U.S. patent application number 10/139988 was filed with the patent office on 2004-02-05 for heat energy utilization system.
Invention is credited to Anson, Donald, Ball, David A., Hanna, William T., Sullivan, Timothy J..
Application Number | 20040020206 10/139988 |
Document ID | / |
Family ID | 23109927 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040020206 |
Kind Code |
A1 |
Sullivan, Timothy J. ; et
al. |
February 5, 2004 |
HEAT ENERGY UTILIZATION SYSTEM
Abstract
A power generation system includes a prime mover subsystem and a
Rankine-cycle heat energy utilization subsystem. The waste heat
stream from the prime mover subsystem provides sufficient thermal
content to power the heat energy utilization subsystem. The heat
energy utilization subsystem can include a hermetically sealed
scroll device, which can expand the working fluid through a single
or dual scroll pair configuration. The heat energy utilization
subsystem may also include a load-splitting controller, quick-start
features and a capacity control module to facilitate rapid response
to variable load conditions, as well as provide stand-alone
operational capability. The load-splitting controller may
incorporate a fuzzy logic controller to coordinate operation
between the two subsystems. Energy generated by the heat energy
utilization subsystem can be in the form of heat for various
domestic and process needs, or can provide supplemental electric
current.
Inventors: |
Sullivan, Timothy J.;
(Dublin, OH) ; Hanna, William T.; (Gahanna,
OH) ; Anson, Donald; (Worthington, OH) ; Ball,
David A.; (Westerville, OH) |
Correspondence
Address: |
Killworth, Gottman, Hagan & Schaeff, L.L.P.
Suite 500
One Dayton Centre
Dayton
OH
45402-2023
US
|
Family ID: |
23109927 |
Appl. No.: |
10/139988 |
Filed: |
May 7, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60289072 |
May 7, 2001 |
|
|
|
Current U.S.
Class: |
60/670 |
Current CPC
Class: |
Y02E 20/14 20130101;
F01K 23/101 20130101; F05D 2270/706 20130101; F05D 2270/707
20130101; F02G 5/02 20130101; Y02T 10/12 20130101; F01C 11/00
20130101; F01K 25/08 20130101; F01C 1/0215 20130101; F01C 13/00
20130101; F02C 6/18 20130101; Y02T 10/166 20130101; Y02E 20/16
20130101 |
Class at
Publication: |
60/670 |
International
Class: |
F01K 013/00; F01K
001/00 |
Claims
What is claimed is:
1. A heat energy utilization system comprising: a thermal circuit;
a pump to circulate a working fluid through said thermal circuit; a
power module comprising: an expander; and a load absorption device
coupled to said expander such that at least a portion of the energy
produced by the expansion of said working fluid in said expander
operates said load absorption device; a first heat exchanger
including: a first inlet and a first outlet together in fluid
communication with said thermal circuit; and a second inlet and a
second outlet together in heat exchange relationship with said
thermal circuit; and a second heat exchanger, wherein said pump,
power module, first heat exchanger and second heat exchanger are
connected via said thermal circuit so as to be in fluid
communication with one another such that, upon exchange of heat in
said first heat exchanger, the increase in energy content in said
working fluid is converted to useable work in said load absorption
device.
2. A heat energy utilization system according to claim 1, wherein
said second inlet in said first heat exchanger is configured to
accept an externally supplied heat stream.
3. A heat energy utilization system according to claim 2, wherein
said power module is hermetically sealed.
4. A heat energy utilization system according to claim 3, further
comprising: a lubricant pump disposed within said power module and
operatively responsive to said expander; and a lubricant circuit in
fluid communication with said lubricant pump, said lubricant
circuit including a lubricant droplet separator, such that upon
operation of a lubricant pump, said lubricant circuit can circulate
a lubricant within said power module.
5. A heat energy utilization system according to claim 4, further
comprising a desuperheating heat exchanger disposed within said
power module, said desuperheating heat exchanger in thermal
communication with said expander, whereby said desuperheating heat
exchanger reduces the thermal content of fluid exiting said
expander.
6. A heat energy utilization system according to claim 5, wherein
said load absorption device is a generator comprising: a
field-generating rotor; and a stator coil mounted to said
hermetically sealed power module so that upon movement of said
field-generating rotor, it electrically interacts with said stator
coil to produce an electric potential.
7. A heat energy utilization system according to claim 6, wherein
said thermal circuit is a closed loop.
8. A heat energy utilization system according to claim 1, wherein
said working fluid is an organic refrigerant.
9. A heat energy utilization system according to claim 6, wherein
said expander is a scroll device defined by a scroll housing, said
scroll device including at least one scroll pair comprising a pair
of involute spiral wrap members and a rotatable shaft coupled to
said at least one scroll pair such that the expansion of said
working fluid through said at least one scroll pair causes said
rotatable shaft to rotate.
10. A heat energy utilization system according to claim 9, wherein
said field-generating rotor is rotatably coupled to said rotatable
shaft.
11. A heat energy utilization system according to claim 9, further
comprising a second scroll pair coupled to said first pair through
said rotatable shaft.
12. A heat energy utilization system according to claim 11, further
including at least one process heat utilization module in thermal
communication with said thermal circuit, said process heat
utilization module configured to provide process heat to an
external user.
13. A heat energy utilization system according to claim 12, wherein
said at least one process heat utilization module includes a first
process heat utilization module and a second process heat
utilization module, said first process heat utilization module
configured to extract higher temperature energy than said second
process heat utilization module.
14. A heat energy utilization system according to claim 1, further
comprising an auxiliary burner in thermal communication with said
heat stream.
15. A heat energy utilization system according to claim 14, further
comprising: a logic and control module in signal communication with
each of said load absorption device, auxiliary burner, pump, and
adapted to be in signal communication with said heat stream; an
energy storage device in electrical communication with said logic
and control module; and a recharging module in electrical
communication with said load absorption device and said energy
storage device such that said logic and control module is
configured to initiate a start-up sequence for said heat energy
utilization subsystem, and said recharging module recharges said
energy storage device during normal operation of said heat energy
utilization system.
16. A heat energy utilization system according to claim 15, wherein
said energy storage device is an electrical battery.
17. A heat energy utilization system according to claim 16, further
comprising: an accumulator in fluid communication with said first
heat exchanger and expander to collect and store at least a portion
of excess energy from said heat stream; a control valve in fluid
communication with said accumulator; and an isolation valve
disposed within said thermal circuit, said isolation valve to be
used to selectively isolate said first heat exchanger from said
expander, whereby, upon initiation and subsequent operation of said
heat energy utilization system, it is capable of sustained
operation.
18. A heat energy utilization system adapted to be coupled to a
heat source, said heat energy utilization system comprising: a
thermal circuit; a pump to circulate a working fluid through said
thermal circuit; a hermetically sealed power module operating as a
scroll expander, said hermetically sealed power module comprising:
a scroll housing; a plurality of scroll pairs mounted in said
scroll housing, each of which includes a pair of meshed axially
extending involute spiral wrap members; a rotatable shaft coupled
to said plurality of scroll pairs such that the expansion of said
working fluid through said plurality of scroll pairs causes said
rotatable shaft to rotate; a throttle valve disposed in said
thermal circuit to permit a predetermined amount of said working
fluid to enter said scroll expander; and a generator operatively
responsive to said rotatable shaft to produce work; a first heat
exchanger including: a first inlet and a first outlet together in
fluid communication with said thermal circuit; and a second inlet
and a second outlet together in heat exchange relationship with
said first inlet and outlet; and a second heat exchanger, wherein
said pump, first heat exchanger, expander and second heat exchanger
are connected via said thermal circuit so as to be in fluid
communication with one another such that, upon exchange of heat
between said first inlet and outlet and said second inlet and
outlet, the increase in energy content in said working fluid is
converted to electric potential in said generator.
19. A power generation system for providing a primary and secondary
source of output power comprising: a prime mover subsystem
including: means for generating a primary source of power; and
means for generating a heat stream; and a heat energy utilization
subsystem for coupling to said prime mover subsystem, said heat
energy utilization subsystem including: a thermal circuit; a pump
to circulate a working fluid through said thermal circuit; a power
module comprising: an expander; a load absorption device coupled to
said expander such that at least a portion of the energy produced
by the expansion of said working fluid operates to produce power; a
first heat exchanger including: a first inlet and a first outlet
together in fluid communication with said thermal circuit; and a
second inlet and a second outlet together in heat exchange
relationship with said first inlet and outlet; and a second heat
exchanger for cooling said working fluid, wherein said pump, first
heat exchanger, expander and second heat exchanger are connected
via said thermal circuit so as to be in fluid communication with
one another such that, upon introduction of said heat stream from
said prime mover, at least a portion of the increase in energy
content in said working fluid produces useable work in said load
absorbing device.
20. A power generation system according to claim 19, further
including a throttle valve disposed in said thermal circuit to
permit a predetermined amount of working fluid to enter said
expander.
21. A power generation system according to claim 20, wherein said
power module is hermetically sealed in a hermetic shell.
22. A power generation system according to claim 21, further
comprising an auxiliary burner in thermal communication with said
heat stream to augment the thermal content of said heat stream.
23. A power generation system of claim 22, further comprising: a
logic and control module in electrical communication with each of
said generator, auxiliary burner, pump, and means for generating a
primary source of power; an energy storage device in electrical
communication with said logic and control circuit; and a recharging
module in electrical communication with said generator and said
energy storage device such that said logic and control module can
initiate a start-up sequence for said heat energy utilization
subsystem, and said recharging module recharges said energy storage
device during normal operation of said power generation system.
24. A power generation system according to claim 23, wherein said
energy storage device is an electrical battery.
25. A power generation system according to claim 24, further
comprising: an accumulator in fluid communication with said first
heat exchanger and expander to collect and store at least a portion
of excess thermal energy from said heat stream; a control valve in
fluid communication with said accumulator; and an isolation valve
disposed within said thermal circuit, said isolation valve to be
used to selectively isolate said first heat exchanger from said
expander.
26. A power generation system according to claim 25, further
comprising a capacity control module to facilitate the
responsiveness of said heat energy utilization subsystem, said
capacity control module comprising: a speed sensor coupled to said
expander; a feed-back controller operatively responsive to a signal
from said speed sensor so as to actuate said isolation valve; a
bypass valve disposed within said heat stream to control the flow
of said heat stream into said first heat exchanger module; a
plurality of sensors disposed in said thermal circuit to measure
said working fluid temperature and pressure; and a proportional
integral differential logic controller to control said bypass
valve, said pump and said auxiliary burner based on first heat
exchanger sensor input signals.
27. A power generation system according to claim 26, wherein said
speed sensor and feed-back controller are packaged within said
hermetic shell of said power module.
