(12) United States Patent
`Pierson
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,769,258 B2
`Aug. 3, 2004
`
`US006769258B2
`
`(54) SYSTEM FOR STAGED CHILLING OF
`INLET AIR FOR GAS TURBINES
`
`(75) Inventor: Tom L. Pierson, 7910 Arbor Hill Ct.,
`Sugar Land, TX (US) 77479
`
`(73) Assignee: Tom L. Pierson, Sugarland, TX (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 10/206,856
`(22) Filed:
`Jul. 26, 2002
`(65)
`Prior Publication Data
`
`US 2004/0011046 A1 Jan. 22, 2004
`
`Related US. Application Data
`
`(63) Continuation-in-part of application No. 09/961,711, ?led on
`Sep. 24, 2001, now Pat. No. 6,470,686, which is a continu
`ation of application No. 09/369,788, ?led on Aug. 6, 1999,
`now Pat. No. 6,318,065.
`
`(51) Int. Cl.7 ................................................ .. F02C 1/00
`(52) US. Cl. ............. ..
`.. 60/772; 60/728; 62/175
`(58) Field of Search .................... .. 60/772, 728; 62/175
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,444,971 A * 8/1995 Holenberger .............. .. 60/783
`5,465,585 A * 11/1995 Mornhed et al.
`62/59
`5,632,148 A * 5/1997 Bronicki et al.
`60/728
`6,408,609 B1 * 6/2002 Andrepont ................. .. 60/772
`
`OTHER PUBLICATIONS
`
`Holman, J .P., “Thermodynamics”, McGraWHill Kogakusha,
`2nd ed., Tokyo 1974, pp. 452—453.*
`
`* cited by examiner
`
`Primary Examiner—Justine R. Yu
`Assistant Examiner—William H. Rodriguez
`(74) Attorney, Agent, or Firm—Moser,
`Sheridan, LLP
`(57)
`
`ABSTRACT
`
`Patterson &
`
`A method for cooling inlet air to a gas turbine is provided.
`For example, a method is described including passing inlet
`air through a cooling coil that includes an opening for
`receiving the inlet air and that is operably connected to a gas
`turbine poWer plant. The gas turbine poWer plant may
`include at least one gas turbine, and at least one gas turbine
`inlet Which receives the inlet air. The method may further
`include passing circulating Water through a Water chiller at
`a ?rst ?oW rate to reduce the temperature of the circulating
`Water, the Water chiller including a conduit through Which
`the circulating Water is capable of passing and passing the
`circulating Water having the ?rst ?oW rate through the
`cooling coil in an amount suf?cient to loWer the temperature
`of the inlet air. Additionally, the method may include reduc
`ing the How rate of the circulating Water passing through the
`Water chiller, passing the circulating Water through a Water
`chiller at a second ?oW rate to reduce the temperature of the
`circulating Water, the second ?oW rate being loWer than the
`?rst ?oW rate, and passing the circulating Water having the
`second ?oW rate through the cooling coil in an amount
`suf?cient to loWer the temperature of the inlet air.
`
`27 Claims, 9 Drawing Sheets
`
`COOLING TOWER
`
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`PAGE 1 of 27
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`PETITIONER'S EXHIBIT 1305
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`PETITIONER'S EXHIBIT 1305
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`PETITIONER'S EXHIBIT 1305
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`PAGE 4 of 27
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`PETITIONER'S EXHIBIT 1305
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`

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`U.S. Patent
`
`Aug. 3, 2004
`
`Sheet 4 0f 9
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`US 6,769,258 B2
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`em:
`
`Ll
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`PAGE 5 of 27
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`PETITIONER'S EXHIBIT 1305
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`U.S. Patent
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`Aug. 3, 2004
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`Sheet 5 of9
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`US 6,769,258 B2
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`PETITIONER'S EXHIBIT 1305
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`PETITIONER'S EXHIBIT 1305
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`U.S. Patent
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`Aug. 3, 2004
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`Sheet 7 0f 9
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`US 6,769,258 B2
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`HUMIDITY RATIO
`(GRAINS OF MOISTURE PER POUND OF DRY AIR)
`
`
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`DRY BULB TEMPERATURE (°F)
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`PAGE 8 of 27
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`PETITIONER'S EXHIBIT 1305
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`U.S. Patent
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`Aug. 3, 2004
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`Sheet 8 0f 9
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`US 6,769,258 B2
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`PETITIONER'S EXHIBIT 1305
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`PAGE 10 of 27
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`PETITIONER'S EXHIBIT 1305
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`

`
`US 6,769,258 B2
`
`1
`SYSTEM FOR STAGED CHILLING OF
`INLET AIR FOR GAS TURBINES
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a continuation-in-part of US. patent
`application Ser. No. 09/961,711 ?led Sep. 24, 2001 now
`US. Pat. No. 6,470,686, Which is a continuation of US.
