Possible Future Energy Sources

The word "energy" fills the pages of this book, and many forms of energy are described in previous chapters. Energy is, however, really a very tricky and difficult term to define exactly, even for students who have studied physics and engineering for many years. While it is very useful to think of energy as something that can flow like a river from one thing to another, or be stored in a battery, energy really isn't a "thing" at all. Energy does not exist by the gallon or liter, but a gallon or liter of gasoline has a certain amount of energy, an ability to flow through the process of combustion inside a properly designed engine, to turn gears and wheels that move a car.

Scientists and engineers usually describe or define energy as an object's ability to do work, to move things, make things hotter, and so forth. For example, the sun does not transfer a substance called energy to Earth. The nuclear reactions in the sun produce light that travels through space and that increase the energy level of objects the light strikes on Earth. For example, the light strikes objects and the light's own energy or ability to do work then changes molecules in the object that allow them to undergo chemical reactions or make them move and thereby cause the object's temperature to rise. As students advance in their studies their understanding of energy will change.

When thinking about the possible sources of energy to be used in the future, however, it is important to keep in mind that because energy is not a thing itself, but rather something that everything has, we can look for potential sources of useable energy. The world will eventually run out of substances such as oil that can be found and used at a reasonable cost, but the Earth will never run out of energy. The challenge for future generations is the ability to harness and use new sources of energy to do work.

IS ALTERNATIVE ENERGY ENOUGH?

Overuse of fossil fuels such as coal, natural gas, and petroleum as a source of energy can cause pollution, mining damage, and contribute to climate change. They are increasingly limited resources that because they are valuable, can even become a cause of war. Regardless of attempts to make cars, machines, and devices that use fossil fuels more efficiently, fossil fuels will someday be very scarce and hard to find. The world needs other energy sources that are clean, renewable, and affordable.

Most sources of "alternative" energy—which usually means energy from any source other than fossil fuels and nuclear fission—depend on obvious, natural sources of energy. The sun bathes Earth with light, which can either be turned into electricity or used directly for light or heat. The wind and rivers are loaded with kinetic energy (the energy of matter in motion). Tides raise and lower the sea, and hold a potentially useable source of energy.

Words to Know

Cold fusion

Nuclear fusion that occurs without high heat; also referred to as low energy nuclear reactions.

Electromagnetism

Magnetism developed by a current of electricity.

Fusion

The process by which the nuclei of light atoms join, releasing energy.

Heisenberg uncertainty principle

The principle that it is impossible to know simultaneously both the location and momentum of a subatomic particle.

Magnetic levitation

The process of using the attractive and repulsive forces of magnetism to move objects such as trains.

Perpetual motion

The power of a machine to run indefinitely without any energy input.

Superconductivity

The disappearance of electrical resistance in a substance such as some metals at very low temperatures.

Thermodynamics

The branch of physics that deals with the mechanical actions or relations of heat.

Tokamak

An acronym for the Russian-built toroidal magnetic chamber, a device for containing a fusion reaction.

Zero point energy

The energy contained in electromagnetic fluctuations that remains in a vacuum, even when the temperature has been reduced to very low levels.

There is nothing new about these energy sources. People have always used the sun to light spaces, dry food and clothing, and heat buildings. Water wheels and windmills have done useful work for centuries. The challenge for modern scientists and engineers, however, is to find effective ways of harnessing these power sources (and others) on a scale large enough and a cost low enough to meet the needs of the more than six billion people already living on Earth, a number that is expected to increase.

Many alternative or renewable energy sources, especially hydroelectric power, wind, and solar power, are already providing important amounts of energy or are capable of providing significant amounts of energy in the near future. These energy sources have many advantages over fossil fuels, but they also have limitations. One problem with some of them is that to provide truly large amounts of energy, they require huge, expensive facilities. Hydroelectric power needs massive dams that drown land, displace towns and villages, and threaten wildlife habitats (the living environment). Tidal or wave power needs dams across tidal basins and machines for gathering wave energy, all of which would not only be expensive but might spoil wild shorelines and disturb sea life. Solar cells to turn sunlight into electricity are getting steadily less expensive, but a solar power plant big enough to make as much energy as a coal or nuclear plant would cover a large area of land. Today, large windmills can make electricity more cheaply than either coal-burning plants or nuclear power plants, yet wind farms consist of large numbers of towering windmills—often twice the height of the Statue of Liberty—that change landscapes and can kill birds with their whirling blades. In addition, people often need more electricity than can be produced or stored while the sun is shining or when the wind is blowing.

Nuclear power plants produce steady-flowing energy, but not all experts agree that building many new nuclear power plants would be an affordable way to meet the world's energy needs. Quite apart from possible problems like radioactive waste, potential terrorist attacks on reactors, or reactor accidents, nuclear power has always been—and, according to some experts, still is—more expensive than other energy sources. Contrary to popular belief, for example, orders for nuclear plants practically stopped in the United States before the near-disaster at the Three Mile Island nuclear power plant in Pennsylvania in 1979. Nuclear plants were simply too expensive. And they have remained so. Since 1973, orders for new nuclear power plants in the United States have consistently been cancelled. The last non-military nuclear reactor to start operations in the United States was at the Watts Bar nuclear power plant in Tennessee in the late 1990s.

But nuclear power is not the only energy source with problems. Large, centralized renewable-energy projects must be placed in specific geographic locations and may damage the environment. A hydroelectric dam needs to be built on a river, for example, and many rivers have already been dammed in some way. A wave-power or tide-power generating station would have to be built on a specific type of ocean shoreline. Windmills need strong, reliable winds, which are not found everywhere. Solar power does best with steady sunshine, as in deserts and the tropics. Only in certain places is geothermal heat is close enough to the Earth's surface to be useful. There is really not one electrical energy problem but two: the problem of generating electricity and the problem of transporting electrical power.

