passed) has four parts: (1) clean energy, which involves renewable energy, sequestration of carbon, development of clean fuels and vehicles, and a better electricity transmission grid; (2) energy efficiency, for buildings, homes, transportation, and utilities; (3) reduc- tion of carbon dioxide and other greenhouse gases associated with global warming, including programs to reduce global warming by reducing emissions of carbon dioxide in com- ing years; and (4) making the transition to a clean energy economy, including economic incentives for development of green energy jobs, exporting clean technology, increas- ing domestic competitiveness, and finding ways to adapt to global warming.
The United States faces serious energy problems. En- ergy policy, from a local to global scale, has emerged as a central economic concern, a national security issue, and an environmental question. How we respond to energy is- sues will largely define who we are and what sort of world we will live in during this century.
Today energy policy is at a crossroads. One path leads to the “business-as-usual” approach, which consists of finding greater amounts of fossil fuels, building larger power plants, and continuing to use energy as freely as we always have. The business-as-usual path is more com- fortable—it requires no new thinking; no realignment of political, economic, or social conditions; and little antici- pation of coming reductions in oil production.
People heavily invested in the continued use of fossil fuels and nuclear energy often favor the traditional path. They argue that much environmental degradation around the world has been caused by people who have been forced to use local resources, such as wood, for energy, leading to the loss of plant and animal life and increasing soil ero- sion. They argue that the way to solve these environmen- tal problems is to provide cheap, high-quality energy, such as fossil fuels or nuclear energy.
In countries like the United States, with sizable re- sources of oil, natural gas, and coal, people supporting the business-as-usual path argue that we should exploit those resources while finding ways to reduce their environmen- tal impact. According to these proponents, we should
(1) allow the energy industry to develop the available en- ergy resources and (2) let industry, free from government regulations, provide a steady supply of energy with less total environmental damage.
The energy plan put forth by President Bush was largely a business-as-usual approach: Find and use more coal, oil, and natural gas; use more nuclear power; and build more than 1,000 new fossil fuel plants in the next 20 years. Energy conservation and development of alter- native energy sources, while encouraged, were not consid- ered of primary importance.
A visionary path for energy policy was suggested more than 30 years ago by Amory Lovins.18 That path focuses on energy alternatives that emphasize energy quality and are renewable, flexible, and environmentally more benign than those of the business-as-usual path. As defined by Lovins, these alternatives have the following characteristics:
• They rely heavily on renewable-energy resources, such as sunlight, wind, and biomass (wood and other plant material).
• They are diverse and are tailored for maximum effec- tiveness under specific circumstances.
• They are flexible, accessible, and understandable to many people.
• They are matched in energy quality and geographic dis- tribution and are scaled to end-use needs, increasing second-law efficiency.
Lovins points out that people are not particularly in- terested in having a certain amount of oil, gas, or electric- ity delivered to their homes; they are more interested in comfortable homes, adequate lighting, food on the table, and energy for transportation.18 According to Lovins, only about 5% of end uses require high-grade energy, such as electricity. Nevertheless, a lot of electricity is used to heat homes and water. Lovins shows that there is an imbalance in using nuclear reactions at extremely high temperatures and in burning fossil fuels at high temperatures simply to meet needs where the necessary temperature increase may be only a few 10s of degrees. He considers such large discrepancies wasteful and a misallocation of high-quality energy.
Energy for Tomorrow
The availability of energy supplies and the future demand for energy are difficult to predict because the technical, economic, political, and social assumptions underlying predictions are constantly changing. In addition, seasonal and regional variations in energy consumption must also be considered. For example, in areas with cold winters and hot, humid summers, energy consumption peaks dur- ing the winter months (from heating) and again in the summer (from air-conditioning). Regional variations in energy consumption are significant. For example, in the United States as a whole, the transportation sector uses about one-fourth of the energy consumed. However, in California, where people often commute long distances to work, about one-half of the energy is used for trans- portation, more than double the national average. Energy sources, too, vary by region. For example, in the eastern and southwestern United States, the fuel of choice for power plants is often coal, but power plants on the West Coast are more likely to burn oil or natural gas or use hy- dropower from dams to produce electricity.
