introduction
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`has a very high
`terated by also
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`elopment of an
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`
`riahren," Austrian
`'onference, Vienna,
`Power Conl'erencc.
`
`es." Panel Discus
`lice, Vienna £010.
`
`“tilt: GasT‘nggm
`M: C‘;:‘l‘:’mam'l..
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`ants From Stored
`In ference. Vienna.
`
`|
`
`I. S. Undryas
`Project Manager.
`
`D. A. Wilson
`Project Engineer.
`
`M. Kawamoto
`Engineer.
`
`Fluor Daniel Power,
`twine, CA 92730
`
`G. L. Hauh
`Proiect Engineer.
`Kern River Cogeneration Company,
`Bakerstield. CA 93380
`
`Options in Gas Turbine Power
`Augmentation Using Inlet Air
`Chilling
`Gas turbine power augmentation in a cogeneration plant using inlet air chilling is
`investigated. Options include absorption chillers, mechanical (electric driven) chill-
`ers, thermal energy storage. Motive energy for the chillers is steam from the gas
`lurbineexhaust or electrical energyfor mechanical chillers. Chilled water distribution
`in the inlet air system is described. The overall economics of firepower augmentation
`benefits is investigated.
`
`—
`Recent rapid growth in summer electricity demand experi‘
`enced by most of the US. utilities results in the need to build
`power plants that generate maximum output at summer am-
`bient temperature ratings. Due to their short installation time
`and low installation cost, gas turbines are often used to meet
`this peak demand, One disadvantage, however, penalizes the
`gas turbine peaking plant rating, namely the inversely pro-
`portional effect of the ambient temperature on the gas turbine
`output, which is depicted in Fig. 1. The gas turbines typically
`produce 30 percent higher output at 20°F than at 95°F. Thus
`the cost of installing a gas turbine or combined cycle plant
`rated at 95"F is 20—30 percent higher than that rated at 20°F.
`This inherent disadvantage of reduced gas turbine output at
`high ambient temperatures can be mitigated by the reduction
`of the GT compressor inlet air temperature, which w0uld result
`in increase of GT output at a given ambient temperature.
`The traditional way to decrease the compressor inlet air
`[Emperature is the Incorporation of an Inlet arr evaporattve
`cooler. whtch can reduce the inlet air dry bulb ambtent tem-
`Perature by up to 90 percent of the dry bulb—wet bulb tem-
`Dcrature difference. To achieve additional inlet air temperature
`reduction, alternative methods of inlet air cooling must be
`“594, referred here as inlet air chilling.
`.
`.
`ObjecIlVeS
`' Develop a GT power augmentation concept based on
`reducing the GT inlet air temperature below the ambient air
`dew point.
`‘ The power augmentation may be available anytime when
`—__
`Contributed by the International Gas Turbine Institute and presented a! the
`35th International Gas Turbine and Aeroengine Congress and Exposition, Brus
`“15. Belgium, June 11-14, 1990. Manuscript received by the International Gas
`Turbine institute January 16,1990 Paper No. 90-GT250.
`
`the chilled air temperature is below the ambient temperature,
`but especially during summer on-peak hours.
`I GT exhaust heat should be used to generate cooling of
`the cooling media (chilled water), via absorption chilling; how-
`ever, other means (electrically driven chillers) may be used for
`peaking.
`
`'
`
`Application of Inlet Air Chilling
`The GT inlet air chilling, i.e., air cooling below the ambient
`wet bulb temperature, can increase the GT capacity needed
`during peak hours and improve the GT heat rate. Selection of
`the temperature of the chilled air is important. The temperature
`at the compressor inlet must be above 32'F to prevent ice
`buildup on the compressor blades, since the chilled inlet air
`shall be at 100 percent relative humidity due to moisture con-
`densation during the air chilling process. Due to a major in-
`crease in air velocity in the compressor inlet the static
`
`120.
`
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`DESIGN HEAT RATE
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`20.
`
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`100.
`80.
`60.
`40.
`COMPRESSOR INLET TEMPERATURE DEG. F
`FRAME 7E GT OUTPUT VERSUS COMPRESSOR INLET TEMPERATURE
`Fig. 1
`
`140.
