Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 ~7325~ T~XR;002
GENERATION OF ENERGY BY MEANS
OF A WORKING FLUID, AND
REGENERATION OF A WORKING FLUID
This invention relates to the generation of energy
by means of a working fluid, and to the regeneration of a
working fluid. More particularly, this invention relates
to a method of and to apparatus for generating energy by
means of a working fluid and for regenerating such a
working fluid.
In the generation of energy by expansion of a working
fluid, the energy whic/h can be produced by expansion of
the working fluid is limited by the temperatures at which
heating and cooling mediums can economically he provided
for regeneration of the working fluid. The result is,
therefore, that such a working fluid is expanded from a
high pressure charged level to a low pressure spent level,
with the high pressure charged level being governed by the
maximum pressure at which the working fluid can be evapor-
ated with the available heating medium, and with the spent
low pressure level being governed by the minimum pressure
at which the working fluid can be condensed with the
available cooling medium.
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~ 17325~
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In practice, therefore, expansion of the working fluid
is controlled to provide a spent low pressure level at which
the condensation temperature of the working fluid is greater
than the temperature of the cooling medium, to permit con-
densation of the working fluid.
In addition, in practice, regeneration is based on
condensation of working fluid in a condenser wherein the
working fluid is arranged to flow in heat exchange rela-
tionship with an available cooling medium. Because of thedesire to achieve maximum expansion of the working fluid,
regeneration of working fluid is often effected where the
temperature difference between the condensation tempera-
ture of the spent working fluid at the spent level and the
temperature of the available cooling medium is marginal--
often as low as 1C. This of necessity imposes a require-
ment for a large condenser with an extensive heat exchange
surface, and for a large supply of cooling medium, thereby
substantially adding to the operating costs.
This is particularly significant where sevére re-
straints are imposed by the temperatures of available
heating and cooling mediums as in the case of ocean
thermal energy conversion systems.
2S
In accordance with one aspect of the invention, there
is provided a method of generating energy, which comprises
expanding a gaseous working fluid from a charged high
pressure level to a spent low pressure level to release
energy, and regenerating the spent working fluid by, in a
plurality of successive regeneration stages:
; (a) condensing the working fluid in an absorption
stage by dissolving it in a solvent solution
'
3257
-- 3 --
while cooling with a cooling mediurn,the solvent
solution comprising a solvent having an initial
working fluid concentration which is sufici~nt
to provide a solvent solukion boiling range suit-
able for absorption of the working ~luid;
(b) increasing the pressure of the solvent solution
containing the dissolved working fluid and eva-
porating the working fluid being regenerated by
heating in an evaporation stage;
(c) feeding the evaporated working fluid to a suc-
ceeding regeneration stage;
(d) recycling the balance of the solvent ~olution
remaining after evaporation of the working fluid, `~to constitute the solvent solution for the ab-
sorption stage of that regeneration stage; and
(e) withdrawing regenerated charged working 1uid
from a final regeneration stage for re-expansion
to release energy.
In accordance with a further aspect of the invention
there is provided a method of optimizing, within limits im-
posed by available sources of cooling and heating mediums,
the energy supply capability of a gaseous working fluid
which is expanded from a charged high pressure level to a
spent low pressure level to provide available energy, the
method comprising expandiny the gaseous work.ing fluid to
a spent low pressure level where the condensation tempera-
ture of the working fluid is below the minimum temperature
of the available cooling medium, and regenerating the spent
working fluid by, in a plurality of successive incremental
30 regeneration stages: ~.
(a) condensing the working fluid being regeneratad in
an absorption stage by dissolving it in a solvent
solution while cooling with the cooling medium,
the solvent solution ccmprising a solvent having
an initial working fluid concentration which is
sufficient to provide a solvent solution boiling
range suitable for absorption of the working fluid;
~ 4 --
(b) increasing the pressure of the solvent solution
containing the dissolved working fluid, and eva-
porating khe working fluid being regenerated by
heating in an evaporation stage with the avail-
able heating medium;
(c) feeding the evaporated working fluid to a suc-
ceeding regeneration stage for condensation;
(d) recycling the balance of the solvent solution
remaining after evaporation of the working fluid
being regeneratèd, to constitute the solvent
solution for the absorption stage of that regener-
ation stage; and
(e) withdrawing regenerated working 1uid from a inal
regeneration stage.
The spent working fluid may thus be regenerated by
feeding it to a first regeneration stage, feeding the eva-
porated working fluid from each regeneration stage to a
succeeding regeneration stage or further regeneration,
and recycling within each regeneration stage the solvent
solution remaining after evaporation of the working fluid
in the evaporation stage of that regeneration stage for
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3~7
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the recycled solvent solution to constitute the solvent
the solvent solution for the absorption stage of that
regeneration stage.
The working fluid may be expanded to a spent low
pressure leYel where the condensation temperature of the
gaseous working fluid is below the minimum temperature of
the cooling medium in the absorption stage.
Further in accordance with the invention, ~here is
provided a method of opti~i~ing, within limits imposed by
available sources of cooling and hea~ing mediums, the
energy supply capability of a gaseous working fluid which
is expanded from a charged high pressure level to a spent
15 low pressure level to provide available energy, the method
comprising expanding the gaseous working fluid to a spent
low pressure level, and regenerating the spent working
fluid by, in a plurality of successive regeneration
stages, condensing the working fluid and then evaporating
the working fluid at an increased pressure, the working
fluid being condensed in each regeneration stage by
absorbing or dissolving it in a solvent sol~tion while
cooling with the cooling medium, the solvent solution
comprising a solvent having, in each stage, an initial
working fluid concentration which is sufficient to provide
a solvent solution boiling range suitable for absorption
of the working fluid, and the working fluid being evapo-
rated in each stage by increasing the pressure to a level
where the working f~uid being regenerated can be evapo-
rated with the available heating medium, and then evapo-
rating the working fluid.
The invention further extends to apparatus for gen-
erating energy, the apparatus comprising expansion means
for expanding a gaseous working fluid from a charged
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1 17325~
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high pressure level to a spent low pressure level to
release energy, and a plurality of successive regeneration
stages foe regenerating such a spent working fluid, each
regeneration stage comprising:
(a) an absorber for receiving both a spent working
fluid and a solvent solution for dissolving or
absorbing the spent working fluid, the absorber
having cirulation means for circulating a
cooling medium through it to cool it;
(b) a pump for pumping a resultant solvent solution
from the absorber to increase its pressure;
(c) an evaporator for receiving a resultant solvent
solution from the pump, the evaporator having
circulation means for circulating a heating
medium through it to heat it to evaporate such
a working fluid to be regenerated;
(d) a separator for separating such an evaporated
working fluid being regenerated, from such a
solvent solution;
(e) feed means to feed such an evaporated working
fluid to the absorber of a succeeding regenera-
tion stage;
(f) recycle means for recycling a solvent solu~ion
from the separator to the condenser;
and a feed conduit for feeding a regenerated working fluid
from the separator of a final regeneration stage to the
expansion means.
