The Control of Energy

One pound of uranium carries more releasable energy than 1500 tons of coal, and the solar energy that reaches the earth in a single day is equivalent to that released by two million Hiroshima A-bombs. Better control of these and other forms of energy is basic to man's progress, says George Russell Harrison, Dean of the School of Science at Massachusetts Institute of Technology. A scientist who is concerned about the impact of science on human affairs and who writes with clarity for the layman, he is the author of Atoms in Action and How Things Work. In the article which follows, he explains the sources of energy—coal, oil, atomic nuclei, and the sun—and shows how man is progressing in harnessing these forces to his advantage.

By George R. Harrison
1

How many men can live on earth at once, and how long and fully they can live, depend on man's ability to control energy and matter. Those qualities of mind and spirit that give human life its sense and value cannot be developed until each of us has attained a certain minimal material standard of living. Philosophers may differ regarding how adequately a person should be fed, clothed, housed, protected, transported, educated, and entertained for his own best good, but the whole course of evolution shows that increased ability to control energy and matter is what enables any creature to come increasingly alive.

In an economy in which most people are farmers, the energy controlled by humans is stored in food and feed. These consist of complex molecules whose production involves the waste of more than 99 per cent of the solar energy showered on the plants in which they grow, and the.ir use entails much further energy loss. When the United States first became a republic, labor by people furnished about a quarter, and that by animals a half, of all the energy that kept the nation and its inhabitants functioning. In many countries most work is still done by using the human body as a converter of chemical into mechanical energy, with wife and bullock of nearly equal importance. Though in such countries as India more than 90 per cent of human labor is spent in growing and distributing food, not enough can be produced for everyone. As a consequence many starve, and less than one twentieth of human effort is devoted to occupations other than those involving bare subsistence. Storing energy in starches, sugars, and fats to be later released in the sweat of man's brow is expensive, inefficient, and if overdone, in a 70‑hour week, uncomfortable.

Because we in the United States now do most of our work with machines that take energy from simple sources, each citizen can have 2000 times as much energy working for him as was available in 1800. In the last fifty years, we have acquired 4 million farm tractors, and have gotten rid of three fourths of our draft horses and mules, much of whose effort was spent in raising their own feed. A tractor or a bulldozer can do the work of a dozen horses and six men, or of forty men with shovels, on energy costing $1.69 a day. In the United States, productivity per person has been doubling every generation for many years. Now each man, woman, and child has nearly 10 horsepower working for him day and night, instead of the 2 horsepower of 1900. With only 7 per cent of the world's population, we control almost half of its supply of power, and as a result our standard of living is seven times the average of the rest of the world.

Our ability to convert energy efficiently from one form to another continues to increase rapidly. Forty years ago one kilowatt‑hour of electrical energy could be obtained from about 3.5 pounds of coal. Today only one pound is needed, and 12 ounces will soon be enough. The small gasoline engines that have been developed to propel boats, lawn mowers, and snowplows, because they can carry their energy stored in a small tank, are too noisy, dirty, and hard to start to serve the housewife indoors for running her dishwasher, vacuum cleaner, or clothes drier. So electric motors are used, even though they must be fed energy through wires. This motor is a great emancipator of human hands, for it is clean and quiet, can be made to exert any strength desired, is tireless, seldom needs attention, and uses no energy when at rest.

When we buy energy we pay, not for the energy itself, but for the effort that went into gathering it and bringing it to us. One kilowatt‑hour of electric energy costs only a few tenths of a cent to generate with either burning coal or falling water, but ft usually costs ten times as much when delivered to the home. Most of the extra charge is for transmission costs, and for the privilege of turning the power on or off at will.

The cheapest way to carry energy, especially over long distances, at least, until the coming of nuclear power, has been to keep it locked up in molecules of coal or oil, and to carry these in a ship. Overland, when thousands of miles of travel are involved, it is most feasible economically to pump oil or gas through a large pipeline like the Big Inch. This method may also be applied in the future to coal, powdered and floated in water or oil. But even when the cheapest and best of these methods is used, carrying energy to the consumer ordinarily costs from four to ten times as much as getting it out of the ground or scooping it from a waterfall with a hydroelectric plant.