28. A power generation system according to claim 27, further
comprising a load splitting module to analyze and respond to
varying load conditions such that it causes said prime mover
subsystem and said heat energy utilization subsystem to provide
substantially uniform and dynamic load components, respectively, to
the composite electric generation profile.
29. A power generation system according to claim 28, wherein said
load splitting module includes a fuzzy logic controller.
30. A power generation system according to claim 19, further
comprising: a lubricant pump disposed within said power module and
operatively responsive to said expander; and a lubricant circuit in
fluid communication with said lubricant pump, said lubricant
circuit including a lubricant droplet separator, such that upon
operation of said lubricant pump, said lubricant circuit can
circulate a lubricant within said power module.
31. A power generation system according to claim 19, further
comprising a desuperheating heat exchanger disposed within said
power module, said desuperheating heat exchanger in thermal
communication with said expander, whereby said desuperheating heat
exchanger reduces the thermal content of said working fluid exiting
said expander.
32. A power generation system according to claim 19, wherein said
load absorption device is a generator comprising: a
field-generating rotor; and a stator coil mounted to said
hermetically sealed power module so that upon movement of said
field-generating rotor, it electrically interacts with said stator
coil to produce an electric potential.
33. A power generation system according to claim 19, wherein said
thermal circuit is a closed loop.
34. A power generation system according to claim 19, wherein said
working fluid is an organic refrigerant.
35. A power generation system according to claim 19, further
including at least one process heat utilization module in thermal
communication with said thermal circuit, said process heat
utilization module configured to provide process heat to an
external user.
36. A power generation system according to claim 35, wherein said
at least one process heat utilization module includes a first
process heat utilization module and a second process heat
utilization module, said first process heat utilization module
configured to extract higher temperature energy than said second
process heat utilization module.
37. A power generation system according to claim 19, wherein said
prime mover subsystem is a fuel cell.
38. A power generation system according to claim 19, wherein said
prime mover subsystem is a microturbine.
39. A power generation system according to claim 38, where said
microturbine further comprises a recuperator in thermal
communication with said means for generating a heat stream, said
recuperator adapted for preheating air prior to combustion of said
air in said prime mover subsystem.
40. A power generation system according to claim 39, wherein said
combustion takes place in a catalytic combustor.
41. A power generation system according to claim 19, wherein said
expander of said heat energy utilization subsystem is a scroll
device, and includes a scroll housing that contains at least one
pair of meshed axially extending involute spiral wrap members and a
rotatable shaft coupled to said at least one scroll pair such that
the expansion of said working fluid through said at least one
scroll pair causes said rotatable shaft to rotate.
42. A power generation system according to claim 41, further
comprising a second scroll pair of meshed axially extending
involute spiral wrap members coupled to the first scroll pair of
said at least one scroll pair.
43. An integrated power generation system for providing a primary
and secondary source of power, comprising: a microturbine subsystem
configured to generate a heat stream; and a heat energy utilization
subsystem coupled to said microturbine, providing said secondary
source of power, including: a closed-loop thermal circuit; a pump
to circulate a working fluid through said thermal circuit; a first
heat exchanger including: a first inlet and outlet for said
closed-loop thermal circuit; a second inlet and outlet in heat
exchange relationship with said first inlet and outlet, said second
inlet and outlet in fluid communication with said heat stream; a
hermetically sealed power module comprising: a scroll expander to
convert the energy in said working fluid discharged from said first
heat exchanger; and a load absorption device coupled to said scroll
expander such that at least a portion of the energy produced by the
expansion of said working fluid in said scroll expander operates
said load absorption device to produce work; and a second heat
exchanger in fluid communication with said scroll expander, wherein
said pump, first heat exchanger, expander and second heat exchanger
are connected via said thermal circuit so as to be in fluid
communication with one another such that, upon introduction of said
heat stream into said second inlet and outlet, the increase in
energy content in said working fluid is converted to useable work
in said load absorbing device.
44. An integrated power generation system according to claim 43,
further including a throttle valve disposed in said thermal circuit
to permit a predetermined amount of working fluid to enter said
expander.
45. An integrated power generation system according to claim 43,
wherein said load absorbing device is a generator rotatably
responsive to said rotatable shaft to produce an electric
potential.
46. An integrated power generation system according to claim 43,
where said microturbine subsystem further comprises a recuperator
in thermal communication with said heat stream such that during
microturbine operation, said recuperator preheats air prior to
combustion of said air in said microturbine subsystem.
47. An integrated power generation system according to claim 46,
wherein said microturbine subsystem includes a catalytic
combustor.
48. An integrated power generation system according to claim 43,
wherein said heat energy utilization subsystem further comprises an
auxiliary burner in thermal communication with said heat stream to
augment the thermal content thereof.
49. An integrated power generation system according to claim 43,
further comprising: a lubricant pump disposed within said power
module and operatively responsive to said expander; and a lubricant
circuit in fluid communication with said lubricant pump, said
lubricant circuit including a lubricant droplet separator, such
that upon operation of said lubricant pump, said lubricant circuit
can circulate a lubricant within said power module.
50. An integrated power generation system according to claim 43,
further comprising a desuperheating heat exchanger disposed within
said power module, said desuperheating heat exchanger in thermal
communication with said expander, whereby said desuperheating heat
exchanger reduces the thermal content of fluid exiting said
expander.
51. An integrated power generation system according to claim 43,
further comprising a second pair of meshed axially extending
involute spiral wrap members mechanically coupled to said first
scroll pair.
52. An integrated power generation system according to claim 43,
further including at least one process heat utilization module in
thermal communication with said thermal circuit, said process heat
utilization module configured to provide process heat to an
external user.
53. An integrated power generation system according to claim 52,
wherein said at least one process heat utilization module includes
a first and second process heat utilization modules, said first
process heat utilization module configured to extract higher
temperature energy than said second process heat utilization
module.
54. An integrated power generation system according to claim 48,
further comprising a quick-start mechanism in the heat energy
utilization subsystem, said quick-start mechanism comprising: a
logic and control module in electrical communication with each of
said generator, auxiliary burer, pump, and microturbine subsystem;
a battery in electrical communication with said logic and control
module; and a recharging module in electrical communication with
said generator and said battery such that said logic and control
module is configured to initiate a start-up sequence for said heat
energy utilization subsystem, and said recharging module recharges
said battery during normal operation of said heat energy
utilization subsystem.
55. An integrated power generation system according to claim 54,
further comprising: an accumulator in fluid communication with said
first heat exchanger and expander to collect and store at least a
portion of excess thermal energy from said heat stream; a control
valve in fluid communication with said accumulator; and an
isolation valve disposed within said thermal circuit, said
isolation valve to be used to selectively isolate said first heat
exchanger from said expander, whereby, upon initiation and
subsequent operation of said heat energy utilization system, it is
capable of sustained operation.
56. An integrated power generation system according to claim 54,
further comprising a capacity control module to facilitate the
responsiveness of said heat energy utilization subsystem, said
capacity control module comprising: a speed sensor coupled to said
expander; a feed-back controller operatively responsive to a signal
from said speed sensor so as to actuate said isolation valve; a
bypass valve disposed within said heat stream to control the flow
of said heat stream into said first heat exchanger module; a
plurality of sensors disposed in said thermal circuit to measure
said working fluid temperature and pressure; and a proportional
integral differential logic controller to control said bypass
valve, said pump and said auxiliary burner based on first heat
exchanger sensor input signals.
57. An integrated power generation system according to claim 56,
further comprising a load splitting module to analyze and respond
to varying load conditions such that it causes said prime mover
subsystem and said heat energy utilization subsystem to provide
substantially uniform and dynamic load components, respectively, to
the composite electric generation profile.
58. An integrated power generation system according to claim 57,
wherein said load splitting module includes a fuzzy logic
controller.
59. A method of producing power by using a power generation system
that has a prime mover subsystem and a secondary power generation
subsystem, the method comprising the steps of: operating said prime
mover subsystem to energize a first load absorption device;
arranging at least a pump, first heat exchanger, expander and
second heat exchanger to be in fluid communication with one another
via circulated working fluid routed through a thermal circuit as
part of said secondary power generation subsystem, whereby said
first heat exchanger is placed in thermal communication with said
prime mover subsystem; exchanging heat between said prime mover
subsystem and said first heat exchanger; transferring at least a
portion of the thermal content of said heat in said first heat
exchanger to said working fluid, thereby producing an increase in
temperature of said working fluid; regulating the flow of said
working fluid to said expander; coupling said expander to a second
load absorption device; expanding said working fluid in said
expander such that the energy released by said expansion energizes
said second load absorption device; condensing at least a portion
of said expanded working fluid in a second heat exchanger; and
pressurizing the condensed portion of said working fluid with a
pump coupled to said expander.
60. A method according to claim 59, wherein a throttle valve is
used in said step of regulating the flow of said working fluid to
said expander.
61. A method according to claim 59, wherein said second load
absorbing device is an electric generator.
62. A method according to claim 59, further comprising the step of
hermetically sealing said expander and said second load absorption
device in a power module.
63. A method according to claim 62, wherein the expander is a
scroll expander.
64. A method according to claim 63, wherein said scroll expander
includes a plurality of scroll pairs.
65. A method according to claim 59, further comprising the
additional step of operating a lubricant pump and a lubricant
droplet separator in fluid communication with said lubricant pump,
both disposed within said power module and operatively responsive
to said expander such that, upon operation of said lubricant pump,
a lubricant circulates within said power module.
66. A method according to claim 59, further comprising the
additional step of operating a desuperheating heat exchanger
disposed within said power module, said desuperheating heat
exchanger in thermal communication with said expander such that
said desuperheating heat exchanger reduces the thermal content of
fluid exiting said expander.
67. A method according to claim 59, wherein the prime mover
subsystem comprises a microturbine.
68. A method according to claim 67, comprising the additional step
of arranging an auxiliary burner to be in thermal communication
with said first heat exchanger.
69. A method according to claim 59, further comprising the
additional steps of: arranging at least one process heat
utilization module to be in thermal communication with said working
fluid; extracting at least a portion of the thermal content of said
working fluid from said thermal circuit; and heating a fluid medium
in said at least one process heat utilization module with said
extracted thermal content.
70. A method according to claim 69, wherein said process heat
utilization module is in thermal communication with said working
fluid at a location between where said working fluid is discharged
from said first heat exchanger and expanded in said expander.
71. A method according to claim 70, wherein said process heat
utilization module is in thermal communication with said working
fluid at a location between where said working fluid is expanded in
said expander and where it enters said second heat exchanger.
72. A method according to claim 71, wherein a first of said at
least one process heat utilization module is in thermal
communication with said working fluid at a location between where
said working fluid is discharged from said first heat exchanger and
expanded in said expander, and a second of said at least one heat
recovery module is in thermal communication with said working fluid
at a location between where said working fluid is expanded in said
expander and where it enters said second heat exchanger.
