Energy

Energy is the capacity for doing work. In physics, "work" has a more formal definition than in everyday life: it means the ability to exert a force through a distance. If you pick up this book, energy stored in molecular bonds inside your body is released to move the book's mass. The energy was stored in the molecules of the foods you ate and is released through a chemical reaction. Food provides the fuel that gives us energy.

Similarly, whether we are talking about automobile engines or power plant boilers, we need to have a fuel with stored energy that can be released in a useable way. Fossil fuels such as coal, oil, and natural gas provide much of the energy we use in industry and in our personal lives. These fuels were created by geological processes over millions of years, as plants and marine microorganisms consisting largely of carbon became buried under the earth. These fossilized materials were eventually transformed into coal or oil by the high pressures and temperatures inside the planet.

Because of the long time and extreme conditions needed to create fossil fuels, we cannot just replace them at will—they are a nonrenewable resource. Every time we pump oil from the ground we are depleting an irreplaceable natural resource. Eventually, we will exhaust the supplies of fossil fuels in the earth, and we will have to develop alternative energy sources to power our society. Exactly when we will run out of fossil fuels is a subject of great debate. A careful distinction must be made here between "reserves" and "resources." Reserves are defined as economically recoverable with known technology and within a price range close to the present price; resources are theoretical maximum potentials based on geological information, and include reserves. The Energy Information Administration (EIA) of the United States Department of Energy has estimated the worldwide coal resources at 1,083 billion tons; the oil reserve at approximately 1,200 billion barrels, with resources estimated at three trillion barrels; and the worldwide natural gas reserve at 5,500 trillion cubic feet . The nonprofit Corporation for Public Access to Science and Technology (CPAST) in St. Louis, Missouri, has estimated from earlier data published in the United States Department of Energy 1996 Annual Energy Review that these combined fossil fuels resources would last until the year 2111 if usage remained constant at 1995 levels. The EIA predicts that coal resources could last for 220 years at the current usage rates. Estimates change when new technology makes fuel that was previously considered "unrecoverable" suddenly accessible; these numbers should only be used as rough guidelines.

Transforming Energy into Work: Gasoline Engines and Steam Boilers

Gasoline, which consists largely of hydrocarbon molecules—chains of connected carbon and hydrogen atoms—acts as a fuel in an automobile engine. It is a product of the distillation of raw petroleum. The energy that holds these carbon and hydrogen atoms together is stored in the bonds between each atom.

In an automobile, gasoline is mixed with air in the combustion chamber of an engine cylinder, the mixture is compressed by a piston, and a spark from the spark plug ignites the mixture. The ideal chemical reaction for this process is:

The energy is released in the form of heat, which causes the gases to expand and pushes the piston outward. The piston is connected to a rod and a crankshaft that ultimately transform the energy locked up in molecules into the revolution of wheels, setting your car in motion. The combustion products of carbon dioxide and water are expelled through the exhaust system into the atmosphere.

Similarly, a boiler in a power plant relies on the release of energy from burning coal or natural gas to heat water and convert it into steam. The steam turns the blades of a turbine-powered generator that ultimately causes electrons to move through a wire, converting the energy from the fuel into electrical energy that can be used to power appliances in your home.

In each of these cases, energy stored in chemical bonds is transformed into useful energy that can perform work.

Energy and Pollution

In addition, the chemical reaction shown above is an ideal one, but conditions in the real world are usually far from ideal. If the right amounts of oxygen and gasoline are not present in the cylinder of a car engine (because of a dirty air filter or a faulty fuel injection system, for example), poisonous carbon monoxide can form. Similarly, some of the hydrocarbons might escape from the engine unburned, releasing pollutants such as methane into the air. Nitrogen from the air inside the cylinder can combine with oxygen to form the pollutants nitric oxide and nitrogen dioxide, collectively know as NOxcompounds, which can be converted to ground-level ozone in the presence of sunlight. Even carbon dioxide—one of the "ideal" products of complete combustion in an engine or a power plant—has been identified as a "green-house gas" that is partially responsible for global warming.

The coal used in power plants does not emerge from the ground as pure carbon. It is laced with varying amounts of different contaminants, including sulfur, which vary from coal mine to coal mine. These, too, can find their way into the atmosphere as pollutants when the coal is burned to heat the water in a boiler. Most notably, sulfur oxide, emitted into the air, converts to sulfuric

acid, a major component in acid rain. Power plants are required to clean up these emissions before they reach the atmosphere, to varying degrees, but again, no process is 100-percent efficient.

Besides the pollutants associated with the use of fossil fuels, drilling for oil and mining coal can be an additional source of pollution. An oil spill while drilling or transporting oil can lead to disastrous ecological damage, and rain runoff from a strip mine can carry coal particles and chemical byproducts into the local water supply.

Nuclear and Alternative Fuels

Nuclear energy is not based on combustion of fuel. Rather, the energy is released as unstable radioactive compounds decay into more stable forms. For example, radioactive uranium 238 decays to uranium 235, releasing energy in the process. This energy can be used to heat water without burning coal or oil, so its use is therefore cleaner. However, radiation emitted in the event of an accident at a nuclear power plant could harm people and wildlife and contaminate the food supply. Nuclear waste, in the form of spent fuel rods, is a very long-term by-product of nuclear energy.

Cleaner-burning fuels can be produced by processing agricultural products ("biomass") into ethanol. Thousands of acres of corn could be grown specifically for energy production, not consumption by people or animals. Because the ethanol that results comes from a controllable chemical distillation process, it is very pure and uncontaminated, and thus burns cleaner. Also, because a new crop can be grown every year, these are renewable energy sources.