`
`’f the ASME
`
`J°umal ot Engineering tor Gas Turbines and Power
`
`APRIL 1991, Vol. 113 l 203
`
`Page 1 of 9
`
`GE Exhibit 1008
`
`

`

`
`
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`Fig. 2 GT Inlet alr cooling process
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`temperature of air may drop as much as lO‘F. To safeguard
`against this drop the chilled air temperature should be a min—
`imum of 45°F, which includes a 3'F margin.
`Figure 1 shows that the output can be increased by 0.36
`percent with each 1°F inlet air temperature reduction. If the
`chilled air temperature is selected at 52‘F, then the temperature
`drop from 95°F is 43°F or 15.5 percent power boost. If the
`GT unit is or could be equipped with an evaporative cooler,
`which could reduce the ambient (95°F, 20 percent RH.) to
`72"F (85 percent RH.) the benefit of air chilling is only (72 — 52)
`or 20'F or 7.2 percent power boost. The cost of the inlet air
`chilling equipment must be amortized by the economic benefits
`from additional power sales during peak or during operation
`when ambient temperature is above the chilled air temperature.
`
`Inlet Air Heat Exchange
`The ambient conditions (temperature and relative humidity)
`are important factors. The typical summer average on-peak
`ambient temperature in the US. is 95°F dry bulb. In eastern
`and midwest locations the relative humidity (R.H.) may be at
`90 percent level (wet bulb temperature is ~ 90°F) and the air
`enthalpy is ~59 Btu/lb dry air. In the western United States
`(dry climate), the same 95°F dry bulb temperature shall be
`associated with 20 percent R.H. (66°F wet bulb) and enthalpy
`of 34.7 Btu/lb dry air. If the compressor inlet temperature is
`to be lowered to 52°F dry bulb, 95 percent R.H., the enthalpy
`is 20.9 Btu/lb dry air. The required heat removal at high
`humidity location shall be (59u20.9) = 38.] Btu/lb and in
`the dry climate it will be (34.7—20.9) = 13.8 Btu/lb. Thus,
`the duty of the inlet cooling system in humid climates is much
`higher than in the dry climates. In either case, moisture sep-
`aration apparatus should prevent carryover. The cooling pro-
`cess is shown in Fig. 2.
`The temperature at the compressor inlet must be above 32°F
`to prevent ice buildup on the compressor blades, since the
`chilled inlet air shall be at 100 percent relative humidity due
`to moisture condensation during the air chilling process. Due
`to a major increase in air velocity in the compressor inlet. the
`static temperature of air may drop as much as 10°F, which
`includes temperature drop in the compressor bellmouth (At =
`4° F) and in the (open) inlet guide vanes (variable or stationary)
`(AT = ~4°F). Closed variable inlet guide vanes would result
`in additional pressure drop (~5°F) but this would not apply
`while inlet air chilling is used. To safeguard against this drop
`the chilled air temperature should be a minimum of 45‘F.
`Increased wetness in the compressor inlet may induce corro-
`sion, which may require more frequent inspections of com-
`pressor inlet.
`
`Fig. 3 Generator capability
`
`GT Inlet Air Cooling Concepts
`Several concepts may be offered. The GT operates either in
`the simple cycle or in the cogeneration or combined cycle.
`Simple cycle GT shall be able to use all exhaust heat for chilled
`water generation. For a GT in cogeneration or in combined
`cycle service, we may need to evaluate the tradeoff of using
`the exhaust heat for power augmentation in the GT inlet versus
`the economic benefits of exhaust heat sales.
`
`.
`Generator Capability
`The generator rating has to be verified. [f the generator is
`cooled by cooling water it can be provided from two sources:
`cooling tower/river, and dry coolers (fin fan type).
`Since the generator capability is indirectly proportional to
`the cooling water temperature, it is possible in the case of dry
`cooling that the GT output may be increased via inlet air
`chilling while the generator capability would not increase. This
`could result in GT exceeding the generator capability with
`potential overtemperature on the generator winding. The gen-
`erator rating must be carefully checked. The same applies for
`air-cooled generators. Examples of the GT and generator ca-
`pability are shown in Fig. 3.
