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What are the advantages of building car bodies from carbon-fiber or other composite materials?
Regardless of how cars are powered, we can make them much more fuel-efficient by building them out of ultralight and ultrastrong materials. Engineers have built concept cars using carbon-fiber materials, and some racing car bodies contain hemp-fiber composites.
What are three forms of indirect solar energy?
Renewable wind energy, hydropower, wood, and other fuels made from plants (biofuels) are indirect forms of solar energy.
What are three serious environmental problems caused by our dependence on fossil fuels? List three steps that we will have to take, according to the experts, in order to deal with these problems.
1. Outdoor air pollution, primarily resulting from the burning of coal in power and industrial plants, kills at least 1 million people worldwide every year and as many as 68,000 people annually in the United States 2.Climate disruption projected for this century is largely due to the burning of fossil fuels, which adds carbon dioxide (CO2) to the atmosphere faster than the natural carbon cycle can remove it. This is resulting in atmospheric warming that is causing rapid climate change. 3.Increasing ocean acidification, a process in which much of the CO2 that we add to the atmosphere dissolves in the ocean and reacts with ocean water to form carbonic acid. If ocean waters become too acidic, they will slowly dissolve not only the world's coral reefs (Figure 5.27), which are vital aquatic centers of biodiversity, but also the shells of many species of ocean life that form vital links in the ocean's food webs. Some scientists contend that, in the long run, ocean acidification could be our most serious environmental problem. Steps to take 1. Cut our energy waste. This will involve giving top priority to reducing energy waste and improving energy efficiency by squeezing every bit of work that we can out of every unit of energy we use. We need to view the energy we are wasting as the quickest, easiest, cheapest, and least environmentally harmful source of energy that we can tap. 2.Shift to renewable energy resources. We have already begun phasing in a mix of renewable energy resources, including solar energy, wind, hydropower, biomass, and geothermal heat, and we need to fully implement this mix as soon as possible. These forms of energy produce little in the way of the air and water pollutants, greenhouse gases, and long-lasting, dangerous radioactive wastes that we are producing daily by relying on fossil fuels and nuclear power. 3.Reduce environmental harm. We must find and quickly implement ways to lessen the harmful environmental impacts of our use of nonrenewable fossil fuels (especially coal) and costly and potentially dangerous nuclear power.
Define solar thermal system. Describe two types of such systems.
A more high-tech and large-scale way to use direct solar energy is through a solar thermal system, which collects and concentrates direct solar energy to a temperature high enough to boil water and produce steam for generating electricity. In one system, huge arrays of curved mirrors collect and focus sunlight on fluid-filled pipes that run through the center of each collector. The concentrated heat in the fluid is used to produce steam that powers a turbine, which drives an electricity-producing generator. In another type of system, an array of computer-controlled mirrors track the sun and focus reflected sunlight on a central receiver, sometimes called a power tower, to boil water and produce steam that spins a turbine and generates electricity. We can store excess heat produced by these systems in molten salts and use it to produce electricity at night or on cloudy days (which are rare in most of the sunny desert areas where these systems are built).
Define and distinguish between renewable and nonrenewable energy resources and give an example of each.
A renewable energy resource is one that natural processes can replenish within a relatively short time. Ex: Solar energy is continually replenished, and firewood from trees can be replenished within years. Other examples are energy from flowing water and heat stored in the earth's interior (geothermal energy). A nonrenewable energy resource is a resource that can be used up and not replenished on a human time scale. Ex: Supplies of fossil fuels (oil, coal, and natural gas) and of uranium are finite and will not be replaced for millions of years once we have used up our affordable supplies of these resources. The most important renewable energy source, by far, is the sun. Without the sun's heat and light, which plants use to produce food, there would be no life as we know it on the earth. Like plants, we also use solar energy, for example, to heat water and to produce electricity.
Describe the United States' potential for using wind to produce its electricity. ?
According to Amory Lovins, Lester R. Brown, founder and head of the Earth Policy Institute, and many other energy and environmental experts, energy efficiency and wind power have more important advantages and fewer major disadvantages than any other energy resources. Between 1998 and 2011, the amount of electricity produced by tapping into wind energy grew by more than 20-fold, and in 2012, showed no signs of leveling off. Since 1995, the cost of wind-generated electricity has fallen by more than half, making wind increasingly competitive with natural gas and coal for producing electricity. When the harmful environmental effects of using wind, natural gas, and coal are included in cost estimates, wind is easily the least costly. Even without these costs added, wind power may soon rank as the world's least expensive large-scale energy resource. The United States leads the world in total electricity generated by wind, followed closely by China and Germany. China is building wind farms at a fast pace, but the United States has the world's highest potential for wind energy development (Figure 5.24). According to the U.S. Department of Energy (DOE), just four states—North Dakota, South Dakota, Kansas, and Texas—have enough wind resources to satisfy the entire U.S. demand for electricity. In addition, a 2009 study by the DOE estimated that wind resources off the U.S. coasts, especially the East and Gulf Coasts, could also meet the entire country's demand for electricity.
What are the most energy-efficient ways to heat a home, provide hot water, and provide lighting?