`patent application Ser. No. 09/369,788 ?led Aug. 6, 1999,
`now US. Pat. No. 6,318,065.
`
`BACKGROUND OF INVENTION
`
`1. Field of the Invention
`This invention relates broadly to cooling inlet air to a gas
`turbine.
`2. Description of Related Art
`A conventional gas turbine system includes: an air com
`pressor for compressing the turbine inlet air; a combustion
`chamber for mixing the compressed air With fuel and
`combusting the mixture, thereby producing a combustion
`gas; and a poWer turbine that is driven by the combustion
`gas, thereby producing an exhaust gas and useful poWer.
`Over the years, various technologies have been employed
`to increase the amount of useful poWer that the poWer
`turbine is able to produce. One Way of increasing the poWer
`output of a gas turbine is to cool the turbine inlet air prior to
`compressing it in the compressor. Cooling causes the air to
`have a higher density, thereby creating a higher mass ?oW
`rate through the turbine. The higher the mass ?oW rate
`through the turbine, the more poWer the turbine produces.
`Cooling the turbine inlet air temperature also increases the
`turbine’s ef?ciency.
`Various systems have been devised for chilling the inlet
`air to the compressor. One such system uses evaporative
`cooling, Wherein ambient temperature Water is run over
`plates or over a cellular media inside of a chamber, thereby
`creating thin ?lms of Water on each plate, or on the media.
`The turbine inlet air is then draWn through the chamber, and
`through evaporative cooling, the air is cooled to near the Wet
`bulb temperature. This system is limited to cooling the air to
`the Wet bulb temperature, Which is dependent upon the
`atmospheric conditions at any given time. Another system
`uses a chiller to chill Water that is then run through a coil.
`The inlet air is then draWn through the coil to cool the air.
`This system requires parasitic poWer or steam to drive the
`chilling system Which has the further draWback that When
`inlet air cooling is needed the most, ie during the day When
`the temperature is the highest, is also the time When poWer
`demand from the turbine is the highest, ie during the day
`When poWer users are in operation. In order to run the chiller,
`poWer from the turbine is required, but this poWer is needed
`by the users of the turbines poWer. On the other hand, When
`cooling is needed the least, ie at night When the tempera
`tures are the loWest, surplus poWer from the turbine is
`available because the consumers of the turbine’s poWer are
`largely not in operation. Accordingly, a continuing need
`exists for a turbine inlet air cooling system Which: Would
`ef?ciently cool turbine inlet air; Would take advantage of
`surplus poWer available during times of loW consumer
`poWer demand; and Would not drain the system of poWer
`during times of high consumer poWer demand.
