U.S. patent application number 12/696363 was filed with the patent office on 2011-08-04 for system and method for equilibrating an organic rankine cycle.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to Sean P. Breen, Sitaram Ramaswamy.
Application Number | 20110185733 12/696363 |
Document ID | / |
Family ID | 44340413 |
Filed Date | 2011-08-04 |
United States Patent
Application |
20110185733 |
Kind Code |
A1 |
Ramaswamy; Sitaram ; et
al. |
August 4, 2011 |
SYSTEM AND METHOD FOR EQUILIBRATING AN ORGANIC RANKINE CYCLE
Abstract
Embodiments of an ORC system can be configured to reduce ingress
of contaminants from the ambient environment. In one embodiment,
the ORC system can comprise a pressure equilibrating unit that
comprises a variable volume device for holding a working fluid. The
variable volume device can be fluidly coupled to a condenser so
that working fluid can move amongst the condenser and the variable
volume device. This movement can occur in response to changes in
the pressure of the working fluid in the ORC system, and in one
example the working fluid is allowed to move when the pressure
deviates from atmospheric pressure.
Inventors: |
Ramaswamy; Sitaram; (West
Hartford, CT) ; Breen; Sean P.; (Holyoke,
MA) |
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
44340413 |
Appl. No.: |
12/696363 |
Filed: |
January 29, 2010 |
Current U.S.
Class: |
60/651 ;
60/660 |
Current CPC
Class: |
F01K 25/08 20130101;
F01K 13/02 20130101 |
Class at
Publication: |
60/651 ;
60/660 |
International
Class: |
F01K 25/08 20060101
F01K025/08; F01K 13/02 20060101 F01K013/02 |
Claims
1. A system operating as an Organic Rankine Cycle system in an
ambient environment, said system comprising: an integrated system
having in serial flow relationship a pump, a vapor generator, a
turbine, and a condenser; and a variable volume device having
volume in fluid communication with the condenser, wherein the
volume changes from a first volume to a second volume in response
to a change in the pressure of the integrated system.
2. A system according to claim 1, wherein the variable volume
device is directly coupled to the condenser.
3. A system according to claim 1, further comprising a valve unit
coupled to the condenser and the variable volume device, wherein
the valve unit changes amongst a plurality of states in response to
the change in pressure, and wherein the volume changes from the
first volume to the second volume in response to the change in the
state of the valve unit.
4. A system according to claim 1, wherein the volume change results
from a drop in the pressure of the integrated system below a set
point pressure.
5. A system according to claim 4, wherein the set point pressure is
about the pressure of the ambient environment.
6. A system according to claim 1, wherein the variable volume
device comprises a bellows that receives the condensed working
fluid therein, and wherein the bellows comprises a flexible
material that expands to accommodate at least one of the first
volume and the second volume.
7. A system according to claim 1, further comprising in-line with
the condenser and the variable volume device: a pressure
equalization valve responsive to the change in pressure; and a flow
control valve responsive to a volume limit for the variable volume
device, wherein the volume limit is a function of the amount of
condensed working fluid in the variable volume device.
8. A system according to claim 7, wherein the volume limit
comprises a minimum volume limit and a maximum volume limit.
9. A method of equilibrating the pressure of a system for
performing an Organic Rankine Cycle, said method comprising:
integrating in serial flow relation a pump, a vapor generator, a
turbine, and a condenser; coupling in fluid communication a
variable volume device to the condenser; changing the amount of
condensed working fluid in the variable volume device in response
to a change in the pressure of said system.
10. A method according to claim 9, further comprising flowing the
working fluid between the condenser and the variable volume device
through a valve unit, wherein the change in pressure causes the
valve unit to actuate from a first state to a second state, and
wherein the amount of condensed working fluid in the variable
volume device in the first state is less than the amount of
condensed working fluid in the variable volume device in the second
state.
11. A method according to claim 10, wherein pressure in the second
state is less than a set point pressure, and wherein the set point
pressure is at least about atmospheric pressure.
12. A method according to claim 9, further comprising: measuring
the amount of condensed working fluid in the variable volume
device; and metering the flow of the condensed working fluid from
the variable volume device based on the amount of the condensed
working fluid.
13. A method according to claim 12, wherein the condensed working
fluid flows through a flow control valve, and wherein the flow
control valve is responsive to a control that identifies the
amount.
