science universe

Green Market electric utilities

In 1998, restructuring of the electric power utilities opened the market place to “Green Power Markets” that offer environmental features along with power service. Green power sources will provide clean energy and improved efficiency based on technologies that rely on renewable energy sources. Educating the consumer and providing green power at competitive costs are seen as two of the biggest challenges to this new market. The Center for Resource Solutions in California pioneered the Green-e Renewable Electricity Branding Program that is a companion to green power and certifies electricity products that are environmentally preferred.

Results and the future

Efforts to increase public consciousness about energy efficiency issues have had some remarkable successes in the past two decades. Despite the increasing complexity of most developed societies and increased population growth in many nations, energy is being used more efficiently in almost every part of the world. Increased efficiency of energy use increased between 1973 and 1985 by as much as 31% in Japan, 23% in the United States, 20% in the United Kingdom, and 19% in Italy. At the be- ginning of this period, most experts had predicted that

KEY TERMS

Cogeneration—A process by which heat produced as a result of industrial processes is used to generate electrical power.

Mass transit—Any form of transportation in which significantly large numbers of riders are moved within the same vehicle at the same time.

Solar cell—A device by which sunlight is converted into electricity.

changes of this magnitude could be accomplished only as a result of the massive reorganization of social institutions; this has not been the case. Processes and inventions that continue to increase energy efficiency can be incorporated into daily life with minimal disruptions to personal lives and industrial operations.

Energy efficiency has a long way to go, however. In December 1997 in Kyoto, Japan, a global warming agreement was proposed to the nations of the world to cut carbon emissions, reduce levels of so-called “green- house gases” (methane, carbon dioxide, and nitrous oxide), and use existing technologies to improve energy efficiency. These technologies apply to all levels of society from governments and industries to the individual household. But experts acknowledge that the public must recognize the global warming problem as real and serious before existing technologies and a host of potential new products will be supported.

See also Alternative energy sources; Fluorescent light; Hydrocarbon.

Resources

Books

Flavin, Christopher, and Alan B. Durning. Building on Success: The Age of Energy Efficiency. Worldwatch Paper 82. Washington, DC: Worldwatch Institute, March 1988.

Hirst, Eric, et al. Energy Efficiency in Buildings: Progress and Promise. Washington, DC: American Council for an Ener- gy-Efficient Economy, 1986.

Hoffmann, Peter, and Tom Harkin. Tomorrow’s Energy: Hydro- gen, Fuel Cells, and Prospects for a Cleaner Planet. Boston: MIT Press, 2001.

Meier, Alan K., et al. Saving Energy through Greater Efficiency. Berkeley: University of California Press, 1981.

Other

U.S. Congress, Office of Technology Assessment. Building En- ergy Efficiency. OTA-E-518. Washington, DC: U.S. Government Printing Office, May 1992.

David E. Newton

Energy transfer

Energy transfer describes the changes in energy (a state function) that occur between organisms within an ecosystem. Living organisms are constantly changing as they grow, move, reproduce, and repair tissues. These changes are fueled by energy. Plants, through photosynthesis, capture some of the Sun’s radiant energy and transform it into chemical energy, which is stored as plant biomass. This biomass is then consumed by other organisms within the ecological food chain/web. A food chain is a sequence of organisms that are connected by their feeding and productivity relationships; a food web is the interconnected set of many food chains.

Energy transfer is a one-way process. Once potential energy has been released in some form from its storage in biomass, it cannot all be reused, recycled, or converted to waste heat. This means that if the Sun, the ultimate energy source of ecosystems, were to stop shining, life as we know it would soon end. Every day, the Sun provides new energy in the form of photons to sustain the food webs of Earth.

History of energy transfer research

In 1927, the British ecologist Charles Elton wrote that most food webs have a similar pyramidal shape. At the bottom, there are many photosynthetic organisms which collectively have a large biomass and productivity. On each of the following trophic levels, or feeding levels, there are successively fewer heterotrophic organisms, with a smaller productivity. The pyramid of biomass and productivity is now known as the Eltonian pyramid.

In 1942, Raymond L. Lindeman published a paper that examined food webs in terms of energy flow. Lindeman pro- posed that, by using energy as the currency of ecosystem processes, food webs could be quantified. This allowed him to explain that the Eltonian pyramid was a result of successive energy losses associated with the thermodynamic inefficiencies of energy transfer among trophic levels.

Current research in ecological energy transfer focuses on increasing our understanding of the paths of energy and matter within grazing and microbial food webs. Rather little is understood about such pathways because of the huge numbers of species and their complex interactions. This understanding is essential for proper management of ecosystems. The fate and effects of toxic chemicals within food webs must be understood if impacts on vulnerable species and ecosystems are to avoided or minimized.

The laws of thermodynamics and energy transfer in food webs Energy transfers within food webs are governed by the first and second laws of thermodynamics. The first

law relates to quantities of energy. It states that energy can be transformed from one form to another, but it can- not be created or destroyed. This law suggests that all energy transfers, gains, and losses within a food web can be accounted for in an energy budget.

The second law relates to the quality of energy. This law states that whenever energy is transformed, some of must be degraded into a less useful form. In ecosystems, the biggest losses occur as respiration. The second law explains why energy transfers are never 100% efficient. In fact, ecological efficiency, which is the amount of energy transferred from one trophic level to the next, ranges from 5-30%. On average, ecological efficiency is only about 10%.

Because ecological efficiency is so low, each trophic level has a successively smaller energy pool from which it can withdraw energy. This is why food webs have no more than four to five trophic levels. Beyond that, there is not enough energy to sustain higher-order predators.

Components of the food web

A food web consists of several components; primary producers, primary consumers, secondary consumers, tertiary consumers, and so on. Primary producers include green plants and are the foundation of the food web. Through photosynthesis, primary producers capture some of the Sun’s energy. The net rate of photosynthesis, or net primary productivity (NPP), is equal to the rate of photosynthesis minus the rate of respiration of plants. In essence, NPP is the profit for the primary producer, after their energy costs associated with respiration are accounted for. NPP determines plant growth and how much energy is subsequently available to higher trophic levels.