The age of nuclear energy will bring great savings in energy transport, for a pound of uranium carries more releasable energy than 1500 tons of coal. When the new methods of conversion have been better developed, the cost of transferring energy to the power station should become negligible, and power plants to feed big cities should become emancipated from the necessity of being located near the seacoast, or near coal mines, waterfalls, or dam sites.

2

All of the energy we use, except "atomic energy," has come to us from the sun. Three fourths of it came to earth ages ago, and was stored first in the leaf cells of plants and later in coal, oil, and gas deposits, which we now are rapidly depleting. The other fourth, including water power and the energy stored in the molecules of foodstuffs, made its eight minute journey from the sun only recently. This glowing globe sends us 20,000 times as much energy as we use now for every purpose -‑ energy equal in a single day to that released by 2 million atomic bombs of the Hiroshima variety. But we don't know yet how to capture and store this energy effectively enough to make it worth using in large quantities, except through intermediate concentration and storage by nature in plants and in the clouds. Both of these processes are, of course, very wasteful.

All of the energy the earth gets from the sun goes to keep it warm, but this energy could be used for many purposes first, and later would keep the earth warm anyway, like water, which, after dancing in a fountain, can be piped off to keep the garden green. Neither energy nor matter is ever "used up"; they are only converted and modified until they escape into the basic reservoirs of each, where they get out of reach of mankind.

We use energy in three principal ways. In America, roughly a third is used to help control the environment by heating homes and factories, another third goes to process matter in mining and industry, and the remainder is spent in moving ourselves and our possessions from place to place in ships, airplanes, autos, trains, and streetcars.

Until 1880, most of the energy used by man came from burning wood, which was replaceable. Since then we have relied on irreplaceable coal, oil, and gas, whose great value lies in the concentrated form of the energy they hold and in the ease with which this can be released simply by combining their molecules with oxygen. The energy in a pound of gasoline can push an auto twenty times as far as that in a pound of storage battery fully charged.

Seventy billion barrels of oil have been removed from the earth's crust, and in each generation those who should know predict that the supply will near exhaustion by the time another generation has passed. But the main reason we can seldom see more than twenty‑five years' worth of petroleum resources ahead is that the oil industry becomes less diligent in hunting for more oil when its reserves are built up to that degree. Geophysicists are still able to find oil faster than the world can burn it, but their hunting methods must constantly be made more sensitive, and how long they will be able to keep this up is anybody's guess. When all the oil wells do go dry, oil shale, a mixture of rock and petroleum, of which enough is in sight to keep industry going for a hundred years or so, can be processed for fuel. After this is gone, coal can be hydrogenated, though at some loss in efficiency, to form liquid fuels. In South Africa, where there are no oil wells, but where the concentration of automobiles in some cities is as great as in the United States, 3000 tons of coal are now converted into oil each day by the addition of hydrogen atoms.

Though the coal in sight may last the world for a thousand years, less coal is now being mined in America than in 1910. The coal industry needs a heavy dose of technological salts to bring it back to its proper position as a leading supplier of packaged energy. Coal is harder to get out of the ground than oil; it must be carried on land by rail, which is more expensive than pumping oil through pipes; and it leaves ash. These limitations may well be removed by burning, powdering, or fluidizing coal at the mine, and then piping the resulting products to places where they are needed.

Water power is appealing because it is clean, can readily be converted into electric energy, and is constantly being replenished by the evaporation, caused by solar heat, of water that falls again as rain. It is not cheap to collect, however, and only 5 per cent of the energy now used in the United States comes from this source. If all the potential dam sites were developed, the resulting power would fill only one fourth of our present needs. Yet much more can be done to make hydroelectric power available. In such countries as India, hydroelectric sites lie undeveloped while peasants cook their one hot meal a day on burning dung from holy cows.

Despite the advantages of oil and coal, more wood is cut for fuel today in the world than ever before. In Brazil, 85 per cent of all energy used still comes from wood. However, in forward­-looking countries wood is becoming more valuable as matter than as a source of energy. All the cellulose our forests can produce will soon be needed for lumber and paper, and for rayon and other fibers that can be made from cellulose molecules. By A.D. 2000, less than forty‑five years away, our forests should be routinely tidied up to serve as factories that use the energy of sunlight to make complex molecules out of simple carbon dioxide and water from the air.