Hydropower, or the use of moving or falling water to generate energy, is one of the oldest technologies that still contributes significantly to our energy needs. Falling water was often used in old mills to turn a paddlewheel and move the heavy stones that were used to grind grain into flour. Later, the same concept was transferred to the production of electricity. Hydroelectric plants, such as the one in Niagara Falls, divert some of the water from the falls into the power plant. There the kinetic energy (the energy of objects in motion) of the falling water turns turbines and generates electricity that can be sold to residents and industrial users in the area.

Solar power, wind power, and fuel cells powered by a reaction of hydrogen plus oxygen to form water are other alternative energy sources that are being explored.

Industry and Environment

Suppose you are the owner of a manufacturing plant. You need large amounts of fuel to keep your plant running. To maximize your profits, you would like to purchase this fuel very cheaply. The cheapest option would be if the energy company could take the fuel straight from the ground and sell it to you "as is." But fossil fuels must be processed before they can be used. Petroleum products must go to the refinery to be separated into various components such as gasoline and diesel fuel, and contaminants such as sulfur have to be minimized. All these processing steps add cost to the fuel.

Even after you obtain a relatively clean fuel, your manufacturing process may result in pollutants that could find their way into the atmosphere or rivers. Again, efforts to clean up these emissions will cost you money. Chemical systems that scrub the pollutants from the emissions, or filters that capture particulates, are expensive and raise your production costs.

But there may be people who are more concerned about a healthy environment than your profits. They might insist that you take whatever steps are necessary on both the inlet (fuel) side and the outlet (emissions and runoff) side to make the world a better, safer place to live. They may lobby to have laws passed that require you to clean up any emissions from your plant.

You want a clean environment too, but even the most environmentally conscious company must make a profit to stay in business. Environmental regulations add to the cost of producing your product, but this is no different than all the other costs you incur (raw materials, labor, transportation, marketing, etc.). If all competitors in an industry are constrained by the same regulations, then the playing field is level; every company in the field may have to raise its prices to make up for the added costs of compliance, but prices for similar products should remain competitive. However, if competitors in foreign countries are able to operate without these same environmental regulations, they can market their products more cheaply, and make it more difficult for domestic producers to stay in business. It is this kind of imbalance in regulations that lead to job losses, and give the mistaken impression that we must choose either jobs or the environment. If governments can maintain a level playing field in environmental regulations, we can have both jobs and a clean environment worldwide.

The situation may be further confused by an argument among scientists and health professionals as to how much of a health problem a certain chemical represents. Something that seems safe today may be discovered to be a health risk ten years from now. Until we understand how various chemicals interact with our bodies, there may be room for discussion on allowable levels of emission.

Conserving Energy

In light of the depletion of nonrenewable resources, it is important that we try to conserve energy whenever possible. Because the transformation of fuel into useful energy inevitably creates pollutants, we must reduce our energy consumption to reduce pollution. Using your air conditioner less during the summer by setting the thermostat higher can reduce the demand for electricity experienced by your energy provider. Your energy provider can burn less fossil fuel and still meet the needs of its customers, resulting in less pollution. Carpooling removes unnecessary vehicles from the road, reducing gasoline consumption and air pollution. Energy conservation efforts thus help at both ends of the cycle: they slow down the depletion of fuel reserves and, at the same time, clean up the environment.

The Politics of Energy

Because the conditions necessary for the creation of fossil fuels varied geographically throughout the earth's history, fossil fuels are not distributed evenly around the globe. Significant concentrations of oil occur in the Middle East, the North Sea, Russia, Texas, and Alaska, for example. Countries that control the world's access to oil have economic power over countries that need their oil, which can lead to political tensions. The "energy crisis" created by the OPEC (Organization of the Petroleum Exporting Countries) nations in the 1970s, when they artificially reduced the supply of oil available on the world market, was a display of this political and economic power. Iraq's attack on Kuwait in 1991 to take over Kuwaiti oil fields led to the first Persian Gulf War. As long as there is uneven access to energy sources throughout the world, political tensions over the availability and cost of energy will continue.

see also Air Pollution; Alternative Energy; Carbon Dioxide; Coal; Disasters: Nuclear Accidents; Disasters: Oil Spills; Electric Power; Fossil Fuels; Nuclear Energy; Nuclear Wastes; Petroleum; Renewable Energy; Thermal Pollution.

Bibliography

Tipler, Paul A. (1982). Physics, 2nd ed. New York: Worth Publishers.

Other Resources

Brain, Marshall. (2002). "How Car Engines Work." HowStuffWorks. Available from http://www.howstuffworks.com/steam.htm.

Brain, Marshall. (2002). "How Steam Engines Work." HowStuffWorks. Available from http://www.howstuffworks.com/steam.htm.

Energy Information Administration of the United States Department of Energy. (2003). "World Crude Oil and Natural Gas Reserves, Most Recent Estimates." Available from http://www.eia.gov/emeu/international/reserves.html.

Greenpeace. (1997). "Carbon Dioxide Emissions and Fossil Fuel Resources." Available from http://archive.greenpeace.org/~climate/science/reports/carbon/clfull-3.html.

Lawrence Livermore National Laboratory, Energy & Environment Directorate. "U.S. Energy Flow 2000." Available from http://en-env.llnl.gov/flow.

Lawrence Livermore National Laboratory, Energy & Environment Directorate. "U.S. 2000 Carbon Emissions from Energy Consumption." Available from http://en-env.llnl.gov/flow.

Mabro, Robert, ed. (1980). World Energy Issues and Policies: Proceedings of the First Oxford Energy Seminar (September 1979). Oxford: Oxford University Press.

