# Instructions for Retrofit Cost Analyses

November 2008

EPRI, in collaboration w ith a num be r of partic ip ating u t ilitie s, is assem b ling inf o rm ation

to develop an estim ate o f the costs to the indu stry associated with widespread retro f it of

power plant cooling system s from once-throug h cooling to closed-cycle cooling. The

aim of this ef f

o rt is to obtain inf o r m ation from as m a ny plants as po ssible, cu rrently

equipped with once-through cooling, and from this sam p le to extrapolate to a national

estim ate of closed-cy c le cooling retrofit costs.

To expedite the collection of inform ation from the plants, a sim p lified m e thodology has

been develo ped which is to b e prov id ed to each plant in th e fo rm of an ExCel spreads h eet

for organizing the requ ired information an d m a king basic calculations necess a ry to

estim ate the capital and o p erating cos t s associated with a cooling system retrofit. A set of

instru ctions accom p anies the spreads h eet.

A few general comm ents intended to clar ify the approach and request follow:

Approach:

1. The cost estim ates which results from this m e t hodology are in no sense a

substitute for site-specific engineering budget estim a tes.

2. The capital cost es tim ates ar e developed in two steps:

• Step 1: Three separate cost num b er are calcu lated for each unit bas e d

solely on the circulating cooling water flow rate of the existing oncethrough cooling system. These thr ee costs are cons idered to be

representative of an “Ea s y” (lowest cost), “Averag e” (in t erm e diate cost) or

“Difficult” (highest cost) retrofit. Th e costs per gpm of circulating cooling

water flow rate for each catego r y were dete r m ined in a survey of more

detailed retrofit cost estim a tes fr om 50 plants. The m e thodology and

results of this survey are desc ribed in detail in Reference 1.

• Step 2: A wide range of site, pl ant and neighborhood ch aracteristics are

identified an d exam ined for the purp o se of m a king a qualitative judgm ent

as to where in the rang e of “Easy” to “Dif f i cult” the par ticu l a r unit would

be expected to fall.

3. In addition to the project cap ital cost of the re tro f it, there are other costs to be

considered. These inclu d e

i. Higher cooling system operating costs

ii. Higher m a intenance costs

iii. Plant perform a nce penalty costs.

These estim ates of these cos t s are es tim ated in the sp readsheet b a sed on

general guidance or rules-of-thum b for c ooling tower size, typical perf orm a nce

and power requirem e nts as well as local m e teorological conditions and expected

power plant operating profiles.

1

# 4. Capital and operating costs are aggreg ated on a common basis by am ortizing

the cap ita l costs f o r m i d-range e c o n om ic assu mptions and rem a ining plant

lif e.

Request for information:

Using the attached instru ctions and sp readsheet, please provide the following

inform ation.

• Fill ou t W o rksheet 1, 2 a nd 3 com p letely

• Review W o rksheets..... to ensure th at all the relevant “autom a tic”

calculations have filled in and to determ ine whether the def a ult

values given on the worksheets seem appropriate for your plant.

Adjust the default values as seem s appropriate.

• Review all the qualitativ e inf o rm ation requests in W o rksheets and

add descriptive comm ents and identifiers as appropriate.

• Provide all drawings, m a ps, regulatory inform a tion as requested in

the Ins t ructions for each W o rksheet.

• Provide in tabular form

o Plant operating profiles (Worksheet 13)

o Source water tem p erature (W orksheet 11)

o Am bient tem p erature and wet bulb data

(W orksheet 11)

in as m u ch detail as possible.

The Spread sheet works h eets are set up for a m a xi m u m of 10 units per plant which

should be adequate for nearly all cases. If a plant has m o re than 10 units, two separate

spreadsheets can be used.

Please return the filled out worksheets and the requested supporting docum ent s by

January 1, 2008. The spreadsheet should be sent to:

Dave Bailey – dbailey@ epri.com and John Maulbetsch (Independent EP RI Contractor)

m a ulbets@sbcglobal.net

The following m a terial consists of explanatory m a terial for, and instruc t ions for the use

of the accompanying ExCel spread sheets to determ ine th e costs of closed-cycle wet

cooling system retrofits.

