Note: Descriptions are shown in the official language in which they were submitted.
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A SYSTEM FOR HIGH EFFICIENCY ENERGY CONVERSION CYCLE BY
RECYCLING LATENT HEAT OF VAPORIZATION
TECHNICAL FIELD OF THE INVENTION
[001] The present subject matter described herein, in general, relates to
electric power
generation, and more particularly, towards a multi-stage system for
efficiently driving
electric power generating turbines.
BACKGROUND ART
[002] At present most of the world's electricity is generated by heating
water into high
pressure and temperature steam which is then used to rotate a turbine which
rotates a
generator to produce electricity. Any number of means can be used to heat the
water such as
solar, coal, gas, nuclear etc. As the high pressure steam enters the turbine,
it collides with the
turbine blades and imparts some of its energy lo the turbine. After multiple
collisions with
the turbine blades, the steam has lost a significant amount of its energy and
exits the turbine
to enter a condenser at low pressure which cools the steam until it becomes
water. A pump
then pumps this water back into the high pressure input stage of the cycle
where it is heated
back into steam to repeat the cycle continuously.
[003] The problem with this setup is that the condenser has to remove the
latent heat of
vaporization to convert steam back to liquid so that the pumps can pump the
fluid back to the
start of the cycle with minimum energy requirement. This energy is then
discarded to the
surroundings as waste heat. In the case of water, the latent heat of
vaporization is
approximately 2257kJ/Kg, which is an extremely large amount of energy. This is
between
40-60% (depending on the operating temperature) or more of the total heat
energy added to
the working fluid per cycle. Therefore, even the best power plants rarely
achieve an
2
efficiency of even 40%. If this waste latent heat could also be utilized and
converted into
electricity, then a significant improvement in the efficiency of any power
plant is possible.
[004] There are many existing power cycles, the problem with existing power
cycle
such as the Rankine cycle and others is that their efficiency is greatly
limited due the large
amount of low quality waste heat that has to be rejected into the atmosphere
or surroundings.
Most of the latent heat of vaporization (or condensation) has to be rejected
as waste heat and
this greatly limits the efficiency of any cycle.
SUMMARY OF THE INVENTION
[005] This summary is provided to introduce concepts related to a system
(apparatus),
and method thereof for high efficiency energy conversion cycle by recycling
latent heat of
vaporization and the concepts are further described below in the detailed
description. This
summary is not intended to identify essential features of the claimed subject
matter nor is it
intended for use in determining or limiting the scope of the claimed subject
matter.
[005a] In one aspect, there is provided a multi stage electric power
generation apparatus with
at least two stage latent heat exchange mechanism, the electric power
generation apparatus
comprising:
a first stage power cycle comprising a first working fluid, and configured for
electric
power generation, and thereby generating a turbine exit vapour containing
energy of latent heat
of vaporization and/or condensation; and
a second stage power cycle comprising a second working fluid, and configured
for
electric power generation;
wherein the second working fluid absorbs the latent heat of vaporization
and/or
condensation generated from the first stage power cycle at a pressure and a
temperature
sufficiently high so as to cause a complete phase change in both the first
working fluid and the
second working fluid, and thereafter the second stage working fluid being
superheated for
electric power generation.
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[005b]In another aspect, there is provided a method for generating an
electrical power using
an electric power generation apparatus with at least two stage power cycle,
the method
comprising:
generating, in a first stage power cycle comprising a first working fluid, the
electrical power, and a turbine exit vapour containing latent heat of
vaporization and/or
condensation;
generating, in a second stage power cycle comprising a second working fluid,
the electrical power generation, and the latent heat of vaporization and/or
condensation;
wherein
the second working fluid absorbs the latent heat of vaporization and/or
condensation generated from the first stage power cycle in a heat exchange
mechanism at a pressure and a temperature sufficiently high so as to cause a
complete
phase change in both the first working fluid and second working fluid and
thereafter
the second working fluid is super heated for generating electrical power.
[006] TECHNICAL PROBLEM: The condenser has to remove the latent heat of
vaporization to convert steam back to liquid so that the pumps can pump the
fluid back to the
start ofthe cycle with minimum energy requirement. This energy (latent heat)
is then discarded
to the surroundings as waste heat. Therefore, even the best power plants
rarely achieve an
efficiency of even 40%.
[007] TECHNICAL SOLUTION: The present invention provides a mechanism to
efficiently and economically solve the above mention technical problem by
transferring the
latent heat of vaporization of any stage into the input stage of the next
stage instead of rejecting
it into the atmosphere, and thereby greatly increasing the efficiency of any
power cycle.