Another way is to use a programmable thermostat that can cut heating and cooling bills 20% by automatically adjusting nighttime and daytime temperatures. Homeowners can also wrap electric hot water heaters with insulating blankets (not recommended for natural gas-fired heaters). By sealing and wrapping ductwork, a homeowner can reduce energy losses by up to 30%. In the near future, smart houses will save even more energy by making use of light, thin sheets of aerogel insulation, made with the use of nanotechnology, and windowpanes that automatically get darker or lighter to control inputs of light as well as inputs and outputs of heat. Homeowners can use more energy-efficient heating and cooling systems and appliances. For example, the most wasteful and expensive way to heat a building is with electric heat, while a modern natural gas furnace can be as high as 94% efficient. Water heaters and other appliances also vary greatly in their efficiency. For example, a natural gas-fired tank-less instant water heater, which is about the size of a typical suitcase, heats water on demand instead of storing large amounts of heated water. It uses from one-quarter to one-third less energy than a conventional tank water heater uses. (Electric instant water heaters, however, are nowhere near as energy-efficient as the natural gas-fired ones.) Front-loading clothes washers use less than half as much energy and only about two-thirds as much water as top-loading washers use. Lighting is another important area in which homeowners and businesses can save money and energy. Replacing incandescent lightbulbs with CFLs and LEDs would cut U.S. household energy bills and reduce air pollution and greenhouse gas emissions from coal-fired electrical power plants. Another way to save lighting energy is to focus efficient lighting on work areas instead of lighting whole rooms. Still another is the use of motion detectors to turn lights on or off automatically in the presence or absence of people in a room. We can also save some of the energy and money we use to keep televisions, stereo systems, and other devices on standby mode. Consumers can plug their electronic devices into a smart strip that senses when a device is not being used and turns off its standby feature.
Define and distinguish between passive and active solar heating systems.
Another way to take advantage of direct solar energy is through an active solar heating system, which uses a fluid, such as water or an antifreeze solution, that can absorb heat. As the fluid is pumped through tubes mounted inside of flat roof panels that face the sun, it absorbs some of the sun's energy and carries it to a heat storage tank containing gravel, water, clay, or some other heat-absorbing substance. Or, it can be used to heat water that can then be stored in an insulated tank much like a conventional hot water heater. In China, at least one of every ten households heats its water by using inexpensive rooftop solar water heaters, while in sunny Israel, nine of ten households do so. ======= Another approach is to provide much of the heat for a house by using a passive solar heating system, which absorbs and stores heat directly from the sun during daylight hours and slowly releases it throughout the day and night. Passive solar houses typically use brick, stone, adobe, or concrete walls and floors to store the sun's heat. There is nothing new about passive solar heating. For more than 4,000 years, people have been orienting their dwellings toward the sun and using systems such as those described here. Today, we are rediscovering and improving these simple and proven technologies. Passive solar heating is a widely used application of the earth's solar energy sustainability principle
What are some problems associated with producing ethanol from corn and cellulosic sources?
Corn is still used to produce ethanol in the United States. Its promoters argue that it will help the country reduce its heavy dependence on imported oil and that using it instead of gasoline will cut greenhouse gas emissions. However, environmental economist Stephen Polan-sky and other analysts have estimated that if the entire U.S. corn crop were made into ethanol every year, it would satisfy the country's current demand for gasoline for less than three months and thus would not do much to reduce the country's dependence on oil imports. Scientific studies also indicate that, when we factor in the fossil fuels used to plant, harvest, process, and convert corn to ethanol, the net energy yield for this biofuel is low. Brazil runs almost half of its motor vehicles on ethanol or a mixture of ethanol and gasoline, but instead of using corn, it produces fuel from sugarcane grown on large plantations. The process makes use of bagasse, a waste product created when sugarcane is crushed. This ethanol has a moderate net energy yield, compared with the low net energy yields for gasoline and corn-based ethanol. Another alternative to corn ethanol is cellulosic ethanol, which is produced from the cellulose found in plant leaves, stalks, and husks. By using it, we could avoid some of the environmental problems resulting from the use of corn or other crops to produce ethanol. However, an affordable technology for producing cellulosic ethanol has yet to be developed. Experts have estimated that to replace half of the gasoline consumed in the United States with cellulosic ethanol, the country would have to plant fast-growing grasses such as switchgrass on an area of land seven times as large as the land area currently used to produce corn. Researchers estimate that clearing, planting, and fertilizing such vast areas of land and converting the crop to ethanol would produce far more greenhouse gas emissions than burning the amount of gasoline that the ethanol would replace.
Define energy conservation and energy efficiency.
Energy conservation is any reduction in the use or waste of energy. It can be as simple as choosing to walk or bike instead of using a car or turning down the thermostat at night. However, we can accomplish energy conservation on a much larger scale using important strategies to improve energy efficiency—the measure of how much work we can get from each unit of energy we use. The lower the efficiency, the greater the amount of energy we waste. Note that by improving efficiency, we can use less energy and still enjoy the same benefits of using it. For example, most fuel-efficient cars can take us from place to place as quickly and comfortably as a gas-guzzling vehicle can.