Future changes in population densities, as well as in- tensive conservation measures, will probably alter existing patterns of energy use. This might involve a shift to great- er reliance on alternative (particularly renewable) energy sources.19,20 The United States’ energy consumption in the year 2050 may be about 110 exajoules (Figure 14.4a). What will be the energy sources for the anticipated growth in energy consumption? Will we follow our past policy of business as usual (coal, oil, nuclear), or will we turn more to alternative energy sources (wind, solar, geothermal)? What is clear is that the mix of energy sources in 2035 will be different from today’s and more diversified.19-21
All projections of specific sources and uses of ener- gy in the future must be considered speculative. Perhaps most speculative of all is the idea that we really can meet most of our energy needs with alternative, renewable en- ergy sources in the next several decades.
The energy decisions we make in the very near fu- ture will greatly affect both our standard of living and our quality of life. From an optimistic point of view, we have the necessary information and technology to ensure a bright, warm, lighted, and mobile future. But time may be running out, and we need action now. We can contin- ue to take things as they come and live with the results of our present dependence on fossil fuels, or we can build a more sustainable energy future based on careful planning, innovative thinking, and a willingness to move from our dependence on petroleum.
U.S. energy policy for the 21st century is being dis- cussed seriously, and significant change in policy is likely. Some of the recommendations are as follows:
• Promote conventional energy sources: Use more natu- ral gas to reduce our reliance on energy from foreign countries.
• Encourage alternative energy: Support and subsidize wind, solar, geothermal, hydrogen, and biofuels (etha- nol and biodiesel).
• Provide for energy infrastructure: Ensure that electricity is transmitted over dependable, modern infrastructure.
• Promote conservation measures: Set higher efficiency standards for buildings and for household products. Require that waste heat from power generation and in- dustrial processes be used to produce electricity or other products. Support stronger fuel-efficiency standards for cars, trucks, and SUVs. Provide tax credits for installing energy-efficient windows and appliances in homes and for purchasing fuel-efficient hybrids, all-electric cars, and clean diesel vehicles.
• Carefully evaluate the pros and cons of nuclear power, which can generate large amounts of electricity without emitting greenhouse gases, but which has serious nega- tives as well.
• Promoteresearch:Developnewalternativeenergysourc- es; find new, innovative ways to improve existing coal plants and to help construct cleaner coal plants; deter- mine whether it is possible to extract vast amounts of oil trapped in oil shale and tar sands without harming the environment; and develop pollution-free, electric automobiles.
Which of the above points will become policy in fu- ture years is not known, but parts of the key ideas will move us toward sustainable energy.
Integrated, Sustainable Energy Management
The concept of integrated energy management rec- ognizes that no single energy source can provide all the energy required by the various countries of the world.22 A range of options that vary from region to region will have to be employed. Furthermore, the mix of technolo- gies and sources of energy will involve both fossil fuels and alternative, renewable sources.
A basic goal of integrated energy management is to move toward sustainable energy development that is implemented at the local level. Sustainable energy devel- opment would have the following characteristics:
• It would provide reliable sources of energy. • It would not destroy or seriously harm our global, re-
gional, or local environments.
• It would help ensure that future generations inherit a quality environment with a fair share of the Earth’s resources.
To implement sustainable energy development, lead- ers in various regions of the world will need energy plans based on local and regional conditions. The plans will in- tegrate the desired end uses for energy with the energy sources that are most appropriate for a particular region and that hold potential for conservation and efficiency. Such plans will recognize that preserving resources can be profitable and that degradation of the environment and poor economic conditions go hand in hand.22 In other
words, degradation of air, water, and land resources de- pletes assets and ultimately will lower both the standard of living and the quality of life. A good energy plan recog- nizes that energy demands can be met in environmentally preferred ways and is part of an aggressive environmental policy whose goal is a quality environment for future gen- erations. The plan should do the following:22
• Provide for sustainable energy development.
• Provide for aggressive energy efficiency and conservation.