`
`SUMMARY OF INVENTION
`A. Inlet Air Cooling
`Described in greater detail beloW is a method for chilling
`inlet air to a gas turbine poWer plant, Which may include:
`providing a system of circulating chilling Water including a
`chilling system; providing an inlet air chiller for loWering
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`the temperature of the inlet air being fed to a gas turbine
`compressor through heat transfer betWeen the circulating
`chilling Water and the inlet air, providing a thermal Water
`storage tank Which is operably connected to the system of
`circulating chilling Water, the thermal Water storage tank
`containing chilling Water having a bottom; during a charge
`cycle, removing a ?rst portion of chilling Water from the
`thermal Water storage tank, passing the removed ?rst portion
`of Water through the chilling system to loWer the tempera
`ture of the removed ?rst portion of Water and to provide a
`chilled removed ?rst portion of Water, and then introducing
`the chilled removed ?rst portion of Water into the thermal
`Water storage tank at a point proximate the bottom of the
`tank, Wherein the chilled removed ?rst portion of Water is
`introduced to the tank in an amount suf?cient to loWer the
`average temperature of the chilling Water in the thermal
`Water storage tank; and during a discharge cycle, chilling the
`inlet air by removing a second portion of chilling Water from
`the thermal Water storage tank, from a point proximate the
`bottom of the tank and then passing the second portion of
`chilling Water to the inlet air chiller to make heat transfer
`contact betWeen the second portion of chilling Water and the
`inlet air, such that the temperature of the inlet air is loWered.
`In another method that is described herein, the average
`temperature of the chilling Water in the tank may be loWered
`to about 33° F. to about 40° F. during the charge cycle and
`may be raised to about 60° F. to about 70° F. during the
`discharge cycle. In another speci?c embodiment, the times
`of the charge and discharge cycles may be such that, before
`the temperature of the chilling Water proximate the bottom
`of the tank reaches about 36° F. during the discharge cycle,
`the charge cycle is initiated. In another speci?c embodiment
`of the method for chilling inlet air, the ?rst portion of
`chilling Water removed from the thermal Water storage tank
`during the charge cycle may be removed through a top
`outlet. In yet another speci?c embodiment, the chilling Water
`in the tank may have an average temperature that can be
`loWered during the charge cycle and raised during the
`discharge cycle. In a further speci?c embodiment of the
`claimed method, the discharge cycle may be carried out
`during the night-time and the charge cycle may be carried
`out during the day-time. In still another speci?c
`embodiment, the Water level in the tank may remain sub
`stantially constant during the charge and discharge cycles. In
`still a further speci?c embodiment, the one or more chillers
`may be deactivated during the discharge cycle. In another
`speci?c embodiment, the discharge cycle may occur during
`peak poWer usage of the gas turbine poWer plant. In another
`speci?c embodiment, the discharge cycle may be performed
`after the removing of at least a portion of the volume of
`chilling Water from the thermal Water storage tank during the
`charge cycle, such that the chilled removed Water that is
`introduced into the thermal Water storage tank at a point
`proximate the bottom of the tank may remain substantially
`at the point proximate the bottom of the tank. In another
`speci?c embodiment, the ?rst portion of chilling Water
`removed during the charge cycle may be suf?cient to chill
`substantially all of the Water in the thermal Water storage
`tank to a temperature beloW the temperature of maximum
`Water density. In yet another speci?c embodiment of the
`claimed method, the second portion of chilling Water
`removed during the discharge cycle may be substantially all
`of the chilling Water in the tank. In a further speci?c
`embodiment of the method of the present invention, the
`thermal Water storage tank contains a volume of chilling
`Water that is suf?cient to loWer the temperature of the inlet
`air to a range of from about 45° F. to about 55° F. for a period
`of betWeen about 4 hours to about 12 hours.
`Also described herein is a method of chilling Water
`delivered to the air chiller in a gas turbine poWer plant
`system having at least one air chiller for loWering the
`
`PAGE 11 of 27
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`PETITIONER'S EXHIBIT 1305
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`

`
`US 6,769,258 B2
`
`3
`temperature of inlet air, at least one air compressor for
`compressing the inlet air, at least one combustor for burning
`the compressed air and providing combustion gas, and at
`least one poWer turbine driven by the combustion gas for
`producing useful poWer, a method of chilling Water deliv
`ered to the air chiller, the method including the steps of:
`providing the at least one air chiller With an air chiller inlet
`that may receive Water, and an air chiller outlet that may
`expel Water; providing a thermal Water storage tank, having
`a bottom portion, a top portion, at least one bottom opening
`proximate the bottom portion and at least one top opening
`proximate the top portion, and containing a volume of stored
`Water having an average temperature, and temperature of
`maximum Water density; performing a charge cycle, by
`introducing through the at least one bottom opening a ?rst
`quantity of chilled Water Which has a chilled Water tempera
`ture that is beloW the temperature of maximum Water
`density, thereby loWering the average temperature of the
`volume of stored Water, Wherein the ?rst quantity of chilled
`Water being introduced through the bottom opening is suf
`?cient to loWer the average temperature of the volume of
`stored Water to a temperature that is beloW the temperature
`of maximum Water density; and performing a discharge
`cycle by removing a second quantity of chilled Water from
`the tank through the at least one bottom opening and passing
`the second quantity of chilled Water to the air chiller inlet,
`to loWer the temperature of the inlet air, thereby raising the
`temperature of the second quantity of chilled Water and
`providing high temperature Water, then introducing the high
`temperature Water to the at least one top opening in the tank.