So, while the energy of the wind, sun, oceans, and atoms is inexhaustible, our ability to capture it is limited by geography, money, safety, and other considerations. In fact, experts argue that these sources of power will never be able to safely, cleanly, and affordably supply the world with all the energy it needs. Furthermore, all the sources of energy mentioned so far in this chapter are sources of electricity, but not all our energy needs can be met by electricity. Heating buildings with electricity is very expensive, and electric cars and trucks that can compete with the power and speed of fossil-fuel-powered vehicles do not yet exist. Electricity, whether it comes from windmills or nuclear power, cannot help us to break our addiction to the liquid fossil fuel known as "oil,"—petroleum, from which gasoline and other fuels are made.

However, defenders of new energy sources have at least possible answers to many problems and objections. Just as advocates of nuclear power argue that with new reactor designs, nuclear power can be made safer and cheaper, supporters of windmills and solar power argue that new designs will eliminate limitations of these technologies. For example, large windmills might coexist with ranching on the wide-open landscapes of the American Midwest or be located far out to sea, while smaller, more efficient, vertical-axis windmills (which resemble upside-down eggbeaters and do not harm as many birds as other designs) can be placed on rooftops. Solar panels can also be placed on rooftops, producing power where it is needed without using more land. And by using electricity from windmills or solar panels to break water (H₂O) into hydrogen and oxygen and then using the hydrogen in fuel cells (a type of chemical battery) to make electricity, we can get power from the wind and sun even when the wind is not blowing or the sun is not shining. Hydrogen can also power cars and trucks, and biofuels may also help fuel vehicles.

As for whether renewable energy sources can make all the energy that modern civilization needs, many experts argue that by using energy more efficiently we can reduce our energy demand to the point where we can rely on what renewables can give us without giving up any of the advantages of a high-technology lifestyle. Some experts also argue that nuclear power will, in fact, be necessary. This remains a controversial subject.

But apart from increasing efficiency—which has already reduced energy use for many tasks and could reduce energy usage much more—no alternative perfect solutions are yet available. Solar panels are still too expensive to put on every rooftop (though Japan and Germany, with their huge government-backed solar programs, may be changing that). Claims of greater safety and lower cost for new nuclear power-plant designs are still just promises. Vertical-axis windmills have not yet been widely installed or tested. As of early 2006, the closest thing to an alternative-energy "revolution" is what is happening in wind power: large windmills have been the cheapest, mostly rapidly-growing source of new electricity worldwide since the early 2000s. Yet some people are objecting to plans to build large wind farms in visible or fragile locations, such as the mountaintops of Vermont or off the coast of Massachusetts. Windmills are still making only a small fraction of our electricity, and until it is affordable to use them to make hydrogen for fuel cells on a large scale—which it is not, yet—we will not be able to obtain most of our electricity from wind no matter how many windmills we build.

DREAMS OF FREE ENERGY

Many of these problems with alternative energy sources will undoubtedly eventually be solved. In the long run, some mixture of wisely-used alternative sources could power our civilization for as long as need be. Yet some people still dream of very inexpensive, inexhaustible energy from exotic or unproved sources. Nuclear power itself began as one such dream. In 1954, the chairman of the U.S. Atomic Energy Commission said in a speech that that "it is not too much to expect that our children will enjoy electrical energy too cheap to meter." (Metering is the process of measuring how much a given amount of electricity costs.) Some scientists even predicted that small nuclear plants would someday power individual homes, cars, and airplanes. Those dreams or predictions did not come true, mostly because nuclear energy still requires dangerous and complex technology. Far from being too cheap to meter, nuclear power is as expensive as any other standard way of making electricity.

But could some other technology, something completely new, fulfill the dream of cheap, endless power? Most energy experts and engineers urge us not to expect an energy miracle, and to be prudent in the use of resources we have and know, but scientists and inventors continue the search for new sources of energy.

Some of the methods that have been proposed for making cheap, endless power have no scientific basis and are simply "fake science" ("pseudoscience.") The most famous of these fake energy sources is perpetual motion. Some other proposed methods, such as "zero point energy," have some slight scientific basis, but most scientists still think they are not useable given human and Earth's own limitations. Still other possible energy sources (such as cold fusion and sonofusion) are studied seriously by a number of real scientists, but the majority are still not convinced that they can produce useable energy in the foreseeable future. Finally, there are some methods that all scientists agree are physically possible, such as hot fusion and solar power satellites, but many experts do not agree that these schemes will ever be practical. A number of possible cheap-energy schemes, from the silly to the serious, are discussed in the rest of this chapter.

Johann Bessler and the Bessler Wheel

One of the most famous figures in the dubious history of perpetual motion was German engineer and inventor Johann Bessler (1680–1745). In 1712 Bessler unveiled his first machine, called the Bessler wheel, which he claimed was a perpetual motion machine that drew its power from gravity. Throughout his career, Bessler attempted to sell the machine, wanting the money to establish a Christian-based school of engineering. He never found any buyers and he refused to reveal the "secret" of the machine until he was paid. Never able to find a buyer for his machine, he died in poverty without having revealed the "secret" of the Bessler wheel.

Skepticism (a preexisting doubt in the truth of a matter) was increased when one of Bessler's maids testified that she and other servants were manually turning the wheel with a crank from another room, which was attached to the wheel by a rod and series of gears.

Bessler allegedly encoded the "secret" of his perpetual motion machine in the text of his books, including Apologia Poetica (Poetic Defense, published in 1716), Das Triumphirende Perpetuum Mobile Orffyreanum (The Triumphant Orffryrean Perpetual Motion, published in 1719), and Maschinen Tractate (Tract on Machines, published in 1722).

