Everyday Science and Mechanics,
December 1931
The material as well as intellectual progress of Man
is becoming ever more dependent on the natural forces and energies he is putting to his service.
While not exactly a true measure of well being and enlightenment, the amount of power used is a reliable
indication of the degree of safety, comfort and convenience, without which the human race would be
subject to increasing suffering and want and civilization might perish.
Virtually all of
our energies are derived from the sun,
and the greatest triumph we have achieved in the utilization of
its undying fire is the harnessing of
waterfalls. The hydro-electric process, now universally employed,
enables us to obtain as much as
eighty-five percent of the solar energy with machines of
elementary simplicity which, by resorting to the
latest improvements in the technical arts, might be made capable
of enduring for centuries. These
advantages are entirely exceptional, very serious handicaps and
great, unavoidable losses confronting us
in all other transformations of the forces of nature. It is,
therefore, desirable in the interest of the
world as a whole, that this precious resource should be exploited
to the limit. Judging from the average
height of the water discharged annually from the clouds, and the
mean fall over the aggregate land
surface, the total terrestrial water power may be theoretically
estimated at ten billions of horse power. Of course, only a part of
that is suited for practical development and relatively little is
actually utilized—twenty-five percent, perhaps, in the most advanced
countries, less in others, and there are some in which not even the
ground has been broken. Great waterfalls exist in many inaccessible
regions of the globe and new ones are being discovered, all of which
will be eventually harnessed when the wireless transmission of energy is
commercialized. There is foundation for hope, however, that our
present limitations in the amount of available power may be removed in
the future. Three-quarters of the earth's surface are covered by the
oceans and the rainfall over all this vast area is useless for our
purpose. Much thought has been given to artificial production of rain,
but none of the means proposed offers the slightest chance of success.
Besides, so far only the precipitation in a limited region was
contemplated, leaving the total quantity of moisture for the *?*untired
land unchanged except as modified through the natural tendency of the
oceans to divert more and more water from the continents. The real and
important problem for us to solve is not to bring about precipitation
in any chosen locality, but to reverse this natural process, draw the
vapors from the seas and thereby increase, at will, the rainfall on the
land. Can this be done?
The arrangement of one of the great terrestrial power plants of the future.
Water is circulated to the bottom of the shaft, returning as steam to drive the turbine, and then returned to liquid form in the condenser, in an unending cycle.
The sun raises the
water to a height where it remains in a state of delicate suspension
until a disturbance, of relatively insignificant energy, causes
condensation at a place where the balance is most easily disturbed.
The action, once started, spreads like a conflagration for a vacuum is
formed and the air rushing in, being cooled by expansion, enhances
further condensation in the surrounding masses of the cloud. All life
on the globe is absolutely dependent on this gigantic trigger mechanism
of nature and my extended observations have shown that the complex
effects of lightning are, in most cases, the chief controlling agents.
This theory, formulated by me in 1892, was borne out in some later
experiments I made with artificial lightning bolts over 100 feet long,
according to which it appears possible, by great power plants suitably
distributed and operated at the proper times, to draw unlimited
quantities of water from the oceans to the continents. The machines
being driven by the waterfalls, all the work would be performed by the
sun, while we would have merely to release the trigger. In this manner
we might obtain sufficient energy from falling water to provide for all
our necessities. More than this, we could create new lakes and
rivers, induce a luxuriant flora and fauna and convert even the arid
sands of deserts into rich, fertile soil.
But the full
realization of this idea is very remote. The hard fact is that unless
new resources are opened up, energy derived from fuel will remain our
chief reliance. The thermo-dynamic process is wasteful and barbarous,
especially when burning coal, the mining of which, despite of modern
improvements, still involves dangers to the unfortunates who are
condemned to toil deep in the bowels of the earth. Oil and natural gas
are immensely superior in this and other respects and their use is
rapidly extending. It is quite evident, though, that this squandering
cannot go on indefinitely, for geological investigations prove our fuel
stores to be limited.