`In yet another method of chilling Water, the temperature
`of maximum Water density may be from about 20° F. to
`about 392° F. In another speci?c embodiment, the tempera
`ture of maximum Water density may be about 392° F. In
`another speci?c embodiment, the temperature of the stored
`Water may have a temperature of from about 34° F. to about
`40° F. In yet another speci?c embodiment of the claimed
`method the temperature of the stored Water may have a
`temperature corresponding to the maximum Water density of
`about 392° F. In another speci?c embodiment sodium
`nitrate may be added to depress the freeZing temperature of
`the Water thereby alloWing stored Water to be in the range of
`about 25° F. to about 34° F. In another speci?c embodiment
`of the method of the present invention, the useful poWer
`produced by the poWer turbine may be consumed at a
`variable rate, and the charge cycle may be performed When
`the rate is at a minimum. In a further speci?c embodiment,
`the useful poWer produced by the poWer turbine may be
`consumed at a variable rate, and the discharge cycle may be
`performed When the rate is at a maximum. In yet another
`speci?c embodiment of the method of the present invention,
`the quantity of Water expelled during the discharge cycle
`may be less than the volume of stored Water. In a further
`speci?c embodiment, the quantity of chilled Water may be
`chilled by passing Water through at least one chiller. In still
`another speci?c embodiment of the claimed method, the
`temperature of inlet air may be loWered from a high tem
`perature of from about 85° F. to about 95° F. to a loW
`temperature of from about 45° F. to about 55° F. In still a
`further speci?c embodiment, the high temperature may be
`about 90° F. and the loW temperature may be about 50° F. In
`yet another speci?c embodiment, the output of the gas
`turbine poWer plant system may be from about 50 mega
`Watts to about 250 megaWatts.
`Also described beloW is a gas turbine poWer plant system,
`Wherein the system includes: one or more air chillers for
`loWering the temperature of inlet air; one or more air
`compressors for compressing the inlet air; one or more
`combustors for burning the compressed air and providing
`combustion gas; and one or more poWer turbines driven by
`the combustion gas for producing useful poWer, and an
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
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`55
`
`60
`
`65
`
`4
`improvement that may include: a thermal Water storage tank
`for containing chilled Water, Wherein the thermal Water
`storage tank has a bottom portion With a bottom outlet and
`a top portion, and the tank is operably connected to the air
`chiller such that the chilled Water passes from the bottom
`outlet to the air chiller to loWer the temperature of the inlet
`air and is returned to the thermal Water storage tank; and a
`Water chilling system for chilling the Water in the thermal
`Water storage tank, Wherein the Water chilling system is
`con?gured to receive high temperature Water from the top
`portion of the tank, and Wherein the system is con?gured to
`introduce loW temperature Water to the bottom portion of the
`tank, such that the average temperature of the Water in the
`tank is loWered; and Wherein the Water chilling system
`includes one or more chillers for loWering the temperature of
`the high temperature Water from the top portion of the tank
`to provide loW temperature Water.
`In an example of such a gas turbine poWer plant system,
`the thermal Water storage tank may have a bottom, and the
`bottom outlet may be positioned at a height that is less than
`about 10 feet from the bottom of the tank. In another speci?c
`embodiment of the gas turbine poWer plant system, the
`thermal Water storage tank may have a bottom, and the
`bottom outlet may be positioned at a height that is less than
`about 5 feet from the bottom of the tank. In another speci?c
`embodiment, the thermal Water storage tank may have a
`bottom, and the bottom outlet may be positioned at a height
`that is less than about 18 inches from the bottom of the tank.