`
`Systems Options
`The complete inlet air cooling system consists of several
`systems, such as:
`' Water chilling system
`0 Absorption chiller thermal source
`0 Chilled water system
`0 Cooling system
`The following options exist for each system;
`Chilling System
`C Absorption chiller utilizing:
`(a) Lithium bromide absorbent.
`(b) Ammonia absorbent.
`0 Mechanical chilling utilizing compression with freon re-
`frigerant.
`Steam jet refrigeration.
`' Hybrid chilling system utilizing both absorption and me-
`chanical chilling systems.
`0 TBS (Thermal Energy Storage)
`
`204 I Vol. 113l APFllL 1991
`
`Transactions of the ASME
`
`Journal
`
`Absorpl
`provide or:
`on using:
`0
`LOW
`in a
`o Tie-i
`plict
`exch
`- Gen
`amn
`0 Dire
`absc
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`Chilled
`ing schem
`turbine in
`-
`Inst:
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`botl'
`Inst:
`prin
`Inst:
`prin
`
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`
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`SOLUTII
`
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`SOLUTION
`
`Flg. 4
`
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`«mg m
`
`mom.“ i;
`"I I: bur-M
`
`Page 2 of 9
`
`GE Exhibit 1008
`
`

`

`Absorption Chiller Thermal Source. A thermal source to
`provide operating force to absorption chillers was studied based
`on using:
`
`Low-pressure steam generated in a new HRSG installed
`in a simple cycle GT exhaust.
`Tie-in to existing steam export line in cogeneration ap-
`plications to generate steam through a low-pressure heat
`exchanger (i.e., reboiler).
`Generation of hot water from the above methods for the
`ammonia absorption chiller.
`Direct integration of HRSG preheat coil with ammonia
`absorption chillcr to provide desorption heat in simple
`cycle GTs.
`
`Chilled Water Distribution System. Review of the foIIOW-
`ing schemes to provide chilled water to/from the chilled gas
`turbine inlet air:
`
`.
`
`Installation of PVC media similar to the evaporative
`cooler media downstream of the inlet air filter, using
`both the evaporative and direct contact principle.
`Installation of chilled water coils using the convection
`principle (indirect cooling).
`Installation of freon-cooled coils using the convection
`principle.
`
`
`
`ABSORBER
`
`
`
`40F
`AIR CONDITIONING
`LOAD
`55F
`
`REFRIGERAN‘I’
`
`
`SOLUTION PUMP5
`REFRIGERANT PUMP
`Flg. 4 Absorption chiller schematics (courtesy of Trans Corp.)
`
`0
`
`Indirect evaporative cooling for distribution of chilled
`water within the inlet air filter.
`
`Cooling System. Study of the following cooling water sys-
`tems:
`
`0 Mechanical draft cooling tower.
`- Closed-loop water to air cooled system (tin fan).
`
`Description of Considered System
`The system evaluation is based on retrofitting four General
`Electric Frame 7E GTGs with inlet air chilling system.
`Existing System: 4x Frame 7E GTGs
`
`65.000 kW
`12.200 Btu/kWh-LHV
`70 GPM
`Natural gas
`14.31 psia
`95°F
`70.8“F
`30 percent
`34.7 Btu/lb d.a.
`700 ft.
`2,074,982 Ib/h each
`
`5 in. WC
`
`0 Power output
`0 Heat rate
`' NO; control—water injection
`O Fuel
`0 Barometric air pressure
`0 Ambient dry bulb temperature
`0 Ambient wet bulb temperature
`. Relative humidity
`'
`Inlet air enthalpy
`'
`Site elevation (ASL)
`I
`'
`Inlet air flow rate
`Inlet system pressure drop (filter.
`evaporative cooler, silencer)
`' Openings available:
`Inlet duct, I opening (Wx H) 25’ x 25'
`Filter house, 6 openings 25 ’ X 5'
`80 percent
`0 Evaporative cooler efficiency
`72°F
`Temperature after evaporative cooler
`80 percent
`Humidity
`Heat Recovery: 80 percent steam quality HRSG for EOR
`Inlet temperature
`970°F
`Stack temperature
`260°F
`Feedwater temperature
`150°F
`Steam output @ 800 psig, 80 percent quality
`418,000 1b/h each
`10 in. WC
`
`Gas side pressure dr0p
`Retrofit With Inlet Air Chilling:
`' Retrofitted inlet air temperature (dry bulb)
`Retrofitted inlet air humidity
`Inlet air enthalpy
`Air chilling duty
`or
`
`52°F
`95 percent
`21 Btu/lb d.a.