So great has been the drain on them of late years that the specter
of exhaustion is looming up threateningly in the distance, and
everywhere the minds of engineers and inventors are bent upon increasing
the efficiency of known methods and discovering new sources of power.
Nature has provided
an abundant supply of energy in various forms which might be utilized
if proper means and ways can be devised. The sun's rays falling upon
the earth's surface represent a quantity of energy so enormous that but a
small part of it could meet all our demands. By normal incidence the
rate is mechanically equivalent to about 95 foot pounds per square foot
per second, or nearly 7300 horse power per acre of ground. In the
equatorial regions the mean annual rate is approximately 2326 and in our
latitudes 1737 horse power for the same area. By using the heat to
generate steam and operating a turbine under high vacuum probably 200
horse power per acre could be obtained as net useful power in these
parts. This would be very satisfactory were it not for the cost of the
apparatus which is greatly increased by the necessity of employing a
storage plant sufficient to carry the load almost three-quarters of the
time.
The ambitious scheme proposed here draws power from the
depths of the sea, utilizing the warmth of one layer, brought into contact with the cold of another, to operate great power plants. Its practicability as well as the theory of its operation, is analyzed in this remarkable article.
The energy of light
rays, constituting about 10% of the total radiation, might be captured
by a cold and highly efficient process in photo-electric cells which may
become, on this account, of practical importance in the future. Some
progress in this direction has already been achieved. But for the time
being it appears from a careful estimate, that solar power derived from
radiant heat and light, even in the tropics, offers small opportunities
for practical exploitation. The existing handicaps will be largely
removed when the wireless method of power transmission comes into use.
Many plants situated in hot zones, could then be operatively connected
in a great super-power system to supply energy, at a constant rate, to
all points of the globe.
The sun emits,
however, a peculiar radiation of great energy which I discovered in
1899. Two years previous I had been engaged in an investigation of
radio-activity which led me to the conclusion that the phenomena
observed were not due to molecular forces residing in the substances
themselves, but were caused by a cosmic ray of extraordinary
penetrativeness. That it emanated from the sun was an obvious
inference, for although many heavenly bodies are undoubtedly possessed
of a similar property, the total radiation which the earth receives from
all
the suns and stars of the universe is only a little more than
one-quarter of one percent of that it gets from our luminary. Hence,
to look for the cosmic ray elsewhere is much like chercher le midi dans
les environs de quatorze heures. My theory was strikingly confirmed
when I found that the sun does, indeed, emit a ray marvelous in the
inconceivable minuteness of its particles and transcending speed of
their motion, vastly exceeding that of light. This ray, by impinging
against the cosmic dust generates a secondary radiation, relatively very
feeble but fairly penetrative, the intensity of which is, of course,
almost the same in all directions. German scientists who investigated
it in 1901 assumed that it came from the stars and since that time the
fantastic idea has been advanced that it has its origin in new matter
constantly created in interstellar space!! We may be sure that there is
no place in the universe where such a flagrant violation of natural
laws, as the flowing of water uphill, is possible. Perhaps, some time
in the future when our means of investigation will be immeasurably
improved, we may find ways of capturing this force and utilizing it for
the attainment of results beyond our present imagining.
The tides are often considered as a source of motive power and not
a few engineers have expressed themselves favorably in regard to their
use. But as a matter of fact, the energy is, in most places,
insignificant, the harnessing of the waterfall over an acre of ground
yielding but little more than one horse power. Only in exceptional
locations can the power of the tides be profitably developed.
It has been the dream of many an inventor to utilize the energy of
ocean waves, which is considerable. But although numerous schemes
have been advanced and much ingenuity shown in devising the mechanical
means, nothing of commercial value has so far resulted and the prospects
are very poor on account of technical difficulties and the erratic
character of this power source.
The force of the wind can be much more easily put to our service
and has been in practical use since times immemorial. It is invaluable
in ship propulsion and the windmill must be seriously regarded as a
power generator. If the cost of this commodity should greatly increase
we will be likely to see the countries dotted with these time-honored
contrivances. Unfortunately, the value of all this resources is very
much reduced by periodic and casual variations, and we are driven to
search for a source of constant twenty-four hour power comparable to
that of a waterfall. Thus we are led to consider terrestrial heat as a
possible fountain of unvarying energy supply.
