WHEN COAL AND OIL ARE EXHAUSTED

IN PREVIOUS chapters we have indulged in a great deal of historic retrospect. It may be well at this point, while we are dealing with the subject of power, to look into the future and the prospects that it holds out to us.

It was about fifty thousand years ago, according to conservative estimates, that primitive man first began to use tools, and he managed to exist and thrive and develop to a very high degree of civilization during practically the whole of that period without touching the stores of energy that lay beneath his feet. It was only yesterday that the steam engine was invented, and when it was discovered how to turn heat into work and what a wealth of power was stored up in the deposits of coal there started a lavish and profligate squandering of the precious heritage of the Carboniferous era. The fossilized vegetation of by-gone ages is now employed to drive our locomotives and steamships, to turn our factory wheels, to extract metals from the ore and help us shape them according to our needs and desires, to convert iron into steel and to heat and light our houses. We all know that there is a limited supply of coal in the world and that some day the stores will be exhausted, yet we go on using larger quantities of the fuel each year.

For the last century our demands for coal have been doubling every ten years, until to-day the world is using about 1,200 million long tons per year. It is conservatively estimated that if our demands for coal do not increase there is enough left in the whole world within a mile of the surface to last 1,500 years. Fortunately this country is better supplied than many others, and it is probable that we can get along on our present rations for 2,000 years. England, however, faces exhaustion of her coal supplies within two hundred years.

After living fifty millenniums on earth as a being clearly superior to other animals, man comes into an inheritance which he squanders in one or at most two millenniums. It is not creditable to our civilization that we have taken no precautions to ration out this precious store of fuel.

OUR WASTE OF FUEL

As was shown in a previous chapter, we utilize very little of the energy in coal. Our steam railroads squander from 94 to 96 per cent of the coal they burn and our best turbine power plants throw away about 80 per cent. The coal we burn in domestic furnaces is most wastefully squandered. Maybe we shall learn how to use the energy in coal more efficiently and make it last longer, but eventually it will all be gone and then what are we going to do?

Of the other fuels available, petroleum takes the leading place, but we are hardly more economical in our use of this fuel and our oil supplies are diminishing much more rapidly than the stores of coal. In 1919 the United States produced 376,000,000 barrels of oil and consumed 418,000,000 barrels, having had to draw on Mexico for 42,000,000 barrels. Natural gas cannot last much longer and peat bogs are estimated at about half of one per cent of the coal supplies. Where shall we turn for heat and power when all these stores of energy are gone?

It has been estimated that the water powers of the earth, if fully developed, would probably supply about half of the energy that we now get out of coal. This is a never-failing supply of energy, and no doubt before we have begun to scrape the bottom of our coal magazines every river on earth that is capable of turning a wheel will be doing so to the limit of its capacity. Then there will be a readjustment of the manufacturing centers of the earth and remote regions such as Iceland, for instance, which has more available water power than Switzerland, will hum with machinery, while such countries as Great Britain, which is relatively poor in water powers, will have to give up manufacture and revert to agricultural pursuits.

But are there not other powers that can be used? If we could capture all the energy of the winds we should have ample power to do all the work that is now done on earth with a large margin to spare. It has been estimated that the winds contain 5,000 times as much energy as is obtained from coal, but how may we capture so fickle a power as the wind. It is so variable, sometimes exerting enough power to lift houses from their foundations and uproot giant trees, and again sinking to an absolute calm. In some places wind power is turned into electricity and then stored up in batteries; but the cost of doing this is high and at present uneconomical.

“BLUE COAL”

The ocean Is a vast storehouse of energy. The quiet but powerful rise and fall of ocean tides, and the tremendous energy of ocean waves, have been looked upon with envy by engineers. All sorts of schemes have been devised for capturing a part of this energy and putting it into the service of man. Water power has been aptly called “white coal” and ocean power “blue coal.” Wave energy is but another form of wind energy and hence just as fickle. There is plenty of power to be had, but it is a costly matter to build a power plant on the shores of the ocean and any day a storm may arise which will dash the machinery to pieces and sweep away the whole plant or convert it into a pile of wreckage. In a few places, however, Nature has provided a plant which the ocean has been unable to destroy and man has adopted the plant to furnish him with power. There is a rocky cave on the California coast which is exposed to the ocean swells. As the swells sweep into the cave they compress the air therein and this compressed air is trapped in a reservoir. Then the air that has been pumped by the ocean is put to useful work. There are similar caves on other rocky coasts which could be made to deliver power when coal becomes scarce and it becomes commercially practicable to exploit them, but the amount of power they would furnish would be a mere drop in the bucket.