`In another speci?c embodiment, the tank may have a top
`outlet and a bottom inlet such that, in a charge cycle the high
`temperature Water may be removed through the top outlet
`and may be fed to the one or more chillers, and the loW
`temperature Water may be introduced to the tank through the
`bottom inlet. In a further speci?c embodiment of the gas
`turbine poWer plant system, the tank may have a bottom
`outlet such that, in a discharge cycle, chilling Water may be
`removed from the tank through the bottom outlet. In still a
`further speci?c embodiment of the gas turbine poWer plant
`system, the tank may have a bottom outlet such that, in a
`discharge cycle, chilling Water may be removed from the
`tank through the bottom outlet, fed to the air chiller and is
`returned to the tank, bypassing the one or more chillers of
`the Water chilling system. In still a further speci?c embodi
`ment of the gas turbine poWer plant system, the top portion
`may be separated from the bottom portion by a thermocline.
`In yet another example, during the charge cycle, the
`bottom inlet may receive a quantity of chilled Water that is
`suf?cient to supply the air chiller With Water having a
`temperature beloW the temperature of maximum Water den
`sity for four or more hours. In another speci?c embodiment,
`during the charge cycle, the bottom inlet may receive a
`quantity of chilled Water that is suf?cient to supply the air
`chiller With Water having a temperature beloW the tempera
`ture of maximum Water density for eight or more hours. In
`still another embodiment, during the charge cycle, the bot
`tom inlet may receive a quantity of chilled Water that is
`suf?cient to supply the air chiller With Water having a
`temperature beloW the temperature of maximum Water den
`sity for tWelve or more hours.
`In still another example, the thermal Water tank may have
`a height of from about 25 feet to about 70 feet. In yet another
`speci?c embodiment, the thermal Water tank may have a
`diameter of from about 50 feet to about 250 feet. In another
`speci?c embodiment, the thermal Water tank may have a
`diameter, and a height, and the diameter may be greater than
`the height. In yet another speci?c embodiment of the
`claimed invention, the volume of stored Water may be
`greater than about eight hundred thousand gallons. In still a
`further speci?c embodiment, the temperature of the Water in
`the top portion may be about 15° F. to about 35° F. greater
`than the temperature of the Water in the bottom portion. In
`
`PAGE 12 of 27
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`PETITIONER'S EXHIBIT 1305
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`US 6,769,258 B2
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`5
`another speci?c embodiment, the thermal Water storage
`system may include a plurality of thermal Water storage
`tanks, each of the plurality of tanks may have a bottom inlet
`and a bottom outlet, and each of the plurality of tanks may
`have a top inlet and a top outlet. In another speci?c
`embodiment, the bottom inlet may have a bottom diffuser,
`and the top inlet may have a top diffuser, Whereby the Water
`entering the bottom inlet is diffused, and the Water entering
`the top inlet may be diffused. In yet another speci?c
`embodiment, the temperature of the Water in the top portion
`of the tank may have a temperature ranging from about 60°
`F. to about 70° F. In still a further speci?c embodiment, the
`temperature of the Water in the bottom portion of the tank
`may have a temperature that is above the freezing tempera
`ture. In another speci?c embodiment, the Water chilling
`system may include at least one mechanical chiller. In still
`another speci?c embodiment of the present invention, the
`Water chilling system may include at least one absorption
`chiller. In still a further speci?c embodiment, the Water
`chilling system may include at least one mechanical chiller
`and at least one absorption chiller. In yet another speci?c
`embodiment, the mechanical chiller may receive chilled
`Water from the absorption chiller, and the mechanical chiller
`may further chills the chilled Water. In another speci?c
`embodiment, the gas turbine poWer plant system may addi
`tionally including a heat recovery steam generator and a
`steam turbine, Wherein the absorption chiller may be driven
`by steam from the heat recovery steam generator. Another
`speci?c embodiment of the gas turbine poWer plant system
`may additionally include a heat recovery steam generator
`and a steam turbine, Wherein the absorption chiller is driven
`by back pressure from the steam turbine exhaust. In another
`speci?c embodiment, the inlet air may be loWered from a
`?rst temperature of about from 85° F. to about 95° F. to a
`second temperature of from about 45° F. to about 55° F. in
`the inlet air chiller. In yet another embodiment, the ?rst
`temperature may be about 90° F. and the second temperature
`may be about 50° F. In another speci?c embodiment of the
`gas turbine poWer plant system, the chilling Water being fed
`to the inlet air chiller may have a temperature of from about
`34° F. to about 40° F. In another speci?c embodiment, the
`gas turbine poWer plant system may additionally include a
`steam turbine and a heat recovery steam generator, and the
`heat recovery steam generator may receive exhaust gas from
`the poWer turbine and may provide high pressure steam to
`the steam turbine, and the steam turbine may provide loW
`pressure steam.