Myhr, Franklin. (1998). "Overview of Fossil Fuel Energy Resources." Corporation for Public Access to Science and Technology (CPAST). Available from http://www.cpast.org/articles/fetch.adp?artnum=14.

Tim Palucka

The tiny town of Cheshire, Ohio, lives in the shadow of American Electric Power's giant coal-burning Gen. James M. Gavin generating plant. Each summer, blue clouds of sulfuric acid rain down on the town, an unintended and ironic by-product of AEP's efforts to curb other emissions at the plant. Residents sued and in 2002, AEP agreed to buy the town rather than fight the pollution suit. All but a handful of Cheshire's 221 residents have agreed to sell and move. The cost: $20 million.

Energy

Energy is the capacity to do work. In science, the term work has a very special meaning. It means that an object has been moved through a distance. Thus, pushing a brick across the top of a table is an example of doing work. By applying this definition of work, then, energy can also be defined as the ability to move an object through a distance. Imagine that a bar magnet is placed next to a pile of iron filings (thin slivers of iron metal). The iron filings begin to move toward the iron bar. We say that magnetic energy pulls on the iron filings and causes them to move.

Energy can be a difficult concept to understand. Unlike matter, energy cannot be held or placed on a laboratory bench for study. We know about energy best because of the effect it has on objects around it, as in the case of the bar magnet and iron filings mentioned above.

Energy can exist in many forms, including mechanical, heat, electrical, magnetic, sound, chemical, and nuclear. Although these forms appear to be very different from each other, they often have much in common and can generally be transformed from one to another.

Over time, a number of different units have been used to measure energy. In the British system, for example, the fundamental unit of energy is the foot-pound. One foot-pound is the amount of energy that can move a weight of one pound a distance of one foot. In the metric system, the fundamental unit of energy is the joule (abbreviation: J), named after English scientist James Prescott Joule (1818–1889). A joule is the amount of energy that can move a weight of one newton a distance of one meter.

Potential and kinetic energy

Objects possess energy for one of two reasons: because of their position or because of their motion. The first type of energy is defined as potential energy; the second type of energy is defined as kinetic energy. Think of a baseball sitting on a railing at the top of the Empire State Building. That ball has potential energy because of its ability to fall off the railing and come crashing down onto the street. The potential energy of the baseball—as well as that of any other object—is dependent on two factors: its mass and its height above the ground. The baseball has a relatively small mass, but in this example it still has a large potential energy because of its distance above the ground.

Words to Know

Conservation of energy: A law of physics that says that energy can be transformed from one form to another, but can be neither created nor destroyed.

Joule: The unit of measurement for energy in the metric system.

Kinetic energy: The energy possessed by a body as a result of its motion.

Mass: Measure of the total amount of matter in an object.

Potential energy: The energy possessed by a body as a result of its position.

Velocity: The rate at which the position of an object changes with time, including both the speed and the direction.

The second type of energy, kinetic energy, is a result of an object's motion. The amount of kinetic energy possessed by an object is a function of two variables, its mass and velocity. The formula for kinetic energy is E = ½mv², where m is the mass of the object and v is its velocity. This formula shows that an object can have a lot of kinetic energy for two reasons: it can either be very heavy (large m) or it can be moving very fast (large v).

Imagine that the baseball mentioned previously falls off the Empire State Building. The ball can do a great deal of damage because it has a great deal of kinetic energy. The kinetic energy comes from the very high speed with which the ball is traveling by the time it hits the ground. The baseball may not weigh very much, but its high speed still gives it a great deal of kinetic energy.

Conservation of energy

In science, the term conservation means that the amount of some property is not altered during a chemical or physical change. At one time, physicists believed in the law of conservation of energy. That law states that the amount of energy present at the end of any physical or chemical change is exactly the same as the amount present at the beginning of the change. The form in which the energy appears may be different, but the total amount is constant. Another way to state the law of conservation of energy is that energy is neither created nor destroyed in a chemical or physical change.

As an example, suppose that you turn on an electric heater. A certain amount of electrical energy travels into the heater and is converted to heat. If you measure the amount of electricity entering the heater and the amount of heat given off, the amounts will be the same.

The law of conservation of energy is valid for the vast majority of situations that we encounter in our everyday lives. In the early 1900s, however, German-born American physicist Albert Einstein (1879–1955) made a fascinating discovery. Under certain circumstances, Einstein said, energy can be transformed into matter, and matter can be transformed into energy. Those circumstances are seldom encountered in daily life. When they are, a modified form of the law of conservation of energy applies. That modified form is known as the law of conservation of energy and matter. It says that the total amount of matter and energy is always conserved in any kind of change.

Forms of energy

We know of the existence of energy because of the various forms in which it occurs. When an explosion occurs, air is heated up to very high

Energy Efficiency

Energy can be converted from one form to another, but the process is often very wasteful. An incandescent lightbulb is an example. When a lightbulb is turned on, electrical current flows into the wire filament in the bulb. The filament begins to glow, giving off light. That's what the bulb is designed to do. But most of the electrical energy entering the bulb is used to heat the wire first. That electrical energy is "wasted" since it is lost as heat; the lightbulb is not designed to be a source of heat.

The amount of useful energy obtained from some machine or some process compared to the amount of energy provided to the machine or process is called the energy efficiency of the machine or process. For example, a typical incandescent lightbulb converts about 90 percent of the electrical energy it receives to heat and 10 percent to light. Therefore, the energy efficiency of the lightbulb is said to be 10 percent.