`28 mm Btu/H each
`2333 tons each
`
`emurn vuu salts
`
`AIR
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`:rates either in
`.
`.mbined cycle.
`1eat for chilled -.
`.r in combined
`.deoff of using
`GT inlet versus
`
`the generator is
`om two sources:
`
`rigportional to
`n the case of dry
`sed via inlet at!
`not increase. Thisl
`r capability With-
`vinding. The gen-i
`: same applies for
`and generator ca-I
`
`:onsists of several.
`
`(
`:ssion wrth freon w
`
`1 absorption and ff.
`
`In: Min I———
`'- lsm ill-01
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`"‘ K KIEIHIKIIH
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`nmncw
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`commit M
`
`Fig. 5 Absorption chllllng diagram
`
`-tlons 0' the Asulhumal 0! Engineering lor Gas Turbines and Power
`
`APRIL 1991, Vol. 113 I 205
`
`Page 3 of 9
`
`GE Exhibit 1008
`
`

`

`nun Mm um:
`
`nouns:- In"a ll
`
`mm non um
`
`
`
`—-. «“an
`- urinal“! rm-
`
`— twin ISIWI‘II
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`
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`
`Fig. 6 Mechanlcal chlller schematics (courtesy Carrier Air Condltlonlng
`Co.)
`
`and York. Cost may be estimated at $250 per ton of refrig-
`eration.
`
`Two Stage (LiBr).
`The two-stage lithium bromide absorp—
`tion chiller system will operate with saturated steam pressures
`of approximately 114 to 128 psig allowing the unit to consume
`less steam than a single-stage chiller at l5 psig. The two-stage
`steam consumption is estimated at 9.9 lb per ton versus 19 lb
`per ton for the single stage; thus. less steam will be consumed
`during chiller operation, resulting in a net savings of thermal
`energy over the single-stage chillers.
`The cost estimate for the two-stage chillers is $330 per ton,
`which is approximately 30 percent more than the single stage I
`and twice the cost of a centrifugal chiller. The chiller size is
`limited to 1500 tons for the larger chillers. Manufacturers of
`the two-stage absorption chillers are Hitachi Paraflow, Sanyo-
`Bohn, and The Trane Company.
`‘
`
`Water Chilling via Absorption Chillers (Fig. 5)
`Absorption Chilling System. Absorption chilling systems
`operate with a low-grade thermal source to provide chilled
`water at 44°F. The system contains refrigerant and absorbent
`that cycles at low internal pressures. This pressure in the evap-
`orator section will allow evaporation of the refrigerant liquid
`at a low temperature providing the chilling effect for the in-
`coming chilled water. At slightly higher pressures, the refrig-
`erant vapor and absorbent liquid are combined in the absorber
`section by their strong affinity for combining. As the vapor
`is condensed, heat is released into the condenser water coils
`(cooling water). The resulting solution will be a “strong" ab-
`sorbing solution of refrigerant and absorbent. This solution
`is pumped into the absorbing section where the refrigerant is
`evaporated from the absorbent by a thermal source, either
`low-pressure steam or hot exhaust gases. In the condenser, the
`refrigerant vapor is condensed to liquid by cooling water, and
`the refrigerant liquid is pumped back into the evaporator. The
`“weak” absorbing solution is recirculated into the absorbing
`section. An example is shown in Fig. 4.
`Ammonia and lithium bromide (LiBr) are two types of ab-
`sorption chiller that are available for this chilling service.
`Lithium Bromide Absorption Chilling Systems. The lith-
`ium bromide absorption chilling system can be designed as a
`single or two-stage chiller. These chillers utilize a design with
`a lithium bromide water absorption refrigeration cycle. The
`chilling systems typically provide chilled water at 44°F with
`return water at 54‘F. Consideration was made to lower the
`chilled water temperature to 42°F; however, this would have
`reduced the chiller’s cooling capacity and efficiency. Chilled
`water temperatures less than 42°F are not considered practical
`for absorption units. This is due to the water-based refrigerant
`used in the chiller, which, when operating between 34°F and
`36°F, provides 42°F chilled water and may potentally freeze
`the chilling unit.