Why should we care about energy efficiency and renewable energy?
Everything runs on energy. This includes all living things, as well as all the cars, houses, factories, lights, and appliances on which we depend. Every unit of energy we use costs us something, be it money or some other type of resource. So whenever we waste energy, we waste money or resources or both. This is why we need to care about using energy more efficiently. Probably every one of us wastes energy in some way: by driving vehicles with a low fuel efficiency (getting less than 40 miles per gallon); living in poorly insulated houses; using energy-inefficient lighting and appliances; or leaving lights and computers on or motors running when we are not using them. Also, because our use of energy often has harmful effects on the environment, the more energy we waste, the greater is our ecological footprint. We should also care about the sources of the energy we use. The use of any energy resource has an environmental impact. But our most widely used energy resources—nonrenewable oil, natural gas, coal, and uranium (which fuels nuclear power plants)—have large harmful environmental impacts. By shifting during the next several decades to greater use of renewable energy from the sun, wind, flowing water, and geothermal energy stored as heat in the earth's crust, we can greatly reduce these harmful environmental impacts. When we rely more on renewable energy sources, most of which depend on energy from the sun, we are following one of nature's three scientific principles of sustainability that have sustained life on the earth for about 3.5 billion years. Some scientists argue that by following these principles, we will have a better chance of preserving our species, cultures, and economies than we will if we ignore them. There is a great deal of evidence that certain human activities, in violation of these principles, are degrading the earth's life support system. In these activities, we are wasting huge amounts of energy and relying on environmentally harmful energy resources. The good news is that, by observing the earth's scientific sustainability principles, we can still enjoy many of the benefits of today's affluent societies without wasting so much energy and money, and we can reduce our harmful environmental impacts.
What are some more efficient alternatives to car travel?
Finally, we can improve the overall efficiency of our transportation systems by relying less on cars and more on expanded and improved mass-transit systems. Mass transit systems such as high-speed rail, light-rail, and buses are widely used in parts of Europe and Japan, and more recently in China and certain cities in South America and North America.
What are four drawbacks of wind power?
For one, electricity generated by wind farms has to be routed overland through transmission lines, which are not always welcomed by people living along the power line routes. Also, some people object to the sights and sounds of wind turbines, and every year in the United States, 40,000-100,000 birds and bats die in collisions with large wind turbines. In some cases, another problem is land disturbance resulting from construction of wind farms. Another problem is that winds die down from time to time. This means that wind power suppliers must rely on backup sources such as natural gas-fired, coal-fired, and nuclear power plants. Every wind farm must have a system that causes one of these backup sources to kick in whenever the wind dies. Scientists and engineers are working on ways to store electricity generated by the wind for use during such calm periods. Also, an updated electrical grid could enable wind farms across a region to serve as backup sources for one another, a topic that we discuss later in this module
How could we shift taxes to encourage the production and use of more fuel-efficient vehicles?
For years, European countries and Japan have done this through taxes on gasoline as well as taxes on fuel-inefficient vehicles. Much higher gasoline prices in these countries have also encouraged people to buy more fuel-efficient cars and have motivated car companies to come up with fuel-efficient designs. There would likely be strong opposition to new taxes or gasoline tax increases, but they could be balanced by reductions in payroll and income taxes. In other words, we could shift from taxing hard-earned income to taxing pollution and waste. Such a tax shift would not increase the overall taxes for most consumers. It would, however raise taxes for those who choose to drive fuel-inefficient vehicles. A similar way to shift costs and make fuel-efficient vehicles more attractive to buyers would be to put a stiff tax on purchases of gas-guzzling vehicles and to turn around and give an equally large tax break to buyers of fuel-efficient vehicles. Energy expert Amory Lovins first voiced this idea and coined the term feebate—a combination of a fee and a rebate—to describe such a program. For a number of years, the governments of France, Denmark, Norway, and the Netherlands have heavily taxed fuel-inefficient cars and used the tax revenues to provide rebates to buyers of fuel-efficient cars.
Explain why an energy resource with a low or negative net energy yield must be subsidized to survive in the marketplace.
Generally, an energy resource with a low or negative net energy yield, does not provide enough energy to make it worth developing and using, unless the developers of that resource get outside financial help. Without such help, the energy resource would not survive in free-market competition with comparable energy resources that have medium or high net energy yields. In energy markets, such financial assistance usually comes in the form of government subsidies, or payments designed to help a business survive and thrive. In the United States and other countries, very large government subsidies have been provided to energy companies by taxpayers over the past several decades.
How can governments encourage or discourage the use of a particular energy resource? How can governments and businesses use education to help us find the best mix of energy resources in the future?
