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.
[Illustration: FIG. 55.--THE ESNAULT PELTERIE PLAN OF UTILIZING TIDAL
POWER IN THE ENGLISH CHANNEL]
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.