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[008] In one implementation, a basic objective of the present invention
is to overcome the
disadvantages/drawbacks of the known art by increasing the conversion
efficiency of heat
into electricity of all existing and future power plants.
[009] In one implementation, the present invention provides the conversion
of thermal
energy into electrical energy in a power plant with higher efficiency then is
possible with
current technology.
[0010] In one implementation, the improved efficiency by the use of present
invention is
achieved by reducing the amount of waste heat that is rejected into the
atmosphere in existing
plant cycle designs.
[0011] In one implementation, the present invention provides a mechanism by
creating
multiple turbine cycles where the latent heat of vaporization of the first
cycle is injected into
.. the input stage of the second cycle and the waste heat (latent heat of
vaporization) of the
second cycle into the input stage of the third cycle and so on. Only the waste
heat of the final
cycle is rejected into the atmosphere.
[0012] In one implementation, the present invention enables the utilization of
waste latent
heat and converts the same into electricity, and thereby achieving a
significant improvement
in the efficiency of a power plant. The waste heat exchange mechanism can also
be used with
all heat based power systems even if the final output is some form of non
electrical output.
[0013] In one implementation, by transferring the latent heat of vaporization
of any stage
into the input stage of the next stage instead of rejecting it into the
atmosphere, the present
invention increases the efficiency of any power cycle.
[0014] In one implementation, with proper choice of working fluids, turbine
exit
temperatures and pressures, the present invention enables the transfer of all
the latent heat of
4
vaporization into the next stage thereby greatly reducing the amount of energy
required to heat
the working fluid of that stage to the desired temperature. This results in an
extremely high
efficiency for all stages after the first stage resulting in a very high
overall efficiency.
100151 To improve the overall performance of any power cycle by
transferring the
latent heat of vaporization of any stage into the input stage of the next
stage instead of rejecting
it into the atmosphere, embodiments of the present invention provide a
plurality of aspects of
the present application. The plurality of aspects provides a system/apparatus
and method for
high efficiency energy conversion cycle by recycling latent heat of
vaporization. The technical
solutions are as follows:
[0016] In another aspect, a multi stage electric power generation
apparatus with at least
two stage system is disclosed. The electric power generation apparatus
comprises a first stage
power cycle comprising a first working fluid, boiler, turbine, heat exchanger,
pumps etc., and
configured for electric power generation;
a second stage power cycle comprising a second working fluid, boiler, turbine,
heat exchanger,
pumps, etc., and configured for electric power generation; wherein the second
working fluid
absorbs the waste heat (latent heat of vaporization and/or condensation)
generated from first
stage cycle for electric power generation.
10016a] In another aspect, there is provided a multi stage electric
power generation
apparatus with at least two-stage waste heat exchange mechanism, the electric
power
generation apparatus comprising:
a first stage power cycle comprising a first working fluid, and configured for
electric
power generation, and thereby generating a turbine exit vapour containing
energy of a waste
heat; and
a second stage power cycle comprising a second working fluid, and configured
for
electric power generation;
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wherein the second working fluid absorbs the waste heat generated from the
first stage
power cycle for electric power generation.
[0016b] In
another aspect, there is provided a method for generating an electrical power
using an electric power generation apparatus with at least two-stage power
cycle, the method
comprising:
generating, in a first stage power cycle comprising a first working fluid, the
electrical
power, and a turbine exit vapour containing waste heat;
generating, in a second stage power cycle comprising a second working fluid,
the
electrical power and waste heat;
wherein the second working fluid absorbs the waste heat generated from the
first stage
power cycle in a heat exchange mechanism for generating electrical power.
[0017] In
another aspect, a method for generating electrical power using an electric
power generation apparatus with at least two stage power cycle is disclosed.
The method
comprises:
= generating electricity, using a first stage power cycle comprising a
first working
fluid, boiler, turbine, heat exchanger, pumps, etc;
= generating electricity, using a second stage latent heat exchange
mechanism and
turbine cycle comprising a second working fluid, the electrical power
generation;
characterized in that
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= the second working fluid absorbs the waste heat (latent heat of
vaporization
and/or condensation) generated from first stage in the latent heat exchange
mechanism for generating electrical power.
5 [0018] In one implementation of the present invention, the low quality
waste heat of the
first stage is transferred to the input stage of the second cycle, the waste
heat of the second
cycle transferred to the input stage of the third cycle and so on. The more
stages there are, the
greater will be the final overall efficiency, but there will come a time when
adding more
stages will have diminishing financial returns. In addition, it may not be
possible to find a
sufficient number of working fluids with the right physical properties to have
an unlimited
number of stages. For the purposes of explaining the process in detail, two
stages will be
sufficient to explain the concept and therefore the rest of the explanation
will be based on a
two stage system.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0019] The detailed description is described with reference to the
accompanying figures.