14. A method according to claim 13, wherein the amount comprises a
minimum volume limit and a maximum volume limit.
15. A method according to claim 9, wherein the variable volume
device comprises a bellows that expands to accommodate the amount
of condensed working fluid in the variable volume device.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to Organic Rankine
Cycle ("ORC") systems, and in one particular embodiment to such ORC
systems that reduce contamination of the working fluid by
maintaining pressure of the working fluid in the system.
BACKGROUND
[0002] ORC systems are generally well-known and commonly used for
the purpose of generating electrical power that is provided to a
power distribution system or grid for residential and commercial
use across the country. These systems implement a vapor power cycle
that utilizes an organic fluid as the working fluid instead of
water/steam. Functionally these ORC systems resemble the steam
cycle power plant, in which a pump increases the pressure of the
condensed working fluid, the condensed working fluid is vaporized,
and the vaporized working fluid interacts with a turbine to
generate power.
[0003] Notably the ORC systems are generally closed-loop systems.
However, systems of this type are particularly sensitive to changes
in internal pressure because such changes can permit ingress of
contaminants into the working fluid. These contaminants can not
only reduce the efficiency of the ORC system, but also cause damage
to one or more of the components that are used to implement the ORC
cycle. Repairs, maintenance, and general cleaning of the system can
be costly, as the ORC system must be taken off-line and thus no
longer generates power that can be provided to the energy grid.
[0004] To avoid some issues of contamination, certain approaches
utilize various forms of purge systems, which are fluidly coupled
to the ORC system. These purge systems are typically configured to
extract the working fluid from the ORC system, remove contaminants
from the working fluid, and reintroduce the "clean" working fluid
back into the ORC system. However, while this approach does address
the issue of contamination, the purge systems require
infrastructure, circuitry, and general structure that must be
provided in addition to the components of the ORC system. This
additional equipment can add cost and maintenance time to the ORC
system. Moreover, the purge systems generally do not address the
source of the contamination which is the ingress of contaminated
fluids, such as air from the environment that surrounds the
closed-loop ORC system.
[0005] There is therefore a need for an ORC system and method that
can reduce the likelihood of the ingress of such contaminated air
to address the issue of contamination in ORC systems at the source
of the problem. There is likewise a need for solutions to the
contamination issue that do not require the addition to the ORC
system of substantially new equipment, costs, and control
infrastructure.
SUMMARY
[0006] There is described below embodiments in accordance with the
present invention that can maintain the pressure within ORC system
to reduce the ingress of fluids such as gases from the
environment.
[0007] There is provided in one embodiment a system operating as an
Organic Rankine Cycle system in an ambient environment. The system
can comprise an integrated system having in serial flow
relationship a pump, a vapor generator, a turbine, and a condenser.
The system can also comprise a variable volume device in fluid
communication with the condenser. The system can further be
described wherein the volume changes from a first volume to a
second volume in response to a change in the pressure of the
integrated system.
[0008] There is also provided in another embodiment a method of
equilibrating the pressure of a system for performing an Organic
Rankine Cycle. The method can comprise a step for integrating in
serial flow relation a pump, a vapor generator, a turbine, and a
condenser. The method can also comprise a step for coupling in
fluid communication a variable volume device to the condenser. The
method can further comprise a step for changing the amount of
condensed working fluid in the variable volume device in response
to a change in the pressure of said system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention briefly summarized above,
may be had by reference to the embodiments, some of which are
illustrated in the accompanying drawings. It is to be noted,
however, that the appended drawings illustrate only typical
embodiments of this invention and are therefore not to be
considered limiting of its scope, for the invention may admit to
other equally effective embodiments. Moreover, the drawings are not
necessarily to scale, emphasis generally being placed upon
illustrating the principles of certain embodiments of
invention.
[0010] Thus, for further understanding of the concepts of the
invention, reference can be made to the following detailed
description, read in connection with the drawings in which:
[0011] FIG. 1 is a schematic diagram of an example of an ORC system
that is made in accordance with concepts of the present
invention;
[0012] FIG. 2 is a schematic diagram of another example of an ORC
system that is made in accordance with concepts of the present
invention;
[0013] FIG. 3 is a flow diagram of a method of operating an ORC
system, such as the ORC systems of FIGS. 1 and 2; and
[0014] FIG. 4 is a flow diagram of another method of operating an
ORC system, such as the ORC systems of FIGS. 1 and 2.