Governments have powerful tools available for encouraging the use of one energy resource over another. They can provide money for research and development of a resource, give subsidies and tax breaks to developers and consumers, and enact laws and regulations that favor the use of particular energy resources. Governments have used these tools for decades to help the oil, gas, coal, and nuclear power industries to develop those resources. Many energy analysts and economists say it is now time to shift from providing such benefits to the fossil-fuel and nuclear industries to providing them to the renewable energy and energy-efficiency industries. Governments and businesses alike have one more important tool—namely, education. When consumers understand the important benefits and risks of using various energy resources, they can make wiser and less environmentally harmful choices. Ultimately, what happens in the realm of energy will be up to individuals. The challenge of providing energy in the future is an immense economic and environmental opportunity to develop a more sustainable energy economy.
What is biomass? Distinguish between solid biomass and biofuels as energy resources, and give two examples of each.
Green plants that convert direct energy from the sun into chemical energy stored in their tissues are a form of biomass that we can burn to produce energy. Solid biomass, such as wood, crop residues, and animal manure, provides about 95% of the energy used for heating and cooking in the world's poorest countries. This use of wood is by far the largest form of renewable energy use in the world. Also, wood chips are burned in some industrial processes and used for generating electricity because, as a fuel, wood chips can produce the high-temperature heat necessary for these purposes. We can also convert solid biomass into liquid or gaseous fuels called biofuels. Two common liquid biofuels made from plants and plant wastes are biodiesel and ethanol, both of which are increasingly used to fuel motor vehicles.
What are three problems related to the use of hydropower?
However, hydropower has some serious environmental impacts. When a large dam is built, land is flooded, wildlife habitat is degraded or destroyed, and people living in the area to be flooded are forced off their land. Then, flooded vegetation in the reservoir behind the dam begins to decay, especially in hot tropical areas, and emits methane, a potent greenhouse gas—one of the gases that are contributing to rapid atmospheric warming and projected climate change. Also, hydropower from these dams is not renewable forever, because their reservoirs eventually fill with silt deposited by the river to the point where the hydroelectric plants no longer work. Another potential problem is that some of the rivers used to produce hydropower will likely see decreased flows of water as the mountaintop glaciers that feed them melt due to atmospheric warming projected for the rest of this century.
Define hydropower and list three ways in which we can generate it.
Hydropower is the energy produced by harnessing flowing water to generate electricity, usually by means of a dam-and-reservoir system. The potential energy stored in the water behind the dam becomes kinetic energy as it flows through pipes built into the dam and spins turbines to generate electricity. Hydropower produces more electricity than any other renewable energy source. The world's leading producers of hydropower, in order, are 1. China 2. Canada 3. Brazil 4. the United States 5. Russia 6. Norway. According to the United Nations, only about 13% of the world's potential for hydropower has been developed. China plans to double its hydropower output between 2010 and 2020 and Canada and Brazil may also expand their use of hydropower. The United States has essentially reached the full capacity of its rivers to produce hydropower, while Norway gets 99% of its electricity from hydropower. We can generate electricity at low cost on a much smaller scale by using micro-hydropower generators, which can be placed in a stream or river with little environmental impact. Other hydropower technologies attempt to capture and use the kinetic energy of waves and the daily ebb and flow of ocean tides. Devices with floating tubes are anchored near shorelines of countries such as Portugal to capture energy from the up and down action of waves, which is used to spin turbines and produce electricity. In a few places in the world, such as the Bay of Fundy in Canada, the tides move through very long, narrow formations in the coastal bluffs. This concentrates the force of the moving water, and as the tides flow in and out every day, their kinetic energy can be used to spin turbines and produce electricity. However, there are not many places on the earth where such systems are financially feasible.
How do government fuel-efficiency standards vary among Europe, China, and the United States?
In 1978, the U.S. government passed a law establishing fuel-efficiency standards, which required that all new motor vehicles meet a certain level of fuel efficiency, stated in miles per gallon (mpg). These mpg standards were regularly raised during the next 8 years, but in 1986, the government stopped raising them for the next two decades. In 2007, the government raised the standards to require that new cars get 35 miles per gallon by 2016 and 54.5 miles per gallon by 2025. Meanwhile, in Europe, Japan, China, and Canada, since 2000, fuel-efficiency standards for new vehicles have been much higher than U.S. standards. China now plans to reach an average fuel economy of 40 mpg for new cars by 2015 and 52 mpg by 2020. Joseph Romm and several other U.S. energy experts call for the U.S. government to require all new cars sold in the United States to get at least 100 mpg by 2040. They argue that this would reduce unnecessary energy waste, lessen U.S. dependence on imported oil, decrease air pollution and greenhouse gas emissions, and save consumers huge amounts of money.
Distinguish among a hybrid gasoline-electric vehicle, a plug-in hybrid electric vehicle, and an all-electric vehicle.
Many car buyers and carmakers alike are growing more interested in fuel-efficient vehicles. Sales of gasoline-electric hybrid cars such as the Toyota Prius® have risen steadily since 2005. This type of hybrid carries a small gasoline-powered engine and a battery-powered electric motor that kicks in when the car needs it for accelerating or climbing a hill. The 2012 Toyota Prius has a combined highway/city fuel efficiency of 42 mpg. It also emits about 65% less CO2 per mile than a similar size conventional car. Another option is a plug-in electric hybrid car such as the Chevrolet Volt®. This type of hybrid carries a second, more powerful battery that enables it to run farther on electricity, and it can be plugged in and recharged. It also carries a small gasoline-powered generator that helps to keep the battery charged as needed on the road. According to the U.S. Environmental Protection Agency (EPA), the 2012 Volt has a combined highway/city fuel efficiency of 60 mpg. Still another newer option is an all-electric car that runs only on rechargeable batteries. One such car is the Nissan Leaf® with a fuel efficiency of 99 mpg, as reported in 2012 by the EPA.