Energy efficiency has come to have a new meaning in recent decades. The term also refers to any method by which the amount of useful energy can be increased in any machine or process. For example, some automobiles can travel 40 miles by burning a single gallon of gasoline, while others can travel only 20 miles per gallon. The energy efficiency achieved by the first car is twice that achieved by the second car.

Until the middle of the twentieth century, most developed nations did not worry very much about energy efficiency. Coal, oil, and natural gas—the fuels from which we get most of our energy—were cheap. It didn't make much difference to Americans and other people around the world if a lot of energy was wasted. We just dug up more coal or found more oil and gas to make more energy.

By the third quarter of the twentieth century, though, that attitude was much less common as people realized that natural resources won't last forever. Architects, automobile and airplane designers, plant managers, and the average home owner were all looking for ways to use energy more efficiently.

temperatures. The hot air expands quickly, knocking down objects in its path. Heat is a form of energy also known as thermal energy. Temperature is a measure of the amount of heat energy contained in an object.

Other forms of energy include electrical energy, magnetism, sound, chemical, and nuclear energy. Although these forms of energy appear to be very different from each other, they are all closely related: one form of energy can be changed into another, different form of energy.

An example of this principle is an electric power generating plant. In such a plant, coal or oil may be burned to boil water. Chemical energy stored in the coal or oil is converted to heat energy in steam. The steam can then be used to operate a turbine, a large fan mounted on a central rod. The steam strikes the fan and causes the rod to turn. Heat energy from the steam is converted to the kinetic energy of the rotating fan. Finally, the turbine runs an electric generator. In the generator, the kinetic energy of the rotating turbine is converted into electrical energy.

[See also Conservation laws; Electricity; Heat; Magnetism ]

Energy

In the discussion of energy, the fundamental concept is that of work, which is motion against an opposing force. Energy is the capacity to do work. An object traveling at high speed and impacting on another object can do more work—can drive the object farther against an opposing force—than the same object moving slowly. This contribution to energy, the energy ascribed to motion, is called kinetic energy. The kinetic energy of an object of mass m traveling at a speed υ is ½mυ ². An object may also have energy by virtue of its position. An object high above the surface of Earth has more energy (can do more work) than one at its surface. This contribution to the total energy, the energy due to position, is called potential energy. The relation between the object's position and potential energy depends on the nature of the force field it experiences. The potential energy of a body of mass m at a height h above the surface of Earth is mgh, where g is the acceleration of free fall at the location. More important for chemistry is the potential energy of one charge near another charge. The Coulomb potential energy of a charge q ₁ at a distance r from a charge q ₂ is given by q ₁q ₂/4πϵ₀r, where ϵ₀ is a fundamental constant called the vacuum permittivity. Energy is also stored in the electromagnetic field in the form of photons. The energy of a photon of radiation of frequency υ is hv, where h is Planck's constant.

Energy is conserved. That is, the sum of the kinetic and potential energies of a single body remains constant provided it is free of external influences (forces). Thus, a falling weight accelerates: The fall implies a reduction of potential energy and the acceleration implies an increase in kinetic energy; the sum, though, is constant. A generalization (which can be interpreted as an implication) of the conservation of energy is the first law of thermodynamics, which focuses on a property of a many-body system called the internal energy. The internal energy can be interpreted as the sum of all the kinetic and potential energies of all the particles comprising the system. The first law of thermodynamics states that the internal energy of an isolated system is constant. The first law is closely related to the conservation of energy, but it acknowledges the possibility of the transfer of energy as heat, which is outside the reach of mechanics itself.

The special theory of relativity states that the mass of a body is a measure of its energy: E = mc ², where c is the speed of light. That is, energy and mass are equivalent and interconvertible. Changes in mass are measurable only when changes in energy are considerable, which in practice commonly means for nuclear processes.

In chemistry we are often concerned with the transfer of energy from one location (e.g., a reaction vessel) to another (the surroundings of that vessel). One mode of transfer is by doing work. For example, work is performed when gases evolved in a reaction push back a movable wall (e.g., a piston) against an opposing force, such as that due to the external atmosphere or a weight to which the piston is attached. Another mode of transfer is as heat. Heat is the transfer of energy that occurs as a result of a temperature difference between a system and its surroundings when the two are separated by a diathermic wall (a wall that allows the passage of energy as heat). A metal wall is diathermic, a thermally insulated wall is not diathermic. Finally, energy may leave a system as electromagnetic radiation, for example as in chemiluminescence—the emission of radiation from matter in energetically excited molecular states produced in the course of a chemical reaction, and as a result of spectroscopic transitions. We shall concentrate on the first two modes of transfer, work and heat.

At a molecular level, work is the transfer of energy that makes use of or drives the orderly motion of molecules in the surroundings. The uniform motion of the atoms in a piston driven back by expanding gas is an example of orderly molecular motion. In contrast, heat is the transfer of energy that makes use of or causes disorderly motion in the surroundings. When we say that a chemical reaction gives out heat, we mean that energy is leaving the reaction vessel and stimulating thermal motion (random molecular motion) in the surroundings.

The energy of a chemical system is stored in the potential and kinetic energies of the electrons and atomic nuclei. This stored energy is sometimes referred to as chemical energy; however, this is only a shorthand way of referring to the kinetic and potential energies of all the particles in an element or compound.

The internal energy of a system changes when a chemical reaction occurs because the electrons and nuclei settle into different arrangements, as in the change of partnerships of H and O atoms in the reaction 2 H₂(g) + O₂(g) → 2 H₂O(g). The energy released in a chemical reaction can be transferred to the surroundings (and put to use) in a variety of ways regardless of the manner in which the energy accumulated in the first place. Thus, energy may escape as heat and be used to raise the temperature of the surroundings, including raising the temperature of water that is then employed in a turbine to do work. The energy may also escape as work. We have already discussed expansion work, using the example of a piston being driven. The work may be accomplished electrically, as when electrons are driven through an external circuit and used to drive an electric motor.