DETAILED DESCRIPTION
[0015] In accordance with its major aspects and broadly stated,
embodiments of the present invention are directed to systems and
methods for equilibrating the pressure of a working fluid in power
generating systems such as those systems implementing (and/or
operating) as an ORC system. There is provided in the discussion
below, for example, embodiments of such systems that are configured
to maintain, or limit deviations in, the pressure of the working
fluid in a manner that can substantially reduce ingress of, e.g.,
air, that is found outside of the system. This response can
effectively prevent contaminants and other materials (including
solids, gases, and liquids) that are deleterious to the operation
of the system from mixing with the working fluid. This feature is
particularly beneficial because the inventors have discovered that
unlike the systems discussed in the Background above, which must
purge all of the working fluid to remove such contamination, the
systems of the present embodiments not only reduce the likelihood
of contamination that can result from pressure variations in the
system, but also can maintain operation without the need to
interfere with the system to address such contamination.
[0016] Referring now to FIG. 1, there is shown a schematic
illustration of an ORC system 100 that is made in accordance with
concepts of the present invention. Those familiar with ORC systems
will generally recognized that a working fluid (not shown) such as
a refrigerant (e.g., water, R245fa) can be provided in the ORC
system 100. This working fluid flows amongst the various components
of the ORC system, some of which are discussed in more detail
below. The components are typically coupled together as closed-loop
systems, which are substantially hermetically sealed from the
environment (hereinafter "the ambient environment"). This
implementation of the components is designed to maintain the
pressure, temperature, and other parameters of the working fluid
irrespective of the parameters of the ambient environment around
the ORC system 100.
[0017] In one embodiment, the ORC system 100 can comprise a vapor
generator 102, a turbine generator 104, a pump 106, and a condenser
108. The ORC system 100 can further comprise a pressure
equilibrating unit 110, which in one particular construction can
have as components the condenser 108, a variable volume device 112,
and a valve unit 114 that is coupled to the condenser 108 and the
variable volume device 112. A control unit 116 can be coupled to
one or more of the valve unit 114, the variable volume device 112,
as well as other portions of the ORC system 100 as desired, and as
exemplified in the discussion further below.
[0018] Related to the operation of systems such as the ORC system
100, the vapor generator 102, which is commonly a boiler having
significant heat input to the working fluid, vaporizes the working
fluid. The working fluid vapor that results is passed to the
turbine generator 104 to provide motive power to the turbine
generator 104. Upon leaving the turbine generator 104, the working
fluid vapor passes next to the condenser 108 wherein the working
fluid vapor is condensed by way of heat exchange relationship with
a cooling medium (not shown). The working fluid vapor, now
condensed, is then circulated to the vapor generator 102 by the
pump 106, which essentially completes the cycle of the ORC system
100.
[0019] Focusing on the pressure equilibrating unit 110, the
variable volume device 112 can be configured to accommodate an
amount of the working fluid. This amount can vary such as, for
example, due to the changes in the pressure of working fluid in the
ORC system 100. In one example, the variable volume device 112 can
be provided as a bellows, balloon, and similar device with a volume
that can expand and contract to accommodate more or less working
fluid as required. These devices can be variously constructed from
expandable and/or flexible materials that are compatible with the
working fluid, as well as being resilient to the pressure and
temperatures of the working fluid within the ORC system 100.
Examples of such materials can include, but are not limited to, ERA
7810, ERA 7815, GN 807, Neopren/Hypalon 2012, Nylon-PU, OZ 23, OZ
35, OZ PUR, Perl X 10, VB 42, Monel 400, Inconel 600, and Stainless
Steel 316, among many others.
[0020] The valve unit 114 can be positioned to receive the working
fluid from both the condenser 108 and the variable volume device
112. The valve unit 114 can be configured to meter this flow of the
working fluid such as in response to changes in the pressure of the
working fluid in the ORC system 100. The valve unit 114 can also
operate in and amongst a plurality of states. These states can
correspond to the changes in the pressure of the working fluid in
the ORC system 100. Based on these changes, the valve unit 114 can
operate to prevent or to permit the flow of the working fluid as
between the condenser 108 and the variable volume device 112.