What are the major advantages of shifting from the use of a centralized energy distribution system based on large power plants to a decentralized system based on locally and regionally available renewable energy resources? How could this provide most nations with better overall physical and economic security?
Many energy experts project that the large, centralized coal-fired and nuclear power plants that we now depend on will become less important over the next several decades. These experts foresee a gradual shift to a mix of smaller and more dispersed power systems such as rooftop solar water heaters, passive and active solar heating systems, energy-efficient houses and other buildings, regional and neighborhood wind turbines, small turbines that burn natural gas, and perhaps small stationary hydrogen fuel cells for houses and businesses We can supplement such decentralized, localized systems with some centralized power sources, such as large land-based and offshore wind farms and large solar-cell and solar-thermal power plants that distribute electricity over a new smart grid. However, the decentralization of power sources will give localities and individual consumers more control over the energy resources they use. It will be similar to the shift, starting in the 1960s, from dependence on large centralized computers to widely dispersed home and laptop computers and handheld devices that now give people immense computing power. ------------- This type of system could make greater use of locally and regionally available renewable energy resources. Windy areas would depend more on wind power. Those people living near streams and rivers could use micro-hydropower generators, and those living over high-quality geothermal energy resources could rely on them more than on other resources. A decentralized energy system would also provide us with more physical security than we get from our current centralized system. A terrorist attack, a major accident, or a natural disaster such as an earthquake or tsunami could take out or severely damage any one of the big power plants, refineries, and pipelines on which we now depend. Relying on a diverse, smaller, and more dispersed mix of locally and regionally available renewable energy resources would greatly reduce the chances of disruption from such events. Finally, a decentralized system would provide much better economic security for most nations and for the world. Many economists argue that the renewable energy industries will be the future engines of growth for most of the world. The production, installation, and maintenance of certain types of renewable energy systems have already created millions of jobs worldwide. If consumers eventually save a lot of money and companies make a lot of money by using renewable energy resources, this will only help the national and global economies.
What is wind and how can we harness it to produce electricity?
One of the world's most rapidly growing sources of energy is wind, the movement of air masses driven largely by differences in solar heating across the earth's surface in combination with the earth's rotation. Like flowing water, wind is an indirect form of solar energy. The kinetic energy of wind can turn the blades of a large wind turbine and convert it into electricity that can be transmitted by power lines to users. Some wind turbines are as tall as a 40-story building. Their very long blades—some as long as a small jet passenger plane—capture higher altitude winds that tend to be steadier and stronger than winds near the earth's surface.
What are three reasons why many Americans keep buying gas-guzzling vehicles?
One reason why many people keep buying gas-guzzling vehicles is that they have been conditioned by decades of effective advertising to crave vehicles with size, speed, and power. Automobile and oil companies understandably promote this because they make more money selling such vehicles and the fuels they burn. So for decades there has been a very strong and well-funded effort to convince consumers and politicians to favor fuel-inefficient vehicles, while there has been no comparable political effort to promote fuel-efficient vehicles. As a result, U.S. fuel-efficiency standards are considerably lower than those of China and most European Union countries. This is beginning to change as the United States has increased its motor vehicle fuel-efficiency standards to be met by 2020. However, by 2020, the standards will again be lower than those of many other countries. Another reason for the popularity of gas-guzzlers is that most U.S. consumers do not realize that the true cost of gasoline is much higher than what they pay at the pump. This is because there are hidden costs, including the costs associated with protecting oil company assets in foreign countries; pollution control expenses; higher medical bills and health insurance premiums because of illnesses from air pollution; and taxpayer-funded government subsidies and tax breaks for oil companies, car manufacturers, and road builders. All these costs are paid by the consumers at some point. The International Center for Technology Assessment has estimated that the hidden costs of gasoline for U.S. consumers are at least $12 per gallon. So, assuming a pump price of around $4 per gallon, the real cost of gasoline in the United States is about $16 per gallon. Because most consumers are not aware of this, they have little incentive to drive readily available fuel-efficient cars that would save them money and reduce threats to their health and to the environment. Another problem is that most fuel-efficient vehicles are currently more expensive than many of the less-efficient vehicles. At this point, most consumers cannot afford to buy the most fuel-efficient models. However, as demand for such vehicles increases, it's likely that their prices will come down.
What is the major problem with using solid biomass as a fuel?
Solid biomass, especially wood, is renewable only when it is not used faster than nature can replenish it. In 2010, about 2.7 billion people in 77 less-developed countries were relying mostly on wood, charcoal made from wood, dried animal manure, or dung, and other forms of biomass for fuel. Populations in these countries are growing and so are firewood shortages, as people burn wood or convert it to charcoal fuel faster than it can be replenished. Some countries have tried to deal with depletion of their biomass resources by planting grasses or fast-growing trees such as poplars in biomass plantations. In some tropical countries, vast plantations of oil palms are being planted and used to produce liquid biofuels such as biodiesel.