1 1~3257!
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Since the solvent solution in each regeneration stage
is recycled, the solvent solution constitutes a closed
loop in that stage, and is separate from the solvent
solution in each other regeneration stage. Furthermore,
in each regeneration stage, the quantity o~ working fluid
being regenerated is dissolved in the solvent solution of
that stage, and the equivalent quantity of working fluid
being regenerated is evaporated from the solvent solution
in the evaporation stage of each regeneration stage.
It will be appreciated that the quantity of solvent
solution, and the initial concentration of working fluid
in the solvent solution in each regeneration stage will be
separately adjusted as may be required for specific oper-
ating conditions, and as may be required for variationsin the minimum temperature level of an available cooling
medium.
The solvent of the solvent solution may be any suit-
2~ able solvent which is a solvent for the working fluid,which has a boiling point above the maximum temperature
which wil] be attained in any evaporation stage, and which
will provide a solvent solution when working fluid is dis-
solved therein, which has a boiling point which decreases
as the concentration of worlcing fluid increases.
While the solvent solution is preferably a binary
solution, it will be appreciated that it may be a solution
of a plurality of li~uids.
A number of working fluids which would be suitable,
are known to those skilled in the art. Any of such
working fluids may be employed in this invention.
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1 17325~
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In one embodiment of the invention, the working
fluid and solvent may be in the form of hydrocarbons
having appropriate boiling points. Thus, for example, the
solvent may be in the form of butane or pentane while the
working fluid may be in the form of propane. In an
alternative example, the working fluid may be an appro-
pria~e freon compound, with the solvent being an appro-
priate solvent for that compound.
In a preferred embodiment of the invention, the
working fluid is in the form of ammonia and the solvent is
in the form of water. In this embodiment of the inven-
tion, at a pressure of one atmosphere the boiling point of
water is 100C whereas the boiling point of pure ammonia
is -33C~ As the concentration of ammonia in water
increases, the boiling point of the aqueous ammonia
solution will decrease. From binary phase diagrams of
water and ammonia solutions, the appropriate initial
concentration of ammonia in the solvent solution for each
regeneration stage, can readily be determined for this
invention from the pressure and temperature which will
prevail in each condensation stage.
In a preferred embodiment of the invention~ the
initial concentration of working fluid in the solvent
solution in each regeneration stage, and the proportion of
solvent solution to working fluid to be regenerated will
be selected so that after complete absorption of the
working fluid being regenerated in the absorption stage of
that regeneration stage, the solvent solution will have a
boiling point marginally above the minimum temperature
attained in that absorption stage during use.
1 173257
g
In practice, therefore, the minimum quantity of
solvent solution will be employed which will satisfy this
requirement thereby reducing cooling medium requirements
to the minimum, and thereby further reducing heating
medium requirements to the minimum.
It will be appreciated that since the pressure is
increased between the absorption stage and evaporation
stage of each regeneration stage, there will be a step-
wise or incremental increase in pressure between eachpreceeding regeneration stage and each succeeding re-
generation stage. It follows, therefore, that the initial
concentration of working fluid in the solvent solution for
each successive regeneration stage will be correspondingly
lS higher to provide a boiling range for the solvent solution
in each stage which is suitable for dissolving or absorb-
ing the working fluid at the pressure prevailing in that
stage.
In a preferred embodiment of the invention~ the
pressure is increased between the absorption and evapora-
tion stages of each regeneration stage, to the maximum
pressure at which the working fluid being regenerated can
be evaporated effectively in the evaporation stage by the,
or by a heating medium, available for heating the evapor-
ation stage.
The pressure is, therefore, preferably increased in
each regeneration stage to the maximum level where the
solvent solution in each evaporation stage will, after
evaporation of the working fluid in that stage, have a
boiling point marginally below the maximum temperature
attainable in that evaporation stage.
1 173~5~
--1 o--
By appropriate control of the pressure, evaporation
of the required quantity of working fluid being regener-
ated can be readily effected in each evaporation stage.
Control valve means may, however, be provided to control
the quantity of evaporated working fluid which is fed from
each regeneration stage to each succeeding regeneration
stage. Thus, if a greater quantity of working fluid than
that required Eor regeneration has been evaporated in an
evaporator stage, only the required quantity will pass to
the succeeding regeneration stage. The balance will be
recycled with the solvent solution.
The method of this invention may preferably include
the step of, in each regeneration stage, feeding the
solvent solution and evaporated working fluid from the
evaporation stage to a separation stage for separating the
working fluid being regenerated.
The separator stage may be provided by a separator of
any conventional suitable type known to those skilled in
the artO
The solvent solution which is recycled to the absorp-
tion stage in each regeneration stage, is conveniently
expanded to reduce its pressure to a pressure correspond-
ing with or approaching that of the pressure of the
working fluid being regenerated in that absorption stage.
In a preferred embodiment of the invention, in
each regeneration stage, the solvent solution which is
recycled, is recycled in heat exchange relationship with
the evaporation stage to thereby reduce the heating medium
requirements for the evaporation stage.
1 ~7325~
-1 1-
The solvent solution which is recycled in each
regeneration stage, may be recycled at least partially in
heat exchange relationship with the absorption stage.
Where the recycled solvent solution is recycled in
heat exchange relationship with an absorption stage, the
coolinc medi~m requirement will decrease because the
quantity of heat to be removed will remain constant, but
the capacity of the absorption stage will have to be
increased. Conversely, if the recycled solvent solution
is not recycled in heat exchange relationship with the
absorption stage, the capacity of the absorption stage
will decrease while the requirement of cooling medium will
increase.
In practice, therefore, depending upon the source
and availability of the cooling medium, on the basis of
economic considerations, the reduced cost o supplying
lesser quantities of cooling medium can he balanced
against the capital costs of increasing the capacity of
the absorption stages to determine whether the rec~cled
solvent solution should be recycled in heat exchange
relationship, or at least partially in heat exchange
relationship with the absorption stages, or not at all.