Primary consumers are organisms that feed directly on primary producers, and these comprise the second trophic level of the food web. Primary consumers are also called herbivores, or plant-eaters. Secondary consumers are organisms that eat primary consumers, and are the third trophic level. Secondary consumers are carnivores, or meat-eaters. Successive trophic levels include the tertiary consumers, quaternary consumers, and so on. These can be either carnivores or omnivores, which are both plant- and animal-eaters, such as humans.

The role of the microbial food web

Much of the food web’s energy is transferred to the often overlooked microbial, or decomposer, trophic level. Decomposers use excreted wastes and other dead biomass as a food source. Unlike the main, grazing food web, organisms of the microbial trophic level are extremely efficient feeders. Various species can rework the

KEY TERMS

Biomass—Total weight, volume, or energy equivalent of all living organisms within a given area.

Ecological efficiency—Energy changes from one trophic level to the next.

First law of thermodynamics—Energy can be transformed but it cannot be created nor can it be destroyed.

Primary consumer—An organism that eats primary producers.

Primary producer—An organism that photosynthesizes.

Second law of thermodynamics—When energy is transformed, some of the original energy is de- graded into less useful forms of energy.

same food particle, extracting more of the stored energy each time. Some waste products of the microbial trophic level re-enter the grazing part of the food web and are used as growth materials for primary producers. This occurs, for example, when earthworms are eaten by birds.

See also Ecological pyramids; Energy budgets.

Resources

Books

Bradbury, I. The Biosphere. New York: Belhaven Press, Pinter Publishers, 1991.

Incropera, Frank P., and David P. DeWitt. Fundamentals of Heat and Mass Transfer. 5th ed. New York: John Wiley & Sons, 2001.

Miller, G. T., Jr. Environmental Science: Sustaining the Earth.

3rd ed. Belmont, CA: Wadsworth Publishing Company, 1991.

Stiling, P. D. “Energy Flow in Ecosystems.” In Introductory Ecology. Englewood Cliffs, NJ: Prentice-Hall, 1992.

Periodicals

Begon, M., J. L. Harper, and C. R. Townsend. “The Flux of Energy Through Communities.” In Ecology: Individuals, Populations and Communities. 2nd ed. Boston: Blackwell Scientific Publications, 1990.

Engineering

Engineering is the art of applying science, mathematics, and creativity to solve technological problems.

The accomplishments of engineering can be seen in nearly every aspect of our daily lives, from transportation to communications, and entertainment to health care. And, although each of these applications is unique, the process of engineering is largely independent. This process be- gins by carefully analyzing a problem, intelligently de- signing a solution for that problem, and efficiently trans- forming that design solution into physical reality.

Analyzing the problem

Defining the problem is the first and most critical step of the problem analysis. To best approach a solution, the problem must be well-understood and the guidelines or design considerations for the project must be clear. For example, in the creation of a new automobile, the engineers must know if they should design for fuel economy or for brute power. Many questions like this arise in every engineering project, and they must all be answered at the very beginning if the engineers are to work efficiently toward a solution.

When these issues are resolved, the problem must be thoroughly researched. This involves searching technical journals and closely examining solutions of similar engineering problems. The purpose of this step is two-fold. First, it allows the engineer to make use of a tremendous body of work done by other engineers. And second, it ensures the engineer that the problem has not already been solved. Either way, the review allows him or her to intelligently approach the problem, and perhaps avoid a substantial waste of time or legal conflicts in the future.

Designing a solution

Once the problem is well-understood, the process of designing a solution begins. This process typically starts with brainstorming, a technique by which members of the engineering team suggest a number of possible general approaches for the problem. In the case of an auto- mobile, perhaps conventional gas, solar, and electric power would be suggested to propel the vehicle. Generally, one of these is then selected as the primary candidate for further development. Occasionally, however, if time permits and several ideas stand out, the team may elect to pursue multiple solutions to the problem. More refined designs of these solutions/systems then “compete,” and the best of those is chosen.

Once a general design or technology is selected, the work is sub-divided and various team members assume specific responsibilities. In the automobile, for example, the mechanical engineers in the group would tackle such problems as the design of the transmission and suspension systems. They may also handle air flow and cli- mate-control concerns to ensure that the vehicle is both

Green Market electric utilities

In 1998, restructuring of the electric power utilities opened the market place to “Green Power Markets” that offer environmental features along with power service. Green power sources will provide clean energy and improved efficiency based on technologies that rely on renewable energy sources. Educating the consumer and providing green power at competitive costs are seen as two of the biggest challenges to this new market. The Center for Resource Solutions in California pioneered the Green-e Renewable Electricity Branding Program that is a companion to green power and certifies electricity products that are environmentally preferred.

Results and the future

Efforts to increase public consciousness about energy efficiency issues have had some remarkable successes in the past two decades. Despite the increasing complexity of most developed societies and increased population growth in many nations, energy is being used more efficiently in almost every part of the world. Increased efficiency of energy use increased between 1973 and 1985 by as much as 31% in Japan, 23% in the United States, 20% in the United Kingdom, and 19% in Italy. At the be- ginning of this period, most experts had predicted that

KEY TERMS

Cogeneration—A process by which heat produced as a result of industrial processes is used to generate electrical power.

Mass transit—Any form of transportation in which significantly large numbers of riders are moved within the same vehicle at the same time.

Solar cell—A device by which sunlight is converted into electricity.

changes of this magnitude could be accomplished only as a result of the massive reorganization of social institutions; this has not been the case. Processes and inventions that continue to increase energy efficiency can be incorporated into daily life with minimal disruptions to personal lives and industrial operations.

Energy efficiency has a long way to go, however. In December 1997 in Kyoto, Japan, a global warming agreement was proposed to the nations of the world to cut carbon emissions, reduce levels of so-called “green- house gases” (methane, carbon dioxide, and nitrous oxide), and use existing technologies to improve energy efficiency. These technologies apply to all levels of society from governments and industries to the individual household. But experts acknowledge that the public must recognize the global warming problem as real and serious before existing technologies and a host of potential new products will be supported.