73. A method according to claim 72, further comprising the
additional steps of: inserting elevated temperature and pressure
working fluid into an accumulator; and storing said elevated
temperature and pressure working fluid in said accumulator.
74. A method according to claim 68, further comprising the
additional step of initiating a start-up sequence in said secondary
power generation subsystem by: providing electric current to a
control module; sending start-up signals from said control module
to at least one of said auxiliary burner, said pump, said first
heat exchanger or said first load absorption device; and energizing
said thermal circuit by operating said auxiliary burner such that
the thermal content produced by said combustor enables the
self-sustaining operation of said heat energy utilization
subsystem.
75. A method according to claim 68, further comprising the
additional step of initiating a start-up sequence in said heat
energy utilization subsystem by: providing electric current to a
control module; sending start-up signals from said control module
to at least one of said auxiliary burner, said pump, said isolation
valve, said first heat exchanger or said first load absorption
device; and energizing said thermal circuit by releasing said
elevated temperature and pressure working fluid stored in said
accumulator.
76. A method according to claim 68, further comprising the
additional steps of: providing a load-splitting module that
accumulates, through a load-splitting controller, the steady-state
and dynamic load requirements of an end-user; and sending out
signals to determine what portion of the supplied power will be
supplied by said heat energy utilization subsystem, and what
portion will be supplied by said prime mover.
77. A method according to claim 76, further comprising the
additional step of providing a capacity control module that, based
on temperature and pressure data gathered from said first heat
exchanger, calculates said heat energy utilization subsystem
response to changes in power requirements.
78. A method according to claim 76, further comprising the
additional step of incorporating a fuzzy logic controller into said
load-splitting module, said fuzzy logic controller configured to
provide output signals to said prime mover and secondary power
generation subsystems.
79. A method of operating a heat energy utilization subsystem using
a quick-start mechanism, the method comprising the steps of:
arranging at least a pump, first heat exchanger, expander and
second heat exchanger to be in fluid communication with one another
via circulated working fluid routed through a thermal circuit;
arranging an auxiliary burner, fuel supply and an auxiliary burner
exhaust line such that said auxiliary burner exhaust line is placed
in thermal communication with said thermal circuit; initiating a
start-up sequence in said heat energy utilization subsystem by:
providing electric current to a control module; sending start-up
signals from said control module to at least one of said auxiliary
burner, said pump, said first heat exchanger or said first load
absorption device; and energizing said thermal circuit by operating
said auxiliary burner such that the thermal content produced by
said auxiliary burner enables the self-sustaining operation of said
heat energy utilization subsystem; transferring at least a portion
of the thermal content of said auxiliary burner exhaust line to
said working fluid, said transfer of said thermal content producing
an increase in temperature of said working fluid; regulating the
flow of said working fluid to said expander; expanding said working
fluid in an expander such that the energy released by said
expansion turns said load absorbing device; condensing said
expanded working fluid in a condenser; and pressurizing said
working fluid with a pump coupled to said expander, whereby said
heat energy utilization subsystem is capable of sustained,
stand-alone operation.
80. A method according to claim 79, wherein a throttle valve
disposed within said first thermal circuit is used in said step of
regulating the flow of working fluid to said expander.
81. A method according to claim 79, further comprising the step of
hermetically sealing said expander and said first load absorption
device in a power module.
82. A method according to claim 81, wherein the expander is a
scroll expander.
83. A method according to claim 82, wherein said step of expanding
said working fluid is through a plurality of scroll pairs.
84. A method according to claim 82, further comprising the
additional step of operating a lubricant pump and a lubricant
droplet separator in fluid communication with said lubricant pump,
both disposed within said power module and operatively responsive
to said expander such that, upon operation of said lubricant pump,
a lubricant circulates within said power module.
85. A method according to claim 81, further comprising the
additional step of operating a desuperheating heat exchanger
disposed within said power module, said desuperheating heat
exchanger in thermal communication with said expander such that
said desuperheating heat exchanger reduces the thermal content of
fluid exiting said expander.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to a power
generation system capable of providing dual-mode (cogeneration)
power demands, and more particularly to the use of a Rankine-cycle
heat energy utilization subsystem in conjunction with a prime mover
subsystem, wherein the otherwise unusable waste heat from the prime
mover's exhaust stream is routed through the heat energy
utilization subsystem for the production of supplemental mechanical
or electrical power. Such combination yields a cogeneration system
that can provide control over varying power demands and increase
overall cycle efficiency, thereby reducing unwanted emissions.
[0002] Many commercial and industrial concerns, as well as
residential users, consume widely disparate levels of electricity
during the course of daily or seasonal operation. When such
electricity is supplied over the grid, these concerns are often at
the mercy of circumstances beyond their control, including
emergency and planned service outages, as well as brownouts or
blackouts stemming from heavy usage by others on the grid. In such
circumstances, the electricity supplier (normally a utility
company) must themselves purchase electricity from other suppliers
on the grid, usually at a dramatically inflated price. This extra
price is then typically passed on to the end user. In addition,
even in periods where power is uninterrupted, the costs of the same
quantum of electricity can be considerably higher during peak
periods, which often coincides with normal business operating
hours, thus rendering the option of operating during off-peak hours
to get the lower electric rate unfeasible.
[0003] One way to meliorate the uncertainty of off-site electricity
generation is for the using concern to generate the power on-site.
The simultaneous production of electric power and useable heat from
a common fuel or energy source is known as cogeneration, or
combined heat and power (CHP). While large industrial entities have
long been engaged in cogeneration through steam-producing boilers
or reciprocating engines, the bulkiness, as well as the level of
support and maintenance, of establishing such a system is
prohibitive in smaller operations, such as private residences,
restaurants, small commercial and light duty industrial businesses,
or in geographic locations where the transmission and distribution
infrastructure is inadequate or doesn't exist.
[0004] Even in circumstances where on-site generation is physically
possible, the cost of installation and operation can be formidable,
where new systems are extremely costly, and older systems require
dedicated service and maintenance, often by skilled, highly paid
specialists. In addition, the generation of energy can also carry
with it hidden or hitherto unforeseen costs. Perceived impacts to
the environment, in the form of gaseous, liquid and solid
byproducts of the power generation cycle, such as SO.sub.X, CO,
NO.sub.X, thermal pollution of cooling water sources, and increased
ash (in the case of coal fired generators) have come under
increasing levels of government and private scrutiny. Traditional
power generation systems require additional effluent treatment
equipment to bring air- and water-borne pollutants down to
acceptable levels. The additional costs associated with installing
and maintaining such equipment, as well as the cost of monitoring
and compliance with strict pollution requirements, is manifest.
[0005] Microturbine technology is a relatively new field that finds
its roots in conventional gas turbine engines for auxiliary power
units and transportation applications. It is also part of a growing
trend in electric power production, namely that of distributed
generation (DG), which arose out of a need to provide alternatives
to traditional grid-based power sources for small to medium-sized
users. Microturbines are generally much more compact than
steam-based, or even central gas turbine power units, and can
provide cleaner, lower maintenance power than traditional
reciprocating engines at a reasonable cost per kilowatt-hour. In
addition, the relative compactness of microturbines, with or
without a Rankine-cycle heat energy utilization subsystem, readily
lends itself to increased system modularity, portability and
upgradeability.
[0006] Configurationally, a microturbine has much in common with
other gas turbine engines, including an engine housing, one or more
rotating shafts, a generator, compressor, combustor, turbine, and
exhaust duct. In some microturbines, the compressor, generator and
turbine are coupled to a single shaft, and rotate as a unit.
Normally, the shaft itself is mostly or entirely contained within
and coupled to the housing, often through a
bearing-mount-strut-frame arrangement well known to those skilled
in the art. In a typical gas turbine system, ambient air enters
through a generator section and into a compressor, which typically
pressurizes the air from three- to ten-fold. From the compressor,
it next goes into an optional recuperator, where the air can be
preheated prior to entering the combustor to increase overall cycle
efficiency. The preheating of the compressed air in the recuperator
arises out of a heat exchange process with hot exhaust gas from the
turbine discharge. Higher preheated air temperature leads to higher
cycle efficiency, which can have dramatic impacts on life-cycle
fuel usage. In addition, preheated air has the requisite
temperature to facilitate a form of combustion, known as catalytic
combustion (discussed below), which has been identified as a
promising way to prevent the onset of NO.sub.X formation, which is
becoming a major concern in urban airsheds. After the warmed,
compressed air exits the recuperator, it enters the combustor,
where the air mixes with high pressure fuel, with the resulting
mixture burned in a combustion chamber. The hot gas next enters the
turbine section and impinges on the turbine rotor, so that as the
gas expands through one or more stages of the turbine section, it
causes the rotor to spin, which in turn drives the compressor. A
generator may also be driven by that rotor, or by a second turbine
rotor driven from the exhaust of the first rotor. Upon leaving the
turbine section, the hot exhaust gas gives up some of its excess
heat in the aforementioned recuperator to heat up the incoming air.
Finally, the exhaust gas is ducted through an exhaust into the
atmosphere.
[0007] While microturbines are particularly well-suited to
providing prime mover power in a cogeneration system, it is not
necessary that the prime mover be a microturbine. For example,
conventional gas turbines, steam boilers (powered by burners fired
by natural gas, coal, oil, or possibly even nuclear reactors),
diesels, fuel cells, thermoelectric, thermophotovoltaic and even
renewable sources, such as solar energy and combustible biomass all
provide viable alternatives. These cogeneration approaches are part
of a larger class of power plants often referred to as "combined
cycle", where a higher-temperature thermodynamic cycle rejects its
heat to a lower-temperature thermodynamic cycle that typically
utilizes a different working fluid. The two cycles making up a
combined cycle are typically known as topping and bottoming cycles,
with the topping cycle often referred to as a prime mover
subsystem, and the bottoming cycle as a waste heat recovery, or
energy utilization, subsystem. Combined cycle operation is common
in larger size units, such as systems with a power output of 10
megawatts (MW) or greater. These systems often employ a gas turbine
topping cycle and a steam turbine Rankine bottoming cycle, where
the high temperature exhaust gas from the prime mover subsystem is
used to drive a waste heat steam turbine. However, when the prime
mover subsystem is a smaller unit, such as a microturbine, the
addition of a similar steam turbine system results in a degree of
complexity that sacrifices many of the microturbine's modular
features, as well as paving the way for significant cost growth,
both in initial purchase price and the higher cost of maintenance.
Moreover, the use of conventional steam based systems with which to
exploit the waste heat's useful energy necessitates the use of high
vacuum condensers and cooling towers. In addition, steam systems
and many other heat energy utilization systems are not hermetically
sealed, thus exposing the user to increased mess and maintenance
issues. In either case, such configurations present unacceptable
situations to small commercial and residential users.