Com p rehensive re trof it c o st estim a tes m u st include:

• Initial capita l cost of the retrof it itself

• Additional operating power costs

• Additional O&M costs

• Plant perform a nce penalty costs

• Assorted ad dition a l m i scellaneous c o sts

2

# The accom p anying ExCel file {Retrofit_Cost_Analyses.x l s} contain s 14 worksheets for

com p iling and organizing the required inform ation and for executing m a ny of the

required calculations for de veloping a cost es tim ate.

Descriptions of the individua l worksheets and instruc tion s f o r f illing them out are

provided below.

Worksheet 1 : Plant Information

Worksheet 1 asks for general location and co ntact inform ation fo r the plan t a nd is

essentially self-explanatory.

• The contact person should be som e one capable of answering (or of identifying

other staff capable of answering) a broa d range of questions about turbine and

cooling system design and operation, pl ant site layout and constraints and

pertinent en vironm ental constra i nts a t the s ite.

• The plant inlet water f

l ow should reflect the m a xi m u m water intake to the

plant for all purposes. It m u st be ente red in units of “gallons per m i nute”

(gpm ). If it is norm a lly available in other units, common conversions are

• 1 m gd ( m illion gallons p e r day) = 6 9 4.4 gpm

• 1 cfs (cubic feet per second) = 448.4 gpm

Worksheet 2 : Unit Infor m ation

Worksheet 2 asks for u n it-sp ecific inform ation for each un it at th e plan t. There is the

possibility f o r conf usio n in the ca se of com b ined-cyc le plants sin c e s o m e com p anies

designate the com bustion turbine and steam tu rbine portions of com b ined-cycle plants

with different unit numbers while others a assign single unit number to the entire

com b ined-cycle unit.

For the case of si m p le c y cle com bus tion tu rbine units, only infor m ation under “All unit

types” is required. For com b ined-cycle units , the gross cap acity of the steam turbin e is

desired in a ddition to th e tota l (C T’s + steam turbine) capacity. The condenser cooling

water flow refers to the steam condens er cooling water flow only.

3

# 4 W o r k s h e e t 1 : P l a n t I n f o r m a t i o n Pl ant N a m e

Owne r ( s )

O p er at i n g C o mp a n y

Loc a t ion

S t reet

Ci t y

St a t e

Zip C ode

L a ti tu d e

Longit ude

E l e vat i o n

C onta c t pe r s on

Na me

Ti t l e

P hone

E- m a il

Pl a n t C a p a c i ty

, n e t (MW )

P l an t W a t e r I n t a ke

Flow, gpm 

# PL A N T I N F O RMA T I O N5Worksheet 2:Unit InformationUnit123456 78910UnitType(1)Forallunit typesUnitCapacity, gross(MW)FuelYearonlineCapacity factor,%20062002 -2006 AverageForsteam unitsCondensercoolingwaterFlow, gpmFor combinedcycleunitsSteam turbine capacity,gross (MW)CondensercoolingwaterFlow, gpm(1)Unittype:CT(Combustionturbine); S (Steamcycle); CC(Combined-cycle)UNITINFORMATION

# Worksheet 3 : Capital Cost Information

Worksheet 3 calculates a range of initial retrof it cap ita l co sts based on the results of a

survey of 50 plants co nducted by Maulbetsch Consultin g in 2002. The only input

required is the condenser circulating water fl ow rate for each unit. The spreadsheet will

return three costs for each unit class i fied as “Easy”, “Average” or “Dif f i cult” retrof its.

The judgm e n t as to which category best descri bes the situation at the individual plant and

unit will be based on qualitative, descrip tiv e inf o rm ati on as requested in subsequent

worksheets. These are:

• Worksheet 4 : Tower size

• Worksheet 5 : Site characteris tics

• Worksheet 6 : Drift calcu lations

• Worksheet 7: Neighborhood characteristics

• W o rksheet 8 : Alterna tive water sour ce s.