See also Alternative energy sources; Fluorescent light; Hydrocarbon.

Resources

Books

Flavin, Christopher, and Alan B. Durning. Building on Success: The Age of Energy Efficiency. Worldwatch Paper 82. Washington, DC: Worldwatch Institute, March 1988.

Hirst, Eric, et al. Energy Efficiency in Buildings: Progress and Promise. Washington, DC: American Council for an Ener- gy-Efficient Economy, 1986.

Hoffmann, Peter, and Tom Harkin. Tomorrow’s Energy: Hydro- gen, Fuel Cells, and Prospects for a Cleaner Planet. Boston: MIT Press, 2001.

Meier, Alan K., et al. Saving Energy through Greater Efficiency. Berkeley: University of California Press, 1981.

Other

U.S. Congress, Office of Technology Assessment. Building En- ergy Efficiency. OTA-E-518. Washington, DC: U.S. Government Printing Office, May 1992.

David E. Newton

Energy transfer

Energy transfer describes the changes in energy (a state function) that occur between organisms within an ecosystem. Living organisms are constantly changing as they grow, move, reproduce, and repair tissues. These changes are fueled by energy. Plants, through photosynthesis, capture some of the Sun’s radiant energy and transform it into chemical energy, which is stored as plant biomass. This biomass is then consumed by other organisms within the ecological food chain/web. A food chain is a sequence of organisms that are connected by their feeding and productivity relationships; a food web is the interconnected set of many food chains.

Energy transfer is a one-way process. Once potential energy has been released in some form from its storage in biomass, it cannot all be reused, recycled, or converted to waste heat. This means that if the Sun, the ultimate energy source of ecosystems, were to stop shining, life as we know it would soon end. Every day, the Sun provides new energy in the form of photons to sustain the food webs of Earth.

History of energy transfer research

In 1927, the British ecologist Charles Elton wrote that most food webs have a similar pyramidal shape. At the bottom, there are many photosynthetic organisms which collectively have a large biomass and productivity. On each of the following trophic levels, or feeding levels, there are successively fewer heterotrophic organisms, with a smaller productivity. The pyramid of biomass and productivity is now known as the Eltonian pyramid.

In 1942, Raymond L. Lindeman published a paper that examined food webs in terms of energy flow. Lindeman pro- posed that, by using energy as the currency of ecosystem processes, food webs could be quantified. This allowed him to explain that the Eltonian pyramid was a result of successive energy losses associated with the thermodynamic inefficiencies of energy transfer among trophic levels.

Current research in ecological energy transfer focuses on increasing our understanding of the paths of energy and matter within grazing and microbial food webs. Rather little is understood about such pathways because of the huge numbers of species and their complex interactions. This understanding is essential for proper management of ecosystems. The fate and effects of toxic chemicals within food webs must be understood if impacts on vulnerable species and ecosystems are to avoided or minimized.

The laws of thermodynamics and energy transfer in food webs Energy transfers within food webs are governed by the first and second laws of thermodynamics. The first

law relates to quantities of energy. It states that energy can be transformed from one form to another, but it can- not be created or destroyed. This law suggests that all energy transfers, gains, and losses within a food web can be accounted for in an energy budget.

The second law relates to the quality of energy. This law states that whenever energy is transformed, some of must be degraded into a less useful form. In ecosystems, the biggest losses occur as respiration. The second law explains why energy transfers are never 100% efficient. In fact, ecological efficiency, which is the amount of energy transferred from one trophic level to the next, ranges from 5-30%. On average, ecological efficiency is only about 10%.

Because ecological efficiency is so low, each trophic level has a successively smaller energy pool from which it can withdraw energy. This is why food webs have no more than four to five trophic levels. Beyond that, there is not enough energy to sustain higher-order predators.

Components of the food web

A food web consists of several components; primary producers, primary consumers, secondary consumers, tertiary consumers, and so on. Primary producers include green plants and are the foundation of the food web. Through photosynthesis, primary producers capture some of the Sun’s energy. The net rate of photosynthesis, or net primary productivity (NPP), is equal to the rate of photosynthesis minus the rate of respiration of plants. In essence, NPP is the profit for the primary producer, after their energy costs associated with respiration are accounted for. NPP determines plant growth and how much energy is subsequently available to higher trophic levels.

Primary consumers are organisms that feed directly on primary producers, and these comprise the second trophic level of the food web. Primary consumers are also called herbivores, or plant-eaters. Secondary consumers are organisms that eat primary consumers, and are the third trophic level. Secondary consumers are carnivores, or meat-eaters. Successive trophic levels include the tertiary consumers, quaternary consumers, and so on. These can be either carnivores or omnivores, which are both plant- and animal-eaters, such as humans.

The role of the microbial food web

Much of the food web’s energy is transferred to the often overlooked microbial, or decomposer, trophic level. Decomposers use excreted wastes and other dead biomass as a food source. Unlike the main, grazing food web, organisms of the microbial trophic level are extremely efficient feeders. Various species can rework the

KEY TERMS

Biomass—Total weight, volume, or energy equivalent of all living organisms within a given area.

Ecological efficiency—Energy changes from one trophic level to the next.

First law of thermodynamics—Energy can be transformed but it cannot be created nor can it be destroyed.

Primary consumer—An organism that eats primary producers.

Primary producer—An organism that photosynthesizes.

Second law of thermodynamics—When energy is transformed, some of the original energy is de- graded into less useful forms of energy.

same food particle, extracting more of the stored energy each time. Some waste products of the microbial trophic level re-enter the grazing part of the food web and are used as growth materials for primary producers. This occurs, for example, when earthworms are eaten by birds.

See also Ecological pyramids; Energy budgets.

Resources

Books

Bradbury, I. The Biosphere. New York: Belhaven Press, Pinter Publishers, 1991.

Incropera, Frank P., and David P. DeWitt. Fundamentals of Heat and Mass Transfer. 5th ed. New York: John Wiley & Sons, 2001.

Miller, G. T., Jr. Environmental Science: Sustaining the Earth.