`Typical flow calculations for each of the absorption chiller
`units are based on the following:
`0 Leaving chilled water temperature = entering temper-
`ature — temperature drop
`0 Leaving condenser water temperature = entering tem-
`perature + temperature rise
`
`Cooling load (tons) x 24
`temperature drop
`0 Chilled water flow (gpm) =
`- Steam Flow (lb/hr)
`Cooling load (tons)x9.9 (two
`stage)
`Cooling load (tons)>< 19 (single
`stage)
`
`Ammonia Absorption Chilling System. The ammonia ab-
`sorption system is an engineered refrigeration system specif-
`cally designed for the tons of cooling required. The ammonia
`system can produce lower chilled water temperature than Iith—
`ium bromide systems, from +50°F through —50°F chilled
`medium temperatures. Low-pressure steam (175 to 265 psig)
`or turbine exhaust gases can be used as the thermal source for
`the ammonia absorption cycle. However, the ammonia system
`requires higher capital costs, approximately 3650/ton of cool-
`ing. Also, larger plot space is required, approximately 30 ‘ X 30'
`for a 1,000 ton chiller installation. The ammonia system field
`installation requires significant structural steel to support the
`various ammonia storage tanks, heat exchangers, and other
`Cooling load (tons)><44 vessels. Manufacturers of the Ammonia Absorption Chillers
`are: Lewis Refrigeration Co., Houston, Texas, and Borsig
`temperature drop
`GmbH.
`
`- Condenser water flow (gpm) =
`
`Single Stage (LiBr). The chiller design utilizes a single shell
`hermetic construction that will enhance the integrity of the
`unit. These chillers operate on low-pressure saturated steam
`at 15 psig, consuming approximately 19 [b/hr per ton of chill-
`ing. Hot water at 270T can also be used as the thermal energy
`source. The single-shell design helps prevent air leakage, which
`can cut the capacity and promote corrosion. A pro-packaged
`system can be delivered completely assembled with available
`size range from 101 to 1,660 tons. The single-stage system will
`operate at a vacuum and may be susceptible to air leakage,
`which could cause some damage. However, if the proper op—
`erating and maintenance procedures are followed, i.e. , periodic
`purging of the system and operation above 42°F, there should
`be no problems during normal operation. A total loss of power
`would cause the solution of the absorption chiller to solidify
`into a solid mass within one hour. Manufacturers that currently
`produce the single-stage absorption chillers are Trane, Carrier.
`
`Water Chilling Via Mechanical Chillers (Fig. 7)
`The Mechanical Chiller is a vapor compression cycle with a
`compressor, liquid cooler (evaporator), condenser, and com-
`pressor drive. Water at 54°F returning from the inlet cooling
`coils enters the chiller (evaporator) where it is cooled to 44°F
`by the refrigerant liquid evaporating at a lower temperature-
`The refrigerant gas produced is compressed to a higher pressure
`and temperature so that it may be condensed by the cooling
`water in the condenser. The condensed refrigerant is returned
`to the evaporator through an expansion/metering valve.
`Mechanical chillers may be provided with different types of
`compressors: reciprocating, screw, or centrifugal. Recipro-
`cating and screw type compressors are generally used for sizes
`less than 1000 tons. Centrifugal liquid chillers are used for
`sizes greater than 1000 tons, with factory-assembled units 1113
`
`to 1600 tons
`tons.
`Chillers fr
`shelf units th
`to 3000 tons
`chillers. The
`compressor :
`unit. Three
`Manufacture
`of providing
`chiller will c
`system.
`Typical fl
`are based or
`
`0 Leavin
`ature
`' Leavir
`peratu
`
`' Chiller
`
`' Conde
`
`The temp
`This value <
`chiller unit.
`ing water fr
`of the chilIt
`The selec
`on the cost
`Based on n
`Chillers wer
`
`1000—1
`1500—5
`Over 5
`
`The smal
`Chase based
`and require
`Chillers. Th
`required a
`Chiller wou
`
`206 I Vol. 113, APRIL 1991
`
`Transactions of the ASME
`
`Journal 0
`
`Page 4 of 9
`
`GE Exhibit 1008
`
`

`

`It Condltionlng
`
`on of refrig.