There are several vast sources of energy that we do not now find it worthwhile to tap. A storm of the sort that passes occasionally, giving the normal rainfall, develops several hundred billion horsepower, and inventors have always dreamed of using the energy of the wind. Even a minor hurricane releases energy as fast as a thousand atomic bombs exploding each second. But this power is hard to harness; and a source of energy, to be industrially useful, must be dependable and not too variable in output. To be effective as a power converter, a windmill must be very large. Calculations show a good diameter to be 225 feet, topping a twenty-story building, and for industrial power, such a windmill should give out at least 2000 kilowatts, no matter how fast the air is moving. However, when a breeze blows up to merely twice its former speed, it does eight times as much work as before. A zephyr blowing at less than 920 miles an hour is too weak to give the needed power; when it rises to a hurricane of 100 miles an hour, five times as fast, it is able to do 125 times as much work but is likely to blow the windmill away. As a consequence, we use more energy to make wind with electric fans and airplane propellers than we take from sails or windmills to operate machinery.

Much energy is stored in the ocean, as temperature difference between the warm surface and cooler depths, in waves, and in the tides. The great size needed and losses from storms have in the past kept installations for collecting energy from the ocean and waves from being successful. Attempts to take energy from the tides ‑‑ which might well succeed in places where a great head of water rushes in and out at every tidal flow and ebb, as in the Bay of Fundy ‑‑ have run up against economic difficulties, because usually such locations are not near enough to cities that need the power, and power transmission costs are high.

Recently we have become increasingly aware of two great sources of energy that appear inexhaustible: the sun and the nuclei of atoms. Will solar nuclear power run the industries of the future? The answer is: Both, plus all the energy sources we exploit at present. Energy is so important to man that his need for it is endless; he uses every new source to supplement rather than to supplant his older supplies.

3

The matter in an atom is all energy, as Einstein indicated in 1905 with his famous formula E = mc2. Scientists have now learned to release about one thousandth of this energy by the process of nuclear fission, and as much as a hundredth by nuclear fusion. Even these small fractions are millions of times greater than those released in chemical combustion by fire, which taps only the external reaches of the atom.

In a nuclear chain reaction, explosion of a complex and unstable nucleus such as that of uranium releases neutrons which, when slowed down by colliding with other atoms (such as carbon or deuterium) used as "moderators," react with the nuclei of neighboring explosive atoms to cause them to rearrange into new patterns and release still further showers of neutrons. A pound of U 235, the isotope of uranium which, when separated from ordinary uranium, was first found able to support a nuclear chain reaction, can thus be made to release as much energy as 3 million pounds of coal gives when burned. But only one atom out of 139 of mined uranium consists of this isotope. This scarcity is offset by the fact that U 238, a more plentiful isotope, can be converted into plutonium atoms by bombarding its atoms with neutrons, and the newly produced atoms can then be used as nuclear fuel. The development of the breeder pile, which produces this nuclear fuel, has greatly increased our visible energy stores. The operator of a breeder pile is somewhat in the position of a householder who shovels coal and ashes in to his furnace, heats his house adequately, and then shovels out, instead of ashes, tons of coke that he can sell to the neighbors.

If it were not for the dangerous radiations produced by its activity, a nuclear reactor could be rather light. As it is, heavy shields are needed to protect its operators from radiations which, besides being directly damaging to living cells, produce lethal rays when they strike sand or air or any other surrounding material. Nearby innocuous atoms may be converted into unstable atoms, many of which are likely to explode and emit more rays at some future time. The automobiles powered by "pea‑sized plutonium engines" predicted by some journalists have lost much of their appeal because of the necessity of placing a concrete shield several feet thick under the driver's seat, and of providing heavy concrete fenders to protect the passers‑by.

Any nuclear reactor must be carefully supervised in its operation, because of the dangers of contamination from waste products that might escape after an accident. This dampens our enthusiasm for nuclear‑driven locomotives. Mopping up contaminated wreckage is a tedious and, if care is not taken, a dangerous job; and it is not always feasible.

Literally hundreds of different types of nuclear reactors have been designed, and these will soon evolve into as great variety as have ordinary engine‑driven vehicles, which are differentiating into thousand forms from tractors to helicopters. Airplanes driven by nuclear power seem practicable if the shielding problem for personnel can be solved, as by putting the power plant in a tractor plane, and the pilots and passengers into one or more gliders far enough behind to escape dangerous rays. Ships are already being driven by nuclear power, though their ability to carry enough stored energy to propel them for life will be limited by the need for occasionally sifting out nuclear ash from the fuel. Nuclear fuel can already compete in cost with oil for driving ships, but the first cost of a nuclear power plant is still much greater than that of an oil-­burning power station.