3rd ed. Belmont, CA: Wadsworth Publishing Company, 1991.

Stiling, P. D. “Energy Flow in Ecosystems.” In Introductory Ecology. Englewood Cliffs, NJ: Prentice-Hall, 1992.

Periodicals

Begon, M., J. L. Harper, and C. R. Townsend. “The Flux of Energy Through Communities.” In Ecology: Individuals, Populations and Communities. 2nd ed. Boston: Blackwell Scientific Publications, 1990.

Engineering

Engineering is the art of applying science, mathematics, and creativity to solve technological problems.

The accomplishments of engineering can be seen in nearly every aspect of our daily lives, from transportation to communications, and entertainment to health care. And, although each of these applications is unique, the process of engineering is largely independent. This process be- gins by carefully analyzing a problem, intelligently de- signing a solution for that problem, and efficiently trans- forming that design solution into physical reality.

Analyzing the problem

Defining the problem is the first and most critical step of the problem analysis. To best approach a solution, the problem must be well-understood and the guidelines or design considerations for the project must be clear. For example, in the creation of a new automobile, the engineers must know if they should design for fuel economy or for brute power. Many questions like this arise in every engineering project, and they must all be answered at the very beginning if the engineers are to work efficiently toward a solution.

When these issues are resolved, the problem must be thoroughly researched. This involves searching technical journals and closely examining solutions of similar engineering problems. The purpose of this step is two-fold. First, it allows the engineer to make use of a tremendous body of work done by other engineers. And second, it ensures the engineer that the problem has not already been solved. Either way, the review allows him or her to intelligently approach the problem, and perhaps avoid a substantial waste of time or legal conflicts in the future.

Designing a solution

Once the problem is well-understood, the process of designing a solution begins. This process typically starts with brainstorming, a technique by which members of the engineering team suggest a number of possible general approaches for the problem. In the case of an auto- mobile, perhaps conventional gas, solar, and electric power would be suggested to propel the vehicle. Generally, one of these is then selected as the primary candidate for further development. Occasionally, however, if time permits and several ideas stand out, the team may elect to pursue multiple solutions to the problem. More refined designs of these solutions/systems then “compete,” and the best of those is chosen.

Once a general design or technology is selected, the work is sub-divided and various team members assume specific responsibilities. In the automobile, for example, the mechanical engineers in the group would tackle such problems as the design of the transmission and suspension systems. They may also handle air flow and cli- mate-control concerns to ensure that the vehicle is both

Energy efficiency

Energy efficiency refers to any process by which the amount of useful energy obtained from some process is increased compared to the amount of energy put into that process. As a simple example, some automobiles can travel 40 mi (17 km) by burning a single gallon (liter) of gasoline, while others can travel only 20 mpg (8.5 km/l). The energy efficiency achieved by the first car is twice that achieved by the second car. In general, energy efficiency is measured in units such as mpg, lumens per watt, or some similar “output per input” unit.

History of energy concerns

Interest in energy efficiency is relatively new in the history of modern societies, although England’s eighteenth century search for coal was prompted by the de- cline of the country’s forest resources. For most of the past century, however, energy resources seemed to be infinite, for all practical purposes. Little concern was expressed about the danger of exhausting the world’s supplies of coal, oil, and natural gas, its major energy resources.

The turning point in that attitude came in the 1970s when the major oil-producing nations of the world suddenly placed severe limits on the amounts of petroleum that they shipped to the rest of the world. This oil embargo forced major oil users such as the United States, Japan, and the nations of Western Europe to face for the first time the danger of having insufficient petroleum products to meet their basic energy needs. Use of energy resources suddenly became a matter of national and international discussion.

Energy efficiency can be accomplished in a number of different ways. One of the most obvious is conservation; that is, simply using energy resources more careful- ly. For example, people might be encouraged to turn out lights in their home, to set their thermostats at lower temperatures, and to use bicycles rather than automobiles for transportation. Energy efficiency in today’s world also means more complex and sophisticated approaches to the way in which energy is used in industrial, commercial, and residential settings.

Energy efficiency in buildings

Approximately one-third of all the energy used in the United States goes to heat, cool, and light buildings. A number of technologies have been developed that im- prove the efficiency with which energy is used in buildings. Some of these changes are simple; higher grades of insulation are used in construction, and air leaks are plugged. Both of these changes reduce the amount of heated or air-conditioned air (depending on the season) lost from the building to the outside environment.

Other improvements involve the development of more efficient appliances and construction products. For example, the typical gas furnace in use in residential and commercial buildings in the 1970s was about 63% efficient. Today, gas furnaces with efficiencies of 97% are readily available and affordable. Double-glazed windows with improved insulating properties have also been developed. Such windows can save more than 10% of the energy lost by a building in a year.

Buildings can also be designed to save energy. For example, they can be oriented on a lot to take advantage of solar heating or cooling. Many commercial structures also have computerized systems that automatically ad- just heating and cooling schedules to provide a comfort- able environment for occupants only when and in portions of the building that are occupied.

Entirely new technologies can be used also. For example, many buildings now depend exclusively on more efficient fluorescent lighting systems than on less efficient incandescent lights. In some situations, this single change can produce a greater savings in energy use than any other modification. The increasing use of solar cells is another example of a new kind of technology that has the potential for making room and water heating much more efficient.

Transportation

About one-third more of the energy used in the United States goes to moving people and goods from place to place. For more than two decades, governments have made serious efforts to convince people that they should use more energy-efficient means of transportation, such as bicycles or some form of mass transit (buses, trolleys, subways, light-rail systems, etc.). These efforts have had only limited success.

Another approach that has been more successful has been to encourage car manufacturers to increase the efficiency of automobile engines. In the 1970s, the average fuel efficiency of cars in the United States was 13 mpg

(5.5 km/l). Over the next decade, efficiency improved nearly twice over to 25 mpg (10.6 km/l). In other nations, similar improvements were made. Cars in Japan, for example, increased from an average efficiency of 23 mpg (9.8 km/l) in 1973 to 30 mpg (12.8 km/l) in 1985.

