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
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.
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.
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 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
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.
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.
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 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