SETTING TIDES TO WORK

The ocean tides are also immensely powerful, but the rise and fall of the water is so slight and so gradual in most places that an enormous plant is required to obtain any appreciable amount of power. In certain regions, however, tidal power is actually in use to-day. At high tide water flows into a large basin and at the ebb of the tide the outflow of the basin operates a water wheel or turbine. Power can be obtained while the basin is filling as well as while it is emptying. One serious objection to this plan is that the turbine operates intermittently and at irregular intervals, sometimes by day and sometimes by night, depending upon the tide. However, tide mills need not be exposed to the fury of ocean storms as are plants that seek to employ the power of ocean waves. In certain localities the conformation of the coast is such as to accumulate the tidal flow and produce enormous differences of level between ebb and flood tide. In the Bay of Fundy, for instance, the tide rises seventy feet and an appreciable amount of power could be obtained from the flow of water into and out of the bay. If a sea-level canal were dug across the Isthmus of Panama there would be a flow of water back and forth through it because the tides at the Pacific side have a rise and fall of only two feet while on the Atlantic side the tide rises twenty-two feet. Some power might be obtained from the tidal flow through this canal, but a fall of twenty feet in fifty miles would not produce a very swift current.

If tidal power is to be utilized at all it must be done on a grand scale. A French engineer, R. Esnault Pelterie, has proposed a vast tidal power system in the English channel where the tide rises high. (See map Fig. 55.) The plan is a most ambitious one, but the power that could be obtained is enormous. He proposes to build concrete dikes across the channel at the Straits of Calais inclosing a large basin about twenty miles wide and turbines would be operated by the flow of water into and out of this basin. Of course locks would have to be provided to permit the passage of ships through the basin. Other and larger basins could be formed by walling off the estuary of the Thames and the bay of the Seine on the French coast. The Gulf of St. Malo could be inclosed by running a dike from Cape La Hague to the island of Guernsey and thence to the mouth of the Trieux. These basins would furnish a minimum of 800 horsepower for each square mile, hence the basin across the Straits of Calais alone would furnish nearly half a million horsepower while the Gulf of St. Malo would furnish about a quarter of the power that France now uses in her industries. The first cost of the installation would be heavy, but there would be no expense for fuel and the supply of power would be endless. It has been proposed to dam the estuary of the Severn (England) where the spring tides rise thirty feet, and it has been estimated that half a million horsepower would be developed. Part of the power would be used to pump water into an elevated reservoir which would serve as a storage battery, so that when the tidal plant was idle because of the turn of the tide, water flowing out of the reservoir would operate an auxiliary plant, thereby furnishing a continuous supply of power.

POWER FROM SUNSHINE

With the exception of the tides all the energy we use on earth comes from the sun. It is the sun’s energy that is stored in coal beds and oil fields; it is the sun’s energy that raises water from the ocean to the tops of our mountains; it is the sun’s energy that makes the winds blow, and through them disturbs the surface of the ocean, and even the tides owe a part of their energy to the attraction of the sun. Why can we not utilize the energy of the sun directly, instead of at second hand? In the sunshine that beats upon the earth there is seventy-thousand times as much energy as we now obtain from coal. Unfortunately the energy of the sun is so widely dispersed that it cannot be used economically except in a very few places where clouds do not often interrupt the direct passage of the rays to the earth’s surface.