Atomic nuclei are also centers of energy storage as a result of their internal structures. This energy is released when the nucleons (protons and electrons) undergo rearrangement and thereby change the strength of their interactions. The changes in energy are so great that they give rise to measurable changes of mass. For all chemical processes, the changes in mass accompanying acquisition or loss of energy are totally negligible.

see also Chemiluminescence; Chemistry and Energy; Electrochemistry; Heat; Physical Chemistry; Spectroscopy; Temperature; Thermodynamics.

Peter Atkins

Bibliography

Atkins, Peter, and de Paula, Julio (2002). Atkins' Physical Chemistry, 7th edition. New York: Oxford University Press.

Smith, Crosbie (1998). The Science of Energy: A Cultural History of Energy Physics in Victorian Britain. Chicago: University of Chicago Press.

Tipler, Paul Allen (1999). Physics for Scientists and Engineers, 4th edition. New York: W.H. Freeman and Worth Publishers.

Energy

BIBLIOGRAPHY

The broadest definition of energy is the ability to do work. Human societies tap into various forms of energy, including chemical energy in biomass, natural gas, coal, and petroleum; nuclear energy in uranium; gravitational energy captured in hydroelectric plants; wind energy; and solar energy. Energy is usually measured in British thermal units (BTUs). A BTU is defined as the amount of heat energy that will raise the temperature of one pound of water by one degree Fahrenheit. In 2005 the world economy obtained about 40 percent of its nonsolar energy from petroleum, about 23 percent each from natural gas and coal, 8 percent total from hydroelectric, wind, and thermal sources, and about 6 percent from nuclear. Most of this energy is used in the industrialized world, although the most rapid growth in energy use is occurring in the industrializing world, especially China. The largest use of energy by far is for industrial production and transportation.

Energy has been a crucial factor in human cultural evolution. The evolution of increasingly complex human societies was driven by the capacity to harness energy. Harnessing energy may have also played a key role in our biological evolution. The large human brain, unique even among primates, has enormous energy requirements. The human brain represents about 2.5 percent of body weight and accounts for about 22 percent of resting metabolic needs. This large energy requirement was met by a much higher proportion of protein in the diet of early humans and the use of fire to predigest meat. The use of fire played a role in the anatomical development of our species— larger brains and shorter guts—and paved the way for further advances in technological and cultural evolution.

Beginning about 10,000 years ago, early agricultural technology harnessed flows of solar energy in the forms of animal-muscle power, water, and wind. With the widespread use of wood for fuel, humans began to tap into stocks of solar energy rather than flows. The use of stocks of energy made it possible to capture ever larger amounts of energy per capita with smaller amounts of effort. Wood, wind, and water power fueled the industrial revolution, which began in the early eighteenth century. In the nineteenth century, ancient solar energy, fossil hydrocarbons in the form of coal, rapidly became the fuel of choice. During the twentieth century, petroleum and natural gas replaced coal as the dominant fuel. Each step in the history of energy use has been characterized by a dominant fuel type that is increasingly flexible and substitutable.

Since our industrial economy depends so heavily on fossil fuels, an obvious question is, “Are we running out of it?” Most economists answer this question with an emphatic “No!” As energy becomes scarce, its price will increase, calling forth substitutes, increasing conservation efforts, and encouraging more exploration for new supplies. Economists point out that past warnings of impending shortages have proved to be greatly exaggerated. Critics of the economic argument counter that the inverse relationship between energy supply and energy demand may be trivially true, but this does not mean that the increasing scarcity of an essential resource like petroleum can be easily accommodated. The economic argument also ignores the geopolitical consequences of the waning of the petroleum age.

A useful supplement to the price-based analysis of economists is the concept of energy return on investment (EROI). This is a measure of how many units of energy can be obtained from a unit of energy invested. If the EROI is less than one, it makes no sense to tap that energy source, no matter how high the price.

Although the world uses many types of energy, none of them have the flexibility and high EROI of petroleum. Of paramount concern is when world petroleum production will peak and start to decline. Most predictions of when worldwide oil production will peak are based on variations of a model developed by the geophysicist M. King Hubbert in the 1950s. He created a mathematical model of the pattern of petroleum exhaustion assuming that the total amount of petroleum extracted over time would follow a bell-shaped pattern called a logistic curve. Past experience for individual oil fields shows that once peak production is reached, production tends to fall quite rapidly. A number of petroleum experts argue that technological advances in the past decade or so have extended the peak of the Hubbert curve for specific oil fields, but this has made exhaustion more rapid after the peak occurs. Since oil is limited, policies promoting technology to make more energy available today mean that less will be there in the future.

Estimates of when world oil production will peak run from 2005 (production has already peaked) to 2030, with most predictions clustering around the years 2010–2012. Predicted consequences of declining oil production range from catastrophic scenarios as agricultural and industrial outputs plummet, to relatively mild scenarios as the world’s economies endure inflation and temporary economic hardships to adjust, to the rosy scenarios of free-market fundamentalists who claim that markets will quickly call forth substitutes and conservation that overcome the scarcity of any particular fuel type.

It is impossible to predict how the world’s economies will adjust to the end of the fossil-fuel age. So far energy policies in the developed and developing worlds have shown little concern for the limited amount of fossil fuels. What happens in the future depends on how much developing economies (especially China) grow and how energy-dependent they become. Also of concern is how the rest of the world will react to the growing concentration of petroleum reserves in politically volatile areas and to the increasingly ominous effects of global climate change.