PERPETUAL MOTION, AN ENERGY FRAUD AND SCAM

Some people argue that a "perpetual motion machine" can be built that will produce endless energy without having to burn fuel or harvest energy from an outside source such as the wind or sun. The search for such a magical machine dates back to at least the thirteenth century, when French artist Villard de Honnecourt drew fanciful pictures of perpetual motion machines. Since that time, many inventors and tinkerers have sought, without success, to design a machine that produces energy without any need for energy to be put in. Some fake perpetual motions have even been built to fool the public or steal money from investors.

Any so-called perpetual motion machine would violate laws of thermodynamics, which places limits on the nature and direction of heat transfer and the efficiencies that can be achieved by any type of system. This means it is impossible to construct any such system or machine with 100% efficiency. An important but complex part of the laws of thermodynamics is termed entropy. Entropy essentially means that without the use of energy, all systems or machines must move to disorder (experience decayed or diminishing efficiency) over time. Accordingly, the only way anything can be perpetual is to use energy to maintain the system or machine. Any statement to the contrary (against) violates the laws of physics.

Despite the claims of scam artists or "inventors," scientists agree that perpetual motion can never be an energy source. It is impossible to get more energy out of a machine than you put into it: machines can only change the form that energy is in. The laws of physics say that you can't get something for nothing—at least, not for long. In a sense, it is possible to store "energy" for a while in some devices, but batteries and other storage devices (which also decay over time) can only give back whatever energy is put into them. Perpetual motion machines will never supply the world with energy.

ADVANCES IN ELECTRICITY AND MAGNETISM

As scientists continue to explore the nature of electricity and magnetism (actually different aspects of a combined fundamental force appropriately termed electromagnetism) so, too, are engineers advancing ways to convert this knowledge into useable forms of energy, and to improve the efficiency of power transmission, transportation, and so forth. Although improved efficiency does not provide new energy, it can have the same impact as developing new sources because it allows existing sources to do more things or last longer.

Magnetism

People have known about the power of magnetism for thousands of years. In ancient Greece, near the city of Magnesia, mysterious stones with the power to attract iron were first discovered. Later, the Chinese discovered that if one of these stones was stroked with a needle, the needle became magnetic. Around the year 1000 the Chinese discovered that when such a needle was suspended, it would point in the direction of the North and South Poles. The result of this discovery was the magnetic compass, which helped to open the world's oceans to navigation and exploration.

It was not until the nineteenth century that physicists began to understand magnetism and magnetic fields. Essentially, magnetism is a force that attracts such substances as iron, but also cobalt and nickel, at a distance. What causes the attraction is decribed by lines of flux ("lines" on a plane that cross or include magnetic poles) that come from electrically charged particles that spin. These lines flow from one end of an object to the other. The ends are commonly referred to as the north and south poles, similar to the terms applied to Earth's poles. In a magnetic field, the flux flows from the north to the south. While individual particles such as electrons can have magnetic fields, so can larger objects, such as the magnets that hold notes and shopping lists to the door of a refrigerator. When an object with a magnetic field exerts its force on another object with a magnetic field, the result is magnetism.

The north pole of one magnet attracts the south pole of another and, conversely, the north pole (or south pole) repels the north pole (or south pole) of another magnet. The lines of flux cause this attraction or repulsion. Just as these lines flow from the north to the south of one object, they can flow from the north of one object to the south of another, pulling the two objects together, almost like two spinning gears in a car that mesh smoothly together. When like poles—for example two north poles—are brought together, the lines of flux are flowing in opposite directions, causing the two objects to, in effect, bounce off each other, like two spinning tops that collide and bounce away.

Electromagnetism

In the twenty-first century magnetism powers devices such as tape drives, speakers, and read/write heads for computer hard drives. The energy is captured through electromagnetism, which is based on the simple principle that an electrical current, which consists of a flow of electrons passing through a wire, creates its own magnetic field. This magnetic field moves in a direction perpendicular to the flow of the current in the wire. This force is called the Lorenz force, named after Dutch scientist Henrick Antoon Lorenz (1853–1928).

A simple electromagnet can be created with a battery and a piece of wire. If the wire is connected to the positive and negative poles of the battery, the electrons collecting at the negative pole will "flow" through the wire to the positive pole, rapidly depleting, using up, the battery. Generally, something is attached to the middle of the wire—a radio, a lightbulb, a toaster—so that the electricity can do work while at the same time offering resistance so the battery does not quickly go dead. The magnetic field of a single strand of wire, however, is likely to be relatively weak, because the Lorenz force weakens as the distance from the wire increases. One way to strengthen the magnetic field is to coil the wire, in effect recruiting multiple strands of wire to create a magnetic field that pulls (or pushes) in the same direction. The more coils of wire, the stronger the magnetic field.

This is the basic science behind magnetic levitation. In its application, magnetic levitation is a process by which train cars are "levitated," or raised, so that rather than riding on tracks, they ride on a cushion of air. The chief advantage of "maglev" trains is that this cushion of air, combined with the trains' aerodynamic design, virtually eliminates the energy lost because of friction. The result is lower cost per operating mile and lower maintenance costs because of less wear and tear on the equipment. Although exact estimates of savings vary, the operating cost of a maglev train in terms of cost per passenger mile traveled is only a fraction of the cost of auto and air transport.

ZERO POINT ENERGY

Zero point energy sounds like magic or science fiction: energy that comes straight out the vacuum of empty space. A handful of scientists argue that zero point energy can be harnessed to provide power. Most scientists, however, are very skeptical (doubtful) that it can ever be turned into a practical power source.

The idea of the nature and potential of a vacuum has long interested scientists. In ancient Greece, the philosopher Aristotle (384–322 BC) argued that "nature abhors a vacuum." That is, he taught that it was impossible for any region of space to be totally empty. For almost two thousand years, scientists accepted Aristotle's teachings, but by the middle of the seventeenth century they had come to reject it. In 1644, an Italian scientist named Evangelista Torricelli (1608–1647) invented an early barometer, a standing glass tube filled with mercury. The top of the tube was sealed and the bottom curved back up to an opening so that the atmosphere could push on the exposed mercury. When the pressure of the atmosphere rose or fell due to the weather, it would push on the mercury with changing pressure, causing it to rise and fall in the glass tube. Torricelli noticed that even if the tube was made without air above the mercury, an open space would appear there. Because air cannot pass through mercury, Torricelli reasoned that this empty space at the top of the tube had to be a true vacuum—a volume of space containing no matter. In later experiments, other scientists confirmed his arguments.