`
`nide absorp.
`am pressures
`t to consume
`'he two-stage
`
`be consumed
`
`Flg. 7 Mechanical chllltng dlagram
`
`mine rn-r-
`
`to 1600 tons, and field-assembled machines to about 10,000
`tons.
`Chillers from 100 tons to 1500 tons are packaged off-the‘
`shelf units that are hermetically sealed. Chillers from 1500 tons
`to 3000 tons are generally the open-drive centrifugal water
`chillers. These units are not hermetically sealed because the
`compressor and motor drive are mounted outside the chiller
`unit. Three thousand tons and larger are customized units.
`Manufacturers such as Carrier, Trane, and York are capable
`of providing chillers in the 1000 ton to 3000 ton size. Each
`chiller will operate in ‘parallel, to increase availability of the
`system.
`Typical flow calculations for each centrifugal chiller unit
`are based on the following:
`
`0 Leaving chilled water temperature = entering temper-
`ature
`temperature drop
`' Leaving condenser water temperature = entering tem-
`perature + temperature rise
`
`' Chilled water flew (gpm)=
`
`° Condenser water flow (gpm)=
`
`Cooling load (tons) x 24
`temperature drop
`Cooling load (tons) x 29
`temperature drop
`
`The temperature rise and drop is generally limited to 10°F.
`This value can be increased at the expense of derating of the
`chiller unit. For example, the increase temperature of the cool-
`ing water from 10°F to 15'F will derate the chilling capacity
`01' the chiller by approximately 5 percent.
`The selection of the 1500 ton centrifugal chiller was based
`on the cost per ton, delivery, and electrical load requirements.
`Based on manufacturer's information, the costs per ton for
`chillers were:
`
`1000—1500 ton chillers
`1500-5000 ton chillers
`Over 5000 ton chillers
`
`$133/ton
`$320/ton
`$145/ton
`
`The smaller centrifugals would be the most economical pur-
`chase based on capital cost; however, the cost of the installation
`and required area would be much greater than for the large
`Chillers. The larger tonnage chillers were either too costly or
`required a large motor driver far their operation. A 5000 ton
`Chiller would require a motor size of approximately 4300 hp.
`
`This type of motor would be custom built and associated with
`long delivery. In addition,
`these units would require high-
`voltage electrical devices.
`The mechanical chillers need only electricity and condenser
`water to provide all chilled water requirements; there is no
`need to provide steam or another thermal energy source. Also,
`the mechanical chillers provide more tons of cooling in one
`machine than in other types of chillers. This will result in lower
`installation costs and less plot space required.
`However, the consumption of electricity will reduce the po-
`tential output of the plant, reducing the electrical energy gen-
`erated. Although chlorinated fluorocarbons (CFC) have been
`in use for years as part of refrigerants used in direct expansion
`refrigeration such as centrifugal chillers, these CFCs may po-
`tentially be banned from use because of their damaging effect
`on the ozone layer in the atmosphere, The mechanical chillers
`will require high-voltage electrical devices to support the chiller
`motors, MCCs, relays, motor starters, etc. This additional cost
`will increase the overall price of the chillers. Manufacturers
`of the Mechanical Chillers are: Carrier Corp., The Trane Com-
`pany, and York, Division of Borg-Warner.
`
`Thermal Energy Storage Systems
`The GT can take advantage of on—peak and midpeak energy
`costs by using mechanical chillers and the Thermal Energy
`Storage Systems or TES. The TES system is based on a storage
`medium with high specific or latent heat, ice, water, or eutectic
`salts. This storage will contain the cooling produced during
`the low-cost off-peak hours for utilization during the high-
`cost on-peak hours.