Terrestrial Energy
It is noteworthy that already in 1852 Lord Kelvin called
attention.to natural heat as a source of power available to Man:. But,
contrary of his habit of going to the bottom of every subject of his
investigations, he contended himself with the mere suggestion. Later,
when the laws of thermo-dynamics became well understood, the prospects
of utilizing temperature differences in the ocean, solid earth or the
atmosphere, have been often examined. It is well-known that there
exists, in tropical seas, a difference of 50° F between the surface
water and that three miles below. The temperature of the former, being
subject to variations, averages 82° F, while that of the latter is
normally at least, at 32° F, or nearly so, as the result of the slowly
influx of the ice-cold polar stream. In solid land these relations are
reversed, the temperature increasing about one degree Fahr. for every
64 feet of descent. Very great differences are also known to exist in
the atmosphere, the temperature diminishing with the distance above the
earth's surface according to a complex function.
But while all this was of common knowledge for at least 75 years
and the utilization of the heat of the earth for power purposes a
subject of speculation, no decided attempt to this end seems to have
been made until an American engineer, whose name I have been unable to
ascertain, proposed to operate engines by steam generated in high vacuum
from the warm surface water and condensed by the cold water pumped from
a great depth. A fully and carefully worked out plan of this kind,
supported by figures and estimates, was submitted by him to prominent
capitalists and business men of New York about 50 years ago. He not
only contemplated the production and distribution of power for general
use but intended even to propel boats by energy derived in the same
manner, using, preferably, ether as working fluid. On account of his
death, or for other reasons, the project was not carried into practice.
Of this I learned much later when I interested in my alternating
system Alfred S. Brown, a well known technical expert, called upon to
examine the merits of my investigations, and C. F. Peck, a
distinguished lawyer, who organized a company for their commercial
introduction. These men were among the first approached by the
engineer and considered his plan rational in principle, but the pipe
lines, pumps, engines, boilers and condensers involved too great an
outlay and, besides, a profitable disposal of the power was difficult
and uncertain. My discovery of the rotating magnetic field brought
about a change in the situation and in their attitude. They thought
that if the energy could be economically transmitted to distant places
by my system and the cost of the ocean plant substantially reduced, this
inexhaustible source might be successfully exploited. Mr. Peck had
influential connections, among them John C. Moore, the founder of the
banking house bearing his name. With the exception of the late J. P
. Morgan, who towered above all the Wall Street people like Samson
over the Philistines, Moore was probably the strongest personality. I
was given to understand that if I could evolve a plan satisfactory to
Mr. Brown and other engineers, all the capital required for an
enterprise on a very large scale, as contemplated by them, would be
promptly furnished. No encouragement from my associates was needed for
determining me to undertake the task, as the idea appeared, at first,
wonderfully promising and attractive although there was nothing about it
fundamentally new.
Undoubtedly, the essential conditions required to operate a steam
or other thermo-dynamic engine could be fulfilled, a considerable
temperature difference being available at all times. No proof had to
be furnished that heat would flow from a higher to a lower level and
could be transformed into mechanical work. Nor was it necessary to
show that the surface water, although much below its normal boiling
point of 212° F, can be readily converted into steam by subjecting it to
a vacuum which causes ebullition at any temperature however low. It
is of common knowledge that, due to this same effect, beans cannot be
cooked or eggs hard-boiled on high mountains. Also, for a like reason
turbines have been wrecked in steam power plants with the boilers
completely shut off, the slightly warm water in the system of connecting
pipes being evaporated under a high vacuum inadvertently applied.