[0008] Accordingly, there exists in the art a need for a system
which can provide compact, clean, inexpensive, reliable, low
maintenance, on-demand power with flexibility to tailor electrical
or mechanical power output to the users' particular needs.
SUMMARY OF THE INVENTION
[0009] The present invention satisfies the aforementioned need by
providing a means by which heat from a prime mover subsystem is
used to drive a secondary subsystem that generates additional
power.
[0010] According to an embodiment of the present invention, a heat
energy utilization system includes a heat engine that is made up of
at least a thermal circuit, a pump, a power module and a pair of
heat exchangers. As defined herein, a "thermal circuit" is piping
or ducting designed to carry fluid through a path that
interconnects the various heat energy utilization system
components. Similarly, the term "pump" includes any device that can
be used to increase the fluid flow rate or pressure. The power
module is itself made up of at least an expander and a load
absorbing device. The load absorbing device can be another pump,
gearing, generator or similar energy conversion apparatus. The heat
energy utilization system is designed to be run as either a
stand-alone power generation source, or as an optional bottoming
cycle for a larger system such that it extracts heat from the heat
stream of a prime mover such as an exhaust gas waste heat stream,
or a dedicated heat producer. In either configuration, when the
heat energy utilization system is operational, it generates useable
work via vapor expansion of a working fluid through the thermal
circuit. In the present context, the term "useable work" is that
which is capable of producing a tangible mechanical or electrical
effect, such as rotating or reciprocating motion in a shaft or
related device against a resistance (in the case of mechanical
work) or an electric current flow and potential (in the case of
electric work). As such, the mere creation of any non-recoverable
work is excluded from the instant definition of "useable work", and
that the operation of all thermodynamic cycles produces at least
some heat that is non-useable. Nevertheless, the present inventors
have discovered that the waste heat or exhaust gases emitted from a
microturbine are capable of performing additional useable work, as
they are well-suited to powering a Rankine-cycle subsystem to
recover and reuse the exhaust gas energy as additional power, thus
further enhancing the efficiency of the overall power generation
cycle. The present inventors have also recognized that the while
the heat energy utilization system can be of either open or closed
variety, the preferred configuration is closed, comprising a
continuous loop requiring no external fluid makeup, save that
associated with normal system losses occurring over long periods.
The chief advantage of the closed system is that it is
self-contained, and therefore more adaptable to modular uses, as
well as uses where maintenance and cleanliness/neatness issues are
important. In the present closed cycle heat energy utilization
system, the working fluid can be any number of compounds, such as
organic refrigerants, water, ammonia, propane or N-butane. The pump
pressurizes the working fluid, which is then routed to a first of
the heat exchangers (such as an evaporator) that boils the working
fluid by absorbing heat from an external heat stream. From the
evaporator, the working fluid passes to an expander in the power
module. The expanding working fluid can then impart work to the
expander, which can then turn a coupled shaft to produce
mechanical, or, if attached to a generator, electrical, work. After
passing through the expander, the working fluid is cooled and
condensed in the second heat exchanger (typically a condenser) so
that it can return to the pump and start the cycle all over
again.
[0011] The inventors have recognized that a primary advantage of
the heat energy utilization system of the present invention is that
key components, including pumps, expanders, heat exchangers and
electric generators can be contained within individual hermetically
sealed modules in the heat energy utilization system. This is
especially relevant to a power module where the expander is coupled
to an electric generator. Thus, for example, a "hermetically
sealed" expander would have self-contained moving parts, including
bearings, orbiting shafts, rotating shafts and disks, armature
coils and optionally heat exchange and lubricant-circulating
devices that are contained within a module shell so as to be sealed
from the external environment. Thus, save fluid inlet and outlet
ports, and possibly an access port through which additional working
fluid or lubricant may be added to periodically replenish that lost
during normal operation, and electrical connectors to carry
electricity to or from the generator, the power module operates in
complete autonomy, thus avoiding maintenance issues and the mess
associated with lubricants, leaky seals and noisy machinery. In
addition to permitting application in places where cleanliness is
paramount, such as around people, foodstuffs, sensitive electronic
equipment and damage-susceptible chattels, the system exploits its
inherent modularity to permit it to be moved or upgraded as
requirements demand.
[0012] One way the power module is able to remain hermetically
sealed is through the use of a scroll expander. While hermetic
operation is not unique to scroll configurations, the present
inventors recognize that, by virtue of the low number of moving
parts (with attendant reduction in maintenance) in a scroll device,
its configuration is an especially good fit with the limited access
inherent in sealed environments. In a scroll (also known as an
involute spiral wrap) device, which can be operated as either an
expander or compressor, one or more pairs of meshed axially
extending involute spiral wrap members, one fixed to the housing,
the other attached to and orbiting with a shaft, are axially meshed
to define a plurality of crescent-shaped chambers which, by virtue
of the orbital motion of one wrap member relative to the other
changes the shape and size of the crescents, which in turn changes
the pressure of the fluid contained therein. In an expansion mode,
the fluid enters through a central port, and proceeds circuitously
in a radially outward direction, causing the crescent chambers to
move, which, through an anti-rotation mechanism (such as an Oldham
link or a ball coupling ring assembly), consequently turns an
eccentric linkage, coupled to the orbiting scroll. The linkage is
attached to a rotating shaft with an offset functionally equal to
the radial distance from the rotational axis of the shaft, thereby
transforming the scroll orbital motion into rotating motion in the
shaft. Conventional needle bearings can be placed in the eccentric
aperture to reduce friction between the linkage and the orbiting
scroll.
[0013] As mentioned above, the scroll expander could further
incorporate two scroll pairs, each disposed on opposing ends of a
common rotating shaft. Each pair is in turn made up of the
aforementioned pair of meshed axially extending involute spiral
wrap members for symmetric bearing loading, annular cooling
channels, an optional external armature for supplemental electrical
power generation, and axial compliance features to avoid thermal
expansion mismatches. This dual scroll configuration is especially
valuable in providing a third, hybrid operational mode, where one
of the spiral wrap members can be operated in expansion mode while
the other concurrently operates in compressor mode. This and
additional features of the scroll device with an integral
field-generating rotor are described in copending application, U.S.
Ser. No. 09/681,363, INVOLUTE SPIRAL WRAP DEVICE, filed Mar. 26,
2001, by Sullivan et al., herein incorporated by reference.
Regardless of being configured as a single or dual scroll device,
the scroll of the present invention is a low maintenance device
largely due to the rolling versus sliding contact of the scroll
wall flanks, the elimination of dynamic seals, and the elimination
of valves. The inventors have recognized that the use of a scroll
expander in the present invention heat energy utilization system
has significant advantages over traditional bottoming cycle
devices. The small number of parts associated with the scroll
design, coupled with its inherently simple motion ensures a low
maintenance part that can be placed in an infrequently-accessed
sealed container. The hermetic sealing unique to this approach
facilitates an entirely integrated, modular power generation
system. Additionally, the compact nature of the expander can be
made even more diametrically compact through the use of dual
opposed scroll wrap members, such as those described in the
aforementioned copending application. Many significant advantages
of the scroll machine have been proven with the successful use of
scroll compressors in the refrigeration and air conditioning
industry.
[0014] In the case where the desired power output is electrical,
the load-absorbing device can be a generator made up of a
field-generating rotor situated around the periphery of a rotating
shaft. A stator coil in inductive proximity to the field rotor
could be affixed to the outer portion of the scroll housing, but
still within the module's larger hermetic seal shell. When the
scroll device is operating in expansion mode, alternating current
electricity could be passed from the generator, through the
hermetic shell via electrical conductors, and to attached
electrical connectors. Thus, power output can be effected without
having to pass a shaft (and attendant sealing mechanisms) through
the hermetic housing, thereby alleviating concerns over seal
boundaries and leakage/contamination paths.
[0015] Another option to the heat energy utilization system is the
inclusion of one or more process heat utilization modules that can
extract heat from the thermal circuit for various process needs,
while still providing supplemental power from the heat energy
utilization system's power module. Preferably, the heat recovery
modules include at least a low temperature unit to provide for
lower temperature process requirements (such as warming air in
dwelling spaces occupied by people, referred to as space heat), and
a high temperature unit to provide higher temperature process
requirements, such as domestic hot water or steam. This feature has
the advantage of accommodating additional user needs, beyond just
electricity requirements, to provide hot water, heated air or
steam, among others.
[0016] Another option includes a heat energy utilization system
quick-start module. The quick-start module permits the heat energy
utilization system to either pre-start prior to the operation of an
optionally attached prime mover, thus speeding up its response
time, or to operate as the sole provider of power in dynamic (i.e.:
rapidly fluctuating) or lower power modes where operating a prime
mover would be impractical. All modern power generation systems,
including microturbines, require initiation, or start-up, of their
operating sequence. Typically, this is effected by a logic and
control module that is capable of sending control signals to the
various components within the system. An energy storage (or
auxiliary power) unit, such as an electrical battery, of sufficient
size is included to power the logic and control module and related
equipment. A recharging module can be disposed between the load
absorbing device and the energy storage unit such that extra power
generated by the load absorbing device can be used to keep the
energy storage device fully charged. The sequence of using the
quick-start operation includes igniting an auxiliary burner and
powering the pump to increase the pressure and temperature of the
working fluid, which can then pass through the expander to generate
power and thereafter render the system self-sustaining. The
quick-start feature allows the less cumbersome heat energy
utilization system to start with minimal stored energy, thus
reducing the size of the energy storage unit. Once started, the
heat energy utilization system can provide sufficient power to the
prime mover to allow for a complete start, or, if necessary, as the
sole provider of power in low or dynamic power situations, thus
comprising a self-sufficient system rather than as a subsystem to a
larger combination. An optional variant of the quick-start
mechanism includes a high-pressure accumulator connected through
one or more control and isolation valves between the evaporator and
the expander. Upon cessation of normal power generation system
operating conditions, the accumulator collects high thermal and
pressure content working fluid. Under the quick-start mode, a
control valve is opened, allowing the high pressure and temperature
working fluid to boil off and enter the thermal circuit such that
it can expend its excess energy in the expander. Optional pre-start
activation of the auxiliary burner ensures that the working fluid
will contain adequate thermal and pressure properties upon
quick-start. An isolation valve can be used to direct heat from the
auxiliary burner directly to the accumulator during the starting
sequence. The chief advantage of the start-up module without the
high pressure accumulator is in its simplicity. The optional high
pressure accumulator, on the other hand, while requiring a separate
function in the control module to synchronize pump, valve and
burner sequencing, will result in a more rapid response from the
expander, leading to shorter start-up sequences.