Worksheet 3: Range of retrofit costs Ret r of it P r o j e c t Co st E s t i m a te s

E n te r da ta



# Pl a n t : 0 A u t o mat i c ca l c u l at i o n

U n it N o

. C ir c u la t i ng W a te r Flow

( g p m ) E asy A ver ag e D i f f i cu l t

1 0 1 $ 0 $ 0 $ 0

2 0 2 $ 0 $ 0 $ 0

3 0 3 $ 0 $ 0 $ 0

4 0 4 $ 0 $ 0 $ 0

5 0 5 $ 0 $ 0 $ 0

6 0 6 $ 0 $ 0 $ 0

7 0 7 $ 0 $ 0 $ 0

8 0 8 $ 0 $ 0 $ 0

9 0 9 $ 0 $ 0 $ 0

10 0 10 $ 0 $0 $0

P l a n t T o ta l $ 0 $ 0 $ 0 

# C i rc ul a t i n g Wa t e r F l o w R a t e s R a n g e o f Ret r of it Cos t E s tim a t e s

De gr e e o f D i ffi c u l t y Un it No

.



# Worksheet 4 : Tow er si z e

Worksheet 4 return s the tower size as num b er of cells and the length and width of the

tower footprint as a function of circulating water flow ra te and a num ber of default

assum p tions listed on th e worksheet. These are:

Flow rate per cell: 10,000 gpm

Cell dim e nsions: 50’ x 50’

Basin dim e nsions: Extends 4’ beyond tower in all directions

These default values m a y be changed to accom m odate individual desig n preferences.

7

# The prim ary arrangem ent is in -line. The num ber of cells is rounded up to the nearest

integer.

Back-to-back tower arrangem e nts may be cons id ered if the in -lin e ar range m e nt is too

long to be sited any where on the plant propert y. The worksheet also returns dim e nsions

for back-to

- back arrang em ents. In this case, if the num ber of cells calculated for the inline tower is odd, it is incr eased by +1 to have an even num be r of cells.

Note that b a ck-to-b ack towers are bu ilt som e what ta lle r in or der to prov ide the nec e s s ary

air inle t are a which is no w lim ited to one side of the cell. This will af f

ect the addition a l

pum p ing power for a given recirculating water flow as the head rise to the hot water

distribution deck is incr eased. (See Worksheet 9 )

Worksheet 5: Site Cha r acteristic s for Judging Degree of Difficu lty

The approac h to a clo s ed -cycle re trof it used in th is analys is is the f o llowin g :

The existing once-through cooli ng system equipm ent is left in tact to the extent po ssible;

that is, the condenser, the ci rculating water pum ps and the piping connections to the

condenser inlet and exit waterboxes are kept the sam e . Hot water leaving the condenser

is diverted away from the ex isting discharge structure and is discharged into a sum p. The

sum p serves as the inlet bay for new circ ulating water pum ps which pump the hot water

through new circulating water line to the hot water distribution deck on top of the cooling

tower.

Cold water from the tower basin drains by gravity through a new circulating water line

back to the intake bay of the existing once- through cooling w a ter pum ps. Provisions must

be m a de for bringing m a ke-up water to the closed cycle system and for discharging

blowdown from the system . In some instances , these m a y be easily in tegrated into the

existing once-through cooling inta ke and discharge structures. In others, new structures

of the appropriate size and new tr ansport lines m a y be required.

A num b er of factors determ ine the degree of difficulty and h e nce the co st. W o rksheet 5

(Site chara c teris tic s) id e n tif ies the so m e of the ite m s and the inf o rm ation needed to a s sess

the difficulty and provides a place to docum ent the conclusions.

Tower location....An exam ination of the site plan determ ines if open areas of sufficient

size are available to locate the tower on th e plan t property. Ad jacen t property m a y be

purchasab le.

Existing structures m a y have to be torn down and relocated, such as storage sheds,

parking garages and parking lots, equipm ent shelters, office buildings, etc. Locations

with ta ll s t ru ctures upwind f r om the tower are no t desirable since they m a y crea te

downdrafts or slow distortions which im pair tower perform a nce.