This behavior of water, or liquids in general, was long before
beautifully exemplified in the classical device called “cryophoros”
consisting of two communicating and exhausted bulbs partially filled
with liquid, which is evaporated in one and condensed in the other. It
was invented by W. H. Wollaston, a great English scientific man and
investigator (1766-1828), who first commercialized platinum and was
credited by some to have anticipated Faraday in the discovery of
electromagnetic rotation. The original instrument brought out at the
beginning of the nineteenth century had one of the bulbs packaged in ice
with the result of freezing water in the other. Conformably to the
views of that time it was thought that the cold of the ice was carried
to the water and so the Greek name, meaning “cold-carrier”, was given to
the device. But now we know that the process is of opposite
character, the freezing being brought about by the transport of the
latent heat of evaporation from the warm to the cold bulb. One would
naturally infer that the operation would cease as soon as the water is
frozen at the surface, but curiously enough the ice itself continues to
yield steam and it is only because of this that all of the water is
solidified. We may imagine how puzzling this phenomenon appeared more
than one century ago!
The “cryophorus” is well-known as a scientific toy,
exemplifying also the principle of refrigerating machinery.
The ocean plant proposed by the engineer was nothing else but
Wollaston's device of huge proportions, adapted for continuous operation
and having an engine interposed between the two communicating vessels.
In estimating its thermo-dynamic performance the first results I
arrived at through the medium of pad and pencil fairly bewildered me.
To illustrate by an example, suppose that equal quantities, say,
one-half pound of the warm and of the cold water, respectively, at 82°
and 32° Fahrenheit, are mixed or put in thermal equilibrium otherwise.
The first will then give up to the second 12.5 heat units, mechanically
equivalent to 9725 foot pounds—the same energy which would be developed
in the fall of one pound from so great an altitude as 9725 feet. The
dream of my life had been to harness Niagara, but here was a fall sixty
times higher and of unlimited volume. To raise the cold water to the
surface from any depth whatever, required but a trifling effort and as
other losses also seemed negligible I concluded that if only a small
portion of this hypothetical fall could be utilized, one of the greatest
problems confronting humanity would be solved for all times to come.
I knew that it was to good to be true, nevertheless I followed
this ignis fatuus for years until, little by little, through close
reasoning, calculation and experiment, I got the true bearings in the
swamp of my ignorance and doubt. Then this scheme of harnessing the
ocean revealed itself to my mind as one of the crudest imaginable.
Just to transport a little heat, water has to be pumped and disposed of
in quantities so enormous that a large installation of this type would
present new problems in engineering. Contrary to the opinion I had
previously formed, this involved the expenditure of a great amount of
energy. Then I realized that the gases contained in the water can be
only partially extracted and have to be continuously removed from the
condenser to prevent the rise of back pressure which might reduce the
speed and eventually stop the engine.
Furthermore, due to certain conditions, the deep sea water must
enter the pipe warmer than it should conformably to soundings, so that
the full temperature difference cannot be obtained, and I discovered
other peculiar causes which, after some time, might seriously interfere
with the proper functioning of the mechanism. The steam, raised
directly from the surface water, is of the poorest quality, mere mist
under small pressure, and its consumption per horsepower hour was likely
to be twenty times greater than in modem plants. In hydro-electric
stations, as before stated, eighty-five percent of the energy of falling
water may be captured, while in this case hardly more than two-tenths
of one percent of the theoretical fall can be utilized. Worst of all,
the size and cost of the equipment is utterly out of proportion to the
greatest possible returns. These and other limitations and
difficulties forced themselves upon me in studying the plans as first
submitted.
The introduction of my alternating system started a scramble for
the most valuable water power sites and no attempt was made to harness
the ocean. But my interest was aroused to such a degree that I
continued the work and made a number of improvements which are thought
to possess some merit. Satisfied that pipes supported by floats or
hung in submarine abysses were impracticable, I proposed a sloping
tunnel, lined with heat insulating cement, affording a smooth and
unbroken passage for the deep sea water. I found ways of simplifying
and cheapening the apparatus and making it more effective by reducing
the moisture of the steam and otherwise, and these advances may
eventually prove of practical value.