In the figures, the left-most digit(s) of a reference number identifies the
figure in which the
reference number first appears_ The same numbers are used throughout the
drawings to refer
like features and components.
[0020] Figure 1 illustrates a simplified schematic of existing power plant
cycles (Prior-art).
[0021] Figure 2 illustrates a simplified schematic of a multistage cycle that
will achieve
very high efficiencies, in accordance with an embodiment of the present
subject matter.
[0022] Figure 3 illustrates an example of what a 2 stage system could look
like if water
and ammonia are used as working fluids, in accordance with an embodiment of
the present
subject matter.
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[0023] Figure 4 illustrates a method for generating an electrical power using
an electric
power generation apparatus with at least two stage latent heat exchange
mechanism, in
accordance with an embodiment of the present subject matter.
[0024] Figure 5 illustrates a method performed during the first stage latent
heat exchange
mechanism 1000, in accordance with an embodiment of the present subject
matter.
[0025] Figure 6 illustrates a method performed during the second stage latent
heat
exchange mechanism 2000, in accordance with an embodiment of the present
subject matter.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0026] The following clearly describes the technical solutions in the
embodiments of the
present invention with reference to the accompanying drawings in the
embodiments of the
present invention. Appaiendy, the described embodiments are merely a part
rather than all of
the embodiments of the present invention. All other embodiments obtained by a
person of
ordinary skill in the art based on the embodiments of the present invention
without creative
efforts shall fall within the protection scope of the present invention.
[0027] A detailed description of one or more embodiments of the invention is
provided
below along with accompanying figures that illustrate the principles of the
invention. The
invention is described in connection with such embodiments, but the invention
is not limited
to any embodiment. The scope of the invention is limited only by the claims
and the
invention encompasses numerous alternatives, modifications and equivalents.
Numerous
specific details are set forth in the following description in order to
provide a thorough
understanding of the invention. These details are provided for the purpose of
example and the
invention may be practiced according to the claims without some or all of
these specific
details. For the purpose of clarity, technical material that is known in the
technical fields
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related to the invention has not been described in detail so that the
invention is not
unnecessarily obscured.
[0028] It may be noted that, it will be understood that a basic minimum
understanding of
Thermodynamics exists with the reader in order to understand the explanation.
[0029] Referring now to figure 1 illustrates basic layout of existing plant
cycles as a prior-
art.
[0030] While aspects are described for high efficiency energy conversion cycle
by
recycling latent heat of vaporization may be implemented in any number of
different
systems, environments, and/or configurations, the embodiments are described in
the context
of the following exemplary system.
[0031] Referring now to figure 2 illustrates a simplified schematic of a
multistage cycle
that. will achieve vet)/ high efficiencies, in accordance with_ an embodimeni.
of die pieseni
subject matter.
[0032] In one implementation, the low quality waste heat of the first stage is
transferred to
the input stage of the second cycle, the waste heat of the second cycle
transferred to the input
stage of the third cycle and so on. The more stages there are, the greater
will be the final
overall efficiency, but there will come a time when adding more stages will
have diminishing
financial returns. In addition, it may not be possible to find a sufficient
number of working
fluids with the right physical properties to have an unlimited number of
stages.
[0033] In one implementation, for the purposes of explaining the process in
detail, two
stages will be sufficient to explain the concept and therefore the rest of the
explanation will
be based on a two stage system.
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[0034] Referring now to figure 3 illustrates an example of what a 2 stage
system could
look like if water and ammonia are used as working fluids, in accordance with
an
embodiment of the present subject matter.
[0035] In one implementation, for purposes of simplicity only a high pressure
and low
pressure turbine are shown in stage A 1000, and only a single stage turbine
has been shown
in stage B 2000. In addition, all existing techniques such as regenerative
heat, open feed
water heater and other minor modifications already in existence to improve
cycle efficiencies
and performance have been intentionally left out. All existing techniques at
efficiency
improvement may still be used in every stage of the proposed improved design.
All values of
thermo physical properties mentioned in this entire document have been taken
from the
National Institute of Standards and Technology (NIST) website at www.nist.com
or more
specifically from webbook.nist.govichemistry/fluid/.