`B. Additional Methods and Systems
`Embodiments of the invention additionally include pass
`ing inlet air through a cooling coil that includes an opening
`for receiving the inlet air and that is operably connected to
`a gas turbine poWer plant. The gas turbine poWer plant may
`include at least one gas turbine, and at least one gas turbine
`inlet Which receives the inlet air. The method may further
`include passing circulating Water through a Water chiller at
`a ?rst ?oW rate to reduce the temperature of the circulating
`Water, the Water chiller including a conduit through Which
`the circulating Water is capable of passing and passing the
`circulating Water having the ?rst ?oW rate through the
`cooling coil in an amount suf?cient to loWer the temperature
`of the inlet air. Additionally, the method may include reduc
`ing the How rate of the circulating Water passing through the
`Water chiller, passing the circulating Water through a Water
`chiller at a second ?oW rate to reduce the temperature of the
`circulating Water, the second ?oW rate being loWer than the
`?rst ?oW rate, and passing the circulating Water having the
`second ?oW rate through the cooling coil in an amount
`sufficient to loWer the temperature of the inlet air.
`Additional embodiments may include providing a system
`of circulating liquid chilling Water including a chilling
`system that includes a ?rst mechanical chiller and a second
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`mechanical chiller, the ?rst and second mechanical chillers
`being arranged in series and passing at least a portion of the
`liquid chilling Water through the ?rst mechanical chiller and
`the second mechanical chiller, the liquid chilling Water
`passing through the ?rst mechanical chiller being loWered to
`a ?rst temperature, and the liquid chilling Water passing
`through the second mechanical chiller being loWered to a
`second temperature that is loWer than the ?rst temperature,
`thus providing a staged liquid chilling Water temperature
`drop, Wherein the staged liquid chilling Water temperature
`drop is from about 20° F. to about 34° F. The method may
`further include providing an inlet air chiller, comprising a
`cooling coil through Which liquid chilling Water passes, for
`loWering the temperature of inlet air being fed to the
`compressor through heat transfer betWeen the liquid chilling
`Water passing through the cooling coil and the inlet air,
`Wherein the inlet air chiller provides a liquid chilling Water
`temperature rise of from about 20° F. to about 34° F. and
`chilling the inlet air by directing the liquid chilling Water to
`the inlet air chiller and passing the liquid chilling Water
`through the cooling coil of the inlet air chiller to make heat
`transfer contact betWeen the liquid chilling Water and the
`inlet air. Preferably, the method additionally includes adding
`potassium formate to the circulating Water in an amount
`suf?cient to depress the freeZing point of the circulating
`Water. In the alternative, or additionally, the method may
`include contacting the inlet air leaving the cooling coil With
`a control system, a temperature sensor, and a relative humid
`ity sensor to monitor the leaving air temperature and relative
`humidity of the leaving air and varying the How or the
`temperature of the circulating Water to maintain a relative
`humidity of the coil to beloW about 95% to about 99% RH
`for optimal efficiency in a combined cycle system.