Reactors to produce electric power from nuclear fuels are now being built both here and abroad, and some soon to be designed should give enough power to fill the needs of the largest city. All of the electrical power now used in the United States could in theory be produced from 60 tons of uranium. Though this nuclear fuel would last for many years, it would need repurification occasionally when it became too full of spent nuclei. Reactors for producing electric power now being built in England are expected to save 20 million tons of coal a year.

Nuclear power can already compete with domestic power costs for fuel and upkeep where these are above 2 cents a kilowatt‑hour wholesale, but the first cost and carrying charges are still too high. In Europe, where anything approaching a cent per kilowatt‑hour can compete, the price of uranium need only be cut in half to make it a commercial success as a fuel for power. Though it is unlikely to put the coal or oil industries out of business, it should by 1975 compete with them strongly in large power operations, especially in regions far from marine transportation.

There is a great deal of uranium in the world. Some living cells tend to concentrate it, and it is likely to be found with coal. Though sea water contains only 2.5 parts per billion of uranium, one ton of the granite of the hills could give the energy of 50 tons of coal once its content of these atoms was separated out.

A few years ago, when only uranium atoms of the U 235 isotope seemed fit for industrial energy release, the nuclear fuel in sight was equivalent to about 600 billion tons of coal, or one sixth of the world's reserves of fuel. The breeder pile, however, has raised visible nuclear energy reserves to the equivalent of 90 trillion tons of coal, and our visible energy store of all kinds is increased perhaps 25-fold over what could be seen a few years ago. Thus man is given extra ability either to destroy himself or to build more stately mansions for his soul.

4

Basking in the sunshine on a bright June day, we are not likely to think of our sun as the stabilized H‑bomb that it is. If all the light and heat radiated by this hydrogen reactor were focused on the earth, it would vaporize the oceans and shrivel our planet in a matter of seconds. At the center of the sun, at temperatures like those in the center of an A‑bomb, the nuclei of hydrogen atoms fuse into helium nuclei, thus converting about one per cent of the matter in each nucleus into energy ‑just enough to keep the earth comfortably warm.

The sunlight that falls on a single acre of the welcoming earth contains enough energy to keep a thousand people healthy, active, and comfortable. Instead of doing this, most of it is wasted, and the remainder now serves only one or two persons. A 16‑mile‑square area in any desert receives enough sunshine to satisfy all the energy needs of the American people today. Someone has calculated that the sun gives the earth every three days as much energy as would be released by burning all the forests and all the coal and oil and gas in the world.

Thus there is lots of solar energy, and it appears to be free to anyone who wishes to scoop it up. But anyone who tries is likely to become disheartened by the many ways in which sunshine eludes his grasp, and is missing when he needs it most. The sun is overhead only part of the time. To light a city at night, solar energy should be held for at least twelve hours. To heat houses, it should be stored for days or months. We lack a cheap and efficient method of storing energy in quantity. In the photosynthesis on which all life depends, nature has developed a storage system that will hold energy for years in plant cells, but this operates at too low an efficiency to compete with the coal and oil that took thousands of times longer to produce than it does to burn. Fuel alcohol from potatoes or other crops, one of the best methods of storing solar energy, now costs four or five times as much as gasoline to produce.

Seventy‑four hundred horsepower flow continuously into the top of the atmosphere above each acre of land or sea facing the sun; but absorption and scattering by the molecules of the air and the inclination of the earth's axis in the latitude of New York reduce this to less than 4000 horsepower by the time it reaches the ground. Cloudy weather cuts it further to a yearly average of about 800 horsepower per acre. This is still a great deal of energy, but unfortunately storing it, carrying it to where it is to be used, and transforming it into the chemical, electrical, mechanical, and thermal forms we want for industry are likely to waste more than 85 per cent of the remainder, or to require setting tip installations which are too expensive to be practical. Some of the losses arise from immutable laws of nature, but others can be avoided by ingenuity and scientific acumen, and therein lies great hope for the future.