Yet, even more efficient automotive engines appear to be possible. Many authorities believe that efficiencies approaching 50 mpg (21 km/l) should be possible by the year 2001. As of 1987, at least three cars with fuel efficiencies of more than 50 mpg (21 km/l) were already in production (the Ford Escort, Honda City, and Suzuki Sprint). Experimental cars with efficiencies close to 100 mpg (42.5 km/l) were also being tested; the Toyota AXV has achieved 98 mpg (41.7 km/l) on test tracks, and the Renault VESTA has logged 124 mpg (52.7 km/l).

To a large extent, automobile manufacturers have been slow to produce cars that have the maximum possible efficiencies because they question whether consumers will pay higher purchase prices for these cars. Improvements continue to be made, however, at least partly because of the legislative pressure for progress in this direction.

Energy efficiency in industry

The final third of energy use in the United States occurs in a large variety of industrial operations such as producing steam, heating plants, and generating electric- ity for various operations. Improvements in the efficiency with which energy is used in industry also depends on two principal approaches: the development of more efficient devices and the invention of new kinds of technologies. More efficient motors are now available so that the same amount of work can be accomplished with a smaller amount of energy input. And, as an example of the use of new technologies, laser beam systems that can both heat and cut more efficiently than traditional tools are being given new applications. Industries are also finding ways to use computer systems to design and carry out functions within a plant more efficiently than traditional resource management methods.

One of the most successful approaches to improving energy efficiency in industry has been the development of cogeneration systems. Cogeneration refers to the process in which heat produced in an industrial operation (formerly regarded as “waste heat”) is used to generate electricity. The plant saves money through cogeneration because it does not have to buy electrical power from local utilities.

Other techniques for increasing energy efficiency

Many other approaches are available for increasing the efficiency with which energy is used in a society. Recycling has become much more popular in the United States over the past few decades at least partly because it provides a way of salvaging valuable resources such as glass, aluminum, and paper. Recycling is also an energy efficient practice because it reduces the cost of producing new products from raw materials. Another approach to energy efficiency is to make use of packaging materials that are produced with less energy. The debate still continues over whether paper or plastic bags are more energy efficient, but at least the debate indicates that people are increasingly aware of the choices that can be made about packaging materials.

Government policies and regulations

Most governmental bodies were relatively unconcerned about energy efficiency issues until the OPEC (Organization of Oil Exporting Countries) oil embargo of 1973-74. Following that event, however, they began to search for ways of encouraging corporations and private consumers to use energy more efficiently. One of the first of many laws that appeared over the next decade was the Energy Policy and Conservation Act of 1975. Among the provisions of that act were: a requirement that new appliances carry labels indicating the amount of energy they use, the creation of a federal technical and financial assistance program for energy conservation plans, and the establishment of the State Energy Conservation Program. A year later, the Energy Conservation and Production Act of 1976 provided for the development of national mandatory Building Energy Performance Standards and the creation of the Weatherization Assistance Program to fund energy-saving retrofits for low-income households. Both of these laws were later amended and updated.

In 1991, the U.S. Environmental Protection Agency (EPA) established two voluntary programs to prevent pollution and reduce energy costs. The Green Lights Partnership provided assistance in installing energy-efficient lighting, and the Energy Star Buildings Partnership used Green Lights as its first of five stages to improve all aspects of building efficiency. The World Trade Center and the Empire State Building in New York City and the Sears Tower in Chicago (four of the world’s tallest structures) joined the Energy Star Buildings Partnership as charter members and have reduced their energy costs by millions of dollars. The EPA also developed software with energy management aids for building operators who enlist in the partnership. By 1998, participating businesses had reduced their lighting costs by 40%, and whole- building upgrades had been completed in over 2.8 billion ft2 (0.3 billion m2) of building space. The EPA’s environ- mental interest in the success of these programs comes not only from conserving resources but from limiting carbon dioxide emissions that result from energizing industrial plants and commercial buildings and that cause changes in the world’s climate.

Energy efficiency

Energy efficiency refers to any process by which the amount of useful energy obtained from some process is increased compared to the amount of energy put into that process. As a simple example, some automobiles can travel 40 mi (17 km) by burning a single gallon (liter) of gasoline, while others can travel only 20 mpg (8.5 km/l). The energy efficiency achieved by the first car is twice that achieved by the second car. In general, energy efficiency is measured in units such as mpg, lumens per watt, or some similar “output per input” unit.

History of energy concerns

Interest in energy efficiency is relatively new in the history of modern societies, although England’s eighteenth century search for coal was prompted by the de- cline of the country’s forest resources. For most of the past century, however, energy resources seemed to be infinite, for all practical purposes. Little concern was expressed about the danger of exhausting the world’s supplies of coal, oil, and natural gas, its major energy resources.

The turning point in that attitude came in the 1970s when the major oil-producing nations of the world suddenly placed severe limits on the amounts of petroleum that they shipped to the rest of the world. This oil embargo forced major oil users such as the United States, Japan, and the nations of Western Europe to face for the first time the danger of having insufficient petroleum products to meet their basic energy needs. Use of energy resources suddenly became a matter of national and international discussion.

Energy efficiency can be accomplished in a number of different ways. One of the most obvious is conservation; that is, simply using energy resources more careful- ly. For example, people might be encouraged to turn out lights in their home, to set their thermostats at lower temperatures, and to use bicycles rather than automobiles for transportation. Energy efficiency in today’s world also means more complex and sophisticated approaches to the way in which energy is used in industrial, commercial, and residential settings.

Energy efficiency in buildings

Approximately one-third of all the energy used in the United States goes to heat, cool, and light buildings. A number of technologies have been developed that im- prove the efficiency with which energy is used in buildings. Some of these changes are simple; higher grades of insulation are used in construction, and air leaks are plugged. Both of these changes reduce the amount of heated or air-conditioned air (depending on the season) lost from the building to the outside environment.