Tow er elev ation

8

# The tower should be sited at a higher eleva tion than the existing cooling system intake

bay in order to allow gravity return of the cold water. If this is not possible, grading m a y

be required to elevate the tower basin. Abse nt this, a second set of new circulating water

pum p s to return the cold water m a y be required.

Interferences

Underground interferences in th e path of the new circulating water lines o r at the loc a tion

of the hot water sum p and new circulating wa ter pum p s m a y add greatly to the tim e a nd

cost of the installation.

Overhead in terferen ces include trans m issions lines. The m o ist plum e and drift from the

fan stacks of m echanical draft towers shoul d not impinge on transm ission lines or plant

switchgear.

Excluded areas

There m a y be areas on th e site reserv ed for security purposes, storage of h azardous

m a terials, turn-around areas for large vehicles, etc. which cannot be relocated or blocked.

This m a y be particularly tr ue for nuclear facilities.

Tie-ins to existing coo l ing system

Existing inta ke/dis charge struc t ures a r e siz e d for the full recirculating flow rate which is

much greater (10 to 50 tim e s) than the m a ke -up and blowdown flows from a closed-cycle

system of the sam e cooling capacity. They m a y need to be abandoned

and replaced with properly sized facilities. In so m e cases, they can be partially b l ock e d

to accomm odate th e low e r flows.

Details of cooling water syst em circuitry around the condenser are highly variable. The

general arrangem e nt drawings m u st be exam ined with the idea of determ ining how to

bring cold water to the pum p inlets and diverting condenser discharge to a newly

constructed intake sum p for the new circul ating water pum ps. The am ount of space

available, the arrangem e nt of existing pi ping and surrounding structural walls will all

affect the effort and cost requi red to convert this portion of the system to closed cycle.

The new circulating water pum ps must be lo cated close to th e exis ting co ndenser

discharge area and power m u st be provided. If there are insu fficient on-s ite aux i liary

power f acilities, th ey m u st be prov id ed at add itio nal tim e , cost and spac e r e quirem e nts

. A sum p m u s t be provided as an intake ba y for the new circulating water pum p s. The

sum p must be large enough to provide ade quate storage tim e for the circulating water

flow (typically several hundred thousand gall ons per m i nute). Finding adequate space for

the sum p m a y be difficult at m a ny plants.

9

# 10 Site soil conditions

Unfavorable soil conditions can add substantially to the cost of the retrofit. Saturated

soils may require extensive drainage, pumpi ng and the installation of liners to allow

installation of the circulating water lines, sumps and tower basin. Pilings may be

required to support heavy st ructures on unstable soils.

Conversely, bedrock close to the surface may re quire blasting and excavation in order to

place the lines. On some sites, previous usage and spillage may have resulted in

contaminated soil which, if disturbed, beco mes subject to costly clean-up or disposal

requirements.

It is difficult to provide rigorous guidan ce on how the consideration of each of these

times be translated into th e categorization of the proj ect and “easy”, “average” or

”difficult”. However, if none of the item s presents any obvious problems, an “easy”

retrofit might beWorksheet 4:Tower size calculationsRetrofitProjectTowerSizeEstimatesAssumptions:EnterdataFlow ratepercell,gpm:Cell length, ft.:Plant:0DoAutomatic calculationCellwidth,ft.:notBasinextends4 ft.beyonderaseCirculatingWaterFlow(gpm)# ofcellsLengthWidthArea1 00(- )Ft.Ft.Sq.Ft.2 0013 0024 0035 0046 0057 0068 0079 0081000910# ofcellsLengthWidthArea(- )Ft.Ft.Sq.Ft.12345678910Circulating WaterFlowRate InformationTowerSize---Back-to-back arrangementUnitNo.UnitNo.TowerSize---In-linearrangementUnitNo.1112COOLING SYSTEM RETROFIT ANALYSISPlant:0ADDITIONAL SITE INFORMATION---To determine difficultyof installationSite descriptionDrawings AvailableDescriptive NotesPlant site boundariesExisting structuresTypeLocationGround elevation profilesUnderground utilitiesTypeLocationDepthAreas excluded from consideration as cooling towerlocationExisting cooling systemSchematics/general arrangementdrawingsIntake/discharge structuresCondenser inlet/exit pipingCirculating water pumpsSite geologySaturated orunstable soilsAreas requiring rock excavationContaminatedsoil areasWorksheet 5:Site characteristics