For several hundred years after Torricelli, scientists argued that a vacuum was a region of space in which "nothing" existed. In the early twentieth century, however, physicists discovered the strange properties of matter that are obvious only for very small objects such as atoms and electrons. The new knowledge, called quantum physics, forced scientists to question whether the vacuum was in truth entirely empty. It became clear that Aristotle had been right (though for the wrong reasons), and that there is really no such thing as empty space. (In physics, "space" does not mean outer space, but rather any volume, including the space inside an atom, a bottle, or a room.)

Quantum physics is that branch or subdivision of the study of physics that started with the observation that an atom is like—and yet unlike—a tiny solar system. The atom's nucleus—a very small object or particle, much heavier than anything else in the atom—is positioned like a microscopic "sun,", and electrons, many times smaller than the nucleus, orbit it in some ways like tiny "planets." A question that puzzled physicists in the nineteenth century was why the orbiting electrons of an atom do not quickly radiate away their energy in the form of light and fall into the nucleus. On the contrary, they never do so. To explain this fact, modern physicists developed quantum physics, which explains matter and energy as having both wave- and particle-like features. They found that energy does not flow smoothly, but always changes in small jumps or fixed quantities. They called each of these jumps a "quantum", thus giving the new physics its name, "quantum physics." Quantum physicists showed that electrons orbiting an atom's nucleus are not really like tiny planets at all, except as we may picture them in our minds.

The German physicist Werner Heisenberg (1901–1972) deepened our understanding of quantum physics in 1927, when he announced what is now called the "uncertainty principle." The uncertainty principle states that by the very nature of matter and energy, it is impossible to measure everything about an object with perfect accuracy. For example, the better one's measurement of the position of an electron gets, the poorer one's knowledge of its momentum (a measure of both mass and velocity) gets, and that the reverse is also true because the better the understanding of momentum, the less one can know about position. There is no way to make better measurements: as Heisenberg proved, the uncertainty or lack of ability to know is not a form of ignorance, but arises from the nature and laws of the universe itself. It isn't that we don't know what the precise values are; the precise values simply don't exist.

According to the uncertainty principle, which has been tested many thousands of times in laboratories, there is a certain amount of fuzziness or uncertainty about all physical phenomena. This includes the vacuum. In fact, the uncertainty principle says that there can be no such thing as a perfect vacuum. Perfect emptiness or vacuum would mean that there was zero matter and energy, but "zero" is a precise value, and absolutely precise values are forbidden by the nature of the universe.

Instead, physicists now know that "virtual" particles are continuously popping into and out of existence everywhere, throughout all space, including the "vacuum"—the apparently empty space found between atoms and stars, and also at the top of Torricelli's glass tube. These virtual particles include photons (particles of light). All particles and waves are forms of energy, as German scientist Albert Einstein (1879–1955) proved in 1905, so the existence of virtual particles means that the "vacuum" is boiling invisibly with energy all the time, everywhere. This energy is called "zero point energy." A few physicists—but not most—argue that zero point energy can provide energy for human use.

A physicist working in the field of zero point energy, Dr. Hal E. Puthoff of the Institute for Advanced Studies in Austin, Texas, explains zero point energy in these terms:

When you get down to the tiniest quantum levels, everything's always 'jiggly.' Nothing is completely still, even at absolute zero. That's why it's called 'zero point energy,' because if you were to cool the universe down to absolute zero—where all thermal motions were frozen out—you'd still have residual [leftover] motion. The energy associated with that 'jiggling' will remain, too.

Absolute zero temperature then is not zero energy, but the minimum energy that can exist.

Scientists agree that zero point energy is real. This energy cannot usually be felt or easily measured because it surrounds everything equally. Thus, its forces in effect cancel one another out, exerting pressure in all directions at once, just as the pressure of the Earth's atmosphere can't be felt because it pushing on the outside of your chest and on the inside of your lungs at the same time.

Puthoff is one of the scientists who argue that the amount of zero point energy in the vacuum is very large. "It's ridiculous," he says, "but theoretically, there's enough [zero point] energy in the volume of a coffee cup to more than evaporate all the world's oceans. But that's if you could get at all of it, and you obviously can't."

Whether the zero point energy is useable is a question, but it is certainly there. Physicists have measured a number of effects that prove its existence. One is called the Lamb effect or Lamb shift, named after physicist Willis Lamb (1913–). The Lamb effect refers to small changes in light given off by an excited atom. This is predicted as a side effect of zero point energy.

A Childhood Genius

When Werner Heisenberg was in his early teens, another, older student needed a calculus tutor. Heisenberg had not studied calculus, because it was not taught at his school. So he taught himself calculus so that he could tutor the older student—while also practicing to become an accomplished musician. Heisenberg won the Nobel Prize for physics in 1932 and, besides his scientific work in quantum physics, wrote many books about the relationship of physics to philosophy.

A more impressive demonstration of zero point energy is the Casimir effect, measured in 1948 by Dutch physicist H. B. G. Casimir (1909–2000). Casimir showed that if two metal plates are brought very close together, they attract each other very slightly. As the plates are drawn or pushed together (whether to describe it as drawn or pushed depends on the exact explanation of zero point energy used), it is at least potentially possible to extract energy from their motion.

So not only is zero point energy real, physicists agree that it can be made to do work. But they do not agree that zero point energy can ever be made to do enough work to be useful. The fact that something happens in the realm of quantum physics doesn't prove that it can be made to happen in the world of everyday objects.