In an embodiment of the invention, all of the absorp-
tion stages of the regeneration stages may be carried out
separately in a single composite absorption stage which is
cooled by means of cooling medium from a common source.
Furthermore, all of the evaporation stages may be carried
out separately in a single composite evaporation stage
which is heated by means of a heating medium irom a common
source.
1173257.
-12-
The apparatus of this invention may, therefore,
include a single composite absorption unit and a single
composite evaporation unit, with all the absorbers of the
various regeneration stages being incorporated in the
absorption unit, and all the evaporators of the various
regeneration stages being incorporated in the evaporated
unit.
While this invention may have various applications,
1~ and while various types of cooling and heating means known
to those skilled in the art, may be employed, this inven-
tion can have particular application in regard to the
utilization of readily and economically available cooling
and heating mediums for the generation of energy.
The invention can, therefore, have specific applica-
tion where low temperature diEferential heating and
cooling mediums are employed.
A pre~erred application of the invention would,
therefore, be in the field of thermal energy conversion
using cool water withdrawn from a body of water as the
cooliny medium, and using, as heating medium, hot water
from a body of water, water heated by sclar heating,
hot water heated additionally by solar heating means, or
water or heating fluid in the form of waste heat fluids
from industrial plants.
A preferred application of the invention would,
3~ therefore, be in the field of ocean thermal energy con-
version [OTEC] where ocean surface water is used as the
heating medium and ocean water withdrawn from a sufficient
depth from an ocean is used as the cooling medium, thereby
resulting in a low temperature diferential between the
heating and cooling mediums.
1 173257.
-13-
Normally, ocean water would be withdrawn from a depth
of about 200 feet to provide the most economi~al cooling
medium at the lowest temperature. The temperature does
not tend to decrease significantly beyond a depth of about
200 feet.
A further preferred application of the invention
would be in regard to solar ponds for supplying the
heating medium, and also the cooling medium if desired.
The invention further extends to a method of increas-
ing the pressure of a gaseous working fluid from an
initial low pressure level to a high pressure level
utilizing an available heating medium and utilizing an
available cooling medium, which comprises incrementally
increasing the pressure of the working fluid by, in a
plurality of successive incremental regeneration stages:
(a) absorbing the working fluid being regenerated
in an absorption stage by dissolving it in a
solvent solution while cooling with such an
available cooling medium; the solvent solution
comprising a solvent having an initial working
fluid concentration which is sufficient to
provide a solvent solution boiling range suit-
able for absorption of the working fluid;
(b) increasing the pressure of the solvent solution
containing the dissolved working fluid, and
evaporating the working fluid being regenerated
in an evaporation stage by heating with such an
available heating medium;
~ 1732~
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(c) feeding the evaporated working fluid which is at
an increased pressure level, to a succeeding
regeneration stage for absorption;
(d) recycling the balance of the solvent solution
remaining after evaporation of the working fluid
being regenerated, to constitute the solvent
solution for the absorption stage of that regen-
eration stage; and
(e) withdrawing regenerated working fluid from a
final regeneration stage.
The expansion of the working fluid from a charged
high pressure level to a spent low pressure level to
release energy may be effected by any suitable conven-
tional means known to those skilled in the art, and the
energy so released may be stored or utilized in accordance
with any of a number of conventional methods known to
those skilled in the art.
In a preferred embodiment of the invention, the
working fluid may be expanded to drive a turbine of
conventional type.
In an embodiment of the invention, where the mass
ratio between the solvent solution being recycled through
an absorption stage and the working fluid being regener-
ated is sufficient, the pressure of the solvent solution
leaving the evaporation stage may be utilized to increase
the pressure of the working fluid being regenerated which
is introduced into the absorption stage with the recycled
solvent solution.
3L ~73257
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In this embodiment of the invention, instead of ex-
panding the solvent solution which is recycled to reduce
its pressure to a pressure corresponding with or approach-
ing that of the pressure of the working fluid being
regenerated in an absorption stage, the solvent solution
~ay he injected into the absorption stage in such a manner
as t~ entrain the working fluid and draw the working fluid
into the absorption stage.
Various injection systems are known to those skilled
in the art which could be used for this purpose. As an
example, an injection system such as an injection nozzle
having a restricted zone to create a zone of low pressure
may be used. With such an injection nozzle, the working
fluid will be introduced into the proximity of the re-
stricted zone so that the reduced pressure created will
permit the working fluid to be introduced into the absorp-
tion stage.
It will be appreciated that, depending upon relative
flow rates and pressures, it may still be necessary to
control the pressure of the recycled solvent solution by
expanding it to provide an appropriate pressure.
By utilizing the pressure, or at least part of the
pressure, of the solvent solution which is recycled, this
will contribute to an increase in pressure in the absorp-
tion stage. This can provide the advantage of improving
absorption in the absorption stage, or can be utilized to
permit expansion of the working fluid to an even lower
spent level. In this event, the initial increase in
pressure provided by the solvent solution may be utilized
to increase the pressure in the absorption stage, to a
level where absorption can be effectively achieved in
accordance with this invention.
1 ~7325~
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: Applicant believes that this application of the pres-
sure of the solvent solution will tend to be valuable in
the first stage, and probably the first and second stages
of a multi-stage regeneration system while, in a single
stage system or a system employing only two stages it will
tend to be less valuable. This will primarily be due to
the fact that the mass ratio between the recycled solvent
solution and the working fluid will not be sufficient.
Preferred embodiments of the invention are now de-
scribed by way of example with reference to the accompany
drawings.
In the drawings: -
Figure 1 shows a schematic representation of one
i embodiment of the method and apparatus of this invention;
: Figure 2 shows a fragmentary schematic representation
of the method and apparatus of Figure 1 incorporating amodification to the expansion stage;
Figure 3 shows a fragmentary schematic representation
of a further embodiment of the invention in which injec-
tion means is utilized to inject the working fluid beingregenerated;
Figure 4 shows a schematic representation of a
further embodiment of the method and apparatus of this
invention.
With reference to Figure 1 of the drawings, numeral
50 refers generally to apparatus for use in generating
energy by the expansion of a gaseous working fluid from a
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charged high pressure level to a spent low pressure level
to release energy, and for regenerating the spent working
fluid.
S The apparatus 50 includes expansion means in the
form of a turbine 52 in which a gaseous working fluid is
expanded from a charged high pressure level to a spent low
pressure level to released energy to drive the turbine 52.
The gaseous working fluid at the high pressure level is
fed to the turbine 52 along charged line 54 and is dis-
charged from the turbine 52 along spent line 56.