`Additional embodiments may include a system for chill
`ing inlet air for a gas turbine poWer plant including passing
`inlet air through a cooling coil that includes an opening for
`receiving the inlet air and that is operably connected to a gas
`turbine poWer plant that includes at least one gas turbine,
`and at least one gas turbine inlet Which receives the inlet air,
`passing circulating Water through a Water chiller at a ?rst
`?oW rate to reduce the temperature of the circulating Water,
`the Water chiller including a conduit through Which the
`circulating Water is capable of passing and passing the
`circulating Water having the ?rst ?oW rate through the
`cooling coil in an amount suf?cient to loWer the temperature
`of the inlet air to a desired air temperature setpoint. The
`system may further include reducing the How rate of the
`circulating Water passing through the Water chiller during
`loWer ambient off-design periods to maintain the desired air
`temperature setpoint, passing the reduced ?oWrate circulat
`ing Water through the Water chiller at a second ?oW rate and
`reducing the temperature of the circulating Water to maintain
`the desired air temperature setpoint, the second ?oW rate
`being loWer than the ?rst ?oW rate and passing the circu
`lating Water having the second ?oW rate through the cooling
`coil in an amount sufficient to loWer the temperature of the
`inlet air to the desired air temperature setpoint. The method
`may additionally include reducing the How rate of the
`circulating Water passing through the tWo or more sequen
`tially positioned compressors during loWer ambient off
`design conditions to maintain a higher circulating Water
`delta T thereby alloWing Warmer Water to pass through the
`upstream compressor thus improving the ef?ciency at partial
`load.
`Certain embodiments include passing the circulating
`Water through a heater prior to passing the circulating Water
`through the cooling coil, in Which the circulating Water
`temperature is increased to a temperature that is higher than
`the temperature of the circulating Water leaving the cooling
`coil and higher than the temperature of the air entering the
`cooling coil to maintain the minimum desired leaving air
`temperature.
`
`PAGE 13 of 27
`
`PETITIONER'S EXHIBIT 1305
`
`

`
`US 6,769,258 B2
`
`7
`Certain embodiments include adding an additive to the
`circulating Water in an amount suf?cient to depress the
`freezing point of the circulating Water. Certain embodiments
`may further include adding an additive to the circulating
`Water in an amount suf?cient to depress the freezing point of
`the circulating Water and minimiZing any negative perfor
`mance derating due to the additive effect on the heat transfer
`properties of Water. Certain embodiments may include add
`ing a salt additive to the circulating Water in an amount
`sufficient to depress the freeZing point of the circulating
`Water. The salt additive may be added to the circulating
`Water in an amount suf?cient to depress the freeZing point of
`the circulating Water to a point that Would speci?cally
`provide for protection of the system during loW ambient
`temperature operation and to protect the system during
`shut-doWn periods. Certain embodiments may include add
`ing sodium nitrate to the circulating Water in an amount
`sufficient to depress the freeZing point of the circulating
`Water. In yet other embodiments, the method includes add
`ing potassium formate to the circulating Water in an amount
`sufficient to depress the freeZing point of the circulating
`Water.
`In certain embodiments, the method includes determining
`a set point and reducing the How rate of the circulating Water
`passing through the Water chiller When the temperature
`difference betWeen the circulating Water entering the cooling
`coil and the circulating Water leaving the cooling coil
`reaches the set point. Certain embodiments include deter
`mining a leaving chilled Water temperature set point and
`increasing the setpoint at reduced off-design ambient tem
`peratures to maintain the desired air temperature off the coil
`until the temperature difference betWeen the circulating
`Water entering the cooling coil and the circulating Water
`leaving the cooling coil reaches a minimum set point and
`reducing the How rate of the circulating Water passing
`through the Water chiller and reducing the leaving chilled
`Water temperature setpoint to maintain the desired air tem
`perature off the coil.
`Certain embodiments include passing the circulating
`Water through a pump prior to passing the circulating Water
`through the Water chiller. In yet other embodiments, the
`method includes passing the circulating Water through a
`pump prior to passing the circulating Water through the
`Water chiller, reducing the circulating Water ?oWrate, and
`decreasing the temperature of the circulating Water to main
`tain the desired leaving air temperature. Certain embodi
`ments include passing the circulating Water through one or
`more pumps and reducing the How rate of the circulating
`Water by shutting off at least one of the