[0021] The control unit 116 can also facilitate operation of the
valve unit 114, such as by providing a control to the valve unit
114. This control can be in the form of an electrical signal or
other indicator that is selected to change the valve unit 114 such
as between the open and closed states discussed above. The control
unit 116 can interface with sensors, probes, and the like to
monitor one or more parameters of the working fluid. Deviations
from certain established parameters such as a set point pressure
can cause the control unit 116 to provide the control, which can
influence the operation of the valve unit 114. The set point
pressure can be set to the value of the pressure of the ambient
environment, with the set point pressure of one embodiment of the
ORC system 100 being set to about atmospheric pressure.
[0022] Discussing the operation of one exemplary embodiment of the
ORC system 100, the valve unit 114 can fluidly couple the condenser
108 to the variable volume device 112. When the pressure of the
working fluid in the condenser 108 drops below atmospheric
pressure, the valve unit 114 can change to an open state in which
working fluid moves from the variable volume device 112 to the
condenser 108. This flow can re-equilibrate the pressure in the
condenser 108, at which point the valve unit 114 can change to a
closed state, which effectively stops the flow of the working
fluid.
[0023] Another embodiment of an ORC system 200 can be had with
reference to the schematic diagram illustrated in FIG. 2. Like the
example of FIG. 1, the ORC system 200 can also comprise a vapor
generator 202, a turbine generator 204, a pump 206, a condenser
208, as well as a pressure equilibrating unit 210 with a variable
volume device 212 and a valve unit 214. There can be likewise
provided a control unit 216 in the ORC system 200, which in the
present example can be coupled variously to the ORC system 200.
[0024] By way of non-limiting example, and with particular
reference to the pressure equilibrating unit 210, the valve unit
214 can comprise one or more valves 218 such as the pressure
equilibrating valve 220 and the flow control valve 222. Typically
the valves 218 are sized and configured to permit adequate flow,
temperature, and pressure of the working fluid in the ORC system
200. Examples of valves that can be used include, but are not
limited, solenoid valves, check valves, gate valves, globe valves,
diaphragm valves, pressure relief valves, plug valve, and similar
devices that can be used to control the flow of fluids, e.g., the
working fluid. Moreover, while each of the valves 218 are
illustrated as being single devices, there is further contemplated
embodiments of the present invention that employ more than one of,
e.g., the pressure equilibrating valve 220 and the flow control
valve 222 to instantiated the valve unit 214. Combinations of
various valves, tubing, manifolds, and the like can be used, for
example, to meter the flow of the working fluid amongst the
condenser 208 and the variable vacuum device 212.
[0025] In one embodiment, the pressure equilibrating valve 220 and
the flow control valve 222 can open and close to control the flow
of fluid into and out of the variable volume device 212. The flow
can be controlled based on changes in the pressure of the working
fluid. In one example, these valves can have an actuatable
interface (e.g., the solenoid of a solenoid valve), which can be
activated, e.g., by the control, in response to conditions when the
pressure in the condenser drops below atmospheric pressure. In one
example, the activation of the actuatable interface can open the
pressure equilibrating valve 220 and permit the working fluid to
fill the variable volume device 212. In another example, the
actuatable interface can also be activated, e.g., by the control,
in response to conditions when the amount of working fluid in the
variable volume device 212 reaches a pre-determined level such as a
minimum volume limit and a maximum volume limit, as discussed in
connection with the methods of FIGS. 3 and 4. These methods
illustrate one or more exemplary operations of embodiments of the
ORC systems 100, 200 described below.
[0026] With reference now to FIG. 3, and also to FIG. 2, there is
illustrated an example of a method 300 for equilibrating pressure
in an ORC system, such as the ORC system 100, 200 discussed above.
The method 300 can comprise general operating steps 302, which can
comprise a variety of steps 304-308, some of which are useful for
particular operations and processes of the ORC system. In the
present example, the method 300 can comprise, at step 304,
identifying a pre-determined threshold such as the set point
pressure, at step 306, comparing a parameter such as pressure of
the working fluid in the condenser ("the condenser pressure") to
the pre-determine threshold, and at step 308, determining the
direction of flow of the working fluid based on the comparison.