The apparatus 50 further includes regeneration means
for regenerating the spent gaseous fluid. The regenera-
tion means comprises four successive incremental regener-
ation stages.
For ease of reference the components of each regener-
ation stage have been identified by a letter followed by a
~ 20 suffix in arabic numerals indicating the particular
regeneration stage. In addition, the flow lines for each
regeneration stage have been identified by reference
numerals having a prefix corresponding to that of the
particular regeneration stage.
The first regeneration stage comprises an absorber A1
for condensing the gaseous working fluid by dissolving it
in a solvent sol,ution, a pump P1 for pumping the solvent
solution containing the dissolved working fluid to in-
crease the pressure, evaporator E1 for evaporating the
working fluid, and a separator S~ for separating the
evaporated working fluid from the solvent solution.
The first regeneration stage includes an influent
line 1-1 into which the spent gaseous working fluid from
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1 1~325~
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the spent line 56 and solvent solution from a solvent
solution recycle line 1-13 are fed into the first sta~e
and through the absorber A1.
The resultant solvent solution from the absorber A1
is fed along line 1-2 to the inlet of the pump P1. The
solution is discharged from the pump P1 at an increased
pressure along line 1-3 and through the evaporator E1.
The solvent solution and evaporated working fluid are fed
from the evaporator ~1 along line 1-4 to the separator S1.
The separated evaporated working fluid is fed from the
separator S1 along line 1-5 to the influent line 2-1 of
the second stage. The solvent solution from the separator
S1 is recycled along solvent solution recycle line 1-13 to
the influent line 1-1.
The second, third and fourth regeneration stages
correspond exactly with the first regeneration stage
except that the evaporated, separated working fluid from
the separator S4 is withdrawn along line 4-5 and fed into
the charged line 54 to repeat the cycle.
In the preferred embodiment of the invention, the
gaseous working fluid is ammonia, whereas the solvent is
water. In addition, in the preferred embodiment of the
invention, the apparatus 50 is an apparatus for use in
producing energy by ocean thermal energy conversion.
The apparatus 50 is, therefore, conveniently in-
stalled on the seashore or on a floating platform. In
addition/ the apparatus 50 includes pump means ~not shown]
for pumping surface water from the surface of an ocean to
the evaporators of the apparatus to constitute the heating
1 17325~
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medium for the apparatus, and includes pump means ~not
shown] for pumping cold water from a suf~icient depth of
such an ocean for constituting the cooling medium for
cooling the absorbers of the apparatus 50.
Thus, the absorber A1 includes circulation means
having an inlet 1-9 and an outlet 1-10 for circulating
deep ocean water through the absorber A1. Similarly, the
evaporator E1 includes an inlet 1-11 and an outlet 1-12
for circulating ocean surface water through the evaporator
for heating the evaporator E1.
Yurther, in each regeneration stager the recycle line
1-13, 2-13, 3-13 and 4-13 has an evaporator heat exchange
line 1-15, 2-15, 3-15 and 4-15, respectively~ passing in
heat exchange relationship through the evaporator E.
In addition, in each of the regeneration stages, the
solvent solution recycle line -13 may have a condenser
heat exchange line 1-1G, 2-16, 3-16 and 4-16, respec-
tively, extending in heat exchange relationship through
the absorber A or, alternatively, may completely bypass
the absorber A as indicated by chain-dotted lines 1-18,
2-18, 3-18 and 4-18.
Where the recycled solvent solution passes in heat
exchange relationship through the absorber of each re-
generation stage, it will assist in cooling the absorber
and will thus reduce the quantity of cooling water re-
quired to effect the required cooling in that absorber
since the quantity of heat to be transferred will remain
constant. It will, however, necessitate an increase in
the absorber capacity and thusr in the absorber size.
1 1~3257
-20-
In practice, therefore, the capital cost of an
increase in absorber size can be balanced against the cost
of the additional quantity of cooling medium to decide, on
the basis of pure economics, as to whether the recycle
line should pass through the absorbers, should completely
bypass the absorbers, or should pass partially through the
absorbers.
In the preferred embodiment of the invention, the
recycle lines will bypass the absorbers.
In the preferred embodiment of the invention, the
gaseous working fluid is ammonia, whereas the solvent
solution is a solution of ammonia in water.
The use of the apparatus 50, and thus the process
of this invention, is now described with reference to a
preferred ocean thermal energy conversion system typically
employing, as heating medium~ surface water at a temper-
ature of 27C, and employing as cooling medium, deep oceanwater [typically at a depth of not less than about 200
feet] having a temperature of about 4C.
Since the boiling point of pure ammonia is -33C
at a pressure of one atmosphere, and since the minimum
temperature of the cold water cooling medium is 4C, it
would normally not be possible to regenerate ammonia at a
pressure of one atmosphere by using such a cooling medium.
In other words, regeneration would only be possible if the
ammonia working fluid were at a pressure where the boiling
point of ammonia is above 4C.
In other words, regeneration of the gaseous working
1uid would only be possible if the working fluid is
expanded across the turbine 52 to a pressure at which it
~7~57
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is capable of regeneration with the available cooling
medium. This imposes a direct and severe limitation on
the energy which can be generated since the maximum pres-
sure to which the ammonia working fluid can be regenerated
is also limited by the evaporation capacity of the hot
water heating medium at 27~C.
In practice, utilizing surface water at a temperature
of about 27~C, evaporation of ammonia in the final evapor-
ator E4 can only be achieved in an effective manner at amaximum pressure of about nine atmospheres.
It will be appreciated, thereforel that if the
working fluid can be expanded from a charged level of nine
atmospheres to a spent level pressure of one atmosphere,
as opposed to a spent level pressure of say only four
atmospheres, the quantity of energy released will be
increased substantially.
In the preferred process as illustrated in Figure 1,
the gaseous ammonia working fluid is indeed allowed to
expand across the turbine 52 from a pressure of about nine
atmospheres to a pressure of about one atmosphere.
A specific quantity of gaseous working fluid to be
regenerated, at a spent pressure level of one atmosphere
is, therefore fed to the first stage along influent line
1-1 .
This quantity of gaseous working fluid is condensed
in the absorber A1 by dissolving it in a solvent solution
which is fed along solvent solution recycle line 1-13 into
the in~luent line 1-1 at the same pressure of one atmos-
phere.
n j
ï173~57
-22-
In the preferred embodiment of the invention, the
solvent solutions will not be passed in heat exchange
relationship through the absorbers. Thus, the spent
gaseous ammonia, which may contain about 10% by weight of
liquid ammonia, will be at a temperature of about -33C,
whereas the corresponding solvent solution will be at a
temperature of about 8C.