[0017] According to another embodiment of the present invention, a
heat energy utilization subsystem is adapted to be coupled to a
prime mover subsystem, where the output of the heat energy
utilization subsystem is electric potential. The heat energy
utilization subsystem includes a thermal circuit, pump,
hermetically sealed power module with a plurality of scroll pairs
and a coupled generator to produce the electric output, a throttle
valve to regulate working fluid flow into the power module, and
first and second heat exchangers. The prime mover subsystem can be
any power source that includes some form of thermal energy in a
heat stream. In this regard, prime movers that provide an exhaust
gas from a combustion process (including gas turbines and their
subset of microturbines), steam (from natural gas, coal, oil or
nuclear powered devices), chemical reaction (including fuel cells)
as well as solar, thermophotovoltaic and thermoelectric sources are
all considered valid examples that can be coupled to the heat
energy utilization subsystem.
[0018] According to another embodiment of the present invention, a
power generation system for providing a primary and secondary
source of output power is disclosed. The primary source of output
power comes from a prime mover subsystem, and the secondary source
of power comes from a heat energy utilization subsystem similar to
that of the first embodiment. As with the first embodiment, the
subsystem may include one or more scroll pairs, as well as features
capable of providing heat energy utilization subsystem quick-start,
such as a control and logic module, an energy storage device, an
accumulator, or an auxiliary burner in thermal communication with
the heat stream. An optional throttle valve may be included to
regulate the flow of working fluid to the power module.
[0019] In addition to these and the other options associated with
the earlier embodiments, two additional features that could be
included in the present embodiment are a capacity control module
that uses proportional integral differential (PID) logic, and a
load splitting module that includes a fuzzy logic controller. The
first, the capacity control module, permits the heat energy
utilization subsystem to respond to changes in subsystem power
levels based on the analysis of control signals coming to and going
from the control module. Accordingly, the capacity control module,
which includes a rapid response portion and a slow response
portion, is used to determine power requirements of the heat energy
utilization subsystem in response to loads set on it from elsewhere
(such as from the below-described load-splitting module). The
PID-based controller combines the instantaneous response of
proportional control with the offset correction features of
integral control and the rapid response to error signals of
derivative control. In applications where both the primary and
secondary power output is electrical, the inventors of the present
device are not aware of any prior art that allows for splitting of
the electrical load between the uniform and dynamic components to
be applied to a combined multiengine thermodynamic system.
Components making up the capacity control module include a speed
sensor coupled to the expander, a feed-back controller operatively
responsive to a signal from the speed sensor so as to actuate the
valve that isolates the accumulator, a bypass valve disposed within
the heat stream to control heat stream flow into the first heat
exchanger module, a plurality of sensors disposed in the thermal
circuit to measure the temperature and pressure of the working
fluid, and a proportional integral differential logic controller to
control the bypass valve, pump and auxiliary burner based on first
heat exchanger sensor input signals. Additionally, the speed sensor
and feed-back controller can also be incorporated within the power
module hermetic shell.
[0020] The second, the load splitting module, can be used to
isolate the prime mover subsystem from rapid-response dynamic loads
by using a fuzzy logic controller to set loads for each of the two
power generating subsystems. The load-splitting module analyzes
electrical use requirements in order to set the load on each of the
two power generating subsystems. The optional fuzzy logic
controller is used to determine the substantially uniform load
(also known as a "quasi-steady state" load, typically associated
with the prime mover subsystem) component, and the dynamic load
component (typically associated with the heat energy utilization
subsystem). The practical applications of fuzzy logic have been on
the rise in recent years, providing rule-based ways of determining
continuous, intermediate truth values from vague or incomplete data
sets such that a result, processable by digital computers, can be
obtained. As such, fuzzy logic-based inference engines and
controllers are well-suited to process-driven events, where quick,
accurate monitoring of; and active feedback to, a dynamic
environment can provide improvements in system response, efficiency
and overall operability. Thus, with the fuzzy logic-based load
splitting module, a composite electric generation profile,
comprising component contributions from both the prime mover and
heat energy utilization subsystems, can be produced based on an
interactive controller such that the efficiency of the overall
generation of electricity is maximized.
[0021] Optionally, the prime mover subsystem can be a microturbine,
either without or with a recuperator. In the first instance, since
the turbine exhaust gas does not have to give up its thermal
content in a recuperator to preheat the compressed air going into
the combustor, full exploitation of the exhaust gas can occur at
the heat energy utilization subsystem's evaporator. Thus, the
non-recuperated variant has the advantage of having the simplest
interconnection and operation, as well as the smallest, least
obtrusive footprint, thus maximizing its affordability. Specific
power, a common metric expressed as the ratio of power output to
either weight or displaced volume of the system, is also maximized
in the non-recuperated subsystem. In the second instance, the
microturbine-based prime mover subsystem employs a recuperator,
which is essentially a dual-loop heat exchanger connected between
the compressor discharge and the combustor inlet for the first
loop, and between the turbine exhaust and ambient for the second
loop. The turbine exhaust gas, after giving up its heat in the
recuperator to raise the temperature of the air coming out of the
compressor, will have a lower energy content than that for the
non-recuperated device of the previous embodiment, and therefore
will have less energy to give up to the Rankine-cycle heat energy
utilization subsystem. To make up this difference, the recuperated
subsystem variant can also include a separate prime mover auxiliary
burner which could be included with, but external to, the modules
of the heat energy utilization subsystem for situations requiring
high efficiency. The prime mover auxiliary burner could be placed
at various locations in or around the prime mover to optimize its
effectiveness, such as either upstream or downstream of the
recuperator, or in a mixing relationship with the fluid directly
leaving the turbine exhaust. The benefits of incorporating the
recuperated subsystem features include the aforementioned easy
start-up due to the presence of low pressure pre-start components,
as well as not requiring a high efficiency recuperator to achieve
suitable overall system performance.
[0022] The higher prime mover combustor inlet temperatures made
possible through the use of a recuperator would also permit a
catalytic combustor to be utilized in place of the conventional
combustor. The use of a catalytic combustor permits combustion
byproducts that would otherwise be discharged as gaseous or
particulate pollutants to be burned, or chemically altered to less
objectionable species, thus providing the dual benefit of
generating additional power while simultaneously reducing airborne
pollutants. With a catalytic combustor, when exhaust gases and
particulate come in contact with a noble metal coated ceramic core,
chemical changes occur in the byproducts that permit them to ignite
at relatively low temperatures, thus promoting more complete
combustion, even in lower temperature operating regimes. To be
effective, the air entering the catalytic combustor must itself be
substantially preheated to promote the chemical reaction. The
inventors of the present invention have recognized that a
recuperator and a catalytic combustor can be placed in series with
a supplemental, low pressure burner to reheat a turbine exhaust
stream prior to introduction of that stream into the heat energy
utilization subsystem's evaporator. In addition, multistaged
turbines and compressors could be employed to add more flexibility
to the design, effecting decisions on how much supplemental burner
heating is necessary. From such a configuration, bleed or discharge
ducts could route exhaust streams of appropriate pressure and
temperature to any of several desired locations. The advantage of
this feature is that the coupling of the catalytic combustor and
recuperator, as part of this flexible embodiment, is particularly
well-suited to extremely low emissions operation, and is in keeping
with the overall system's flexibility features.
[0023] In accordance with still another embodiment of the present
invention, the prime mover and heat energy utilization subsystems
are integrated to provide both a primary and secondary source of
power. In the present context, the term "integration" means more
than the mere interconnection of disparate subcomponents, as true
integration is an engineering solution designed around the proper
interrelationship of these subcomponents, especially on how
variations in the performance of one effects not just another, but
the system as a whole. To that end, the system of the present
invention includes, among other factors, considerations of size,
load dynamics isolation and load splitting, heat energy utilization
subsystem capacity control, durability, flow rates, quick-start
sequencing, temperatures, pressures, acquisition and life-cycle
costs, pollution minimization and aesthetics. The approach of this
embodiment is especially beneficial when the prime mover is a
microturbine, which can furthermore be either non-recuperated or
recuperated. This allows system designers the flexibility of
accommodating varying combustor and emissions requirements, such as
the use of a catalytic combustor, into the overall power generating
system. In addition to a microturbine prime mover, the system of
the present embodiment includes a heat energy utilization
subsystem, which in turn includes a closed loop thermal circuit,
pump, first heat exchanger, hermetically sealed power module with
scroll expander and load absorbing device, and a second heat
exchanger. The invention described herein represents a practical
and cost-effective approach to achieving a microturbine combined
cycle (MTCC) at a much smaller scale than gas turbine combined
cycle (GTCC) power plants currently in use.
[0024] The system of the present embodiment may be outfitted with
the same options as that of the heat energy utilization system of
the first embodiment, as well as the optional load-splitting module
and the capacity control module of the previous embodiment. In the
present embodiment, these additions are now integral features the
combination of which can provide a total power generation package.
The advantage of the integrated system is the resulting turn-key
approach to providing solutions to a user's power requirements,
including automated system operation modes. For example, the
load-spitting module will continually monitor actual electrical
load dynamic characteristics and adjust the load split between the
prime mover and heat energy utilization subsystems through the use
of optional sophisticated fuzzy logic that can mimic a variety of
operational parameters without the need for user intervention.
Similarly, the capacity control module will monitor various
parameters (such as evaporator pressure and vapor superheat
temperature) with a distributed network of pressure and temperature
transducers. The capacity control module's smart controller
automatically analyzes evaporator pressure and temperature dynamics
to provide rapid response and control to the pump, valves, and
auxiliary burner firing rate.
[0025] The use of the integrated approach to incorporating the heat
energy utilization subsystem herein described is well-suited to
situations involving low thermal energy heat streams from the prime
mover, where, by adding a low pressure auxiliary burner to energize
the prime mover heat stream, sufficient heat exchange can take
place within the heat energy utilization subsystem's evaporator.
This approach is especially useful in gas turbine prime movers,
where recuperators can be used to heat prime mover incoming air.
Similarly, in non-recuperated prime mover subsystems, where
preheated air for the prime mover subsystem's main combustor is not
required, the heat energy utilization subsystem can be run directly
off the turbine exhaust of the prime mover, thus removing the need
for a burner to reheat the exhaust gas. In such a system, higher
initial compression of the air entering the prime mover could
provide sufficient thermal content to abrogate the recuperator. The
combination of portable, modular features inherent in both
subsystems is further exploited to ensure that a complete power
generation package is available to the user, and can be adapted to
myriad parametric requirements. By tailoring the needs of the heat
energy utilization subsystem with the capabilities of the heat
stream provided by a prime mover, a system optimized for size,
power and emissions output and cost can be effected.