Other improvements involve the development of more efficient appliances and construction products. For example, the typical gas furnace in use in residential and commercial buildings in the 1970s was about 63% efficient. Today, gas furnaces with efficiencies of 97% are readily available and affordable. Double-glazed windows with improved insulating properties have also been developed. Such windows can save more than 10% of the energy lost by a building in a year.

Buildings can also be designed to save energy. For example, they can be oriented on a lot to take advantage of solar heating or cooling. Many commercial structures also have computerized systems that automatically ad- just heating and cooling schedules to provide a comfort- able environment for occupants only when and in portions of the building that are occupied.

Entirely new technologies can be used also. For example, many buildings now depend exclusively on more efficient fluorescent lighting systems than on less efficient incandescent lights. In some situations, this single change can produce a greater savings in energy use than any other modification. The increasing use of solar cells is another example of a new kind of technology that has the potential for making room and water heating much more efficient.

Transportation

About one-third more of the energy used in the United States goes to moving people and goods from place to place. For more than two decades, governments have made serious efforts to convince people that they should use more energy-efficient means of transportation, such as bicycles or some form of mass transit (buses, trolleys, subways, light-rail systems, etc.). These efforts have had only limited success.

Another approach that has been more successful has been to encourage car manufacturers to increase the efficiency of automobile engines. In the 1970s, the average fuel efficiency of cars in the United States was 13 mpg

(5.5 km/l). Over the next decade, efficiency improved nearly twice over to 25 mpg (10.6 km/l). In other nations, similar improvements were made. Cars in Japan, for example, increased from an average efficiency of 23 mpg (9.8 km/l) in 1973 to 30 mpg (12.8 km/l) in 1985.

Yet, even more efficient automotive engines appear to be possible. Many authorities believe that efficiencies approaching 50 mpg (21 km/l) should be possible by the year 2001. As of 1987, at least three cars with fuel efficiencies of more than 50 mpg (21 km/l) were already in production (the Ford Escort, Honda City, and Suzuki Sprint). Experimental cars with efficiencies close to 100 mpg (42.5 km/l) were also being tested; the Toyota AXV has achieved 98 mpg (41.7 km/l) on test tracks, and the Renault VESTA has logged 124 mpg (52.7 km/l).

To a large extent, automobile manufacturers have been slow to produce cars that have the maximum possible efficiencies because they question whether consumers will pay higher purchase prices for these cars. Improvements continue to be made, however, at least partly because of the legislative pressure for progress in this direction.

Energy efficiency in industry

The final third of energy use in the United States occurs in a large variety of industrial operations such as producing steam, heating plants, and generating electric- ity for various operations. Improvements in the efficiency with which energy is used in industry also depends on two principal approaches: the development of more efficient devices and the invention of new kinds of technologies. More efficient motors are now available so that the same amount of work can be accomplished with a smaller amount of energy input. And, as an example of the use of new technologies, laser beam systems that can both heat and cut more efficiently than traditional tools are being given new applications. Industries are also finding ways to use computer systems to design and carry out functions within a plant more efficiently than traditional resource management methods.

One of the most successful approaches to improving energy efficiency in industry has been the development of cogeneration systems. Cogeneration refers to the process in which heat produced in an industrial operation (formerly regarded as “waste heat”) is used to generate electricity. The plant saves money through cogeneration because it does not have to buy electrical power from local utilities.

Other techniques for increasing energy efficiency

Many other approaches are available for increasing the efficiency with which energy is used in a society. Recycling has become much more popular in the United States over the past few decades at least partly because it provides a way of salvaging valuable resources such as glass, aluminum, and paper. Recycling is also an energy efficient practice because it reduces the cost of producing new products from raw materials. Another approach to energy efficiency is to make use of packaging materials that are produced with less energy. The debate still continues over whether paper or plastic bags are more energy efficient, but at least the debate indicates that people are increasingly aware of the choices that can be made about packaging materials.

Government policies and regulations

Most governmental bodies were relatively unconcerned about energy efficiency issues until the OPEC (Organization of Oil Exporting Countries) oil embargo of 1973-74. Following that event, however, they began to search for ways of encouraging corporations and private consumers to use energy more efficiently. One of the first of many laws that appeared over the next decade was the Energy Policy and Conservation Act of 1975. Among the provisions of that act were: a requirement that new appliances carry labels indicating the amount of energy they use, the creation of a federal technical and financial assistance program for energy conservation plans, and the establishment of the State Energy Conservation Program. A year later, the Energy Conservation and Production Act of 1976 provided for the development of national mandatory Building Energy Performance Standards and the creation of the Weatherization Assistance Program to fund energy-saving retrofits for low-income households. Both of these laws were later amended and updated.

In 1991, the U.S. Environmental Protection Agency (EPA) established two voluntary programs to prevent pollution and reduce energy costs. The Green Lights Partnership provided assistance in installing energy-efficient lighting, and the Energy Star Buildings Partnership used Green Lights as its first of five stages to improve all aspects of building efficiency. The World Trade Center and the Empire State Building in New York City and the Sears Tower in Chicago (four of the world’s tallest structures) joined the Energy Star Buildings Partnership as charter members and have reduced their energy costs by millions of dollars. The EPA also developed software with energy management aids for building operators who enlist in the partnership. By 1998, participating businesses had reduced their lighting costs by 40%, and whole- building upgrades had been completed in over 2.8 billion ft2 (0.3 billion m2) of building space. The EPA’s environ- mental interest in the success of these programs comes not only from conserving resources but from limiting carbon dioxide emissions that result from energizing industrial plants and commercial buildings and that cause changes in the world’s climate.

Physical energy budgets

Physical energy budgets consider a particular, defined system, and then analyze the inputs of energy, its various transformations and storages, and the eventual outputs. This concept can be illustrated by reference to the energy budget of Earth.