[0036] In one implementation, there may be a wide range of fluids that can be
employed in
the various stages 1000 or 2000 of the improved system, but for the purposes
of explanation,
we will in this document assume that water is used in stage A 1000 as a first
working fluid
and Ammonia will be used in stage B 2000 as a second working fluid. Stage A
1000 is the
first stage and liquid water is sent from point 13 into the boiler A 2 at high
pressure of say
250 bar (or any other desired pressure) by pump A 1. Here, in boiler 2 it is
heated to a high
temperature of say 600 C (or any other desired temperature) and exits from
boiler A 2 at
point 10 as a supercritical or heated fluid. This high temperature and
pressure supercritical
fluid is then expanded in a high pressure turbine 3 and after a significant
temperature and
pressure drop is sent back to the boiler A 2 to be reheated back to 600 C at
50 bar (or any
other desired temperature and pressure) and sent to a low pressure turbine 4
for final energy
extraction to produce electricity.
[0037] In existing systems, the steam/vapour exits the turbine at point 11 at
near vacuum
conditions and the latent heat of vaporization (or condensation) is removed as
waste heat in
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the condenser using cooling water. This allows the steam to be converted back
into a liquid at
point 12 so that it can be pumped back into the system at high pressure to
repeat the cycle.
[0038] In the present invention, the steam exits the low pressure turbine A 4
at point 11 at
sufficiently high pressure and temperature so as to allow for its latent heat
energy transfer to
the second working fluid which in the example used is ammonia, this is where
the first major
deviation from prior-art is made. Naturally this may result in a slight
decrease in the
efficiency in stage A 1000 when compared with existing prior-art, however, all
the latent heat
of vaporization of stage A 1000 will be transferred to the working fluid of
stage B 2000 in
heat exchanger A100 instead of being wasted into the atmosphere as is the case
with existing
prior-art. In this process of transferring the latent heat energy to stage B
2000, the
steam/vapour of stage A 1000 is converted back into a liquid at point 12 so
that it may be
pumped back into the input stage 13 at high pressure by condensate pump A 1.
[0039] In one implementation, as stage B 2000 has already absorbed the large
amount of
latent heat energy of stage A 1000, much less additional energy needs to be
added in stage B
2000 to achieve the desired temperature. By absorbing the latent heat energy
of the steam in
stage A 1000 in heat exchanger A 100 the ammonia has already been converted to
a high
temperature and pressure vapour at point 14. It may he understood by a person
skilled in the
art that, in this example, with the pressures and temperatures chosen, the
ammonia is a
vapour at point 14. However, the working fluid B in this case ammonia can exit
heat
exchanger A 100 as a liquid, vapour, or super critical liquid or super
critical vapour at point
14 depending on the operating pressures desired for stage B. It then enters
boiler B 5 where it
is heated to the desired temperature before entering turbine B 6 at point 15.
On exiting
turbine B 6 at low pressure at point 16 the ammonia enters heat exchanger B
100 where it is
cooled until it becomes liquid at point 17. Pump B 7 then pumps the liquid
ammonia to the
high pressure (that may be sub critical, critical or super critical pressure)
point 18.
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[0040] In one implementation, as a significant amount of the total amount of
energy added
in stage B 2000 was obtained from the transfer of the latent heat of
vaporization of stage A
1000 to stage B 2000, much less additional energy is required in stage B 2000
to get the
ammonia to the desired temperature. Therefore, all stages after the first
stage will operate at
5 very high efficiencies which will more than compensate for the slight
efficiency drop in stage
A 1000.
[0041] In one implementation, each stage may be isolated from the other stages
and none
of the different stage fluids mix.
[0042] In one implementation, different fluids may be used in each stage. A
person skilled
in the art will understand that same fluid may also be used in subsequent
stages, but at a
lower pressure.
[0043] In one implementation, different pressures and temperatures may be used
in each
stage as desired and as per die requitement of the system/power plant.
[0044] In one implementation, the present invention enables to use any of
existing
techniques such as regenerative heat, open feed water heater, a multi stage
turbines, and the
like can continue to be used in each individual stage.
[0045] In one implementation, the present invention may be used with any heat
source that
may include but not limited to coal, solar, nuclear, and the like.
[0046] In one implementation, the latent heat of vaporization of any stage may
be
transferred into the input of the next stage at a temperature and pressure
sufficiently high so
as to cause a complete or partial phase change from liquid to vapour or super
critical vapour
and in the process the vapour of the first stage may be converted into liquid.
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[0047] In one implementation, the turbine exit pressure in all but the last
stage may be
above atmospheric temperature and pressure.
[0048] In one implementation, any number of stages and choice of working
fluids may be
chosen depending individual requirements.
[0049] In one implementation, it may be understood that the first stage
efficiency of heat to
electricity conversion may be slightly reduced with respect to what is
possible in current
designs. The subsequent stages may have a "virtual" efficiency that may even
exceed 100%,
and is explained in below sections.