[0026] In accordance with another embodiment of the present
invention, a method for producing power by using a power generation
system made up of a prime mover subsystem and a heat energy
utilization subsystem comprises the steps of operating the prime
mover to turn a first electric generator, arranging the components
of the heat energy utilization subsystem such that at least an
evaporator is in a heat exchange relationship with the heat stream
generated by the prime mover, an exchange of heat between the waste
heat stream and the evaporator such that heat is transferred to a
working fluid flowing through a thermal circuit that maintains
fluid communication between the components of the heat energy
utilization subsystem, regulating the flow of the working fluid
with a throttle valve, expanding the working fluid in an expander
that is coupled to a second electric generator, condensing the
expanded working fluid, and then pressurizing the working
fluid.
[0027] Optionally, the method could also include additional
attributes and steps. For example, a throttle valve can be included
to help regulate the flow of working fluid to the expander. In
addition, either or both of the load absorbing devices can be a
generator to generate electricity. Both the expander and second
load absorption device can be hermetically sealed, while the
expander is preferably a scroll device (which itself can comprise
single or dual scroll pairs). A lubricant pump and a lubricant
droplet separator may be used in situations requiring separation of
the working fluid from the lubricating fluid, and both the pump and
separator can be disposed within the hermetically sealed power
module. Another optional step could include operating a
desuperheating heat exchanger such that the high temperature
working fluid exiting the expander can pass through the heat
exchanger; the heat exchanged therein could be used for a DHW or SH
loop. As previously discussed, a microturbine can be used as the
prime mover subsystem. Furthermore, at least one process heat
utilization module can be placed in thermal communication with the
working fluid such that heat can be extracted from the working
fluid and directed to the process heat utilization module.
Similarly, the process heat utilization module can be placed in
thermal communication with the thermal circuit to provide process
heat. Another step includes using an accumulator to receive and
store elevated temperature and pressure working fluid such that the
accumulator can smooth out system operation during certain
conditions. For example, the accumulator can be used to provide
alternate steps to initiate a start-up sequence in the heat energy
utilization subsystem, as can an auxiliary burner. A load splitting
module can be incorporated to coordinate steady-state and dynamic
load requirements in the system, while providing a capacity control
module will assist in promoting better response within the heat
energy utilization subsystem. The load splitting module may further
be based on a fuzzy logic controller that can sense various
instantaneous and historical data to provide output instructions to
the prime mover and heat energy utilization subsystems.
[0028] In accordance with yet another embodiment of the present
invention, a method of operating a heat energy utilization system
is disclosed. The method includes the steps of arranging at least a
pump, first heat exchanger, expander and second heat exchanger to
be in fluid communication with one another via circulated working
fluid routed through a thermal circuit. In addition, an auxiliary
burner, fuel supply and auxiliary burner exhaust line are arranged
such that the auxiliary burner exhaust line is placed in thermal
communication with the thermal circuit. Next, a start-up sequence
is initiated in the heat energy utilization system by providing
electric current to the control module so that it in turn can send
start-up signals to one or more of the heat energy utilization
subsystem components such that the heat produced in the auxiliary
burner and routed through the auxiliary burner exhaust line
exchanges its heat with the first thermal circuit such that a
working fluid flowing through the thermal circuit enables the
operation of the heat energy utilization system to be
self-sustaining. The control of the power level in the heat energy
utilization system is effected in the present method by regulating
the flow of the working fluid to the expander with a throttle valve
disposed within the first thermal circuit. After passing through
the throttle valve, the working fluid goes through an expander such
that the energy released by the expansion process turns the coupled
generator, which in turn produces electricity. After passing
through the expander, the working fluid is routed to a condenser
for cooling, and a pump for circulating throughout the first
thermal circuit. By this entire method, the heat energy utilization
system is capable of sustained, stand-alone operation.
[0029] Optional steps in the method include hermetically sealing
the expander and generator in a power module, as well as utilizing
a scroll device in the power module's expander, as well as placing
a lubrication system within the hermetic shell, and removing excess
heat from the expander through a desuperheating heat exchanger,
both of the last two in a fashion similar to that used in the
previous method. Additional steps that may be embodied in the
current method further include utilizing a microturbine as the
prime mover system, and utilizing either or both high and low
temperature heat recovery modules in thermal communication with the
condenser of the heat energy utilization system, such that the heat
recovery module can extract heat, thereby producing process heat in
addition to, or in place of a secondary electric generation output.
Also, in addition to operating the heat energy utilization system
with quick-start features, the method can incorporate
load-splitting and capacity control, both as described in
conjunction with the previous embodiment.
[0030] Other objects and advantages of the invention will be
apparent from the following description, the accompanying drawings,
and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic illustration of the basic components
of one embodiment of the present invention including a microturbine
prime mover subsystem integrated with a heat energy utilization
subsystem;
[0032] FIG. 2 is a simplified illustration of a scroll
expander-based power module according to an embodiment of the
present invention, illustrating the use of dual spiral wrap members
to drive a rotating electrical generator rotor by means of an
orbiting shaft;
[0033] FIG. 3A is an end view of the one of the dual spiral wrap
members of the scroll expander and annular heat exchanger;
[0034] FIG. 3B is a perspective view of a heat exchanger disposed
in relation to an electric generator stator coil;
[0035] FIG. 4 is a schematic illustration of another embodiment of
the present invention including a catalytic combustor and
recuperator;
[0036] FIG. 5 is a schematic illustration of another embodiment of
the present invention including a secondary atmospheric-pressure
combustor augmented device;
[0037] FIG. 6 is a schematic illustration of a variation of the
embodiment shown in FIG. 5;
[0038] FIG. 7 is a schematic illustration of a variation of the
embodiment shown in FIG. 5;
[0039] FIG. 8 is a schematic illustration of a variation of the
embodiment of FIG. 1, including high temperature and low
temperature heat recovery modules;
[0040] FIG. 9 is a schematic illustration of a variation of the
embodiment of FIG. 1, including details of a first quick-starter
element;
[0041] FIG. 10 is a schematic illustration of a variation of the
embodiment of FIG. 1, including details of a second quick-starter
element;
[0042] FIG. 11 is a general flow diagram showing the use of a
load-splitting module between the prime mover and heat energy
utilization subsystems; and
[0043] FIG. 12 is a schematic illustration of a capacity control
feature of the heat energy utilization subsystem.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] Referring now to FIG. 1, a prime mover subsystem 1 and heat
energy utilization subsystem 10 are shown. While the preferred
source for the prime mover is a microturbine, it will be
appreciated by those skilled in the art that other devices, such as
conventional small gas turbines and reciprocating internal
combustion engines, can be used as a means for generating a primary
source of power. Other previously discussed prime movers, although
not shown, are also within the ambit of the present invention. The
prime mover subsystem 1 comprises generally a compressor 2,
external fuel source 3, combustor 4, turbine 5, alternator 6 and
turbine exhaust 7. As will also be appreciated by those skilled in
the art, all the embodiments shown notionally in the drawings are
equally applicable to single-stage and multi-stage compressor and
turbine devices. Compressor 2, turbine 5 and alternator 6 are shown
in the figure on a common shaft 8. Ambient air 9 enters the
compressor 2, and by the rotation imparted on the rotor (not shown)
from the turning shaft 9, becomes pressurized. Upon discharge from
the compressor 2, the air 9 enters combustor 4, where it is mixed
with fuel from the fuel source 3, and then burned. The now
high-temperature, high-pressure combustion gas enters the turbine
5, where the gas imparts its energy on the turbine rotor (not
shown), which turns the rotor and connected shaft 8, which causes
the compressor 2 to turn, thereby pressurizing the incoming air 9
in a continuous cycle. After passing through and giving up a
significant part of its energy to the turbine 5, the heat stream 7,
in the form of exhaust gas, is discharged through the exhaust (not
shown). The turning of shaft 8 causes the shaft-mounted alternator
6 to produce electricity.
[0045] To take full advantage of the energy produced in the prime
mover subsystem 1, the heat energy utilization subsystem 10 is
provided. The basic components of the heat energy utilization
subsystem 10 include a working fluid routed through a thermal
circuit 20, an expander 30 (shown notionally as a dual expander
with split expansion members 30A and 30B), condenser 40, pump 50
and evaporator 60. The first thermal circuit 20 is in fluid
communication with expander 30, condenser 40, pump 50 and
evaporator 60 to define a closed loop. Many of these individual
components can be housed within separate shells or containers for
the purpose of isolating the components from ambient conditions.
For example, power module 71, the particulars of which are
discussed in extensive detail in the aforementioned copending
application, includes a hermetic housing (or shell) 70 encasing
expander 30 and generator 80. Other load absorbing devices besides
generator 80 are possible. For example, a rotating shaft could be
used to provide mechanical power to a motor or pump. Throttle valve
72, which controls the amount of working fluid allowed to flow
through first thermal circuit 20, may be either encased within, or
positioned on, hermetic housing 70. In addition to power module 71,
condenser module 41, pump/motor module 51 and evaporator module 61
can be hermetically-sealed and individually housed to maximize
system modularity. Lubrication of the rotating components within
the various hermetically sealed modules can be accomplished through
the addition of an autonomous closed-cycle loop. An example, shown
representatively in power module 71 (but equally applicable to any
of the hermetically sealed modules), includes a lubricant pump 75
providing lubricant (not shown) through lubricant circuit 77. When
the load absorbing device is a generator 80, the output from the
power module 71 is carried through electrically conductive lines
79. The electric output through lines 79 is in addition to that
produced in alternator 6, thus resulting in a dual source of
electrical power from the two subsystems 1 and 10.
[0046] Fluid in thermal circuit 20 absorbs heat from the heat
stream 7 of the prime mover in the first heat exchanger, which is
preferably an evaporator 60. Heat exchanger first inlet 60A and
first outlet 60B permit thermal interaction between thermal circuit
20 and heat stream 7, which passes through heat exchanger second
inlet 60C and second outlet 60D. In either the dual electric or CHP
mode, condensed working fluid, which may be an organic-based
refrigerant, such as R22, R123, propane, N-butane, or the like is
transported by pump 50 through thermal circuit 20 to complete the
preferably closed-cycle working fluid loop. The use of such working
fluids is desirable within the context of the instant application
because through their use, the size of the thermal circuits
carrying them is reduced, which is important in space-limited
applications.
[0047] Preferably, power module 71 includes expander 30, which is
an involute spiral wrap, or scroll device, and a load absorber,
preferably in the form of electric generator 80. A detailed side
view of power module 71 is shown in FIG. 2 and a simplified end
view in FIG. 3A. While the involute spiral wrap device shown in
FIG. 2 as a dual scroll device, having two spiral wrap member pairs
30A and 30B disposed at opposing ends of common shaft 120, it will
be appreciated by those skilled in the art that a single spiral
wrap member pair could also be employed. As previously mentioned,
throttle valve 72 may be located within the power module, which may
be hermetically sealed by enclosure in housing 70; by so doing the
need for additional seals, such as actuator shaft seals, is
eliminated. Throttle valve 72 regulates the amount of fluid flowing
through the first thermal circuit 20, thereby acting as the primary
control mechanism for varying the speed of expanders 30A, 30B in
response to changes in requirements of the load absorbing device.