Define net energy yield and give an example that illustrates it.
The amount of energy that is not lost in such an energy production process becomes useful to us and can be thought of as a net energy yield: the total amount of high-quality energy available from an energy resource minus the amount of high-quality energy required to make it available for our use. or Total amount of useful energy available from an energy resource or energy system over its lifetime, minus the amount of energy used, automatically wasted because of the second law of thermodynamics, and unnecessarily wasted in finding, processing, and transporting it to users. is an important factor for comparing and evaluating energy resources. For example, suppose it takes 5 units of high-quality energy to produce 100 units of high-quality electricity from wind. This means that the net energy yield for the entire process is 95 units. Generally, the more steps we have to take in finding, processing, and using a source of energy, the lower its net energy yield will be. (This is similar to the decline in available high-quality energy with each transfer of energy among feeding levels in a food chain or food web).
What are two factors that limit the use of geothermal power?
The major limiting factors for the use of geothermal energy are the cost and the amount of land required. Geothermal energy is widely available, but for most homeowners, tapping into it is too costly and requires more land than they own. Another potential problem for geothermal power plants is the possibility of depleting the heat resource if it is pumped out of underground sources faster than the earth can replenish it. Deeper geothermal sites that might last longer are being evaluated, but so far, exploiting them is also too costly. Depletion of this heat source would not be a problem for most smaller-scale uses of geothermal energy.
What are the two quickest and least expensive ways to make a home or other building more energy efficient?
The two quickest and least expensive ways to reduce unnecessary energy waste from houses and other buildings are to add new, high-quality insulation and to plug up air leaks.
What are three major obstacles to using hydrogen as an energy resource?
There are a number of obstacles to reaching the goal of using hydrogen gas (H2) as a major fuel, starting with the problem of how to make it. The biggest obstacle is that the amount of high-quality energy it takes to produce H2 is greater than the amount we can get from burning it. Thus, unless we find some new technology for producing H2 much more efficiently, its net energy yield will always be negative. This means that hydrogen will have to be heavily subsidized to compete in the marketplace with fuels that have moderate to high net energy yields. A second problem is that the fuel cells used to burn hydrogen are currently very expensive. However, advances in technology and the savings from mass production could lower the cost. A third problem is that while the hydrogen fuel burns cleanly, producing it could add to air pollution, CO2 emissions, and the production of long-lived radioactive wastes.
What is one reason why energy waste continues? What are two factors that contribute to this?
This wasted high-quality energy is a resource that can be used at a lower cost and with a lower environmental impact than any other energy resource. So why are we mostly ignoring this resource and wasting so much energy and money? One reason is that the market prices of the most widely used commercial energy resources—nonrenewable fossil fuels and nuclear power—do not reflect their true costs to consumers. ----Two factors contribute to this. ----- One is that these energy resources continue to receive large government subsidies and tax breaks even though they are mature industries that should be able to compete economically on their own without taxpayer help. The second factor is that the harmful environmental and health costs of the production and use of these and all energy resources are not included in their market prices—a violation of the full-cost pricing principle of sustainability. For this reason, they are called hidden costs. Many economists argue that if these hidden costs were included in energy prices, it would be more obvious to most consumers and businesses that conventional sources of energy are, in reality, very costly. They would learn that reducing energy waste by investing in energy efficiency could save them a lot of money while helping them to reduce their own impacts on the environment.
What are the key problems associated with the use of passive solar heating, solar thermal power plants, and solar cells?
Using direct solar energy to heat houses and water passively has a medium net energy yield. This helps homeowners to lower their heating bills, which in turn helps them to pay for their investments in these passive systems fairly quickly. However, active solar heating systems are more costly than passive solar systems and also require more maintenance and repair. Another problem is that some areas have more exposure to sunlight than others. Also, many houses and other buildings are either not oriented to take advantage of direct solar energy or they are blocked by trees or other structures from receiving enough direct sunlight. Solar thermal power plants that are built in sunny desert areas have ample access to sunlight. However, they have a low net energy yield and high costs, and usually need to be subsidized. Adding to these costs is the fact that updated electric power grids will have to be in place in order to distribute electricity from most of these plants to consumers. The chief problem with solar cells is their high cost. In fact, they are so expensive and valuable that thieves have been stealing solar-cell panels from roadside emergency call stations and from the roofs of some homes. Also, lack of access to sunlight in some areas limits the use of solar cells, and, as with solar thermal systems, updated electrical grids would be necessary for solar-cell power plants to be widely used. Using solar cells to produce electricity has a low to medium net energy yield, although their net energy yields are increasing with new designs.
Why is energy efficiency an energy resource?