All of the many methods of catching sunlight suggested thus far have been found to be too complicated, too inefficient, or too expensive to be practical for industrial use. Most new-­fledged solar energy hunters are smitten with the idea of concentrating sunlight with mirrors. A horsepower per square yard looks very attractive as an inflow of power. Let's put up a reflector 10 yards on a side and concentrate 100 horsepower to run a steam engine! But large mirrors are costly and fragile, must be kept clean and free of dust, and must be turned to hold the sun's image still as the earth rotates. A boiler with all the needed gadgets and a mirror large enough to produce only 2 horsepower on a sunny day costs about $1000.

In India, a government scientific agency has put on the market, at $14, a simple solar‑operated cookstove. This has a mirror about one yard square which concentrates energy on a pressure cooker. The cook need only move the mirror or the pot occasionally to keep the sun's image on it. Using this device may result in saving for fertilizer much of the cow dung now used for fuel, but if enough of this can be saved to enable eucalyptus trees to grow effectively, it may be found cheaper in the long run to let the trees store solar energy, and then burn their wood for cooking.

The trouble with large installations for solar power is that they cost too much to build and to keep up. The solar energy falling on a square mile in a day is worth $200,000 at present power rates. At 5 per cent efficiency of conversion this would give a daily income of $10,000. However, any apparatus yet suggested to capture and convert this much energy would cost more than $50 million a square mile, and the interest on this amount would be more than $10,000 a day. Keeping the glass of the mirrors used shiny and in repair would also be expensive.

There is some hope that better methods of conversion can be found, especially those like the thermopile and the photovoltaic cell, which convert solar radiation directly into electrical power. Greatly encouraging was the announcement in 1953 by scientists of the Bell Telephone Laboratories that a new cell made of thin strips of specially treated silicon gave about 50 watts per square yard when exposed to sunlight. This efficiency of 4 per cent has since been increased to 8 per cent. Though such solar batteries are not likely to be used as an industrial source of power until they can be made more cheaply, in this direction lies hope.

We may be on the verge of using solar energy far more widely for heating our homes and hot water for domestic use. Solar houses have been operated through the winter even in New England with only a 10 per cent addition of furnace heat. For such applications sunlight need not be concentrated, but can be allowed to fall directly on blackened metal absorbers on a house roof, tilted at the best angle to soak up heat during the winter months. These boxes must be well insulated, and covered with one or more layers of very clear glass to act as a heat trap, like a greenhouse. A non‑freezing water solution is circulated under the blackened surface of the collector, and carries the heat to an insulated storage bin and thence as needed to radiators. Such collectors now cost about $2 a square foot; if their cost could be cut in half, solar heating would become very attractive, and larger installations to generate power from solar energy might become feasible.

As much as 20 tons of water, gravel, or a solution of chemical salts is needed to store enough energy to heat a house for a single day, and at least 5 per cent of the useful space of the building must be devoted to insulated heat storage bins. But if at least a ten‑day supply of energy cannot be counted on, central heating must be provided for stand‑by use in cold and cloudy weather. This doubles the cost of a solar house‑healing plant. This extra expense may be justified if the standard heater is of the heat‑pump type, which can be used also for cooling in summer, or even if electric air‑conditioning and heating are used.

Nature's solution of the solar energy storage problem, photosynthesis in the cells of plants, though very inefficient is effective, for it stores energy in chemical form where it will stay indefinitely in the elastic insides of molecules. It has been suggested that furnaces could be run on algae or other simple plants grown for fuel. This would be a ridiculous waste of effort, involving building up at great expense very complicated molecules to do a job that much simpler molecules could do more effectively. Stoking stoves with starch or sugar is as silly as it sounds.

Energy from the sun, though it comes from the nuclei of atoms, by the time it reaches the earth has been made diffuse enough to be safely fed to the delicate complex molecules from which plants and later animals are formed. When nuclear energy is released on earth, it is concentrated and intense, and to gentle it we must control great quantities of dangerous rays. It is natural then for the scientist to plan to use nuclear energy in those cases where he must have high temperatures, pressures, and energy concentrations, and to use solar energy where gentle diffuse actions are required. For the ordinary purposes of industry, solar energy needs concentrating, while nuclear energy needs diffusing. At the moment, scientists are getting on faster with the latter, but both will have great importance in man's future.