Near Cairo, Egypt, there is a plant erected by an American inventor, Mr. Frank Shuman, which develops about fifty horsepower. This consists of a series of five huge trough-shaped mirrors that focus the sun’s rays upon boilers and thus generate low pressure steam. The mirrors measure 13 feet in width and 304 feet in length and these are mounted on a light steel framework with their axes running north and south so that they may be turned from east to west to follow the course of the sun across the sky. In order to prevent the mirrors from shading each other in the early morning and late afternoon they are set twenty-five feet apart. Mirrors are made of thin sheets of window glass, silvered at the back. The troughs are parabolic in cross section and at the focus of each is hung a tubular boiler painted black to absorb the heat rays. The five boilers feed a common steam reservoir from which steam is fed to a pump. This pump raises about 6,000 gallons of water per minute, which is used for irrigating purposes. Of course at night the supply of energy is cut off and on cloudy or rainy days no steam is generated, but such days are few in the region of Cairo, and continuous operation is not essential to the operation of irrigating systems.

There are localities in Africa, Asia Minor, and even in the United States where the lack of water and the pitiless rays of the sun have turned vast regions into deserts. Here the very rays which have parched vegetation may be utilized to pump water over the thirsty lands and convert them into rich agricultural regions.

There is another mighty source of power in the internal heat of the earth. Here and there all over the earth are vent holes through which the pent-up energy makes its escape in the form of steam, gases, or molten lava. There is no question as to the enormous stores of energy in active volcanoes, and as we appreciate the value of heat energy our eyes turn covetously to these great chimneys of the subterranean furnaces.

HARNESSING VOLCANOES

It seems like the height of daring to attempt to harness the volcanoes, and yet there is a plant in Italy which utilizes volcanic energy and develops useful power from it. At Volterra, in the province of Tuscany, there is a volcanic region where jets of very hot steam issue from cracks in the ground. These steam jets, known as soffioni, are laden with gases and mineral matter. For many years the boric acid that they contain was abstracted from them, but the steam was allowed to escape. In some few instances it was piped into houses and used for domestic heating. In 1908 an attempt was made to convert the energy of the steam into useful power. Holes were bored into the earth and steam of a temperature of 302 degrees Fahrenheit came up the pipes. This steam was applied directly to a forty horsepower steam engine, and for the first time volcanic heat was set to work. The steam, however, contained so many impurities that it was impracticable to use it directly in the engine. The valves and cylinders were soon clogged with deposits of boric acid. Then instead of trying to obtain power directly from the steam, the latter was used to heat a boiler in which pure steam was generated. This plan proved perfectly practical and a 300 horsepower condensing steam turbine was driven by the energy thus obtained indirectly from volcanic heat. This power was converted into electricity and the power was transmitted to the surrounding villages. After the World War broke out and Italy began to feel the shortage of fuel, the price of coal having risen to $50 per ton, the use of volcanic power was extended. A 3,000 kilowatt plant was installed and electric current was transmitted to Florence, Leghorn, Volterra, and other towns of Tuscany. The exhaust steam from the boilers was utilized in the boric acid industries.

Other projects for utilizing the internal heat of the earth have been given serious consideration in Italy. Near Naples there is the dormant volcano, Solfatara, the crater of which is filled with a sea of very hot mud underlying a cool thin crust of earth. Holes bored into this mud to a depth of a few feet send forth steam hot enough to do useful work and a plan to utilize this store of energy is under way.

POWER FROM THE CORE OF THE EARTH

There are regions where the ground is red-hot at a depth of a hundred feet. While there is no water present to furnish steam, it is a simple matter to sink a water pipe down to the heated earth and then, around this pipe, to drive a ring of smaller pipes through which steam may find its way up to the top and be fed either into water heaters or directly into steam engines. In fact it has been suggested that such a scheme might be used almost anywhere. If we bore into the earth, we find that the temperature grows higher the deeper we go. The rate of increase of temperature varies with different localities, but it is very evident that anywhere on earth temperatures that will give a steam pressure of ten or more pounds per square inch can be obtained if we dig down far enough, and when we find it worth while to do so we shall probably riddle the earth’s crust with perforations through which water will be sent down to the subterranean furnaces and it will return to us laden with heat energy.

After all, we shall not be plunged into dire want when our stores of coal are exhausted. There will be other sources of power to draw upon, most of which will be inexhaustible. Furthermore, we have recently discovered in atoms of matter stores of energy incomparably greater than any that have heretofore been used to work the will of man. How to utilize this energy we have not yet learned, but the energy is there, and no doubt, some day, probably long before coal takes its place in museum collections, we shall be possessed of a new slave, far more powerful than that which has served us so far.