`
`Chilled Water Storage. The design basis requires chilled
`water to be provided during the peak months of the year, from
`March to November, during the peak hours, averaging 10 hours
`per day. During the off-hours, the operator can take advantage
`of the lower electrical rates by operating the mechanical chill-
`ers, producing 44°F chilled water for the TES system. The size
`of the storage capacity will depend on an economic evaluation
`of the chilling profile. A full-size TES tank would provide all
`of the cooling load during the midpeak and peak hours. A
`partial, load-leveling TES tank will reduce the Overall size of
`the peak cooling load profile and levelize the production of
`chilled water over the 10 hour period. Estimated size of the
`TES tank will be:
`
`Journal of Engineerlng lor Gas Turbines and Power
`
`APRIL 1991, Vol. 113 I 207
`
`Page 5 of 9
`
`GE Exhibit 1008
`
`

`

`
`
`The i1
`tempera
`to 52‘F
`both sen
`water at
`midity il
`existing
`air syste
`corrosio
`structior
`cooling
`Please
`accompl
`Wetted 11
`energy a
`atures. '1
`from set
`medium
`The w
`must pa,
`full com
`Utilized :
`
`Chiller
`ceIJtual a
`44°F Chi
`
`cmu mu can:
`
`All?
`
`rll. it?
`
`5;;
`.......
`,____________|
`
`
`
`
`nun
`
`
`
`-
`m...
`113%?
`
`
`
`tum-unmet
`awn-m can."
`
`
`
`_________—. .1.“ m, m“,
`
`_-...] no- m- IP05
`
`”nits! sit»-
`sum-u:
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`wet-c mm
`.. n... ,‘fl
`
`mull “It.“ in ___.__. ———
`Inluutih nrr- np"
`
`_ » ——.-—<__—
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`stmum
`mac-mu M
`
`_“
`
`emu: In.
`
`mm r»-
`
`Fig. 8 Hybrid chilling diagram
`
`
`
`Fig. 9 Chilled water coils (courtesy ol Coll Co. Inc.)
`
`5
`i
`i
`
`| iF
`
`inlet air coils to cool the air from 95°F to 52°F or to 46‘F.
`Application of the hybrid system results in lower chilled water
`temperatures in the chilled water system associated with less
`piping and pumping costs. Also, the cooling coils will be mote
`effective, decreasing the overall size requirements.
`
`F.
`
`Chilled Water Distribution System
`The chilled water distribution system will circulate 44":
`chilled water from the chilled water plant and into each GTG
`inlet filter house and return with 54°F water. The inlet cooling "_
`system will distribute the chilled water through an indirect Of
`"
`a direct contact heat exchanger that should be installed across
`the inlet air flow cross section.
`The installation of the inlet cooling system will result in ii
`Permanent increased pressure loss to the inlet of the GTG‘
`"
`General Electric's performance curves have indicated thaté
`4" water column pressure drop will result in a 1.45 perm“i
`decrease in power output, 0.45 percent increase in heat rate.
`and an increase in exhaust gas temperature of TR We antiC'
`ipate that the inlet pressure loss should not exceed 2“ watel
`column.
`
`3
`-
`i
`
`1'
`
`Transactions of the ASME .
`
`_
`
`Tank Capacity (gal.)
`(be)
`Chiller size (tons)
`Stored cooling (ton/hr)
`Notes:
`
`Full
`Partial
`
`size (1)
`size (2)
`15,120,000
`8,820,000
`360,000
`210,000
`7,500
`4,375
`105,000
`61,250
`
`1 These values assume that the mechanical chillers will not
`operate during midpeak and on-peak.
`2 These values assume mechanical chiller operation 24 hr/
`day at an average load.
`
`The size of the tank that will be required for the TES system
`may result in space constraints and large costs.
`
`Ice Storage. The ice storage system can also be used in a
`scenario similar to the chilled water storage system. The volume
`of ice required will be from 7 to 14 times less than the water
`system (based on 144 Btu/lb ice latent heat of fusion versus
`10 to 20 Btu/lb water heat capacity). However, the equipment
`to provide the 85,000 ft3 to 168,000 ft3 of ice will require large
`real estate.
`
`Hybrid System (Mechanical/Absorption) (Fig. 8)
`The hybrid system is a combination of the lithium-bromide
`(LiBr) and the mechanical centrifugal chiller systems. The LiBr
`system will chill the return water from S4“F to 44°F and the
`mechanical chiller will further reduce the temperature to 38 “F.