The solvent solution comprises water having an
initial ammonia concentration which is sufficient to
provide a binary solution which at the pressure of one
atmosphere, has a boiling point within the temperature
range which will prevail in the absorber A1. Further, the
proportion of solvent solution to the quantity of working
fluid to be regenerated is such that after the solvent
solution has dissolved the quantity of working fluid to be
regenerated in the absorber A1, the resultant binary
solution will have a concentration which will provide, at
the pressure of one atmosphere, a boiling point marginally
above the minimum temperature of the cooling medium. The
boiling point of the solvent solution will thus be in the
region of about 6C where the minimum temperature of the
cold water is about 4C.
In this way it will be insured that the total quan-
tity of working fluid to be regenerated will dissolve in
the solvent solution, and that the minimum quantity of
solvent solution to dissolve that quantity of gaseous
ammonia will be employed thereby reducing the cold water
requirements and the capacity of the absorber A1 to the
practical minimum.
The solvent solution containing the dissolved working
fluid being regenerated, will leave the absorber A1 at a
1 17325~
-~3-
temperature of about 6C and at a pressure of one atmos-
phere, and is pumped by the pump P1 to the evaporator E1
The pump P1 is controlled to increase the pressure
of the solvent solution to the maximum pressure at which
the dissolved ammonia working fluid can be effectively
evaporated in the evaporator E1 by means of the surface
water heating medium at a maximum temperature of 27C.
Preferably, the pressure increase is controlled
so that after evaporation of the quantity of working fluid
being regenerated, the solvent solution in the evaporator
E1 will have a boiling point marginally below 27C, such
as about 25C.
This pressure can readily be determined from a
binary water/ammonia phase diagram in relation to the
prevailing ammonia concentration and temperature range in
the evaporator E1.
It will naturally be appreciated that the initial
concentration of ammonia in water for the solvent solu-
tion, as also the required quantity o~ solvent solution;
which is fed to the absorber A1, can also readily be
determined from such a phase diagram on the basis of the
known pressure and temperature range.
The evaporated working fluid and solvent solution are
fed along line 1-4 to the separator S1, where they are
allowed to separate.
From the separator S1, the solvent solution, at a
temperature of about 25C will be recycled along the
`~
1 :17325~
-24-
solvent solution recycle line 1-13 to constitute the
solvent solution for the first stage. The separated,
evaporated ammonia working ~luid at about 25C is fed from
the separator S1 to the second regeneration stage along
influent line 2-1. As in the case of the first regenera-
tion stage, the quantity of working fluid being regener-
ated, is mixed with a solvent solution recycled from a
separator S2 of the second regeneration stage along the
solvent solution recycle line 2-13 for dissolving the
working fluid in the absorber A2.
Since the pressure in the absorber A2 will be greater
than the pressure in the absorber A1, it follows that the
initial concetration of ammonia in the solvent solution
for the second stage will be correspondingly higher to
insure that an appropriate boiling point is again provided
for effectively dissolving or absorbing the working fluid
being regenerated in the absorber A2.
It will be appreciated that the solvent solution
which is recycled from the separator S to the absorber A
in each stage leaves the separator S at a higher pressure
than the pressure of the influent working fluid. Each
solvent solution recycle line 1-13, 2-13, 3-13 and 4-13,
therefore, includes a pressure-reducing valve V1, V2, V3
and V4, respectively, for reducing the pressure of the
recycled solvent solution to the same pressure as that of
the influent working fluid being regenerated.
For each successive regeneratiGn stage, therefore,
the initial concentration of ammonia in the solvent
solution will increase step-wise in correspondence with
the step-wise increase in pressure provided by the pump
means in each stage.
1 17325~
-25-
- It will be appreciated that the apparatus will
include an appropriate number of regeneration stages until
the quantity of working fluid being regenerated, has been
regenerated to the appropriate charged high pressure level
in a final regeneration stage such as the fourth regener-
ation stage shown in the drawing. It will further be
appreciated that the spent pressure level to which the
working fluid is expandedt wi~l likewise determine the
number of regeneration stages required. Thus if the
working fluid is expanded to only say 3 atmospheres, only
two or three regeneration stages may be required.
In the embodiment illustrated in the drawing, the
pump means P4 will increase the pressure of the solvent
solution to about nine atmospheres thereby yielding a
charged regenerated working fluid at a pressure of about
nine atmospheres which is withdrawn from the separator S4
and fed along the charged line 5~ to the turbine 52.
It will be appreciated that in the preferred embodi-
ment of the invention, the process will be carried out as
a continuous process in which a constant quantity of
working fluid by unit time is continuously being expanded
across the turbine 52 and is then continuously being
regenerated in the regeneration means.
To further illustrate the use of the invention in the
preferred embodiment as illustrated in Figure 1~ typical
parameters of the process are now indicated with reference
to specific theoretical calculations performed on the
basis of 1 kilogram of gaseous ammonia working fluid, and
on the basis of deep ocean water at a minimum temperature
cf 4C as cooling medium, and surface ocean water at a
maximum temperature of 27C as heatiny medium.
-
1 173257
--26--
These parameters as calculated are set out in Tables
I, II, III and IV below for the first, second, third and
fourth regeneration stages, respectively.
In each table, the particular point at which the
parameter has been calculated, is indicated by the appro-
priate reference numeral in the drawing. These points are
listed in the first column of each table.
The columns in the tables are as follows:
(a) First column - reference numerals (RN);
(b) Second column - temperature (t) in C;
(c) Third column - pressure (p) in atmospheres;
(d) Fourth column - ratio by weight of total ammonia
(dissolved and undissolved) to
water plus total ammonia (RATIO);
(e) Fifth column - weight ~w) in kilograms; and
:
(f) Sixth column - Enthalpy (E) in kcal/g.
1 173257.
-27-
TABLE I
RN ~ p RAT I O w E
-
1-0 -32.0 l o O .9920 1.0000 354.45
1-1 + 9.0 1.0 .426622.2556- 642
1-2 + 6.0 1~0 .426622.2556- 20.0
1-3 + 6 1.8 .426622.2556- 20.0
1-4 +25.0 1.8 .426622.255617.9730
1-5 ~25.0 1.8 .99201.0000400.0
1-6 +25.0 1.8 .400021.2556 0.0
1-7 + 8.0 1.8 .400021.2556- 23.4
1-8 + 8.0 1.0 .400021.2556- 23.4
TABLE II
RN t p RATIO w E
2-1 +10.0 1.8 .516017.24579.4125
2-2 + 6.0 1.8 .516017.2457- 10.80
2-3 + 600 3.0 .516017.2457- 10.~0
2-4 ~25.0 3.0 .516017.245728.6905
2-5 ~25.0 3.0 .9920~.0000403.0
2-6 +25.0 3.0 .486716.24575.65
2-7 ~ 8.0 3.0 .486716.2457- 14.63
2-8 + 8.0 1.8 .486716.2457- 14.63
~ 17325~.