5

What is this thing called energy, which man can use for his destruction or to set himself ever freer from control by his environment? We recognize it in many forms, as light or heat or sound or electric power, but all have in common the capacity for doing work. They are merely different external manifestations of three basic forms that exist in the realm of protons, neutrons, and electrons: energy resulting from electrical, magnetic, and gravitational forces.

The deeper we dig into the structure of matter, the greater the amounts of energy we find. The events of the world we contact with our senses are only leftovers, which result from residual forces not balanced out on the more fundamental levels of matter. We have seen that protons combine with neutrons in the nucleus with forces measured in millions of volts. Forces corresponding to a few thousands of volts remain unbalanced, and with these the nucleus collects a family of electrons to form an atom. With still smaller residual forces, from a dozen volts down, these atoms cluster into molecules and crystals. It is the rest of this remnant of a remainder, measured, in thousandths of a volt for each material, that determines whether these molecules shall form "shoes or ships or sealing wax"; and "cabbages and kings" are formed by still more subtle residues.

The flowing of a waterfall, the heating of a house, and the hitting of an enemy with a club utilize only minor routine residues of energy. With the coming of the Industrial Age men learned how to bring the energy of the molecular world, through chemical reactions, directly to bear on mechanical problems, at the same time learning better how to harness the older residual forms of energy. With gunpowder, and later gasoline, they were able to release energy in much more concentrated form and in greater quantity. In the early years of this century scientists sensed the even more concentrated and vaster supply of energy in the nucleus of the atom, and in 1942 they learned how to release this energy directly.

Mastery of the nucleus will mark a much bigger step in man's ability to control his environment than any he has taken before, for it gives him the opportunity to be at home on more fundamental levels of the material world, instead of merely working in the outskirts. Calling the release of nuclear energy a new Promethean fire" is more than just a metaphor or an analogy. The new fire of atoms presents to man an opportunity similar to that he received when he first drew back a burned finger from the fire of molecules, now raised in intensity to a hidden but transcendent power.

When nuclear fission occurs, only about one thousandth of the energy content of an atom is released, and scientists know how to set this energy free from only a few of the heavier kinds of natural atoms. But with the processes of nuclear fusion, up to ten times as much of an atom's energy can be released. In one of its simplest forms, fusion involves the combination of two protons with two neutrons to form the nucleus of a helium atom. The sun gets most of its energy in this way, and most matter in the universe is probably thus formed as a first step. Though the sun is an excellent hydrogen fusion reactor, it is early yet to decide whether we can ever have on earth a small one so well controlled ‑‑ one that will operate at a strong simmer instead of exploding in a millionth of a second, or that, need not he kept a thousand miles away to be of any use, If the speed, instead of merely the extent, of a thermonuclear reaction can ever be controlled, water may well furnish a superfuel better than any of those of which men have dreamed.

Inventors who have tried to develop pills that would make water burn were on the wrong track, for water is already ashes of hydrogen. When hydrogen is burned with oxygen their molecules combine to produce water, and release much chemical energy in the flame. The water remains after the energy is dissipated, and new energy must be used to "unburn" the water as plants do in photosynthesis, or as electric power can be made to do in a hydrogen generator. But if protons are collected from the hydrogen in water and then assembled with neutrons to produce helium nuclei, a vastly greater release of energy results ‑‑ energy from nearer the base of the universal supply. At present no one appears to know how to control this reaction beyond setting it off with an atomic bomb as a primer, thus raising nuclear temperatures to those needed to start a fusion reaction. If this process could be slowed down and controlled, the oceans would provide an inexhaustible reservoir of energy, and man would never need to worry about power again. But he has much to learn before this can come about.

Of equal importance to man's rapidly improving ability to control energy of the most intense forms, like that of the multibillion‑volt cosmic rays, is his increasing mastery of the most subtle forces, those that hold atoms together in complex living molecules. When these forces can be better controlled the physical hungers of all humanity may well be filled by further gentling of the energies of the atom bomb into those of food and warmth. Then will it become apparent that energy from the atom, far from being the evil creation of a few clever but dangerous men, is a beneficent force of nature that has been lying in wait since the beginning of time, until man could awaken to awareness of its availability and learn properly to use and control it.

This article available online at:

http://www.theatlantic.com/magazine/archive/1955/09/the-control-of-energy/305024/