A few scientists explore the idea that zero point power sources might make interplanetary space travel practical, for a spacecraft would be able to extract the energy it needs from the vacuum of space rather than having to carry fuel. Some science fiction writers (and some scientists too) envision a day when zero point energy could power fighter planes flying at four times the speed of sound, power 1,200-seat airliners flying at altitudes of 100 miles (161 kilometers) and covering 12,000 miles (19,312 kilometers) in 70 minutes, and power spacecraft making 12-hour trips to the moon.

But most scientists do not accept that such science-fiction scenarios are possible. It would take billions of Casimir plates to produce a useful amount of power, and more energy would be consumed in constructing and positioning of the plates than the plates could ever produce. Such a machine would use more energy than it made. Therefore, many scientists debate whether money and time spent on zero point energy research should be spent instead on research of other forms of energy. Nevertheless, it is true that unlike mechanical perpetual motion machines, zero point energy is studied by some real scientists. Physicists agree that some energy can be had "for nothing" from the vacuum. It is simply a question of how much.

FUSION

Fusion powers the sun and all other stars. Fusion is, however, very different from the process of generating nuclear power that is used in today's nuclear power plants. These are powered by nuclear fission, meaning that they release energy by splitting atoms apart into smaller atoms ("fissioning" them). This energy is used to turn water into steam, and the steam is used to turn generators that make electricity. Fusion, on the other hand, produces heat by "fusing" atoms, forcing them to come together into larger atoms. Fusion power, unlike fission, would produce only small amounts of radioactive waste and its fuel would not be dangerous to people's health.

But fusion does not yet produce useful power on Earth. For fusion power to be practical, scientists have to figure out how to make fusion happen in a steady, small-scale way, producing neither a fizzle nor an explosion. However, this has turned out to be a difficult trick. Billions of dollars have been spent over the last forty years trying to make fusion work, and success is still decades away—or may never be achieved. Three kinds of fusion research are described below: conventional or "hot" fusion, "cold" fusion, and sonofusion.

Conventional fusion

In nuclear fusion, the nuclei of two light atoms (such as helium or hydrogen, the lightest atoms) bind together to form a single heavier nucleus. For example, the nuclei of two ordinary hydrogen atoms, each of which is simply a proton (a positively-charged particle), merge to form the nucleus of a deuterium atom, which is a neutron and a proton bound together. (A neutron is a particle that weighs about the same as a proton but has no electrical charge. Deuterium is also a kind of hydrogen.) When a deuterium nucleus or other particle is formed by the coming together of smaller particles, its mass is generally less than the total mass of the original particles before they came together. The mass that seems to have disappeared has been released in the form of energy. The amount of this energy can be calculated by using Albert Einstein's famous equation, E = mc ², which means that when the correct units are used, energy (E ) is equal to mass (m ) times the speed of light (c ) squared. Not much mass has to "disappear" for the amount of energy released to be very large. This is because the speed of light is so large: about 300,000 kilometers per second (186,000 miles per hour).

Fusion reactions occur naturally throughout the universe. For example, scientists have learned that the primary component of stars is hydrogen gas. Over time, this hydrogen is turned by fusion into the gas named helium, as the nuclei of four hydrogen atoms combine to form one helium nucleus. Many other fusion reactions take place in stars. In fact, all the heavier elements of which Earth (and our own bodies) are made, such as carbon, iron, oxygen, silicon, aluminum, and uranium, are produced by the fusion of lighter elements in stars.

For fusion to happen, "electrostatic repulsion" must be overcome. Particles with the same electrical charge repel or push each other apart. Electrons have negative charge, protons have positive charge. The closer two negative charges or two positive charges get to each other, the harder they repel and the harder it gets to bring them any closer. If two protons are to fuse together to form a single nucleus, therefore, they must be thrown together at high speed. Where does that energy come from?

It comes from heat. Heat is merely the motion of atoms and molecules. The hotter a piece of metal is, for example, the faster the atoms in it are vibrating. The atoms in a hot gas shoot around freely like balls on a pool table, only much faster. The hotter a gas gets, the faster its particles go. As a gas is heated, for instance, its atoms move with faster and faster, so they collide harder and harder. When the collisions are hard enough, the nuclei of the colliding atoms may fuse, or join together. This type of reaction is called a "thermonuclear" reaction, from the Greek thermo, meaning heat.

The temperature needed for this type of fusion to take place is extreme, on the order of tens or hundreds of millions of degrees. This kind of heat can be found in the centers of stars, including the sun, but does not occur naturally on Earth. It does occur artificially on Earth, however, in fusion laboratories and hydrogen bombs.

Fusion in bombs

Just as the fission process used in nuclear power plants was first applied to make bombs, like the fission bombs used by the United States to bomb the Japanese cities of Hiroshima and Nagasaki in 1945 to end World War II, so was fusion.

To create a hydrogen bomb, scientists begin with a quantity of hydrogen. To create a fusion explosion, the hydrogen must be heated until it is as hot as the core of a star. This is done using a fission bomb. The basic design for a hydrogen bomb, then, is to pack hydrogen in a container around a fission bomb. When the fission bomb explodes, it heats the hydrogen enough to start runaway fusion explosions. This fusion explosion can be tens or even thousands of times more powerful than the fission explosion that started it.

Mike

The detonation of the first thermonuclear bomb, codenamed "Mike," took place on November 1, 1952, on the Eniwetok atoll, a small coral island in the Pacific Ocean. The U.S.-built bomb consisted of a cylinder 20 feet (6 meters) tall and 6 feet, 8 inches (2 m) in diameter, weighing 164,000 pounds (61,212 kg).