- ~8~
TABLE I I I
RN t pRAT I O w E
3-1 +10.0 3Ø6490 8.0000 48.625
3-2 + 6.0 3Ø6490 8.0000 10.00
3-3 + 6.0 5Ø6490 8.0000 10.00
3-4 +25.0 5Ø6490 8.0000 68.688
3-5 +25.0 5Ø9920 1.0000 409.5
3-6 +25.0 5Ø6000 7.0000 20.00
3-7 + 8.0 5Ø6000 7.0000 - 2.00
3-8 + 8.0 3Ø6000 7.0000 - 2.00
TABLE IV
RN t pRAT I O w E
4-1 +10.0 5.00.9000 5.4231124.45
4-2 + 6.0 5.00.9000 5.4231 80.0
4-3 + 6.0 9Ø9000 5.4231 80.0
4-4 +25.0 9.0~9000 5.4231139.59
4-5 +25.0 9Ø9920 1.0000 412.0
4-6 +25.0 9Ø8792 4.4231 78.0
4-7 + 8.0 9Ø8792 4.4231 60.0
4-8 + 8.0 9Ø8792 4.4231 60.0
4-9 + 8.0 5Ø8792 4.4231 60.0
-
11~325~
-2~-
From the above theoretical calculations, the total
heat supplied to the four evaporator stages arnounted to
1258.35 kcals, while the total heat removed from the four
absorption stages amounted to 1200.8 kcals.
The difference of 57.55 is the work put in per
kilogram of working fluid regenerated and thus the theo-
retical amo~nt of work which is available.
The energy required to operate the pumps was cal-
culated to be 2.08 kcals/kg of working fluid regenerated.
The theoretical amount of work available is therefore
55.47 kcal/kg of working fluid.
If it is assumed that the efficiency of the turbine
is 85~, the theoretical thermal efficiency will be 4.408%.
The theoretical thermal efficiency of an ideal
Carnot cycle system operating with a cooling medium at a
constant temperature of 4C and with a heating medium at a
constant temperature of 27C, would be 7.04~. However,
considering that the temperature of the heating and
cooling mediums must change in such a process, the effi-
ciency of the theoretical ideal thermodynamical cycle willbe only about 4.9%.
Therefore, the ratio of the efficiency of a system
in accordance with this invention on the basis of the
theoretical calculations, would be:
(a) 62.55% in relation to an ideal Carnot cycle
system;
5
~732S~
-30-
(b) about 82% in relation to an ideal thermo-
dynamical cycle under corresponding conditions.
It is an advantage of the embodiment of the invention
as illustrated with reference to the drawing, that an
effective system can be provided for generating energy by
using the relatively low temperature differential between
surface ocean water as heating medium and deep ocean water
as cooling medium.
It is a further advantage of this embodiment that a
system can be provided for regeneration of spent gaseous
ammonia at a relatively low level of about one atmosphere
or less.
t5
It is a further advantage of the embodiment of
the invention as illustrated, that because the regenera-
tion range of the gaseous working fluid has been in-
creased, the gaseous working fluid can be expanded from a
high pressure level of about nine atmospheres, to a lo~
pressure level of about one atmcsphere or less. Thus, the
quantity of energy available for release is substantially
greater than would be the case if the working fluid wer-e
expanded from a pressure of about nine atmospheres to a
pressure of only about four or five atmospheres.
The embodiment of the invention as illustrated in
the drawing can provide a further advantage arising from
the fact that the cold water requirements need only be
sufficient to provide a final temperature in each absorber
of about 6C. The temperature of the cold water cooling
medium can thus increase across each absorber as indicated
in the above tables. Thus, th~ cooling medium require-
ments will be substantially less than would be the case if
~ 1732~7
-31-
it were necessary to supply a sufficient quantity of
cooling water at a sufficient rate to approach the Carnot
cycle ideal where the cooling medium would remain at the
constant minimum temperature. The same considerations
apply to the heating medium, where the hot water is
allowed to cool from about 27C to the temperature indi-
cated in the above tables across each evaporator stage
thereby again providing a substantially reduced heating
water requirement over that required by the ideal Carnot
10 cycle operation.
It will ~e appreciated that since, in each absorber,
the cooling range for the solvent solution and working
fluid is substantially the same, and the temperature range
for the cooling medium is substantially the same, the
absorbers of the four regeneration stages can conveniently
be combined into a single composite absorber through which
the lines 1-1, 2-1, 3-1 and 4-1 pass separately for
cooling by means of a single circulating supply of cold
water. In the same way, all the evaporators can be
- combined in a single composite evaporator heated by means
of the circulating hot water from a single source.
It will further be appreciated that, theoretically,
the quantity of solvent solution in each regeneration
stage should remain constant, and that the initial con-
centration of ammonia in water to constitute the solvent
solution, should also remain constant for constant minimum
cooling water temperatures and constant maximum heating
water temperatures.
In practice, however, the quantity of solvent solu-
tion will have to be adjusted during use to compensate for
varying conditions and for losses. In addition, the
.
3~57
--32--
concentration of ammonia in water in each regeneration
stage, will have to be adjusted periodically in relation
to seasonal variations in the minimum temperature of cold
water and maximum temperature of hot water.
It will also be appreciated that where heating of
the hot water can economically be achieved, such as by
solar heating or the like, the effectiveness of the
process of this invention can be improved. Such supple-
10 mental heating will, therefore, be employed under appro-
priate conditions if dictated by economic considerati(>ns.
With reference to Figure 2 of the drawings, numeral
150 refers generally to an alternative embodiment of the
15 method and apparatus of this invention to the embodiment
illustrated in Figure 1.
The apparatus 150 corresponds substantially with the
apparatus 50 and corresponding parts are indicated by
20 corresponding reference numerals.
In the apparatus 150, in place of the single turbine
52 of the apparatus 50, a two-stage turbine system is
employed comurising a first turbine 152 and a second
25 turbine 153.