[0050] In one implementation, for best results (although not essential), the
working fluid of
stage A 1000 may have the highest critical point temperature. Each subsequent
stage e.g.,
2000 may have a working fluid with a lower critical point temperature then the
previous
stage. Therefore, water would generally be the choice of fluid for the first
stage.
[0051] In one implementation, the present invention may be used as the lower
stage of a
gas fired plant.
[0052] In one implementation, in addition to a heat exchanger 100, a heat pump
can also
be used to transfer heat from one stage to the next. Although the heat pump
would consume
energy and reduce the efficiency, it would also allow for removal of the
temperature drop
that may have to be maintained in some cases in the heat exchanger in order to
transfer
energy. The absence of a temperature drop in the heat exchanger would give a
better
efficiency and this would help in negating the energy consumed by the heat
pump. For
example, a heat exchanger could be used to transfer the bulk of the energy
while maintaining
a temperature difference, and the final amount of energy could be transferred
using a heat
pump so that no temperature difference exists. This may be useful in the end
stages.
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[0053] In one implementation, a multi stage electric power generation
apparatus with at
least two stage system is disclosed. The electric power generation apparatus
comprises of: a
first stage power cycle 1000 comprising a first working fluid (not shown), and
configured for
electric power generation, and thereby generating waste heat(latent heat of
vaporization
and/or condensation); a second stage power cycle 2000 comprising a second
working fluid
(not shown), and configured for electric power generation, and thereby
generating waste
heat(latent heat of vaporization and/or condensation); WHEREIN the second
working fluid
absorbs all the waste heat(latent heat of vaporization and/or condensation)
generated from
first stage power cycle for the purpose of electric power generation.
[0054] In one implementation, the first power generating stage comprises: a
first means
configured to pass the first working fluid at a high pressure, a second means
2 configured to
receive the first working fluid at the high pressure; heat the first working
fluid to a high
temperature to generate a heated or superheated fluid or vapour; a third means
3 and fourth
means 4 configured to receive the heated fluid/vapour, and expand it till it
drops to a certain
tempetatute and pressure, middle working fluid exits the power extraction
stage at low
pressure and temperature with its waste heat (latent heat of vaporization
and/or
condensation).
[0055] In one implementation, the present invention comprises a heat exchanger
mechanism 100, wherein the heat exchanger mechanism 100 is configured to
transfer the
waste heat (latent heat of vaporization and/or condensation) generated from
the first stage
1000 to the second working fluid in the second stage 2000, and converts the
second working
fluid into a high temperature and pressure fluid or vapour.
[0056] In one implementation, the heat exchanger mechanism 100 is configured
to receive,
during the first stage power cycle 1000, the first working fluid vapours from
the fourth means
4, and cool it till it is converted to liquid form, and pass it to the first
means 1; or receive,
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during the second stage power cycle 2000, the second working fluid vapours
from the
seventh means 7, and heat it with the waste energy of stage A 1000.
[0057] In one implementation, the second stage power cycle, comprises a fifth
means 5
.. configured to: receive the second working fluid in liquid or vapour form at
a high
temperature and pressure,: and heat the second working fluid in liquid or
vapour form to high
temperature and pressure vapour; a sixth means 6 configured to receive the
heated vapour at
the high temperature and pressure, and generate electric power from the
vapours, and exit the
power extraction stage at low pressure and temperature with its latent heat of
vaporization
and/or condensation to enter a heat exchanger 200 where its waste heat (latent
heat) is either
transferred to the next stage or rejected to the atmosphere; a seventh means 7
configured to
pass the second working fluid in liquid form at a high pressure.
[0058] Referring now to figure 4 illustrates a method for generating an
electrical power
using an electric power generation apparatus with at least two stage latent
heat exchange
mechanism, in accordance with an embodiment of the present subject matte'.
[0059] The order in which the method is described is not intended to be
construed as a
limitation, and any number of the described method blocks can he combined in
any order to
implement the method or alternate methods. Additionally, individual blocks may
be deleted
from the method without departing from the scope of the subject matter
described herein.
Furthermore, the method can be implemented in any suitable hardware, firmware,
or
combination thereof. However, for ease of explanation, in the embodiments
described below,
the method may be considered to be implemented in the above described electric
power
generation apparatus.
[0060] At block 402, electrical power is generated using first working fluid.
The method of
generation is explained in description of figure 5.
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[0061] At block 404, the latent heat of vaporization and/or condensation
(waste heat) of
the first working fluid is transferred to a second working fluid which is
physically isolated
from the first fluid. In the process the first working fluid is converted from
vapour to liquid
phase.