We could use much of this energy in industry, transportation, and housing without inventing any new technologies. In 2009, energy expert Amory Lovins said that energy efficiency is "the largest, cheapest, safest, and fastest way to provide energy services." In addition, he observed that improving energy efficiency in the United States could save "at least half of the oil and gas and three-quarters of the electricity it uses at one-eighth of the cost the country is now paying for these forms of energy."
Why is the sun the most important energy resource?
Without the sun, we would have no wind with which to produce electricity, because wind is a moving mass of air created by differences in solar heating between the earth's equator and its poles, and by the earth's rotation. We would also not have flowing water, because the sun drives the water cycle. It evaporates water, mostly from the oceans, into the atmosphere where some of that moisture then falls to land as rain and snow. Some of this precipitation flows into the rivers we use to produce electricity by means of hydroelectric dams. Without the sun, we would also not have wood to burn, because trees depend on sunlight for life.
What is cogeneration, or combined heat and power (CHP), and how can it save energy and money for businesses?
cogeneration Production of two useful forms of energy, such as high temperature heat or steam and electricity, from the same fuel source. In a conventional power plant, when steam is used to spin turbines that generate electricity, much of the available energy is lost as the steam escapes to the environment. In a cogeneration plant, that steam is captured and used again to heat the plant or other buildings. This more than doubles the overall energy efficiency of the plant itself from about 35% to 80%. As a result, a coal-burning power plant using cogeneration emits about one-third as much CO2 per unit of energy produced as a conventional coal-burning plant.
Define geothermal energy and explain how we can use it to heat and cool a house, and to produce electricity.
geothermal energy Heat transferred from the earth's underground concentrations of dry steam (steam with no water droplets), wet steam (a mixture of steam and water droplets), or hot water trapped in fractured or porous rock. We have learned how to extract and use geothermal energy to heat and cool buildings, and to generate electricity. For example, we can heat and cool our homes by using a geothermal heat pump system. It takes advantage of the temperature differences between the earth's surface and the ground below the frost line at depths of 3 to 10 feet, where the year-round temperature is typically 50-60°F. Such a system can be very energy-efficient, environmentally clean, and reliable.
How can we improve energy efficiency in the freight shipping industry?
A large part of the transportation sector is the freight shipping industry. Researchers have found that the most efficient options for shipping materials and products are trains and barges, while the more commonly used options, trucks and air cargo services, are the least efficient. By relying more on the most efficient options, we could save energy, reduce air pollution, and lower CO2 emissions produced by shipping companies.
How much of the commercial energy used in the United States is put to work? What happens to the rest?
According to the U.S. Department of Energy, only about 16% of the commercial energy used in the United States is actually put to work. The other 84% is wasted. About 41% of this energy is automatically degraded to low-quality heat that ends up in the environment because of the second law of thermodynamics. The remaining 43% is unnecessarily wasted. on the environment.
How is the wind industry dealing with the problem of bird and bat deaths caused by wind turbines
Critics of wind farms point out that many thousands of birds and bats die in collisions with wind turbines—a problem that engineers and scientists are trying to solve. Studies indicate that older wind turbines—built in the 1980s along some bird migration routes—are responsible for most of these bird and bat deaths. The large blades on newer turbines rotate more slowly, and the towers do not have surfaces that make good nesting and resting sites, as some older towers have, and these changes have reduced the number of bird deaths. Also, developers are being careful to locate new wind farms in areas away from known bird migration routes. Wind power proponents also point out that wind farms are nowhere near the biggest cause of bird and bat deaths. According to the National Audubon Society, more than 1.4 billion bird and bat deaths result from collisions with cars, trucks, and buildings and other human structures (including coal-fired and nuclear power plants) and from encounters with domestic cats. The number of birds and bats killed in collisions with wind turbines is a fraction of this total.
How are wind developers dealing with the fact that winds sometimes die down? How would a smart grid help to deal with this problem?
Critics point out that winds die down from time to time. Wind-power developers have dealt with this partly by building taller turbines with long blades that can capture winds at higher altitudes, which tend to blow harder and more steadily than do winds closer to the ground. Another solution to this problem is to locate more wind farms offshore where winds also blow more steadily. A key to the growing use of wind power in the United States, as well as the increased use of electricity from solar-thermal and solar-cell power plants, is the urgent need to build a smart electrical grid—an interactive, super-efficient national electrical grid connecting all wind farms, thermal solar plants, and solar-cell plants. A smart-grid system could distribute the electricity produced by strong winds offshore and in Midwestern states (as well as electricity produced by solar power plants in southwestern states) to electricity consumers throughout the country. In addition, with a smart-grid system, when winds die in one area, the power plants in the rest of the country could make up the difference.
What is a biofuel plantation and what are some environmental problems related to such plantations?