The charged working fluid is partially expanded
across the first turbine 152 into a heat exchange vessel
170.
From the heat exchange vessel 170 the partially
expanded working fluid is led along separate conduits 171
and 172 through the absorber A2 and through the absorber
A1 respectively in heat exchange relationship with the
35 cooling water.
~ ~7325~
-33-
Thereafter the partially spent working fluid is
further expanded across the second turbine 153 to its
final spent level. It is then fed, as before, along the
spent line 56 to the influent line 1-1.
s
Applic~nt believes that by utilizing a two-stage
turbine system with heat exchange of the partially ex-
panded working fluid, the effectiveness of the system can
be improved particularly where the system includes a
number of regeneration stages. Applicant believes that it
will tend to be less significant where fewer stages are
employed.
With reference to Figure 3 of the drawings, the
drawing shows, to an enlarged scale, the apparatus of
Figure 1 which has been adapted in the first and second
regeneration stages for the pressure of the recycled
solvent solution to be utilized in increasing the pressure
of the influent spent working fluid into the absorption
stage A1 and the absorption stage A2 respectively.
As indicated in Figure 3, the absorption stage A1
incorporates an injection system for injecting the re-
cycled solvent solution at a pressure substantially higher
than the pressure of the spent working fluid into the
absorber A1.
The injection system is in the form of an injection
nozzle 180 having an intermediate restricted zone to gen-
erate a zone of low pressure.
The spent line 56 joins the nozzle 180 at the re-
stricted zone and, as is known those skilled in the art,
in an attitude where the reduced pressure generated at the
~ ~7325
--34--
restricted zone by the solvent solution being iniected
through the nozzle 180 into the absorber A1, will draw the
spent working fluid into the nozzle 180 and thus into the
absorber A1.
s
It will be appreciated that the effectiveness of
this system will depend upon the mass ratio between the
solvent solution being recycled and the working fluid
being regenerated.
If the ratio is t~low, it will not be possible to
introduce the total quantity of working fluid being regen-
erated by means of the flow of the solvent solution being
recycled.
In practice therefore, depending upon conditions, it
may be necessary to partially reduce the pressure of the
solvent solution being recycled before entry into the
nozzle 180, or it may be necessary to introduce some of
the working fluid being regenerated through the nozzle
180, and the remainder directly into the absorber A1.
While the absorber A2 has not been illustrated in
Figure 3, it will be appreciated that the working fluid
being regenerated in the second regeneration stage will be
introduced into the absorber A2 by means of an injection
system corresponding to that of the absorber A1.
The embodiment of the invention as illustrated in
Figure 3 of the drawings, can provide the advantage that
the pressure of the solvent solution being recycled in the
first and second stages respectively can be at least
partially utilized to introduce the working fluid being
regenerated, and to increase the pressure in the first and
second absorbers A1 and A2.
~ 1732$~
-35-
This affect can be utilized to improve the effective-
ness of absorption in the first and second absorbers Al
and A2. ~lternatively, or in addition, this feature can
be utilized to permit expansion of the charged working
fluid to a y2t lower pressure across the turbine 52, with
reliance being placed on the pressure contribution of the
solvent solution being recycled to raise the pressure in
the absorber A1 to a level where effective absorption of
the working fluid being regenerated can be effected.
Similarly, if employed in relation to the second regener-
ation stage, the same considerations will apply where the
working fluid introduced into the absorber A2 can be at a
lower pressure, and reliance is placed on the pressure of
the solvent solution being recycled into the absorber A2,
to increase the pressure to a level for effective absorp-
tion in the absorber A2.
Applicant believes that the injection system can be
advantageous in the apparatus 50 particularly in the first
and second stages, but would ~end to have lesser value in
subsequent stages.
With reference to Figure 4 of the drawings, reference
numeral 450 refers generally to yet a further alternative
embodiment of the method and apparatus of this invention.
The system 450 as illustrated in Figure ~, is de-
signed for use where the charged working fluid is expanded
to a relatively higher level than the level described with
reference to Figures 1 to 3, but regeneration of the spent
working fluid is effected in accordance with this inven-
tion to provide an economical system with high efficiency.
:i
.
~ ~7325~
-36-
The apparatus 450 includes a turbine 452, and absorber
A, a pump P, a regenerator R, an evaporator E and a sepa-
rator S.
The spent working fluid expanded across the turbine
452 is fed along spent line 456 to influent line 464.
Solvent solution which is recycled from the separator S
along solvent solution recycle line 465 is fed through a
pressure reducing valve V to reduce the pressure of the
solvent solution to that of the spent working fluid, and
then into the absorber A through the influent line 464.
As described with reference to Figure 1, cooling
medium in the form of cold deep ocean water is circulated
t5 in heat exchange relationship through the absorber A by
means of conduit 461, while heating surface water is
circulated through evaporator R in heat exchange rela-
tionship therewith, along conduit 463.
The spent working fluid is absorbed by the solvent
solution in the absorber A whereafter the solvent solution
containiny the absorbed working fluid has its pressure
increased by the pump P.
The solvent solution containing the absorbed working
fluid is fed from the pump P along line 466 through the
regenerator R and then to the evaporator E for evaporation
of the dissolved working fluid being regenerated.
The solvent solution being recycled along the line
465, is passed in heat exchange relationship with the
solvent solution passed through the regenerator R to
effect heat exchange.
~ 173257
-37-
From the evaporator E, the evaporated fluid being
regenerated and the solvent solution passes to the sep
rator S for separation, whereafter the separated charged
working fluid is fed along charged line 454 to the turbine
452.
To illustrate this embodiment of the invention,
typical parameters of the process of the system of Figure
4, are now indicated with reference to specific theoret-
ical calculations performed on the basis of 1 kilogram ofgaseous ammonia working fluid, and on the basis of deep
ocean water at a minimum temperature of 4C as cooling
medium, and surface ocean water at a maximum temperature
of 27C as heating medium.
These parameters as calculated are set out in Table V
below. The particular point at which the parameter has
been calculated, has been indicated by the appropriate
reference numeral in Figure 4. These points are listed in
the first column of Table V.