# expected. If two or three do, “average” is prob ably appropriate. If m o re, then “difficult”

is appropriate.

Plume and drift considerations

Cooling tow e rs frequently em it visible plum es during periods of cold weather and all

towers em it som e quantity of drif t at all tim es. The im plications of the f r equent pr ese n ce

of a visible plum e and the continuous em ission of drift on the cost of and the ability to

licen se a co oling towe r retr ofit depends strongly on th e characteris tics of the

neighborhood surrounding the plant.

Worksheet 6 : Neighborhood Characteristics

This worksheet is used to identify characte ristics of the neighbor hood in the vicinity of

the plant and organizes item s to consider in determ ining the likelihood that drift or visible

plum e woul d raise serious objections to the siting of a cooling tower on the site.

Visible plumes

Visible plum es can be a problem for safety or aesthe tic reas ons. Saf e ty issues a r is e if the

plum e obscures visibility on roadways or at airp orts. Aesthetic issues can be judged to be

a problem in scenic areas or in resi dential areas where residents object.

Objections to visible plum es can be e lim inated through the specification of plum e

abatem ent towers. However, plum e abatem ent towers can b e far m o re expensive thatn

conventional towers (a factor of x2 to x3 is likely) and require m o re fan and pum ping

power.

Drift

Most m odern cooling towers are equipped with d r ift elim inators which are specified to

lim it drift to 0.0005% of the circ ulating water flow. Two problem s m a y a r ise. From a

regulatory perspective, the dissolved and susp en ded solids in the dr if t (T DS and TSS) can

be catego r ized as PM 10 

# . In som e areas, this m a y be unaccep table or m a y require that

offsets be purchased. Th e costs of offsets can be very high or sim p ly unavailab l e in s o m e

regions.

From an environm ental effects perspective, d r if t, particula r ly if it is h i gh s a lin ity as m a y

be the case for saline or brackish water m a ke-up or for towers operating at very high

cycles of concentration, m a y cause problem s bot h on-site and off-site. On-site problem s

are norm a lly corrosion of downwind equipm ent and structures requiring high levels of

continu i ng m a intenance or som e times prem at ure replacem ent of equipment. Off-site

problem s are norm a lly related to dam a ge to vegetation, m a rring of finishes on

autom obiles or other impact s in residential areas.

13

# 14 Worksheet 7: Drift calculations

The returns the total drift rate and the associated PM 10 

# emissions rate for a specified

circulating water flow rate and assumed valu es of drift eliminator efficiency, source

water TDS and cycles of concentration. The PM 10 

# emissions rate is determined assuming

that all the dissolved solids in the drift are classified as PM 10 

# . While this is widely

acknowledged to be a very conservative a ssumption, it is nonetheless the position taken

by USEPA in their emissions rule. The cost associated with offsetting the PM 10 

# emissions, if this would be required, must be determined from local information on the

limits of emissions and the availability and cost of offsets. There is essentially no way of

reducing the drift rates below the level of 0.0005% of the circulating water flow rate at

this time.