SEE ALSO Energy Sector; Solar Energy

BIBLIOGRAPHY

Hall, Charles, Pradeep Tharakan, John Hallock, et al. 2003. Hydrocarbons and the Evolution of Human Culture. Nature 426: 318–322.

Simmons, Matthew. Various speeches. http://www.simmonscointl.com/research.aspx?Type=msspeeches. A good overview of the evidence for and negative consequences of the oil peak.

Tainter, Joseph. 1988. The Collapse of Complex Societies. Cambridge, U.K.: Cambridge University Press.

John M. Gowdy

ENERGY

Laws and regulations concerning the production and distribution of energy have existed for over one hundred years in the United States. Energy law became recognized as a specialty following the energy crises of the 1970s. It focuses on the production, distribution, conservation, and development of energy resources like coal, oil, natural gas, nuclear power, and hydroelectric power.

In 1876, the U.S. Supreme Court, in Munn v. Illinois, 94 U.S. (Otto) 113, 24 L. Ed. 77, held that "natural monopolies" could be regulated by the government. Munn concerned grain elevators but stood more generally for the principle that the public must be allowed to control private property committed to a use in which the public has an interest. This legal recognition of natural monopolies provides the basis for much of the legal and regulatory control the government exercises over utility companies.

The regulation of energy in the late 1800s was on a local and regional level, and was primarily market driven. The transition from using wood as a primary source of energy to using coal was almost complete, and a second transition from coal to natural gas and oil was beginning.

In 1900, Standard Oil Company controlled 90 percent of the oil market; within a few years, antitrust litigation had reduced its market share to 64 percent. Aside from antitrust enforcement, the federal government was content to let the market control the energy industry. Oil, coal, and natural gas found their greatest structural impediment in the "bottleneck" of distribution—pipelines for oil and natural gas, and railways for coal. The dominant model of energy policy that emerged from this period and existed unchanged until the 1970s was one of support for conventional resources and regulation of industries whose natural monopolies required some government oversight to ensure that their public purpose served a public interest.

On October 17, 1973, the Organization of Petroleum Exporting Countries (OPEC) announced an embargo of oil exports to all countries, including the United States, that were supporting Israel in the Yom Kippur War. Only approximately 10 percent of the United States' oil imports were affected, but the perception of a major oil shortage motivated the next three presidential administrations to exert a strong federal influence over energy.

President Richard M. Nixon created the Federal Energy Office (Exec. Order No. 11,930, 41 Fed. Reg. 32, 399) and appointed an "energy czar" to oversee oil supplies. President Gerald R. Ford's administration saw the passage of the Strategic Petroleum Reserve (42 U.S.C.A. § 6234) and the promulgation of minimum efficiency regulations for automobiles. In 1977, Jimmy Carter's administration created the department of energy (42 U.S.C.A. § 7101), which was the framework for the coordination, administration, and execution of a comprehensive national energy program.

The goal of a comprehensive national energy program was achieved with the passage of the National Energy Act of 1978, which consisted of five distinct pieces of legislation. The National Energy Conservation Policy Act (42 U.S.C.A. § 8201 et seq.) set standards and provided financing for conservation in buildings. The Powerplant and Industrial Fuel Use Act (42 U.S.C.A. § 8301 et seq.) encouraged the transition from oil

and gas to coal in boilers. The public utilities Regulatory Policies Act (15 U.S.C.A. § 2601) granted Congress authority over the interstate transmission of electric power. The Natural Gas Policy Act (15 U.S.C.A. § 3301) unified the gas market and promoted the deregulation of the natural gas industry. The Energy Tax Act (26 U.S.C.A. § 1 et seq.) approved tax credits to promote conservation.

The administration of ronald reagan set policies that marked a significant change in the national energy policy, away from the Carter administration's centralized, governmentally regulated energy plan, which set ambitious goals for market stabilization and energy conservation through government intervention. The Reagan administration favored a more market-driven approach to achieve these goals. Although unsuccessful in its goal to abolish the Department of Energy, the Reagan administration was able to deregulate the natural gas industry through administrative initiatives (under the Federal Energy Regulatory Commission) and the Wellhead Decontrol Act of 1989 (15 U.S.C.A. § 3301).

The administration of george h. w. bush also favored a market-driven approach to the regulation of energy, but the Persian Gulf War against Iraq in 1991 required Congress to respond to volatile conditions in the oil-exporting Middle East. The National Energy Policy Act of 1992 (42 U.S.C.A. § 13201) addressed issues such as competition among electric power generators and tax credits for wind and biomass energy production systems.

The National Energy Policy Plan, issued in 1995 during Bill Clinton's administration, continued the market-focused approach of the Reagan and Bush administrations. Citing as its primary goal a "sustainable energy policy," the plan states that the "administration's energy policy supports and reinforces the dominant role of the private sector" in achieving this goal.

The mid-1990s focus of market-driven, private sector regulation of energy development, conservation, and distribution may have to change in the years ahead. The energy needs of industrialized nations are intensifying, and the developing countries of the world are increasing their energy demands at a rate of 4.5 percent a year. Oil demand in Asia alone grew 50 percent from 1985 to 1995.

Energy policies in the future are likely to include emphasis on the development of more efficient, sustainable sources of energy. Many countries are already exploring the energy potential of biomass, wind, hydroelectric, and solar power.

further readings

Laitos, Jan G., and Tomain, Joseph. 1992. Energy and Natural Resources Law. St. Paul, Minn.: West.