Even the bomb's designers were amazed by its explosive force. Its fireball was 3 miles (4.8 km) wide. Within ninety seconds, the mushroom cloud had risen 57,000 feet (17 m) into the air. Eventually, after five minutes, the cloud reached a height of 135,000 feet (41 m), with a "stem" eight miles (13 km) across. People on ships 100 miles (161 km) away saw the flash. The explosion completely destroyed the island of Elugelab, carving out an underwater crater that was 6,240 feet (1,902 m) wide and 164 feet (50 m) deep and lifting 80 million tons of soil into the air. A bomb of this type would devastate any city on Earth.

The fission bomb that was dropped on Hiroshima was a 20-kiloton bomb, meaning that it had an explosive force equal to that of 20,000 tons of TNT (a chemical explosive). The first fusion bomb exploded with a force equal to that of 10.4 million tons of TNT—some 500 times the power of the Hiroshima bomb. The largest hydrogen bomb ever exploded had a force equal to 50 million tons of TNT, about 2,400 times the explosive power of the bomb dropped on Hiroshima.

Controlled fusion

Just as they did after the first fission bombs were developed in World War II, scientists began to seek ways to provide peaceful energy with nuclear fusion. The basic process they focused on made use of two forms (isotopes) of hydrogen. (An isotope is a form of an element having fewer or more neutrons in its nucleus than other forms of the same element.) These isotopes, known as "heavy hydrogen" because they contain extra neutrons, are called deuterium and tritium. A normal hydrogen atom's nucleus consists of a single proton, but the nucleus of a deuterium atom contains a proton and a neutron. The nucleus of a tritium atom contains a proton and two neutrons.

Heavy hydrogen is used for two reasons. First, these isotopes fuse at lower temperatures than regular hydrogen does. Second, they are relatively common. About 1 in 6,500 of the hydrogen atoms in natural water are deuterium atoms. Tritium breaks down rapidly, so very little of it is found in nature. It is made artificially by exposing the metal lithium to fast-moving neutrons created in a nuclear reactor.

If a mixture of deuterium and tritium is made hot enough, some of the deuterium nuclei fuse with tritium nuclei. One deuterium nucleus fuses with one tritium nucleus to produce one helium nucleus. (Helium is the gas that is used to fill party balloons.) When this happens, energy is given off in the form of a fast-moving neutron. This also happens in a hydrogen bomb, but it doesn't have to happen as a huge explosion: in theory, it could happen as slowly as one atom at a time.

Some scientists argue that fusion could be the "energy of the future" because its fuel—heavy hydrogen—contains an enormous amount of energy by weight. A bottle-cap full of heavy hydrogen contains the same amount of energy as twenty tons of coal. Further, using such fuel would be relatively safe. The major by-product is helium, which is harmless. A fusion explosion could not happen because there would not be enough hydrogen, and it would not be not packed together the right way. In fact, keeping a fusion reaction going at all has been difficult for scientists trying to build fusion generators.

Because of the high temperatures needed to keep a fusion reaction going, no container made of any known substance such as steel or titanium can be used as a vessel for the reaction. A fusion reaction would simply melt the container and could not be contained or used. One possible solution is to use magnets to hold the reaction.

Controlled fusion begins with the making of a plasma, a form of gas so hot that the nuclei of all of the atoms have been stripped of their electrons. This leaves each nucleus with a positive electrical charge (usually the positive charge of each nucleus is balanced out by the atom's negative electrons). Because a plasma is charged, it can be held in place, or "bottled," by magnetic fields. Ordinary solid materials cannot be used because the plasma is too hot; even steel would simply turn into a gas at such temperatures, like boiling water turns to steam. The magnetic bottle method was developed early on by the Russian scientists who invented the device called a tokamak. "Tokomak" is short for "toroidal magnetic chamber" in Russian, where "toroidal" means doughnut-shaped.

A tokomak is a steel chamber shaped like a hollow doughnut. Plasma is held inside the doughnut by magnetic fields and heated. When it is hot enough, fusion begins. The magnetic fields are supposed to keep the plasma from touching the inside walls of the reactor. So far, the main problem with tokamaks is that the plasma leaks out of the magnetic fields when the fusion reaction begins so that the reaction can be kept going for only a few seconds. Only if this problem can be overcome can tokamak containers house useable fusion reactions. Several large tokomaks have been built, but none has produced as much energy as it takes to run.

On June 28, 2005, six partners (China, Japan, South Korea, Russia, the United States, and the European Union) agreed on a site for a tokomak to be called the International Thermonuclear Experimental Reactor (ITER). ITER will be built in Cadarache, north of Marseille, France. This is a multi-billion-dollar project designed to make possible experiments that the sponsors hope will lead to a greater understanding of fusion reactions and eventually to electricity-producing fusion power plants. In December 2005, the ITER site was prepared for construction of the reactor. Its designers currently plan for operation to begin in 2016.

Another way of keeping plasma hot enough for fusion to happen is "inertial confinement." This uses powerful laser beams to blast a tiny pellet of hydrogen fuel from all sides at once, turning it into hot plasma before it can expand and cool. While this method has worked for experimental purposes, scientists doubt whether it can ever be a feasible source of commercial power.

To be a useful power source, a fusion reactor would not only have to make more energy than it uses, but it would have to make that energy more cheaply than other sources of energy can be made. But there seems to be only a small chance that fusion can be made to produce large amounts of power, at any price, for many years to come.

Cold fusion

Because it is so hard to control the star-like temperatures needed for "hot" fusion, some scientists have looked for ways to make fusion happen at low temperatures. This is sometimes called "cold" fusion, a term coined in 1986 by Dr. Paul Palmer of Utah's Brigham Young University. As with zero point energy, all physicists agree that certain forms of cold fusion do happen, but most do not think that cold fusion can ever be a practical source of energy.

The history of cold fusion began in the nineteenth century, when scientists recognized the unique ability of the metals palladium and titanium to absorb hydrogen, much as sponges absorb water. In the twentieth century, scientists thought that these elements might be able to hold deuterium atoms so close together that a fusion reaction would result even at low temperatures. Later, two German scientists claimed to have performed an experiment using palladium that transformed hydrogen into helium at room temperature. However, they later took back their claim, admitting that the helium had probably come from the surrounding air.