The major input of energy to Earth occurs as solar electromagnetic energy. At the outer limits of Earth’s atmosphere, the average rate of input of solar radiation is

2.00 calories per cm2 per minute (this flux is known as the solar constant). About half of this energy input occurs as visible radiation, and half as near-infrared. As noted previously, Earth also emits its own electromagnetic radiation, again at a rate of 2.00 cal/cm2/min, but with a spectrum that peaks in the longer-wave infrared, at about 10 æm. Because the rate of energy input equals the rate of output, there is no net storage of energy, and no substantial, longer-term change in Earth’s surface temperature. Therefore, Earth represents a zero-sum, energy flow-through system. (Actually, over geological time there has been a small storage of energy, occurring as an accumulation of undecomposed biomass that eventually transforms geologically into fossil fuels. There are also minor, longer-term variations of Earth’s temperature surface that represent climate change. However, these represent quantitatively trivial exceptions to the preceding statement about Earth as a zero-sum, flow-through system for energy.) Although the amount of energy emit- ted by Earth eventually equals the amount of solar radiation that is absorbed, there are some ecologically important transformations that occur between these two events. The most important ways by which Earth deals with its incident solar radiations are: (1) An average of about 30% of the incident solar energy is reflected back to outer space by Earth’s atmosphere or its surface. This process is related to Earth’s albedo, which is strongly influenced by the solar angle, the amounts of cloud cover and atmospheric particulates, and to a lesser degree by the character of Earth’s surface, especially the types and amount of water (including ice) and vegetation cover. (2) About 25% of the incident energy is absorbed by atmospheric gases, vapors, and particulates, converted to heat or thermal kinetic energy, and then re-radiated as longer- wavelength infrared radiation. (3) About 45% of the incident radiation is absorbed at Earth’s surface by living and non-living materials, and is converted to thermal energy, increasing the temperature of the absorbing sur- faces. Over the longer term (that is, years) and even the medium term (that is, days) there is little or no net storage of heat. Virtually all of the absorbed energy is re-radiated by the surface as long-wave infrared energy, with a wavelength peak of about 10 æm. (4) Some of the thermal energy of surfaces causes water to evaporate from plant and non-living surfaces (see entry on evapotranspiration), or it causes ice or snow to melt. (5) Because of the uneven distribution of thermal energy on Earth’s surface, some of the absorbed radiation drives mass- transport, distributional processes, such as winds, water currents, and waves on the surface of waterbodies. (6) A very small (averaging less than 0.1%) but ecologically critical portion of the incoming solar energy is absorbed by the chlorophyll of plants, and is used to drive photo- synthesis. This photoautotrophic fixation allows some of the solar energy to be “temporarily” stored in the potential energy of biochemicals, and to serve as the energetic basis of life on Earth.

Certain gases in Earth’s atmosphere absorb long- wave infrared energy of the type that is radiated by heated matter in dissipation mechanisms 2 and 3 (above). This absorption heats the gases, which then undergo an- other re-radiation, emitting even longer-wavelength infrared energy in all directions, including back to Earth’s surface. The most important of the so-called radiatively active gases in the atmosphere are water and carbon dioxide, but the trace gases methane, nitrous oxide, ozone, and chlorofluorocarbons are also significant. This phenomenon, known as the greenhouse effect, significantly interferes with the rate of radiative cooling of Earth’s surface.

If there were no greenhouse effect, and Earth’s atmosphere was fully transparent to long-wave infrared radiation, surface temperatures would average about 17.6°F (-8°C), much too cold for biological processes to occur. Because the naturally occurring greenhouse effect maintains Earth’s average surface temperature about 60 degrees warmer than this, at about 77°F (25°C), it is an obviously important factor in the habitability of our planet. However, human activities have resulted in in- creasing atmospheric concentrations of some of the radiatively active gases, and there are concerns that this could cause an intensification of Earth’s greenhouse effect. This could lead to global warming, changes in the distributions of rainfall and other climatic effects, and severe ecological and socioeconomic damages.

Budgets of fixed energy

Ecological energetics examines the transformations of fixed, biological energy within communities and ecosystems, in particular, the manner in which biologi- cally fixed energy is passed through the food web.

For example, studies of a natural oak-pine forest in New York found that the vegetation fixed solar energy equivalent to 11,500 kilocalories per hectare per year (103 Kcal/ha/yr). However, plant respiration utilized 6.5 X 103 Kcal/ha/yr, so that the actual net accumulation of energy in the ecosystem was 5.0 X 103 Kcal/ha/yr. The various types of heterotrophic organisms in the forest utilized another 3.0 X 103 Kcal/ha/yr to support their respiration, so the net accumulation of biomass by all of the organisms of the ecosystem was equivalent to 2.0 x 103 Kcal/ha/yr.

The preceding is an example of a fixed-energy budget at the ecosystem level. Sometimes, ecologists develop budgets of energy at the levels of population, and even for individuals. For example, depending on environmental circumstances and opportunities, individual plants or animals can optimize their fitness by allocating their energy resources into various activities, most simply, into growth of the individual or into re- production.

However, biological energy budgets are typically much more complicated than this. For example, a plant can variously allocate its energy into the production of longer stems and more leaves to improve its access to sunlight, or it could grow longer and more roots to in-

KEY TERMS

Electromagnetic energy—A type of energy, involving photons, which have physical properties of both particles and waves. Electromagnetic energy is divided into spectral components, which (ordered from long to short wavelength) include radio, infrared, visible light, ultraviolet, and cosmic.

Entropy—The measurement of a tendency to- wards increased randomness and disorder.

crease its access to soil nutrients, or more flowers and seeds to increase the probability of successful reproduction. There are other possible allocation strategies, including some combination of the preceding.

Similarly, a bear must makes decisions about the al- location of its time and energy into activities associated with resting, either during the day or longer-term hibernation, hunting for plant or animal foods, seeking a mate, taking care of the cubs.

See also Energy transfer; Food chain/web.

Resources

Books

Odum, E.P. Ecology and Our Endangered Life Support Systems. New York: Sinauer, 1993.

Ricklefs, R.E. Ecology. New York: W.H. Freeman, 1990.

Physical energy budgets

Physical energy budgets consider a particular, defined system, and then analyze the inputs of energy, its various transformations and storages, and the eventual outputs. This concept can be illustrated by reference to the energy budget of Earth.