To conduce to a more ready understanding of the evolution of the
ocean power plant from the cryophoros and of the nature of some of my
improvements, reference may be made to the drawings in which Fig. 1
represents the original device of Wollaston, comprising two highly
exhausted vessels B and C, respectively, the boiler and condenser,
connected through a channel A. The first named vessel being partly
filled with water or other liquid and the second packed in a freezing
mixture, the vacuum causes the water when slightly warmed to boil
furiously and the well known effect is observed. As the steam
generated in the boiler rushes into the condenser with great speed, it
is capable of producing a considerable mechanical effort.
Fig. 2: Plan of a system whereby the transfer of vapor between
two vessels at different temperatures drives the armature of electrical generator.
Fig. 2 illustrates how the thermo-dynamic transformation of energy
may be effected to obtain useful external work. This particular
arrangement is chosen in order to dispense with the necessity of a
connection to the outside which would call for the employment of a
vacuum pump. A steel armature a, of a diameter nearly equal to that of
the channel A, connecting vessels B and C, and shaped like a fan, is
supported in virtually frictionless bearings b and c, of which the
latter may be designed for taking up the thrust. Surrounding the
armature, or turbine rotor, and in close proximity to the same, are
soft-iron projections as d and e, wound with coils f and 9 and forming
part of a permanent magnet h. The rapid rotation of the armature
results in a periodic shifting of magnetic lines from one to the other
set of projections, this inducing in the coils currents which may be
utilized.
The next step is to adapt the device for continuous operation.
This may be done in two ways: by supplying the evaporating and
condensing water directly to the vessels B and C, or by merely
transmitting and abstracting heat through their walls, in which case the
working fluid is entirely separated and circulated in a closed circuit.
Fig. 3: A more complete sketch of the thermodynamic system,
in which the necessary degree of vacuum is produced by the suction pump E.
The first plan is
diagrammatically shown in Fig. 3. The vessels B and C are cylinders
joined by a turbine D through suitable pipe connections. A suction
pump E, constructed for producing a very high vacuum, is attached to the
condenser C and may be driven by the turbine through a gear or, as
indicated, by an induction motor energized with alternating currents
from the dynamo F coupled to the turbine. The water being under
atmospheric pressure would flow into the evacuated vessels at too great a
speed occasioning corresponding losses, and for this reason it is
necessary to supply and drain it through balancing barometric columns ii
and kk of proper height thereby insuring the desired circulation, the
direction of which is indicated by arrows. Since the latent heat
absorbed in evaporation and set free in condensation is very great, an
immense quantity of water must be circulated through the vessels in
order to prevent changes of temperature sufficient to seriously reduce
the performance of the apparatus. In addition to the devices shown,
separators must be employed for extracting gases from the water before
its entrance into the boiler and condenser. These cannot be of the
effective centrifugal type as they would entail too great a loss of
energy. The only kind practicable is that used from the earliest
beginnings of modern hydraulic, the action of which is based on a slow
reversal of direction of flow and accomplishes only partial
degasification. It should be noted that the gases, by rapid expansion
and attendant cooling, impair greatly the quality of the steam and also,
more or less, the vacuum in the vessels. One of my improvements is to
supply the water in the form of jets, as represented, which furnish the
necessary evaporating and condensing surface while at the same time
carrying away gases which would be liberated if the water were admitted
as usual.
Fig. 4: Here the water, or other fluid operating the turbine D is kept in
a closed system, circulating through condensers immersed in water of different temperatures.
A careful study of
the scheme illustrated in Fig. 3 has satisfied me that it is, for a
number of reasons, disadvantageous and less practicable than that shown
in Fig. 4. In this instance the vessels B and C are surface
condensers of ordinary design but of very great active areas in view of
the excessive steam consumption and small differences of temperature
supplied. They may be of the same size, for although the passage of
heat from the hot to the cold water takes place through the steam, the
law of mixtures is obeyed, the maximum transfer occurring when the
quantities of both are equal. Were it not for that the performance
might be appreciable improved by supplying the hot water, which has to
pass only through short pipes, in greater quantity. The vessels are
connected through a turbine D coupled to a generator F, as before, and
besides the suction pump E a deep well pump G is employed to force the
condensate into the boiler. The water should be sweet and thoroughly
degasified yielding steam of good quality and greatly reducing the work
of the pumps, and both boiler and condenser should be completely
immersed in the circulating media to minimize the heat losses. The
important practical advantages of this plan are that any suitable
working fluids and units of very great capacity may be used.