The Pons-Fleischmann announcement

In the following decades, a few scientists around the world continued to experiment with ways to produce fusion at low temperatures. None succeeded, but by the 1980s, after the energy shortages of the 1970s, a few scientists still worked on the premise that cold fusion held out hope for a future of clean, safe, abundant energy. In 1984, Stanley Pons of the University of Utah and Martin Fleischmann from England's University of Southampton began conducting cold fusion experiments at the University of Utah. On March 23, 1989, Pons and Fleischmann held a press conference at which they made an announcement that startled the world. They claimed that they had successfully carried out a cold fusion experiment that produced excess heat that could be explained only by a fusion reaction, not by chemical processes (such as metal combining with oxygen). At long last, the dream of being able to produce energy on a commercial scale from a bucket of water seemed to be just around the corner.

In their experiment, Pons and Fleischmann used a double-walled vacuum flask to reduce heat conduction. They filled the flask with "heavy water," water made with the deuterium isotope of hydrogen replacing ordinary hydrogen (the "H" in the chemical formula for water, H₂O). They inserted a piece of palladium metal in the heavy water and applied an electrical current. According to their results, nothing happened for a period of weeks. The energy input and energy output of the system were steady, and the temperature of the water stayed at 86°F (30°C). Then the temperature suddenly rose to 122°F (50°C), without any increase in the input power. The water remained at that temperature for two days before decreasing again. This happened more than once. During these power bursts, the energy output was about twenty times greater than the energy input.

Because of the simplicity of the Pons-Fleischmann design, groups of scientists around the world attempted to duplicate their results. For weeks, the topic of cold fusion was on the front pages of newspapers. Some scientists initially reported that they were able to duplicate the Utah experiments, while others failed. What resulted was a mix of claims, theories, explanations, accusations, and arguments that the press dubbed "fusion confusion."

Since 1989, many scientists claim to have produced cold fusion. In some experiments, excess heat is generated. The expected by-products of cold fusion—neutrons, tritium, and charged particles—have been reported. Other laboratories have found the production of an isotope of helium, another potential by-product of fusion. They have also reported isotopes of such elements as silver and rhodium, again suggesting that something is happening at an atomic level.

To a nonscientist, it all sounds pretty convincing. Yet most scientists do not accept that cold fusion has been achieved. There is, to begin with, no theory that would explain it. The minority who argue for cold fusion point out that even though science cannot explain cold fusion, that does not prove that it is not real. They note, for example, that when superconductivity (the flow of electricity through very cold metals with zero loss) was first discovered in the early twentieth century, there was no theory to explain it until decades later. This is true, but in the case of cold fusion, the observations themselves are in doubt. The case for cold fusion is not as certain as a mere list of all the positive reports makes it sound.

First, there have also been many failed cold-fusion experiments. Second, the production of energy by a system is not proof that nuclear reactions are happening; chemical reactions could be supplying the energy. Third, the production of "excess heat" by a system—often reported by scientists working with cold fusion setups—does not necessarily mean that more energy is coming out of the system over the lifetime of the experiment than goes into it. Fourth, there are many possible sources of measurement error when looking for fusion by-products. Extra helium, for example, may come from the air; silver or rhodium (supposedly detected in extremely small amounts) may come from contaminated instruments; neutrons may come from cosmic rays or radioactive elements such as uranium.

As of early 2006, seventeen years after the Pons-Fleischmann announcement, there was still no widely accepted proof that nuclear fusion is happening in the devices built by cold-fusion researchers. The scientific community as a whole has not been convinced that cold fusion is real. That is, they are not convinced that any kind of cold fusion that produces more energy than goes into it is real. There is agreement among physicists that energy-consuming forms of cold fusion do exist. In particular, the phenomenon called "muon-catalyzed fusion" is well-established. Muons are particles that can briefly substitute for electrons in atoms. When they do this they shield the atomic nuclei from each other, reducing the electrical force that keeps them apart and so allowing them to be fused by lower-velocity collisions (cooler temperatures). Muons, however, have a limited lifetime—about 2.2 millionths of a second—and more energy is needed to produce them than they can release through fusion.

In the 1990s, the U.S. Department of Energy suspended funding for cold fusion research. In 2004 it conducted a study in which it concluded that research since 1989 had produced nothing new of substance. Japan continues to fund cold fusion research.

Sonofusion

Claims of another kind of "desktop" fusion (fusion that can be produced by inexpensive, simple equipment rather than multibillion dollar tokomaks) surfaced in 2002. Physicist Rusi Taleyarkhan of Purdue University published a study claiming to have produced fusion using sonoluminescence. Sonoluminescence—the word means, literally, "sound-light"—occurs in some liquids when they are hit by intense sound waves. Tiny, short-lived bubbles appear in the liquid and then collapse. When each bubble collapses, very high temperatures and pressures occur inside it and a tiny flash of light is given off. Temperatures of thousands of degrees are generated in these collapsing bubbles, but physicists are not sure just how hot they are. If the temperature were high enough, it could cause fusion. Most physicists however currently argue that temperatures can not reach this high level.

Dr. Taleyarkhan ran his first experiments at the Oak Ridge National Laboratory in Tennessee, a laboratory owned by the U.S. government. He used a liquid chemical called acetone. The normal hydrogen atoms in the acetone that Taleyarkhan used had been replaced with atoms of deuterium, one of the heavy forms of hydrogen. He hoped that super-high temperatures in collapsing sonoluminescence bubbles would make the deuterium atoms fuse. To see whether fusion was really happening, he placed detectors around his acetone setup to count fast-moving neutrons. Neutrons would prove that fusion was occurring. Taleyarkhan believed that he counted enough neutrons to prove the presence of fusion.