[0062] At block 406, the second working fluid after absorbing all the waste
heat of the first
stage may be further heated to obtain the desired temperature for the purpose
of generating
useable power. The method of generation is explained in description of figure
6.
[0063] At block 408, after power extraction, the remaining energy of the
second working
fluid (waste heat) may be transferred to a third working fluid or to the
surrounding as waste
heat.
[0064] Referring now to figure 5 illustrates a method performed during the
first stage
power cycle 1000, in accordance with an embodiment of the present subject
matter.
[0065] At block 502, the first working fluid at a high pressure is passed
using a first means
1.
[0066] At block 504, the first working fluid at the high pressure is received
by a second
means 2. The second means 2 heats the first working fluid to a high
temperature to generate a
heated fluid.
[0067] At block 506, the heated fluid is received by a third means 3 and
fourth means 4.
The means 3 and 4 expands it till it drops to a certain temperature and
pressure for the
purposes of power generation.
[0068] At block 508, any existing means for enhancing efficiency may also be
utilized as
desired.
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[0069] At block 510, the waste heat (latent heat) generated in this stage is
transferred to the
second stage working fluid in latent heat exchange mechanism A 100. In the
process, the first
working fluid is converted back to liquid phase and again provided to the
first mean 1 and the
5 cycle is repeated in 1000
[0070] Referring now to figure 6 illustrates a method performed during the
second stage
power cycle 2000, in accordance with an embodiment of the present subject
matter.
10 [0071] At block 602, the second working fluid at a high pressure is
passed using a seventh
means 7.
[0072] At block 604, the second working fluid of stage B 2000 absorbs all the
waste heat
(latent heat of vaporization /condensation) of the first working fluid of
stage A 1000 and in
15 the process significantly raises its temperature and energy content.
[0073] At block 606, the second working fluid at high temperature and pressure
exits from
the heat exchanger mechanism 100 wherein the latent heat from stage A 1000 is
provided to
the second working fluid, is received by the fifth means 5 at a high
temperature and pressure
and further heated if desired to the final temperature.
[0074] At block 608, the second working fluid enters the sixth means 6 at high
temperature
and pressure for the purposes of energy generation.
[0075] At block 610, any existing means for enhancing efficiency may also be
utilized as
desired.
[0076] At block 612, the excess waste heat generated in second stage 2000 is
either
transferred to a third working fluid or emitted or ejected out into the
atmosphere by the heat
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exchanger 200. In the process, the second working fluid is converted back to
liquid phase and
again provided to the seventh mean 7 and the cycle is repeated in stage B
2000.
[0077] It is to be noted that the massive amount of energy that is released in
a phase
change of steam to liquid water can only be removed with a phase change
(complete or
partial) in another liquid which in this example is ammonia. The alternative
is to use the
existing technique of massive amounts of cooling water from rivers or oceans
in which case
the latent heat is lost to the environment as low temperature waste heat. The
present
invention enables to transfer all the latent energy of a working fluid at
relatively low pressure
into the high pressure input stage of another turbine cycle. With proper
choice of working
fluids, pressures, and temperatures it is possible to achieve any efficiency
one desires.
[0078] In one implementation, the choice of temperatures and pressures or
coolants used
are just an example to help in understanding the process, and any temperature
or pressure or
coolant could be used depending on individual situations. The important point
is that the
latent. heat is nut 'ejected into the annusphele as waste heat but is
Liansfelled into the next
stage with proper choice of turbine exit pressures and temperatures depending
on the coolant.
The reason why we can exceed the limits set by the Carnot Equations is that
they were never
really applicable to any system that utilizes a phase change in order to
extract energy from
heat. The obvious example to support this statement is the very fact that no
system in
operation has come even remotely close to the efficiencies defined by the
Carnot Equations.
In any system employing a phase change the actual maximum efficiency under
ideal
conditions should be described as :
Efficiency = Qin¨AHvap = 1- AHvap
Qin Qin
Where Qin is the total energy input per kilogram in units of KJ/Kg
And AHvap is the latent heat of vaporization in kJ/Kg at the turbine exit
pressure.
[0079] In the
above equation, the steam exiting the turbine is not a saturated vapour. If a
saturated vapour is allowed or desired, the latent heat value should be
adjusted accordingly.