Technical experts who may examine the merits of the ocean power
scheme will be apt to dismiss lightly the loss of energy involved in the
propulsion of the hot and cold water which in reality, may be very
serious on account of the lift above the mean ocean level. The outlets
are unavoidably very large and if their centers are from three to four
feet above the mean level to insure normal functioning at high tide the
pumping losses will be considerable. Furthermore, the water is
subjected to repeated changes in direction and velocity and suffers a
frictional loss of head, especially in the long conduit, all of which
may be equivalent to an additional life of a few feet, making the total,
say, 7 feet, conservatively estimated.
Now, in the Gulf of Mexico or in Cuban waters, where my associates
intended to build plants, the temperature difference between the hot
and cold water will be hardly more than 36° F as an annual average, and
with the poor steam obtainable the circulation may be as much as 12
Ibs. of each per horse power per second. Consequently, the
mechanical work may be estimated at 108 foot pounds per second and this
figure must be almost doubled because the overall efficiency of
induction motor-driven pump units, which have to be employed, is not
much above fifty percent, as a rule. Since one horse power is a rate
of 550 foot pounds per second this means a loss of about 40 percent.
Besides, the operation of the degasifiers, vacuum and deep well pumps,
will consume energy which has to be supplied from the turbo-generator
and taken at nearly twice its value for the reason pointed out. All
these losses may be reduced in various ways but not to a very great
extent, and the example clearly shows the desirability of doing away
with them. This argument is applicable, even with greater force, to
the cost of the pumping outfits of which I will endeavor to convey an
idea by assuming that a 30,000 horse power plant is installed, requiring
not less than 300,000 pounds of hot and of cold water per second, which
means, approximately, 4,700 cubic feet of each. As a velocity of 3
feet per second should not be exceeded, two pumps of meeting the
requirements would have intake and outlet openings of 1800 square feet,
with the usual allowances. Evidently such monstrous machines could not
be used, for one reason, not to mention others, that the lift would be
very great and the loss incurred prohibitive. This brings to light a
bad feature of the scheme illustrated in Fig. 3, namely, that it is
impracticable to have recourse to very large units and thereby secure
the customary advantages. A great number of small units must be of
necessity used and it follows that the larger the plant the poorer it
will be. Instead of the two pumps each with openings of 1800 square
feet, at least one hundred motor-driven pumps with orifices of 36 square
feet and a corresponding number of boilers and condensers with enormous
inlet and outlet pipes would have to be employed, and at a staggering
cost.
Fig. 5: The basins H and I are filled and emptied by the tide,
saving much of the energy otherwise expended in pumping.
These and other similar considerations have prompted me to devise
the plan schematically shown in Fig. 5 in which I do away entirely with
the water pumps by relying wholly on ebb and tide to bring about the
required circulation of the heating and cooling media, thus simplifying
the plant and obviating great losses and expenditures. The
installation comprises two very large basins lined with heat insulating
cement designated by H and I and provided with suitable supports for
heat-insulating roofs or covers the function of which is to minimize
losses by radiation and influx of heat, respectively, from the hot and
to the cold water. Each of the basins has a controllable opening,
respectively K and L situated close to the bottom, where also the boiler
B and condenser C, are located. The latter are connected through a
turbine D coupled to a generator F, constituting a unit of large
capacity. As in the case before described, a suction pump E and a deep
well pump G are provided, driven by induction motors energized from the
generator. All this machinery is placed on a common foundation, as
indicated. The basins are filled at high tide and the outflow during
the period of ebb is controlled so as to secure the best results.
Although the power plant is subject to periodic variations, the plant
can be operated satisfactorily without the employment of batteries or
other means of storage and thus the cost of this commodity may be
greatly reduced.