Taleyarkhan's work was real science, but that doesn't mean it couldn't be wrong. Some other scientists criticized the details of his work. For example, fusion was not the only possible source of the neutrons that Taleyarkhan was measuring; he was shooting neutrons at the acetone to make bubbles form faster. Therefore, to detect fusion, Taleyarkhan had to measure not just whether there were any neutrons coming out of the experimental setup, but whether there were extra neutrons coming out—a much trickier problem.

Much as with cold fusion, hopes run high for sonofusion. But as of early 2006, no one had been able to duplicate Taleyarkhan's results. However, in early 2006 he announced that he was about to publish new results in the journal Physics Review Letters, an important science journal. Most physicists argue that Taleyarkhan is making an honest mistake in his experiments. The scientific process of presenting evidence and testing new ideas will eventually show whether he is correct.

SOLAR POWER SATELLITES

Solar cells or photovoltaic cells, devices that turn sunlight directly into electricity, work best in outer space. The sun is brighter there because there is no air to block any light, and solar cells can be stationed outside the Earth's shadow so they see the sun all the time. In fact, solar cells were first used, in the 1950s, to power space satellites. Some people have argued that we should use solar cells in space to generate power for the Earth. They say that we should build large arrays of solar cells in orbit around the Earth—solar power satellites.

But there is a problem: it is impossible to run power lines from a satellite to the Earth. Any wire or cable would snap under its own weight long before it was long enough to reach from the Earth's surface into space. Therefore, supporters of solar power satellites propose to beam the power to Earth in the form of radio waves. The kind of radio waves that would be used are "microwaves", the same kind that are used to cook food in microwave ovens.

The system would look like this: a large, flat array of solar cells would orbit the Earth at a height of about 22,000 miles (36,000 km). At that height, it takes a satellite 24 hours to circle the Earth. Since the Earth is spinning once every 24 hours, a satellite at that height (circling in the same direction as the Earth is turning) looks from the ground like it is standing still in the sky (geostationary, that is, remaining above the same point over the ground). Satellites of this kind are used to broadcast satellite TV signals. Also, a satellite that far from the Earth can be positioned so that the Earth's shadow never falls across it and breaks the supply of sunlight.

This giant array of solar cells would make electricity, turn it into radio waves, and beam the radio waves at Earth. A large antenna on the ground would pick up the radio waves and turn them into electricity again. The power would then be transmitted to users through power lines, just as power from ordinary generating plants is.

There are no basic scientific problems with this idea: everything about it uses machines that we already know how to make. The great problem is cost. A solar-cell array and microwave radio transmitter of the size needed would weigh many tons. The cost of launching all that machinery with rockets would be huge—far greater than the cost of building solar power stations, windmills, and other sources of renewable power right here on Earth. Although there is nothing basically wrong with the idea of solar power stations, they would be difficult to finance and build. Only wealthy and technologically advanced governments could currently fund such an effort. Only Japan has announced intentions to at least explore the possibility, but not until 2040.

NO MAGIC BULLETS

Hot fusion and solar power satellites are based on solid science, but there seems to be no current way to make them practical or affordable, at least for the foreseeable future. Cold fusion, sonofusion, and zero point energy, on the other hand, are based on scientific claims that most scientists currently reject. And perpetual motion is a complete fake that is not possible because of the well-tested laws of thermodynamics. Accordingly, there is probably not going to be any near-term "magic bullet" for our energy problems. We already know what tools we have to choose from: fossil fuels, nuclear power, and renewable energy sources such as the wind and sun, geothermal power, biofuels, wave or tide energy, and hydroelectric power.

There is intense disagreement in our society over what the right energy choices are that are both possible and affordable. For example, some people claim that it would be madness to not develop nuclear power on a huge scale, and others say it would be a disaster to do so. Some say that renewable energy can supply all our needs, and others that such energy sources can not meet increasing energy demands. There is no easy answer to the energy problem; even the best answers developed in the near future may be complicated, dangerous, and expensive. However, one thing is certain: all ways of making energy harm the Earth to some extent. Therefore, no matter where our energy comes from, we should not waste it. Living a more energy-efficient life is as easy as reaching out to turn off the nearest unneeded light.

Even as scientists and engineers are working on more efficient refrigerators, cars, computers, lights, and other devices, we can all save a significant amount of energy just by turning off lights, computers, and other devices whenever we aren't using them. Over time, we all make many choices about how much energy to use and how to use it. A more energy-efficient world is a world that is easier to supply with energy, whatever the source.

For More Information

Books

Close, Frank E. Too Hot to Handle: The Race for Cold Fusion. Princeton, NJ: Princeton University Press, 1991.

Cook, Nick. The Hunt for Zero Point: Inside the Classified World of Antigravity Technology. New York: Broadway Books, 2003.

Ord-Hume, Arthur W. J. G. Perpetual Motion: The History of an Obsession. New York: St. Martin's Press, 1980.

Web Sites

Fukada, Takahiro. "Japan Plans To Launch Solar Power Station In Space By 2040." SpaceDaily.com, January 1, 2001. Available at http://www.spacedaily.com/news/ssp-01a.html (accessed on February 12, 2006).

Lovins, Amory. "Mighty Mice: The most powerful force resisting new nuclear may be a legion of small, fast and simple microgeneration and efficiency projects." Nuclear Engineering International, December 2005. Available at http://www.rmi.org/images/other/Energy/E05-15_MightyMice.pdf (accessed on February 12, 2006).

U.S. Department of Energy. Report of the Review of Low Energy Nuclear Reactions. Washington, DC: Department of Energy, December 1, 2004. http://lenr-canr.org/acrobat/DOEreportofth.pdf, accessed on February 12, 2006).

Yam, Philip. "Exploiting Zero-Point Energy." Scientific American, December 1997. Available from http://www.padrak.com/ine/ZPESCIAM.html (accessed on August 2, 2005).