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In the event that two stages as described earlier in the document are used the
Eeqi juva.aption would
be as:
(Q li
tkn tap)+ (41-0-ap + E(Qii3n ¨AHVap)) + Egg, -aA Hilap
Efficiency ¨ (2 ¨ 1 EA
Hap
Olt + EQPn gilt+ 6QPn
Where 0, is the energy input per kilogram in units of KJ/Kg in stage A
And On is the energy input per kilogram in units of KJ/Kg in stage B
And 6,F1 apis the latent heat of vaporization in kJ/Kg at the turbine exit
pressure in stage A
And AHap is the latent heat of vaporization in kJ/Kg at the turbine exit
pressure in stage B
And E if the flow factor to compensate for the different flow rates that may
exist between
stages A and B and would be defined as (mass flow rate of stage B)/(mass flow
rate of stage
A)
Similarly, for more than 2 stages the equation would be as
EnAIALp
Efficiency ¨ 1 A
Qin +6134can
Where n is the number of stages and ar, is the mass flow rate in stage n
divided by the mass
flow rate of stage A.
If energy losses are to be taken into account, the equation would be
En AHUap +Et
Efficiency= 1- _____________________________
Qin-FEBQI3n+ .............................. + criQPn
Where Et is the total energy loss in the entire system.
[0080] Naturally from the above equations, the following observations/
understanding can
be made:
1) The greater the number of stages, the greater will be the overall
efficiency.
2) With an unlimited number of stages in an ideal system, the efficiency
would
approach 100%. However, in practice it will be difficult to find enough
working
fluids to do so and with diminishing output in each additional stage, it would
be
probably best to limit it to 3 or 4 stages to optimize both output and
financial returns.
3) It may seem from the equations that one could simply choose a working
fluid
with a low latent heat of vaporization to increase the efficiency of the
system. This is
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actually the opposite of what would happen. The equations represent what would
happen in ideal conditions where there is no energy, heat, friction, or other
losses. In
real conditions if a fluid of low latent heat was used, the condensate and
feed water
pumps would require a large fraction of the total amount of energy produced.
Apart
from its chemical properties, water is the obvious best choice due to its very
large
latent heat of vaporization. The higher the latent heat of vaporization, the
greater the
expansion volume that occurs upon phase change, and it is this very large
expansion
ratio of steam that allows it to drive turbines efficiently and have a very
small relative
power requirement for the condensate and feed water pumps.
4) Only the latent heat of the final stage is rejected to the atmosphere.
5) The above equations will apply to any system that uses a phase change to
convert heat energy into any other form of useable energy.
6) In current designs, to try and maximize energy extraction the steam
generally
exits the turbine as a saturated vapour and causes damage to the low pressure
turbine
blades. In this design, that is not necessary which will extend turbine blade
life.
WORKING EXAMPLE: THEORETICAL RESULTS
[0081] The following example will show the advantage of the design explained
in this
document. Its sole purpose is only to help in explaining the concept and in no
way limits the
protection scope of the design in any aspect whatsoever to the fluids,
temperatures and
pressures used to explain the process. If it is assume that at point 10 the
super critical fluid is
at 600 C and 250 bar pressure then it has an Enthalpy of 3493kJ/Kg. In current
designs
(assuming no reheat or any other efficiency increasing technique), on exiting
the turbine at
0.1 bar it still has an enthalpy of about 2450kJ/Kg of which about 2257kJ/Kg
is the latent
heat of vaporization (or condensation) which is removed to the atmosphere as
low quality
waste heat resulting in an efficiency of only about 35% ((3493-2257)/3493).
Now all we have
to do is to make sure this waste heat of 2257kJ/Kg is not wasted into the
atmosphere and we
have an extremely efficient system.
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[0082] As an example, if at point 11, let the steam leave the turbine and
enter condenser A
at say 180 C and a pressure of 10 bar, the enthalpy would be about 2777kJ/Kg
on exiting the
turbine. In condenser A this heat energy is transferred to Stage B in which
the working fluid
is Ammonia at say 100 bar at point 18 with a temperature of 40 C and enthalpy
of 536kJ/Kg.
The fluids in cycles A and B are completely isolated from each other and it is
essential that
there is no direct contact of the fluids at any place. This allows the
different stages to operate
at different pressures and temperatures and one can control them according to
their
requirements. At 100 bar Ammonia will undergo a phase change above 125.17 C
whereas
the steam in stage A at 10 bar will change phase below 179.88 C. This
temperature
difference will allow for the energy transfer from stage A to B in heat
exchanger A and as the
Ammonia goes from liquid phase to a vapour phase, the steam in stage A cools
down to a
liquid which can then be pumped to a higher pressure to continue the cycle.
The large amount
of energy released by a phase change of steam to liquid water can only be
absorbed because
the ammonia changes phase from liquid to vapour. When the ammonia leaves the
heat
exchanger A at 180 C with an Enthalpy of 183 lkJ/Kg, it has absorbed all the
latent energy
available in the water in stage A.