Miller, Alan S. 1995. "Energy Policy from Nixon to Clinton: From Grand Provider to Market Facilitator." Environmental Law 25.

Reilly, Kathleen C. 1995. "Global Benefits versus Local Concerns: The Need for a Bird's Eye View of Nuclear Energy." Indiana Law Journal 70.

Tomain, Joseph P. 1990. "The Dominant Model of United States Energy Policy." University of Colorado Law Review 61.

cross-references

Electricity; Energy Department; Environmental Law; Mine and Mineral Law; Public Utilities.

energy in physics, the ability or capacity to do work or to produce change. Forms of energy include heat , light , sound , electricity , and chemical energy. Energy and work are measured in the same units—foot-pounds, joules, ergs, or some other, depending on the system of measurement being used. When a force acts on a body, the work performed (and the energy expended) is the product of the force and the distance over which it is exerted.

Potential and Kinetic Energy

Potential energy is the capacity for doing work that a body possesses because of its position or condition. For example, a stone resting on the edge of a cliff has potential energy due to its position in the earth's gravitational field. If it falls, the force of gravity (which is equal to the stone's weight; see gravitation ) will act on it until it strikes the ground; the stone's potential energy is equal to its weight times the distance it can fall. A charge in an electric field also has potential energy because of its position; a stretched spring has potential energy because of its condition. Chemical energy is a special kind of potential energy; it is the form of energy involved in chemical reactions. The chemical energy of a substance is due to the condition of the atoms of which it is made; it resides in the chemical bonds that join the atoms in compound substances (see chemical bond ).

Kinetic energy is energy a body possesses because it is in motion. The kinetic energy of a body with mass m moving at a velocity v is one half the product of the mass of the body and the square of its velocity, i.e., KE = 1/2 mv² . Even when a body appears to be at rest, its atoms and molecules are in constant motion and thus have kinetic energy. The average kinetic energy of the atoms or molecules is measured by the temperature of the body.

The difference between kinetic energy and potential energy, and the conversion of one to the other, is demonstrated by the falling of a rock from a cliff, when its energy of position is changed to energy of motion. Another example is provided in the movements of a simple pendulum (see harmonic motion ). As the suspended body moves upward in its swing, its kinetic energy is continuously being changed into potential energy; the higher it goes the greater becomes the energy that it owes to its position. At the top of the swing the change from kinetic to potential energy is complete, and in the course of the downward motion that follows the potential energy is in turn converted to kinetic energy.

Conversion and Conservation of Energy

It is common for energy to be converted from one form to another; however, the law of conservation of energy, a fundamental law of physics, states that although energy can be changed in form it can be neither created nor destroyed (see conservation laws ). The theory of relativity shows, however, that mass and energy are equivalent and thus that one can be converted into the other. As a result, the law of conservation of energy includes both mass and energy.

Many transformations of energy are of practical importance. Combustion of fuels results in the conversion of chemical energy into heat and light. In the electric storage battery chemical energy is converted to electrical energy and conversely. In the photosynthesis of starch, green plants convert light energy from the sun into chemical energy. Hydroelectric facilities convert the kinetic energy of falling water into electrical energy, which can be conveniently carried by wires to its place of use (see power, electric ). The force of a nuclear explosion results from the partial conversion of matter to energy (see nuclear energy ).

ENERGY

A Reliance on Oil

Aside from the relatively new atomic energy, the United States relied on crude oil (in refined form) to run its automobiles, to produce electricity in power plants, and for lubricants. Oil use exceeded that of coal or natural gas. In 1953 the United States imported more oil than it exported for the first time. Congress attempted to protect domestic producers of oil with a quota system on imports, initiated in 1959.

The Appliance Boom

Electrical-energy production stood at 329 billion kilowatts in 1950, 232 percent more than the 142 billion in 1940, with the cost per kilowatt steadily declining. Soon after the end of World War II a vast array of new electrical devices made its way into households, including dishwashers, freezers, dryers, vacuum cleaners, ranges and ovens, and refrigerators. The availability of smaller items such as vacuum cleaners increased through door-to-door sales, and larger items benefited from another institution to emerge in the 1950s, the shopping mall. When combined with the new eagerness of banks to lend money for such items, an electric-appliance boom ensued, and with it a demand for more electricity. Production increased to meet the demand: by 1959 the United States generated 798 billion kilowatts. Political power followed consumer demand: in 1953 the National Association of Electric Companies was the best-funded lobbying organization in the United States, with a $268,000 budget, ahead of the Association of American Railroads and even the U.S. Chamber of Commerce.

Energy from Atoms

Americans and the rest of the world had already been convinced that nuclear fission could generate enormous, and destructive, amounts of energy. But by the 1950s many individuals in government and business expected that atomic power could be adapted to peaceful, private industrial uses as well. They focused at first on producing electricity from atomic reactors. In 1956 the Atomic Energy Commission issued permits for construction of the first large-scale, privately run atomic-power plants to Consolidated Edison, which planned to build a $55 million plant capable of generating 140,000 kilowatts when running at full capacity in Indian Point, New York, and Commonwealth Edison of Chicago, which proposed a plant with a capacity of 180,000 kilowatts in Dresden, Illinois. Atomic energy was already being used to generate electricity at the Argonne National Laboratory, indicating its feasibility as a peacetime power source. The first peacetime plant to produce commercial power was at Shippingport, Pennsylvania, in 1957.

The "Atomic Airplane."

Experiments with other uses of atomic power included the short-lived "Atomic Airplane," a project assigned to Lockheed Aircraft in 1956. Researchers reasoned that they could place an atomic reactor in an airplane frame. But the weight of reactors at the time proved prohibitive, and by the 1960s the Department of Defense had given up on the idea.