The main features of the expanders 30A, 30B as a scroll device are
the orbiting scrolls 101 and 111, and stationary scrolls 102 and
112. The high pressure working fluid traversing first thermal
circuit 20 gives up its energy via expansion in crescent shaped
translatable chambers 103 and 113 defined by the orbiting and
stationary scrolls. Due to the relationship between the orbiting
and stationary scrolls, where the orbiting scrolls 101 and 111 are
mounted to eccentric, or offset, ends 121 and 122 (preferably in
the form of axially extending pins) of shaft 120 and secured by a
conventional coupling device, such as a ball-ring assembly or
Oldham coupling (neither of which are shown), they orbit, rather
than rotate, about the stationary scrolls 102 and 112, which are
fixed to end walls 104 and 114. The linkage between the scrolls,
eccentric ends, coupling and shaft permits the shaft to convert the
scroll orbital motion into rotational motion in the shaft 120. The
rotational movement in shaft 120 can be used to turn a
field-generating rotor 80A of electric generator 80, where rotor
80A could be either mounted directly to shaft 120, as shown in the
figure, or to a disk (not shown), which in turn is mounted to shaft
120. A complimentary stator coil 80B is mounted in inductive
proximity to the field-generating rotor 80A such that when the
field-generating rotor 80A moves with respect to the stator coil
80B, an electric current is set up in the windings of the coil 80B,
thereby generating a secondary source of electrical power. In a
preferred embodiment, the stator coil 80B is mounted on an internal
surface of hermetically sealed power module 71, and is electrically
connected to an external current carrier through electrically
conductive lines 79. As specifically shown in FIG. 3B, a heat
exchange passage 150 with fluid inlet 157 and outlet 156 is mounted
adjacent stator coil 80B such that the two are in thermal
communication with one another for keeping the stator coil 80B from
overheating. The use of this arrangement is especially warranted
when the expander 30A, 30B is enclosed within a hermetic shell,
where normal convective cooling routes are either minimal or
nonexistent. The working fluid is shown in FIG. 1 as the coolant
for the stator coil, but other fluids could be utilized given inlet
and outlet ports through the hermetic shell. For example, cooling
water passing through condenser 40 via inlet 40A and outlet 40B
could be routed in place of the working fluid.
[0048] In an alternative embodiment 200 of the invention, as shown
in FIG. 4, in addition to compressor 202, fuel supply 203, turbine
205, generator 206, turbine exhaust duct 207, and shaft 208, the
prime mover subsystem 201 includes a catalytic combustor 204 to
promote low emission burning of the fuel/air mixture. The catalytic
combustor 204 requires the air entering into it from the compressor
202 to be of sufficiently high temperature to promote the catalysis
of combustion byproducts by a noble metal-coated ceramic combustion
core (not shown). Thus, a recuperator 215 is added between the
turbine exhaust duct 207 and heat energy utilization subsystem
evaporator 260 to preheat the compressed air going from compressor
202 to catalytic combustor 204. Recuperator 215 is essentially a
two-circuit heat exchanger that accepts, on its first circuit,
inlet from the compressor 202 discharge, and on its second circuit,
exhaust gas from the turbine exhaust duct 207. By way of example,
the temperature entering into the catalytic combustor needs to be
between 900.degree. F. and 1000.degree. F. to promote adequate
catalysis of the combustion byproducts. The recuperator 215 can be
used to supply these needs while at the same time utilizing
otherwise wasted exhaust gas from the prime mover subsystem 201.
Heat energy utilization subsystem 210 includes, in a
configurational arrangement similar to previous embodiment 10, a
working fluid traversing first thermal circuit 220 that passes
through expander 230 (represented notionally in the figure by a
single spiral wrap member pair), condenser 240, pump 250 and
evaporator 260. Throttle valve 272 regulates the amount of working
fluid that enters the scroll of expander 230. The present
embodiment may further include hermetically sealed power,
condenser, pump and evaporator modules 271, 241, 251 and 261,
respectively, as well as dedicated lubrication loop with pump 275
and circuit 277, in a manner configurationally similar to that
depicted in FIG. 1. Power output 279 is shown as electric potential
coming off a load absorbing device 280, which is preferably in the
form of a generator.
[0049] An alternate embodiment 300 of the system shown in FIG. 4
with catalytic combustor and recuperator is shown in FIG. 5. One of
the requirements peculiar to the system including a recuperator to
heat up a catalytic combustor is that the heat stream used to
charge the working in~ fluid in the heat energy utilization
subsystem could benefit from additional thermal content, as the
recuperator depletes the energy available from that heat stream or
during start-ups. This can be accomplished through the addition of
an auxiliary burner 348 and blower 347, which are placed upstream
of the recuperator 315 to provide both preheated intake air into
the catalytic combustor 304 as well as a high thermal content heat
stream to the heat energy utilization subsystem 310 through
auxiliary burner exhaust line 349. Auxiliary burner 348 mixes low
pressure fuel at line pressures typical of small commercial
applications (approximately 5 to 20 in. water column) from
secondary fuel supply 303B with exhaust gas from the turbine
exhaust 307 to create high temperature air to exchange heat in the
evaporator 360 with the working fluid flowing through first thermal
circuit 320. One advantage of the system shown in the present
figure is that the size of the recuperator 315 can be reduced, as
the added thermal content from auxiliary burner 348 can provide
adequate energy to evaporator 360, even after giving up some of its
heat in recuperator 315. Another advantage relates to the use of
the blower itself, which can enhance overall system flexibility by
providing sufficient airflow to the heat energy utilization
subsystem 310, even if the prime mover 301 is not operative, which
can occur during stand-alone operation of heat energy utilization
subsystem 310. In other regards, the configuration of the elements
in the prime mover subsystem 301, including compressor 302, primary
fuel supply 303A, catalytic combustor 304, turbine 305, generator
306, turbine exhaust 307, shaft 308, recuperator 315, as well as
the elements in the heat energy utilization subsystem 310,
including working fluid traversing first thermal circuit 320,
expander 330, condenser 340, pump 350, evaporator 360 and throttle
valve 372, are similar to that of previous embodiment 200.
Hermetically sealed power, condenser, pump and evaporator modules
371, 341, 351 and 361, respectively, are shown in a manner
configurationally similar to that depicted in FIGS. 1 and 4.
[0050] In still another embodiment 400 of the invention, as shown
in FIG. 6, it can also be seen that the turbine exhaust 407, in a
path similar to that of embodiment 200, passes through both a
recuperator 415 and auxiliary burner 448. In contrast with the
previous embodiment, the auxiliary burner 448 does not exchange any
of its heat in the recuperator 415, instead injecting increased
thermal content downstream and entirely in series with the heat
stream leaving the recuperator 415. This configuration has the
advantages that a smaller auxiliary burner 448 can be used, and
that no additional blower (such as was shown in the previous
embodiment) is required. This method of adding thermal content to
the prime mover heat stream requires sufficient oxygen content in
the heat stream to support combustion. As before, the configuration
of the elements in the prime mover subsystem 401, including
compressor 402, primary fuel supply 403A, catalytic combustor 404,
turbine 405, generator 406, turbine exhaust 407, shaft 408,
recuperator 415, as well as the elements in the heat energy
utilization subsystem 410, including working fluid traversing first
thermal circuit 420, expander 430, condenser 440, pump 450,
evaporator 460 and throttle valve 472, are similar to that of
previous embodiments. As with the previous embodiments, the heat
energy utilization subsystem includes a power module 471,
evaporator module 461, pump module 451 and condenser module
441.
[0051] The embodiment 500 is shown in FIG. 7, and is a variation of
the embodiment shown in FIG. 6. The major difference between the
two embodiments relates to the placement of auxiliary burner 548,
which is now upstream of the recuperator 515 such that it is
disposed between turbine 505 and recuperator 515. As with the
previous embodiment, the series relationship between the
recuperator 515 and the auxiliary burner 548 obviates the need for
a separate blower, while the heat generated in auxiliary burner
exhaust line 549 can provide a heat stream to add to that of
turbine exhaust 507. An advantage of this approach, similar to that
of the embodiment shown in FIG. 5, is that by adding heat to one of
the heat exchange circuits passing through the recuperator 515, the
size of the recuperator 515 can be reduced.
[0052] Referring now to FIG. 8, a variation on the embodiment of
FIG. 1 is shown, wherein the output from expander 630 could be
routed to one or more heat recovery modules 644, 646, 647 which in
CHP operation could provide heated water, air or other fluid medium
for related process and thermal transport requirements. The modules
of the CHP configuration can be used individually or in combination
with one another. The first, high temperature heat recovery module
644 (in effect a condenser), is connected to thermal circuit 620
downstream of evaporator 660, but prior to an expander 630, in
order to extract heat from the working fluid at its generally
hottest condition. The high temperature heat recovery module 644,
which can be configured as a simple co-flow heat exchanger, could
be for handling very hot water for sterilization, such as may be
used as at a restaurant or laundry. It can also be configured as a
coil in a storage water tank, such that it could also be used for
DHW. The second, low temperature heat recovery module 646 connects
to the thermal circuit 620 after the working fluid has given up a
portion of its energy to the expander 630 in power module 671, and
can be placed either upstream of the condenser 641, or, as shown in
the figure, connected to the cold side circuit. Low temperature
heat recovery module 646 can be, for example, a DHW storage tank,
in which cold water enters through inlet 646A and hot water exits
through outlet 646B. The third heat recovery module 647 can be
connected in parallel to low temperature heat recovery module 646
to act as an SH heat exchanger, such as a radiator, where heat from
the secondary circuit of condenser 640 can thermally interact with
a fluid in the SH loop that enters via inlet 647A and exits via
outlet 647B.
[0053] Referring now to FIGS. 9 and 10, an embodiment of the heat
energy utilization subsystem 710 is shown with two variants of
quick-start features incorporated therein. In the first variant,
shown in FIG. 9, an energy storage device, such as an electric
battery 792, is electrically connected to a logic and control
module 790, which in turn is signally connected to each of an
auxiliary burner 748, pump 750, prime mover subsystem 701 and load
absorption device, preferably in the form of a generator 780, via
signal carriers 790a-d. Power module 771 is made up of at least
expander 730, desuperheating heat exchanger 770 and generator 780.
To initiate heat energy utilization subsystem 710 operation,
battery 792 is turned on to energize the logic and control module
790, which in turn sends current through one or more signal
carriers 790a-d to start the pump 750, auxiliary burner 748 and
generator 780 in accordance with user-defined power requirements.