[0083] The flow rate of stage B could be higher or lower than that of stage A
so as to
match the amount of energy that needs to he transferred between stages. In
heat exchanger A
the steam releases 2027kJ/Kg (2777kJ/Kg-750kJ/Kg) whereas the ammonia can
absorb only
1295kJ/Kg (183 1kJ/Kg-536kJ/Kg). To transfer all this energy in this
particular example, the
mass flow rate of Ammonia would have to be 1.56 (2027kJ/Kg/1295kJ/Kg) times
greater
than the mass flow rate of water in order to absorb all the energy required to
convert it to
liquid. If a lower or higher flow rate ratio is preferred for the ammonia
cycle, one need only
to simply increase or decrease the turbine exit pressure and temperature of
stage A according
to the requirements.
[0084] It is assumed that about a 50 C temperature difference is maintained in
the heat
exchanger to allow for energy transfer from one stage to the next and a heat
pump can be
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used for the final amount of energy transfer if desired or necessary. If a
lower or higher
temperature difference is desirable, the calculations would be adjusted
accordingly. A heat
pump can also be used to transfer heat from one stage to the next in which
case the
temperature difference could be zero or even negative if required in certain
cases. This would
5 result in a slightly higher efficiency for each stage but the energy used
by the heat pump must
also be taken into consideration to determine if it is beneficial to do so.
[0085] Although, the system shown in figure 3 may have reduced the efficiency
of stage A
slightly, we have transferred the latent heat of stage A into the input of
stage B and made the
10 working fluid a high pressure vapour at point 14 and all that is needed
is a little extra energy
in boiler B to take the ammonia temperature from 180 C to 420 C or about
781kJ/Kg as
shown in fig. 3 (2612kJ/Kg-1831kJ/Kg=781kJ/Kg). By comparison 3484kJ/Kg is
added in
stage A. This gives a 'virtual' efficiency for stage B as ((2612-1637)/(2612-
1831))*100 =
125%. The average efficiency for the first two stages is (total energy output)
/ (total energy
15 input) = ((3493-2926)+(3667-2777)+1.56*(2612-1637))/(3493-750+3667-
2926+1.56* (2612-
1831)) = 63.3%. This figure of course is an approximation since no energy
losses have been
taken into account. However, with just 2 simple (utilizing only 1 reheat in
stage A) stages,
the design has already greatly exceeded all performance limits possible with
current design
systems. The third stage will result in an efficiency that will exceed those
set by the Carnot
20 equations thus invalidating them. With an unlimited number of stages and
ideal systems, one
could actually approach near 100% efficiency.
[0086] Exemplary embodiments discussed above may provide certain advantages.
Though
not required to practice aspects of the disclosure, these advantages may
include:
= that the cost per unit of power will decrease. Pollution will be reduced
as less
fuel will have to be burnt for the same amount of electricity output.
= on a planet which is facing a significant danger of a runaway increase in
temperature due to pollution, this will provide significant relief.
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= Another benefit is that the existing electricity generating capacity will
increase
significantly with relatively small additional investment.
[0087] It may be noted and understood by the person skilled in the art that
there are
various means used in the present invention. Each means is a specific device
for performing
specific functions as disclosed above. For example,
First means and Seventh means may include but not limited to pumps and the
like devices having similar functionality or purpose as that of the pump.
Second means and Fifth means may include but not limited to boilers and the
like devices having similar functionality or purpose as that of the boilers.
Third means, Fourth means, and Sixth means may include but not limited to
high pressure turbines, low pressure turbines, and the like devices having
similar
functionality or purpose as that of the high / low pressure turbines.
[0088] Although implementations for a system for high efficiency energy
conversion cycle
by recycling latent heat of vaporization have been described in language
specific to structural
features and/or methods, it is to be understood that the appended claims are
not necessarily
limited to the specific features or methods described. Rather, the specific
features and
methods are disclosed as examples of implementations for a system for high
efficiency
energy conversion cycle by recycling latent heat of vaporization.
[0089] The examples mentioned in this entire document are meant only to assist
in
understanding the basic concept of the design and in no way limit the scope of
the design.
The important point is that the latent heat of vaporization/condensation
(waste heat) is
transferred into subsequent stages to increase the efficiency of heat to
electricity conversion
instead of rejecting it to the atmosphere as is the current practice. All
designs with minor
modifications or alterations that seek to utilize the latent heat of
vaporization/condensation
(waste heat) as described in this document are also covered by the scope of
this patent.