• Provide for diversity and integration of energy sources.
• Develop and use the “smart grid” to optimally manage energy flow on the scale of buildings to regions.
• Provide for a balance between economic health and environmental quality.
• Use second-law efficiencies as an energy policy tool— that is, strive to achieve a good balance between the quality of an energy source and end uses for that energy.
An important element of the plan involves the energy used for automobiles. This builds on policies of the past 30 years to develop hybrid vehicles that use both an electric motor and an internal combustion engine and to improve fuel technology to reduce both fuel consumption and emission of air pollutants. Finally, the plan should factor in the marketplace through pricing that reflects the economic cost of using the fuel, as well as its cost to the environment. In sum, the plan should be an integrated energy-management statement that moves toward sus- tainable development. Those who develop such plans rec- ognize that a diversity of energy supplies will be necessary and that the key components are (1) improvements in en- ergy efficiency and conservation and (2) matching energy quality to end uses.23
The global pattern of ever-increasing energy consump- tion led by the United States and other nations cannot be sustained without a new energy paradigm that includes changes in human values, not just a breakthrough in technology. Choosing to own lighter, more fuel-efficient automobiles and living in more energy-efficient homes is consistent with a sustainable energy system that fo- cuses on providing and using energy to improve human welfare. A sustainable energy paradigm establishes and maintains multiple linkages among energy production, energy consumption, human well-being, and environ- mental quality.23
CritiCAl thinking issue
Use of energy Today and in 2030
Note: Before proceeding with this exercise, refer back to A Closer Look 4.1 to be sure you are comfortable with the units and big numbers.
The Organization for Economic Cooperation and Devel- opment (OECD) is a group of 30 countries, 27 of which are classified by the World Bank as having high-income econo- mies. Non-OECD members are not all low-income coun- tries, but many are. The developing countries (all of which are non-OECD) have most of the world’s 7 billion people and are growing in population faster than the more affluent countries. The average rate of energy use in 2010 for an individual in non-OECD countries is 46 billion joules per person per year (1.5 kW per person), whereas for the OECD countries it is 210 billion joules per person per year (6.7 kW per person). In other words, people in OECD countries use about 4.5 times more energy per person than those in non-OECD countries. In 2010, each group—OECD and non-OECD—used about 250 EJ (1 EJ is 1018 J). The world average is 74 billion joules per person per year (2.3 kW per person).24
If the current annual population growth rate of 1.1% con- tinues, the world’s population will double in 64 years. However, as we learned in Chapters 1 and 4, the human population may not double again. It is expected to be about 8.5 billion by 2030. More people will likely mean more energy use. People in non- OECD countries will need to consume more energy per capita if the less-developed countries are to achieve a higher standard of living; thus, energy consumption in non-OECD countries as a group is projected to increase by 2030 to about 55 billion joules per person per year (1.7 kW per person). On the other hand, energy use in OECD countries is projected to decline to about 203 billion joules per person per year (6.4 kW per per- son). This would bring the global average in 2030 to about 80 billion joules per person per year (2.5 kW per person), up from 74 billion joules in 2010. If these projections are correct, 58% of the energy will be consumed in the non-OECD countries, compared with 50% today.
With worldwide average energy use of 2.3 kW per person in 2010, the 6.8 billion people on Earth use about 16 trillion
watts annually. A projected population of 8.5 billion in 2030 with an estimated average per capita energy use rate of 2.5 kW would use about 21 trillion watts annually, an increase of about 33% from today.24
A realistic goal is for annual per capita energy use to remain about 2.5 kW, with the world population peaking at 8.5 billion people by the year 2030. If this goal is to be achieved, non- OECD countries will be able to increase their populations by no more than about 50% and their energy use by about 70%; OECD nations can increase their population by only a few per- cent and will have to reduce their energy use slightly.
Critical Thinking Questions
1. Using only the data presented in this exercise, how much energy, in exajoules, did the world use in 2010, and what would you project global energy use to be in 2030?