Fig. 6: A floating thermo-electric power plant, in which
the condenser C is suspended beneath the boiler B and the condensate circulates vertically.
Another way of deriving power from the temperature differences in
the ocean without the use of water pumps is illustrated in Fig. 6.
The apparatus comprises the same essential parts which have been already
described, namely, a tubular boiler B and like condenser C connected
through a turbine D driving a generator F, a high vacuum pump E and a
small reciprocating deep-well pump G for lifting the condensate from the
condenser into the boiler. The latter is supported in the warm
surface water by a floating structure carrying all the machinery , while
the former is suspended at a suitable depth in the cold water. Both
of these parts are arranged with the tubes in vertical position insuring
a good circulation of the heating and cooling media. This arrangement
is very simple and effective but the raising of the condensate by pump G
consumes considerable work. I have designed wireless power plants on
this plan with practical objects in view and they may perhaps find
valuable uses in the future.
Fig. 7: Design of a vessel to be propelled by energy derived from
temperature differences in the water. The symbols designating the operating mechanism are explained in the text.
Fig. 7 represents a partial view of a boat with apparatus for
propelling it solely by the heat energy abstracted from the water. I
was not informed just how the American engineer intended to propel his
vessel and the scheme illustrated is my own. Two rotary pumps M and N
are employed to force the warm and cold water, respectively, through the
tubes of the boiler B and condenser c. This apparatus is placed
slightly below the waterline for minimizing the losses involved in the
circulation of the heating and cooling media. The pumps are supposed
to be driven by induction motors, as illustrated, and are connected to
the discharge pipes and other parts in such a way that the water cannot
enter the hold of the vessel. The boiler intake O is near the oceans
surface while that of the condenser is at the requisite depth; a
streamline shaped duct O 1, open in front, being employed for the
purpose. As the temperature of the water diminishes very rapidly
through a limited distance from the surface of the ocean, sufficient
energy can be abstracted from the water using a duct of fifty feet
length to propel the boat by the streams escaping through the discharge
pipes. No other means of propulsion is necessary and even the steering
can be accomplished by suitably regulating the volume of the two
streams discharged astern as shown. The turbine D, generator F, high
vacuum pump E, deepwell pump G and other parts serve the same purposes
as before. Some stored energy must be provided to start the vacuum
pump and thereby initiate the operation of the apparatus.
The ocean power plan of the illustration on page 208 seems very
inviting when considering that the energy obtained is proportionate to
the quantity of the water pumped and, therefore, virtually unlimited.
But it must be remembered that the true merit of such a scheme can only
be measured by the returns. We have still greater and more readily
available resources which are unused because they are unprofitable. On
closer investigation many discouraging facts are unearthed. The deep
sea water is, normally, at a low temperature but at any time a warm
current of water may be produced and render the plant useless. It has
been observed that there may be differences of 35° F or even more in the
temperature of water at the same depth. Just as convection currents
occur in the air so they may also be produced in the ocean and this is
an ever present menace to an undertak ing of this kind. It also
appears the actually obtainable temperature difference must be always
appreciably smaller than might be inferred from soundings. The raising
of the denser water below a certain niveau into the less dense above it
involves a performance of work which must be done by the pump but is
not lost as the volume of the water discharged at the top of the
deep-sea duct is correspondingly increased. This does not hold true of
the water above the niveau and, consequently, the flow into the intake
of the duct takes place preponderatingly from above, that is, in the
direction of the downward convection current. Owing to this, warm
water from above enters the intake thus reducing the temperature
difference. Another curious fact cannot be ignored. The sea is
densely populated with organisms which are subject to changes caused by
age. As they grow older the life stream deposits more and more solid
matter, they become specifically heavier and sink gradually until
finally at great depths life is extinct. If this floating matter could
be removed by the pump at a constant rate, as the water, it would give
relatively little trouble. But as water is removed the concentration
of this matter continuously increases and may become so great as to
interfere seriously with the operation of the plant. Impairment of
performance, if not interruption, might also be brought about by rust
and deposits in the pipes, loosening of joints and other mishaps and for
this reason I consider a tunnel as the practicable means for
transporting the cold water.