`This will be a series type system: two 50 percent capacity trains
`of absorption and mechanical chillers (reference drawing Fig.
`8).
`This system will initially take advantage of the steam avail~
`able at the facility and will enable the mechanical chillers to
`consume less power during the production of colder chilled
`water. The system is sized for one-half of the cooling by ab-
`sorption and the other by centrifugal chilling, which will con-
`sume approximately one-half of the total required power than
`the mechanical chiller system. The 38°F chilled water supply
`will increase the temperature differential of the cooling coil
`inlet and outlet (38"F to 54"F). The larger differential tem-
`perature will reduce the overall chilled water flow rate, reducing
`pumping costs as well as piping requirements.
`The lower chilled water temperature can be used in the GTG
`
`208 I Vol. 113, APRIL 1991
`
`Page 6 of 9
`
`GE Exhibit 1008
`
`

`

`ysis utilizing PVC cooling tower media in direct contact with
`44‘F chilled water for gas turbine inlet cooling was performed.
`The medium is cooling tower packing placed in the straight
`crossflow position and sprayed with chilled water to create a
`direct contact chilled water evaporative cooler with an ap-
`proximately 90 percent relative humidity saturation capacity,
`shown in Fig. 10.
`A computer multiple alternative analysis examined three
`flow rate conditions consisting of 8, 12, and 16 gallons per
`square foot of face area and comparing two face veloeities of
`500 and 750 feet per minute, respectively.
`To obtain the 52"F inlet temperature requirement necessi—
`tates a face velocity of 500 feet per minute and 12 gallons per
`square foot, i.e., 12,000 gallons per minute and 1000 square
`feet of surface area or 750 feet per minute and 16 gallons per
`square foot, i.e., 650 square feet of surface area and 10,000
`gallons per minute, respectively.
`The advantage of direct contact cooling is lower first cost
`and relatively low pressure drop. The disadvantage is the need
`for extensive water treatment associated with continuous blow-
`down, Potential for biological buildup exists, resulting in higher
`maintenance than a closed system. Also, large circulation water
`quantities are required, depending on performance, from 8 to
`16 gallons per square foot.
`
`Indirect Evaporative Cooling. The indirect evaporative
`cooling method lowers the dry bulb temperature without the
`increased moisture content of the GTG inlet supply air, ef-
`fectively reducing the wet bulb temperature of the air and the
`Overall energy content.
`The indirect method is accomplished by using a plate-type
`air-to-air heat exchanger, shown schematically in Fig. 11:
`c On one side, outside air is directed to one end of the
`exchanger as scavenger air. Water is sprayed onto the plate
`surface in contact with this air stream where evaporation takes
`place, cooling the plate approaching the wet bulb temperature.
`The water is collected in a sump and is recirculated back into
`the exchanger. The air is then exhausted above the unit into
`the atmosphere by an axial fan unit.
`' 0n the other side, the GTG inlet air supply passed across
`the plate and is cooled by convection to near the wet bulb
`temperature and passes into the gas turbine.
`
`This type of cooling is effective when there is adequate water
`available. The dry bulb air temperature can be reduced without
`increasing the latent heat at minimal cost of water and elec~
`tricity.
`For example, if the outside ambient air temperature is 95°F
`dry bulb and 71 aF wet bulb, the indirect evaporative method
`of cooling will reduce the GTG inlet dry bulb air temperature
`to approximately 74‘F, effectively reducing the total cooling
`load by 40 percent. This would translate into approximately
`4000 tons of cooling.
`Although the indirect cooling system will reduce the inlet
`air temperature to 75 °F, cooling coils will be required to reduce
`the air temperature further to 52°F. The pressure drop through
`the indirect cooler is estimated to be from 3” to 4” of water,
`which would reduce the gas turbine power output by approx-
`imately 1.45 percent. In addition, the cooling coils will add
`another 1" to 1.5” of water pressure drop.
`Due to the overall size of the cooling unit, there may be
`some problems of system installation. There is limited space
`available within the filter house for an installation of this type
`and significant GTG downtime.
`The saturated air exhaust from the indirect cooler is located
`at the filter house, which would defeat the purpose of this
`system; the air will potentially recirculate back into the inlet,
`adding the latent heat that was absorbed. Ducting