~ ~732S~
38-
~ ~ oo o o ;r u~ o ~ D
m ~ OD ~ u~ u~ O u~ ,_
z ~ ~ er r r oo o
W ;!~;
u~ . o ~ In u) ~ u~ o u~
u~ ~ o 1` r~ o 1` r~ r~
O
H C O CO 0 CO O :) 0 O t~ ~ N
E~ ~ v a~
z z :3 ~ a~ ~ ~ o~ o~ a ct~ c~ co
C~ ~ O O O O O O O O O O O
O ~n
In ~ o o o o o o Lt~
In U~
o U~ ~ . + + .~ + +
~ O ~ ~ ~ ~ U~
` ~173Z5~
-39-
It will be noted from ~able V that the working fluid
is expanded from a charged level of 9 atmospheres to a
spent level of 5.5 atmospheres. It will further be noted
that the spent working fluid and solvent solution enter
the absorber A at a temperature of 12~C, and that the
solvent solution containing the absorbed working fluid
being regenerated, leaves the absorber A at a temperature
of about 8C.
By using an absorber A for absorbing the spent
ammonia working fluid, and by having an appropriate
initial concentration o~ ammonia in water for the solvent
solution being recycled, absorption of the ammonia working
fluid can commence in the absorber A at a temperature of
12C or slightly higher, and complete absorption will have
occurred by the time the temperature has been reduced to
about 8C by the cooling medium at 4~C.
There is therefore a significant temperature differ-
ence between the temperature of the cooling medium and theminimum temperature required for complete absorption of
the working fluid being regenerated.
In contrast with a system employing a conventional
condensation stage for the condensation of a working fluid
such as ammonia, condensation of gaseous ammonia at SOS
atmospheres would only commence at a temperature of about
5C resulting in a marginal difference of 1C between the
temperature of condensation and the temperature of the
available cooling medium, which is at 4~C.
Thus, before condensation can occur in a condensation
stage, the temperature of the working fluid would have to
be reduced to about 5~C by the cooling medium at 4C. It
1173~
-40-
will be appreciated that because of the marginal temper-
- ature difference, the requirements of cooling water will
be substantial and a substantial heat transfer surface
will be required.
In contrast therewith, by utilizing an absorber in
accordance with this invention, while both the working
fluid being regenerated and the solvent solution being
recycled will have to be cooled, because absorption of
working fluid can commence at a temperature substantially
above the temperature of the cooling medium, and can be
completed at a temperature substantially above the temper-
ature of the cooling medium, the amount of cooling water
required can be reduced substantially and/or the heat
transfer surface requirement can be reduced substantially.
In practice, on the basis of economics/ the cooling
water requirements, the heat transfer surface area, and
the temperature difference between the temperature of the
cooling water and the temperature re~uired for complete
absorption of the spent working fluid, can be balanced to
achieve the most economical system in the light of the
operating parameters and capital costs.
Because the solvent solution containing the working
fluid being regenerated would leave the absorber A at a
temperature higher than the temperature of a condensed
working fluid leaving a condenser, evaporation in the
evaporator E will be facilitated. By additionally cir-
culating the solvent solution being recycled and the
solvent solution containing the absorbed working fluid in
heat exchange relationship through the regenerator R9 both
absorption in the absorber A and evaporation in the evapo-
rator E will be improved.
~ 17325'~
The system 450 therefore provides the advantaye of an
increased enthalpy drop across the turbine 452 and pro-
vides a system of increased efficiency and economy.
To illustrate the advantages of the system in accor-
dance with this invention, calculations have been per-
formed to compare the system illustrated in Figure 4 with
a conventional OTEC system utilizing a conventional
Rankine cycle under the same operating parameters imposed
by the temperatures of the heating and cooling mediums.
The parameters for the Rankine cycle system were obtained
from the publication entitled "OTEC Pilot Plan Heat
Engine" by D. Richards and ~. L. Perini, John Hopkins
University, OTC 3592, 1979.
This comparison is set out in Table VI below.
1 1~325~
-~12
~ 'xxx
H I V CO O O 11-\ 0 0 ~0 0~ ~ OQ 0 ~D ~ O
v O - er 1~ . o ~ . o o o r` u~ o
O : D + + + + .
0~ ~
H Z E-~ _ O O O
V '-- H H X X X O 11')
~ ~ Z ~ I` ~ u~ o o - OD O ~ ~ O O O ~ OD - ~ ~
H H l L1 0
m ~ z
~: ~ a er c~ v ~V ,~ 3 ~3 ,Y X ~ V V
H U~ E13
V V ~ O ~
'U~ 3 aJ 1~ C ~ J g
UJ u~ 3 C ~ QJ O ~ 3
F ra u~ C D Q o Q~ o
~ ~ v ~ v ~ x ~ ~ ~ c
3 P~ O ~ Z
~ 173~7
--43--
xxx ~ r
c~ ~ o~ ~D
~ CDI-~ 0~ ~_o~l_
` ~D~r ~r ~ ~ ~ o a~ er
~ oo~ ~
D 1~-- L~ ~o
U:~9 ,
_ oo Or~oO~
_, O~D
l XX ~
Z ~ ~ . U~ ~ /~ ~
H CO Irlt~l ~ 11~ ~
~ Ll~ I` O~D 1~ 0~ _~
~ Z CJ~ I` O ~D ~r I ~ ~) o~ ~
H ~ O a~ ~ ~ ll ll ll
Z 1`0 1- r_
H .C 5 L: _.
m X.Y ~: ~ E~ E~ E d~ ~ ,_
E~ a) c
c ~ a)cu~
~ SJ SJ
.~ ~ ~ 0'~ ~
a
a r1 0
u~ ~ .a
Q
o0 )~ O ~ ,a~ v q)
R ~ o ~ ~ u~ fl ~ t~
~ ~ ~ ~ 0 ~ ~ ,~ c
o ~ ~ o ~a 0 u~ ~J U~ ~ ~ O ~ ~ 3 0
~J O ~ ~ ~ ~ C a) ~ o ~ ~ ~ ,1 o
s ~ a) ~ a~ o ~ c ~ v ~ 0 a
v ~ w ~ 0~ ~ 0 u~ s~ .,~
3 o a) c ~ ~0 0 ~ c c a
c ~ J~ h ~ 0 c ~ ~ E a~ ~
o ~ ~ c ~ c: x :, o a~ o a) ~ 0 x
5:: ~ 3 a
~5 SJ ~ h ~ J-
~: ~ ;r~ Z E~ ~r
~ 17325~
-44-
The significant advantages of the system of Figure 4
in relation to the conventional Rankine cycle system are
clearly apparent from Table VI above. It is clear that
the system in accordance with this invention can provide
significant imporvements in efficiency and economy. This
is particularly significant in OTEC systems and related
systems where the severe restraints imposed by the temper-
atures of the available heating and cooling mediums have
heretofore presented a serious barrier to commercial
utilization of OTEC systems.