The major input of energy to Earth occurs as solar electromagnetic energy. At the outer limits of Earth’s atmosphere, the average rate of input of solar radiation is

2.00 calories per cm2 per minute (this flux is known as the solar constant). About half of this energy input occurs as visible radiation, and half as near-infrared. As noted previously, Earth also emits its own electromagnetic radiation, again at a rate of 2.00 cal/cm2/min, but with a spectrum that peaks in the longer-wave infrared, at about 10 æm. Because the rate of energy input equals the rate of output, there is no net storage of energy, and no substantial, longer-term change in Earth’s surface temperature. Therefore, Earth represents a zero-sum, energy flow-through system. (Actually, over geological time there has been a small storage of energy, occurring as an accumulation of undecomposed biomass that eventually transforms geologically into fossil fuels. There are also minor, longer-term variations of Earth’s temperature surface that represent climate change. However, these represent quantitatively trivial exceptions to the preceding statement about Earth as a zero-sum, flow-through system for energy.) Although the amount of energy emit- ted by Earth eventually equals the amount of solar radiation that is absorbed, there are some ecologically important transformations that occur between these two events. The most important ways by which Earth deals with its incident solar radiations are: (1) An average of about 30% of the incident solar energy is reflected back to outer space by Earth’s atmosphere or its surface. This process is related to Earth’s albedo, which is strongly influenced by the solar angle, the amounts of cloud cover and atmospheric particulates, and to a lesser degree by the character of Earth’s surface, especially the types and amount of water (including ice) and vegetation cover. (2) About 25% of the incident energy is absorbed by atmospheric gases, vapors, and particulates, converted to heat or thermal kinetic energy, and then re-radiated as longer- wavelength infrared radiation. (3) About 45% of the incident radiation is absorbed at Earth’s surface by living and non-living materials, and is converted to thermal energy, increasing the temperature of the absorbing sur- faces. Over the longer term (that is, years) and even the medium term (that is, days) there is little or no net storage of heat. Virtually all of the absorbed energy is re-radiated by the surface as long-wave infrared energy, with a wavelength peak of about 10 æm. (4) Some of the thermal energy of surfaces causes water to evaporate from plant and non-living surfaces (see entry on evapotranspiration), or it causes ice or snow to melt. (5) Because of the uneven distribution of thermal energy on Earth’s surface, some of the absorbed radiation drives mass- transport, distributional processes, such as winds, water currents, and waves on the surface of waterbodies. (6) A very small (averaging less than 0.1%) but ecologically critical portion of the incoming solar energy is absorbed by the chlorophyll of plants, and is used to drive photo- synthesis. This photoautotrophic fixation allows some of the solar energy to be “temporarily” stored in the potential energy of biochemicals, and to serve as the energetic basis of life on Earth.

Certain gases in Earth’s atmosphere absorb long- wave infrared energy of the type that is radiated by heated matter in dissipation mechanisms 2 and 3 (above). This absorption heats the gases, which then undergo an- other re-radiation, emitting even longer-wavelength infrared energy in all directions, including back to Earth’s surface. The most important of the so-called radiatively active gases in the atmosphere are water and carbon dioxide, but the trace gases methane, nitrous oxide, ozone, and chlorofluorocarbons are also significant. This phenomenon, known as the greenhouse effect, significantly interferes with the rate of radiative cooling of Earth’s surface.

If there were no greenhouse effect, and Earth’s atmosphere was fully transparent to long-wave infrared radiation, surface temperatures would average about 17.6°F (-8°C), much too cold for biological processes to occur. Because the naturally occurring greenhouse effect maintains Earth’s average surface temperature about 60 degrees warmer than this, at about 77°F (25°C), it is an obviously important factor in the habitability of our planet. However, human activities have resulted in in- creasing atmospheric concentrations of some of the radiatively active gases, and there are concerns that this could cause an intensification of Earth’s greenhouse effect. This could lead to global warming, changes in the distributions of rainfall and other climatic effects, and severe ecological and socioeconomic damages.

Budgets of fixed energy

Ecological energetics examines the transformations of fixed, biological energy within communities and ecosystems, in particular, the manner in which biologi- cally fixed energy is passed through the food web.

For example, studies of a natural oak-pine forest in New York found that the vegetation fixed solar energy equivalent to 11,500 kilocalories per hectare per year (103 Kcal/ha/yr). However, plant respiration utilized 6.5 X 103 Kcal/ha/yr, so that the actual net accumulation of energy in the ecosystem was 5.0 X 103 Kcal/ha/yr. The various types of heterotrophic organisms in the forest utilized another 3.0 X 103 Kcal/ha/yr to support their respiration, so the net accumulation of biomass by all of the organisms of the ecosystem was equivalent to 2.0 x 103 Kcal/ha/yr.

The preceding is an example of a fixed-energy budget at the ecosystem level. Sometimes, ecologists develop budgets of energy at the levels of population, and even for individuals. For example, depending on environmental circumstances and opportunities, individual plants or animals can optimize their fitness by allocating their energy resources into various activities, most simply, into growth of the individual or into re- production.

However, biological energy budgets are typically much more complicated than this. For example, a plant can variously allocate its energy into the production of longer stems and more leaves to improve its access to sunlight, or it could grow longer and more roots to in-

KEY TERMS

Electromagnetic energy—A type of energy, involving photons, which have physical properties of both particles and waves. Electromagnetic energy is divided into spectral components, which (ordered from long to short wavelength) include radio, infrared, visible light, ultraviolet, and cosmic.

Entropy—The measurement of a tendency to- wards increased randomness and disorder.

crease its access to soil nutrients, or more flowers and seeds to increase the probability of successful reproduction. There are other possible allocation strategies, including some combination of the preceding.

Similarly, a bear must makes decisions about the al- location of its time and energy into activities associated with resting, either during the day or longer-term hibernation, hunting for plant or animal foods, seeking a mate, taking care of the cubs.

See also Energy transfer; Food chain/web.

Resources

Books

Odum, E.P. Ecology and Our Endangered Life Support Systems. New York: Sinauer, 1993.

Ricklefs, R.E. Ecology. New York: W.H. Freeman, 1990.