Sources:

Ronald Clark, The Greatest Power on Earth: The Story of Nuclear Fission (London: Sidgwick & Jackson, 1980);

William Laurence, Men and Atoms: The Discovery, the Uses, and the Future of Atomic Energy (New York: Simon & Schuster, 1959).

energy The ability to do work. The SI unit of energy is the joule, and nutritionally relevant amounts of energy are kilojoules (kJ, 1000 J) and megajoules (MJ, 1,000,000 J). The calorie is still widely used in nutrition; 1 cal = 4.186 J (approximated to 4.2). While it is usual to speak of the calorie or joule content of a food it is more correct to refer to the energy yield.

The total chemical energy in a food, as released by complete combustion (in the bomb calorimeter) is gross energy. Allowing for the losses of unabsorbed food in the faeces gives digestible energy. Allowing for loss in the urine due to incomplete combustion in the body (e.g. urea from the incomplete combustion of proteins) gives metabolizable energy. Allowing for the loss due to diet‐induced thermogenesis gives net energy, i.e. the actual amount available for use in the body.

The following factors are used for energy yields of foods: protein 17 kJ (4 kcal); fat, 37 kJ (9 kcal); carbohydrate, 16 kJ (4 kcal); alcohol, 29 kJ (7 kcal); sugar alcohols, 10 kJ (2.4 kcal); organic acids, 13 kJ (3 kcal).

en·er·gy / ˈenərjē/ • n. (pl. -gies) 1. the strength and vitality required for sustained physical or mental activity: changes in the levels of vitamins can affect energy and well-being. ∎  a feeling of possessing such strength and vitality. ∎  force or vigor of expression. ∎  (energies) a person's physical and mental powers, typically as applied to a particular task or activity. 2. power derived from the utilization of physical or chemical resources, esp. to provide light and heat or to work machines. 3. Physics the property of matter and radiation that is manifest as a capacity to perform work (such as causing motion or the interaction of molecules): a collision in which no energy is transferred. ∎  a degree or level of this capacity possessed by something or required by a process.

energy In physics, capacity for doing work. It is measured in joules (J). Power, the rate at which energy is produced or consumed, is measured in watts (W). Potential energy is an object's ability to do work because of a change in the object's position or shape. Kinetic energy is the energy an object has because it is moving. Many forms of energy include electrical, nuclear, thermal, light and chemical. Energy can be transferred from one body to another through work processes, heating, electromagnetic radiation and electricity. The law of conservation of energy states energy cannot be created or destroyed. Albert Einstein established the idea that mass is a form of energy, recognizing that energy (E) and mass (m) could be transformed into each other according to the relation E = mc², where c is the velocity of light.

ENERGY

Energy means work. It refers to the effort required to move a weight for some distance. The heavier the weight or the longer the distance, the more energy is required. Energy is measured in units called "joules," or sometimes as the heat equivalent to these joules, called "calories." In nutrition, both terms are used. A calorie is the amount of heat needed to warm one gram of water by one degree centigrade. A more convenient unit is the kilocalorie (kcal), which equals one thousand calories. In physical terms, energy has several forms, all of which can be converted into heat. These include potential energy, kinetic energy, chemical energy, and heat energy.

George A. Bray

(see also: Fats; Krebs Cycle; Nutrition )

energy A measure of a system's ability to do work. Like work itself, it is measured in joules. Energy is conveniently classified into two forms: potential energy is the energy stored in a body or system as a consequence of its position, shape, or state (this includes chemical energy in food substances, etc.); kinetic energy is energy of motion and is usually defined as the work that will be done by the body possessing the energy when it is brought to rest.

energy vigour of expression XVI; working, operation; power displayed XVII; vigour or intensity of action XIX. — F. énergie or late L. energīa — Gr. enérgeia, f. energḗs active, effective, f. EN-2 + érgon WORK; see -Y3.
So energetic(al) †powerfully operative; full of energy. XVII. — Gr. energētikós active. energize XVIII.

energy •haji • algae • Angie •argy-bargy, Panaji •edgy, sedgy, solfeggi, veggie, wedgie •cagey, stagy •mangy, rangy •Fiji, gee-gee, squeegee •Murrumbidgee, ridgy, squidgy •dingy, fringy, mingy, stingy, whingy •cabbagy • prodigy • effigy • villagey •porridgy • strategy • cottagey •dodgy, podgy, splodgy, stodgy •pedagogy •Georgie, orgy •ogee • Fuji •bhaji, budgie, pudgy, sludgy, smudgy •bulgy •bungee, grungy, gungy, scungy, spongy •allergy, analogy, genealogy, hypallage, metallurgy, mineralogy, tetralogy •elegy •antilogy, trilogy •aetiology (US etiology), amphibology, anthology, anthropology, apology, archaeology (US archeology), astrology, biology, campanology, cardiology, chronology, climatology, cosmology, craniology, criminology, dermatology, ecology, embryology, entomology, epidemiology, etymology, geology, gynaecology (US gynecology), haematology (US hematology), hagiology, horology, hydrology, iconology, ideology, immunology, iridology, kidology, meteorology, methodology, musicology, mythology, necrology, neurology, numerology, oncology, ontology, ophthalmology, ornithology, parasitology, pathology, pharmacology, phraseology, phrenology, physiology, psychology, radiology, reflexology, scatology, Scientology, seismology, semiology, sociology, symbology, tautology, technology, terminology, theology, topology, toxicology, urology, zoology • eulogy • energy • synergy • apogee • liturgy • lethargy •burgee, clergy •zymurgy • dramaturgy