However, biofuel farming can become unsustainable and thus nonrenewable. For one thing, the repeated growing and harvesting of biofuel plantation crops eventually depletes soil of its important nutrients, especially in tropical forest areas where soils are not rich in plant nutrients to begin with. In addition, clearing grasslands, tropical forests, and other old-growth forested areas to make way for these plantations degrades or destroys the rich biodiversity of such areas. One reason some people promote biofuels is that, when burned, they are supposed to produce less greenhouse gases than fossil fuels. However, a 2007 study by Paul Crutzen, a Dutch atmospheric chemist who won the Nobel Prize in Chemistry, made this less certain. Crutzen estimated that intensive biofuel crop farming, including the use of fertilizers that release the greenhouse gas nitrous oxide, along with the burning of biofuels, would emit more greenhouse gases than would burning the amount of fossil fuels that the biofuels would replace. Another problem with biofuels is that when food crops such as corn are diverted from the food supply to make biofuels, food prices rise. In 2010, because of a massive taxpayer subsidy, about 40% of the corn grown in the United States was converted to ethanol that was mixed with gasoline to fuel cars. Until the subsidies expired in 2012, they made it more profitable for farmers to grow corn to fuel cars than to raise corn as a food crop. The result was a sharp rise in corn prices, which led to riots and other forms of protest by poor people in countries such as Mexico where corn was a staple.
Distinguish between hydrothermal reservoirs and hot, dry rock as sources of geothermal energy.
In about 40 countries, engineers have tapped into deep reservoirs of hot water that is heated by geothermal energy. To extract heat from these hydrothermal reservoirs, a hole is drilled into the reservoir and a pipe is inserted to pump steam or hot water to the surface. The steam, or hot water converted to steam, spins turbines to produce electricity. It can also be used to heat interior spaces and water within homes and to heat greenhouses in order to grow vegetables and other plants. Iceland gets almost three-fourths of its energy and almost all of its electricity from hydroelectric power and geothermal energy, while California gets about 6% of its electricity from geothermal energy. If we drill deep enough—3 miles or more—almost anywhere on the planet, we find hot, dry rock. We could also use heat from this source to boil water and make steam to generate electricity. So far, tapping into these deeper sources of geothermal energy is too costly, but scientists and engineers are trying to learn how to tap into this immense source of heat at an affordable price.
List two other ways in which businesses can save energy.
Industries are also saving money by replacing inefficient single-speed electric motors with variable-speed motors that run at the speeds needed for particular tasks. Industries are also saving energy and money by replacing inefficient incandescent lightbulbs (which are being phased out in many countries) with more efficient and much longer-lasting compact fluorescent bulbs (CFLs), and even more efficient and longer-lasting light-emitting diode (LED) bulbs. LEDs are expensive but prices are dropping sharply, as they did with CFLs, because of mass production and improved designs. Recycling is another way in which industries are increasing their energy efficiency. For example, producing steel from recycled scrap iron rather than from iron ore cuts the energy needed to make the steel by 75% and also reduces CO2 emissions. This is an application of the earth's chemical cycling principle of sustainability
List four energy resources that we use to supplement the sun's energy.
Nonrenewable energy resources provide about 87% of this supplemental energy—81% from burning fossil fuels and 6% from electricity produced at nuclear power plants, fueled mostly by uranium. Renewable energy resources, including hydropower, wind, solar energy, bio-fuels, and geothermal energy, supply the remaining 13% of our supplemental energy, often called commercial energy. See Image for more Info
How can we make hydrogen into a fuel? What is the main problem with hydrogen fuel that keeps us from using it widely?
Some scientists say that the fuel of the future is hydrogen gas (H2). The problem is that H2 is not found in the earth's atmosphere. However, we can use electricity to decompose water (H2O) to produce H2 gas (which we can then collect and burn) and oxygen (O2) gas. Another way to produce H2 gas is to strip it from the methane (CH4) found in natural gas and from gasoline molecules. However, these processes require more energy than the amount of energy that we can get from burning the H2 fuel that is produced. That is, hydrogen fuel has a negative net energy yield. Even so, some people see hydrogen as a promising energy resource. We have learned how to burn H2 by combining it with O2 in devices called fuel cells. While burning fossil fuels produces a variety of air pollutants and releases climate-changing CO2 into the atmosphere, burning H2 in a car powered by a fuel cell emits no air pollutants and no CO2. The only thing coming out of the car's exhaust pipes is water vapor. For several years, major car companies have been developing and testing fuel-cell cars (Figure 5.14) and buses that run on hydrogen.
In order for hydrogen to be a clean fuel (cleanly produced as well as clean-burning), how must it be produced?
This would be the case if we were to use coal-burning or nuclear power plants to generate the electricity used to produce H2 by decomposing water. However, using renewable resources such as wind turbines or solar cells to generate this electricity would add little air pollution or CO2 to the atmosphere. The process of stripping hydrogen fuel from coal, methane, or gasoline compounds would add much more CO2 to the atmosphere per unit of energy produced than would burning these fuels directly.
What are photovoltaic (PV) or solar cells? Explain how they can be used in solar cell power plants.
photovoltaic (PV) cells Device that converts radiant (solar) energy directly into electrical energy. Also called a solar cell. A typical solar cell is a small piece of material—mostly purified silicon (Si)—that is about the thickness of a human hair and has no moving parts. Each cell emits electrons when sunlight strikes it. When many solar cells are wired together, they can generate large amounts of electricity in solar cell power plants. Newer, thin, and flexible solar cells can be incorporated into fabrics and other common materials.