2. The average person emits as heat 100 watts of power (the same as a 100 W bulb). If we assume that 25% of it is emit- ted by the brain, how much energy does your brain emit as heat in a year? Calculate this in joules and kWh. What is the corresponding value for all people today, and how does that value compare with world energy use per year? Can
this help explain why a large, crowded lecture hall (indepen- dent of the professor pontificating) might get warm over an hour?
3. Can the world supply one-third more energy by 2030 with- out unacceptable environmental damage? How?
4. What would the rate of energy use be if all people on Earth had a standard of living supported by energy use of 10 kW per person, as in the United States today? How do these to- tals compare with the present energy-use rate worldwide?
5. In what specific ways could energy be used more efficiently in the United States? Make a list of the ways and compare your list with those of your classmates. Then compile a class list.
6. In addition to increasing efficiency, what other changes in energy consumption might be required to provide an aver- age energy-use rate in 2030 of 6.4 kW per person in OECD countries?
7. Would you view the energy future in 2030 as a continuation of the business-as-usual approach with larger, centralized en- ergy production based on fossil fuels, or a softer path, with more use of alternative, distributed energy sources? Justify your view.
suMMaRy
• The first law of thermodynamics states that energy is neither created nor destroyed but is always conserved and is transformed from one kind to another. We use the first law to keep track of the quantity of energy.
• The second law of thermodynamics tells us that as en- ergy is used, it always goes from a more usable (higher- quality) form to a less usable (lower-quality) form.
• Two fundamental types of energy efficiency are derived from the first and second laws of thermodynamics. In the United States today, first-law efficiencies average about 50%, which means that about 50% of the energy produced is returned to the environment as waste heat. Second-law efficiencies average 10–15%, so there is a high potential for saving energy through better match- ing of the quality of energy sources with their end uses.
• Energy conservation and improvements in energy effi- ciency can have significant effects on energy consump- tion. It takes three units of a fuel such as oil to produce one unit of electricity. As a result, each unit of electricity conserved or saved through improved efficiency saves three units of fuel.
• Arguments can be made for both the business-as-usual path and changing to a new path. The first path has a
long history of success and has produced the highest standard of living ever experienced. However, present sources of energy (based on fossil fuels) are causing seri- ous environmental degradation and are not sustainable (especially with respect to conventional oil). A second path, based on alternative energy sources that are re- newable, decentralized, diverse, and flexible, provides a better match between energy quality and end use and emphasizes second-law efficiencies.
• The transition from fossil fuels to other energy sources requires sustainable, integrated energy management. The goal is to provide reliable sources of energy that do not cause serious harm to the environment and ensure that future generations will inherit a quality environment.
• Due to discovery of large amounts of oil and natural gas in the United States (mostly from tight, shale con- tinuous deposits), we are approaching a time, when in a few decades, we will likely achieve energy inde- pendence. However, using more fossil fuels will come with the increased possibility of additional environ- mental consequences—from air and water pollution to climate change.
Botkin, Daniel B. Environmental Science: Earth as a Living Planet, 9th Edition. Wiley, 2013-12-23. VitalBook file.
Multimedia
1. Bryce, R. (2011, November 30). What’s a watt? [Video clip]. Retrieved from http://www.youtube.com/watch?v=1__KjuGNzxc
· Transcript
2. energynownews. (2011, July 14). What you don’t know about gas prices [Video clip]. Retrieved from http://www.youtube.com/watch?v=yQaRaCtCuzE
· Transcript
3. energynownews. (2011, October 3). Energy 101: Electricity generation [Video clip]. Retrieved from http://www.youtube.com/watch?v=20Vb6hlLQSg
· Transcript
4. Hickey, K. (2010, July 1). Life cycle assessment – It’s the only way to drive! [Video clip]. Retrieved from http://www.youtube.com/watch?v=ZlJ3HKXSdhc
· Transcript
Recommended Resources Websites
1. Department of Energy. (n.d.). Energy sources. Retrieved from http://energy.gov/science-innovation/energy-sources
2. Department of Energy. (n.d.). Fossil. Retrieved from http://energy.gov/science-innovation/energy-sources/fossil
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