I have studied this plan of power production from all angles and
have devised apparatus for bringing down all losses to what I might call
the irreducible minimum and still I find the performance too small to
enable successful competition with the present methods.
The utilization of temperature differences in the solid earth
presents several important advantages. It would make it unnecessary to
go to the tropics where power is of smaller value. Indeed, the colder
the climate the better. A shaft could be sunk in the midst of a
densely populated district and a great saving effected in the cost of
distribution. The shaft would be costly, of course, but the apparatus
cheap, simple and efficient. The first drawing, on page 208,
illustrates its essential parts comprising a boiler at a great depth, a
condenser, cooled by river or other water available, on the ground, a
turbine coupled to a generator, and a motor-driven high vacuum pump.
The steam or vapor generated in the boiler is conveyed to the
turbine and condenser through an insulated central pipe while another
smaller pipe, likewise provided with an adiathermanous covering serves
to feed the condensate into the boiler by
gravity (see also "Sea
Power Plant Designed by Tesla"). All that is necessary to
open up unlimited resources of power throughout the world is to find
some economic and speedy way of sinking deep shafts.
* * *
* *
Whether we shall
have to rely on power derived from terrestrial heat must be left to the
future. If we should exhaust our present resources without opening up
new ones, this possibility might arise. Undoubtedly, our stores of
coal and oil will be eventually used up and there is not enough water
power to supply our needs. The idea of obtaining motive energy from
atoms or change of elements is unscientific and illusionary and cannot
be condemned too emphatically. The same is true of the scheme of
harnessing the energy supposed to be liberated at such temperatures as
40,000,000 degrees C (Centigrade) recently suggested. The fundamental
fallacy in all these proposals is that it takes more energy to
disintegrate than can be usefully recovered even in an ideal process.
Glaringly fallacious theories are responsible for such chimerical
hopes. Probably the worst of these is the electron theory. Of the
four or five atomic structures which have been suggested not a single
one is possible. Not more than one in a thousand men of science knows
that an electron -whatever it be—can only exist in the perfect vacuum of
intermolecular and interstellar spaces or highly exhausted tubes and
that the nucleus stripped of electrons, is devoid of energy.
It was clear to me many years ago that a new and better source of
power had to be discovered to meet the ever increasing demands of
mankind. In a lecture delivered before the American Institute of
Electrical Engineers at Columbia University May 20, 1891, I said: “We
are whirling through endless space with inconceivable speed, all around
us everything is spinning, everything is moving, everywhere is energy.
There must be some way of availing ourselves of this energy
more directly. Then, with the light obtained from the medium,
with the power derived from it, with every form of energy obtained
without effort, from the store forever inexhaustible, humanity will
advance with giant strides.”
I have thought and worked with this object in view unremittingly
and am glad to say that I have sufficient theoretical and experimental
evidence to fill me with hope, not to say confidence, that my efforts of
years will be rewarded and that we shall have at our disposal a new
source of power, superior even to the hydro-electric, which may be
obtained by means of simple apparatus everywhere and in almost constant
and unlimited amount.
* * *
* *
Excerpt from "Sea
Power Plant Designed by Tesla," ". . . while the
condensed water flows by gravity through another pipe reaching to depth
at which the temperature of the ground exceeds that of the condensate.
By circulating the steam in great volume through the turbine and
condenser I am able to maintain a considerable temperature difference
between the ground and the interior of the shaft, so that a very great
quantity of heat flows into the same continually; to be transformed into
mechanical work. The only requisite is a sufficient volume of cooling
water.
"By this method it
is practicable to supply all the power which a small community may
require from a shaft of moderate depth, certainly less than a mile.
And for isolated dwellings a few hundred feet depth would be ample,
particularly if such a fluid such as ether is employed for running the
turbine."
[New York Times, Nov. 8, 1931.]
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