[0027] The steps 304-308 illustrate at a high level one operation
of the ORC systems of the present invention. The direction of flow,
for example, can comprise a direction wherein the working fluid
moves from the condenser (and/or ORC system) toward the variable
volume device. This direction may correspond to conditions in which
the condenser pressure drops below atmospheric pressure. The
direction of flow can also comprise a direction wherein the working
fluid moves from the variable volume device toward the condenser
(and/or ORC system). This direction may correspond to conditions in
which the condenser pressure is greater than atmospheric
pressure.
[0028] For a more detailed operation of ORC systems such as the ORC
systems 100, 200, reference can now be had to the method 400 that
is illustrated in FIG. 4 and described below. In this example, and
like the method 300 described above, the method 400 can comprise
general operating steps 402, which can comprise at step 404
identifying a pre-determined threshold such as the set point
pressure, at step 406, comparing a parameter such as the condenser
pressure to the pre-determine threshold, and at step 408,
determining the direction of flow of the working fluid based on the
comparison.
[0029] Moreover, the method 400 can comprise start-up operating
steps 410 and shut-down operating steps 412. Each of the operating
steps 402, 410 and 412 can be implemented together as part of the
operative configuration of the ORC system. In other embodiments of
the ORC system, one or more of the operating steps 402, 410, and
412 can be implemented separately or as part of different operating
procedures and processes for the ORC system.
[0030] Discussing first the start-up operating steps 410 for the
ORC system, there is shown in the FIG. 4 that the method 400 can
comprise at step 414 receiving a startup completed signal, and at
step 416 opening the flow control valve. The method can further
comprise at step 418 comparing the pressure of the working fluid at
the condenser to the set point pressure, and in one example the set
point pressure is atmospheric pressure. The method can also
comprise at step 420 determining whether the condenser pressure
deviates from the set-point pressure, and in one particular
implementation the method 400 comprises, at step 422, opening the
pressure equilibrating valve in response to conditions in which the
condenser pressure is greater than the set point pressure. The
working fluid can then flow from the condenser toward the variable
volume device.
[0031] In one embodiment, the method 400 can comprise at step 424
monitoring the amount of working fluid in the variable volume
device, and also at step 426 determining whether the amount has
reached a volume limit for the variable volume device such as the
maximum volume limit and the minimum volume limit discussed above.
One exemplary method 400 can also comprise at step 428 closing the
flow control valve when the amount reaches the maximum volume
limit. This step 428 stops the movement of the working fluid from
the condenser to the variable volume device.
[0032] Referring next to the shut-down operating steps 412, there
is shown in FIG. 4 that the method 400 can comprise, at step 430,
receiving a shutdown complete signal, and at step 432, opening the
flow control valve. The method 400 can further comprise at step 434
comparing the pressure of the working fluid at the condenser to the
set point pressure. The method can also comprise at step 436
determining whether the condenser pressure deviates from the
set-point pressure, and in one particular implementation the method
400 comprises, at step 438, opening the pressure equilibrating
valve in response to conditions in which the condenser pressure is
less than the set point pressure. The working fluid can then flow
from the variable volume device toward the pressure condenser.
[0033] In one embodiment, the method 400 can comprise at step 440
monitoring the amount of working fluid in the variable volume
device, and also at step 442 determining whether the amount has
reached the volume limit for the variable volume device. One
exemplary method 400 can go to step 428 closing the flow control
valve when the amount reaches the minimum volume limit. This step
428 stops the movement of the working fluid from the condenser to
the variable volume device.
[0034] It is contemplated that numerical values, as well as other
values that are recited herein are modified by the term "about",
whether expressly stated or inherently derived by the discussion of
the present disclosure. As used herein, the term "about" defines
the numerical boundaries of the modified values so as to include,
but not be limited to, tolerances and values up to, and including
the numerical value so modified. That is, numerical values can
include the actual value that is expressly stated, as well as other
values that are, or can be, the decimal, fractional, or other
multiple of the actual value indicated, and/or described in the
disclosure.
[0035] While the present invention has been particularly shown and
described with reference to certain exemplary embodiments, it will
be understood by one skilled in the art that various changes in
detail may be effected therein without departing from the spirit
and scope of the invention as defined by claims that can be
supported by the written description and drawings. Further, where
exemplary embodiments are described with reference to a certain
number of elements it will be understood that the exemplary
embodiments can be practiced utilizing either less than or more
than the certain number of elements.
* * * * *