In addition, logic and control module 790 can send control
instructions to the prime mover subsystem 701 to ensure
coordination between the two subsystems. The auxiliary burner 748,
upon initiation, burns fuel to generate a heat stream that is
introduced into turbine exhaust 707 and expander 760 through
auxiliary burner exhaust line 749. After initiation of heat energy
utilization subsystem 710 operation, either the prime mover
subsystem 701 operation can be commenced, or the auxiliary burner
748 can continue to provide sufficient heat stream thermal content
through a heat energy utilization subsystem stand-alone mode of
operation. Note that although the presently shown embodiment does
not have the heat stream generated by the auxiliary burner 748
cooperating with a recuperator (as shown in FIGS. 5-7), such
configuration is within the scope of the present invention. In
addition to generating useful work 779 (shown in the figures as
electric potential), generator 780 provides, through recharging
module 791, the ability to recharge the battery 792. One advantage
of the quick-start approach is that the benefits of the heat energy
utilization subsystem 710 can be realized immediately, rather than
waiting for it to catch up with the already-operating prime mover
subsystem 701. A second advantage of the quick-start feature is
that in low-power and rapidly fluctuating dynamic power
requirements, where it would be impractical to start the prime
mover subsystem 701, the heat energy utilization subsystem 710
could be the sole provider of power. Desuperheating heat exchanger
770 is fluidly connected to the outlet of the secondary circuit of
condenser 740 to provide additional heat output from the system and
provide a lower temperature environment around the generator 780
windings. The heat output from condenser 740 and desuperheating
heat exchanger 770 is potentially useful for SH or DHW (neither of
which are presently shown). The desuperheating heat exchanger 770
can provide a higher temperature output from the overall system
compared to a condenser-only configuration. The quantity of heat
may well be the same in both configurations, but by separating the
heat exchange process into two pieces, (desuperheater and
condenser), a higher fluid temperature may result. Desuperheating
heat exchanger 770 must be in heat exchange communication with the
vapor leaving the expander 730, possibly by having desuperheating
heat exchanger 770 situated inside the shell of power module 771
and having open flow from the exit port of the expander 730 into
the power module 771 shell.
[0054] In the second variant, shown in FIG. 10, an accumulator 796
and accumulator control valve 797 (which could be a conventional
solenoid-based valve) are added upstream of the evaporator 760 in
turbine exhaust 707. Isolation valve 798 is placed in front of
evaporator 760 such that during heat energy utilization subsystem
710 startup, the hot exhaust coming from auxiliary burner 748 can
be routed to accumulator 796 to charge it prior to normal heat
energy utilization subsystem 710 operation. Alternatively,
accumulator 796 may be precharged during the previous system
shut-down such that it retains this heat until the next start-up
sequence of heat energy utilization subsystem 710. The residual
heat and pressure content of the fluid in the accumulator 796 can
thus function as a power delivery smoothing device, in that it can
be used in place of the auxiliary burner 748 or the prime mover 701
for brief intervals, thus saving on fuel and wear and tear on the
equipment that would otherwise be continuously cycled. Logic and
control module 790 has, in addition to signal carriers 790a-d, an
additional electrical connection 799 to the accumulator control
valve 797 to control the flow of working fluid in first thermal
circuit 720. Thus, accumulator control valve 797 and isolation
valve 798 are used to control heating fluid flow during subsystem
710 starting, while the throttle valve 772 controls working fluid
flow during normal operation of subsystem 710. Partial actuation of
valves 797 and 798 allow both power generation and recharging of
accumulator 796. The inclusion of the accumulator 796 and related
valves 797 and 798 permits even more rapid heat energy utilization
subsystem 710 starting, which improves overall power generation
subsystem 700 efficiency.
[0055] Referring now to FIG. 11, a block diagram of the
load-splitting module 810 for the integrated power generation
system is shown. Load-splitting module 810 continually monitors the
status of the power generation patterns 820 and 830 from both the
heat energy utilization subsystem (not shown) and the prime mover
subsystem (not shown). Active feedback features in the
load-splitting module 810 compare the power generation pattern
information to predetermined load parameters, and adjust as needed
the output between the two power-generating subsystems to promote
load dynamics isolation. Plot 850 is a representation of an
optimized composite electric generation profile under
load-splitting module operation. The heart of the load-splitting
module is a fuzzy logic controller 840, that incorporates
multivalued logic to process sensed values, then provides active
feedback control features to set the load requirements in the prime
mover and heat energy utilization subsystems so that the electrical
end user is delivered power in the most efficient, cost effective
manner. The fuzzy logic controller 840 has as it primary functions
the separation of an electrical load into two parts (a steady
portion and a dynamic portion), and the outputting of two power
control signals (a slow response signal and a fast response
signal).
[0056] Fuzzy logic controller 840 responds to instantaneous values
of load and to recent average values of load to form a likely
history of loads that can be generalized according to factors such
as load current, load voltage, power factor, input of basic system
characteristics (such as a table of information for system set-up
parameters), and history of recent loads, seasonal (calendar) and
time-of-day attributes, or the like so that future loads can be
anticipated to a useful extent. Once the fuzzy logic controller 840
of load-splitting module 810 generates the likely value of steady
load for the next interval of time, it can then determine how much
load can be apportioned to each of the heat energy utilization and
prime mover subsystems. The nature of the two cooperative
subsystems is such that the prime mover subsystem is relatively
more efficient but slower in response to load fluctuations, while
the heat energy utilization subsystem is more rapidly responsive,
although less efficient. The load the system responds to includes a
base component that changes slowly, if at all, and a dynamic
component. To maximize efficiency of operation of the overall
system, the prime mover should be operated as often as possible,
but not so much that it must make frequent changes to its output. A
first output from the fuzzy logic controller 840 can function as
the throttle setting for the prime mover such that the torque, but
not the speed, voltage, or frequency of the prime mover are varied.
A second output from the controller 840 can be coupled to the fast
response heat energy utilization subsystem such that speed control
is maintained by adjusting the throttle. In situations where the
two power generators are both generating electric output, and are
connected in parallel with the same load, they will stay
synchronized with one another as they follow the load. The
controller 840 can be programmed so that it would always maximize
the load on the more efficient prime mover generator, consistent
with the need to not make any rapid load changes on it, but also
protective against situations leading to overload of the entire
system. Through the fuzzy algorithm, the most efficient steady load
distribution is produced, while the unsteady load swings of the
lesser efficient but more rapidly controllable heat recovery
subsystem are kept to a level that is always within the capability
of that system. Either artificial intelligence or user
preprogramming can be used to assist the fuzzy logic controller 840
to anticipate load changes in both extent and timing.
[0057] Although the basics of the fuzzy logic controller 840 were
first developed for use with the heat energy utilization system in
this application, the characteristics of controller 840 make it
potentially applicable to a power and heat system using a fuel cell
and a thermally driven engine of any sort which provides more rapid
response to load changes than does a fuel cell. Fuel cells often
have waste heat which can be utilized in many ways; however, fuel
cells tend to be slow to respond to load changes, which can be very
rapid in practical applications. While batteries, flywheels or the
like may be used to smooth normal load changes for a fuel cell
system, these add-on technologies have their own limitations, in
addition to contributing to overall system cost and complexity. By
coupling a fast response generator as part of the heat energy
utilization system to the fuel cell, the system can achieve the
significant response advantages associated with the aforementioned
load-smoothing devices, without the negative impacts on system
compactness, operating time, weight, cost or maintenance. As with a
system that employs a microturbine-based prime mover, the fuzzy
logic controller 840 can be used to parse out the loads among the
two subsystems, a fuel cell that can only be loaded and unloaded
slowly, and the supplemental heat energy utilization subsystem
capable of fast load changes. The controller 840 takes data on
recent load profiles and outputs two load signals, a relatively
steady one to the fuel cell and the other which has all the rapid
load changes to the heat energy utilization subsystem acting in its
peaking capacity. The controller 840 limits the load on the peaking
system to loads which are likely to be within its capacity, thus
placing as much of the load as possible on the more efficient fuel
cell.
[0058] Referring now to FIG. 12, capacity control is achieved with
heat energy utilization subsystem 910 that includes two separate
controllers made up of speed-throttle control under rapid response
portion 911 and evaporator-pump-waste gate valve control under slow
response portion 915. Together, rapid and slow response portions
911, 915 respectively, comprise capacity control module 919. In the
rapid response portion 91 1, shaft speed coming off expander 930 of
power module 971 is sensed by sensors 985A in close-coupled control
mechanism 985, which sends a signal via feed-back controller 985B
to throttle valve 972 to adjust valve position, thus effecting
rapid and robust shaft speed correction and control to the dynamic
load being imposed on the heat energy utilization subsystem 910. In
the slow response portion 915, a PID logic controller 990, which,
in response to pressure and temperature signals 961, 962
corresponding to evaporator 960 conditions (collectively known as
superheat), sends out actuation signals 994a-c to control the pump
950, auxiliary burner 948 (with secondary fuel supply 903B) and
prime mover turbine exhaust 907 through waste heat bypass valve 995
coming from the prime mover subsystem 901. By actively adjusting
the flow rate through pump 950 and waste gate valve 995 position,
as well as optional firing of the auxiliary burner 948 and
introduction into auxiliary burner exhaust line 949 of additional
heat, the slower, system-level control of slow response portion 915
promotes the acquisition and maintenance of an equilibrium point
for heat energy utilization subsystem 910 by smoothly adjusting
individual component settings with the PID logic controller 990. In
addition, time rate of change information from generator 980 can be
fed through power signal 981 into the PID controller 990, thus
providing additional control logic capability to the heat energy
utilization subsystem 910. Considerable increases in both heat
energy utilization subsystem 910 as well as overall system 900
flexibility can be realized by permitting the heat energy
utilization subsystem 910 to respond to volatile load changes,
thereby increasing the efficiency of the prime mover subsystem 901.
In addition, fuzzy logic controller 940 can be used in a manner
similar to that of the previous embodiment, to ensure adequate load
splitting among the heat energy utilization and prime mover
subsystems, 910 and 901 respectively.
[0059] While the embodiments and systems discussed herein have been
directed to particular embodiments of a prime mover subsystem
coupled with a heat energy utilization subsystem, it is within the
scope of the present invention to provide an adaptable operating
system incorporating features responsive to varying user demands.
Furthermore, although the preferred embodiments incorporate a
microturbine prime mover as the heat stream generating source, it
is within the scope of the invention to adapt the heat energy
utilization subsystem to fit with any prime mover, including
conventional reciprocating, steam and gas turbine engines, as well
as non-combustion based and renewable prime mover sources, so long
as the prime mover heat stream possesses sufficient thermal
content. Thus, having described the present invention in detail and
by reference to the embodiments thereof, it will be apparent that
modifications and variations are possible without departing from
the scope of the invention in the following claims.
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