While there is little evidence in the literature suggesting that off-site drift damage has

ever been a serious problem at tested sites, it is likely that attention to drift in siting

hearings would lead to extended and cos tly objections which may or may not be

eventually over come.Worksheet 6:Neighborhood characteristicsRural/remoteHighdensity/urbanCommercialResidentialOtherGeneralcharacterofneighborhood(1)Descriptivenotes(1)Check allthatapplyTypeDistancefromplant,milesResidential neighborhoodHightrafficroadwayAirportSchoolsRetirementcommunityHospitalsPlacesofworshipScenicareasCoastlineNationalParkOtherNEIGHBORHOODFEATURES/FACILITIESNEIGHBORHOOD CHARACTERISTICSName,IdentifierorDescription16Worksheet 7:Drift calculations17Retrofit Project Cost EstimatesEnterdataPlant:0Automatic calculationUnitNo.CirculatingWater FlowDriftRatePM10(gpm)gpmtons/year1 02 03 04 05 06 07 08 09 0100Drifteliminatorefficiency0.0005%SourcewaterTDS500Cyclesofconcentration5DRIFTCALCULATIONSAssumptions:

# 18 Alternative water sources

The normal assumption is that the make-up wate r for the retrofitted closed-cycle cooling

system will be drawn from the same water source that supplies the existing once-through

cooling system. Similarly, the cooling tower blowdown is assumed to be discharged to

the waterbody that the once-th rough cooling water was returned to. In a limited number

of situations, this may not be the case.

Make-up alternatives:

For example, for coastal plan ts using ocean water for on ce-through cooling, the salinity

of the drift from a cooling tower with seawat er make-up may be sufficiently high that the

calculated PM 10 

# emissions would exceed regulatory limits and require offsets which may

not be available. In that case, with no op tions for reducing drift rates, lower salinity

make-up sources would have to be consid ered. Options could include reclaimed

municipal waste water, groundwat er, irrigation drainage, produ ced water, mine drainage

or perhaps others.

Worksheet 8 : Alternative Water Sources

This worksheet identifies these water source s and requests information on availability,

amount, water quality, distance of source from plant and some information on the

neighborhood through which the supply and return lines would have to be installed and

any local regulatory impediment s to the use of the water.

Similarly, cooling tower blowdown may not be permitted to be discharged to the same

receiving water as the once-through cooling was returned to. While this would be

expected to be a rare situation, increased salinity, the presence of different water

treatment chemicals or other reasons may pertain.

Such restrictions may require the installati on and operation of additional water treatment

processes up to and possibly including zero liquid discharge equipment and associated

solids disposal. If this were the case, the costs could be comparable to those for the

cooling tower itself. To determine what might be required, local aqueous discharge

regulations must be reviewed and interpreted.20Worksheet 8:Alternative water sourcesCharacteristicsMunicipalreclaimedwaterGroundwaterIrrigationdrainageProducedwaterMinedrainageAvailabletoplant(1)Quantityavailable,mgdWaterqualitypHTSS,ppmTDS,ppmOtherDistance fromplant,milesNatureofarea betweensourceand plantRegulationsaffecting use(1) CheckallthatapplyALTERNATIVEWATER SOURCES

# Additional operating power costs

Additional operating power costs are those as sociated with the additional pum ping power

and fan power required f o r the operation of the cooling tower and the circulating water

loop between the condenser and the tower. These costs are calculated in Worksheets 9

and 10.

These works h eets are au tom a tically filled and activated by en tering the circulating water

flow rates for each un it in W o rksheet 3.

Worksheet 9: Pumping Pow er

The results in W o rksheet 9 (Pum ping power) also require inform ation about elevation

changes on the site, the s i zing of the circu l at ing water lines, the ci rculating water pump

efficiency and the pum p m o tor efficiency. Default values for these quan t ities are

displayed on the W o rksheet and can be changed if desired to bette r ref l e c t the situatio n at

the individual site or proj ect d e signer preferences.

The pum ping power calculated in Worksheet 9 is only that addition a l power required f o r

the new circulating water line between the condenser and th e cooling tower. It is

assum e d that water is de live r ed to th e tower onl y when the plant is op era t ing and tha t it is

the sam e whether the unit is ope rating at full or part load.

The pum ping power for the existing once-throug h cooling c i r c uit will be sim ilar to w h at

it was before the retrofit. However, the operating schedule m a y change. At som e pl ants,

with once-through cooling, the c ooling water flow rate was m a intained even when the

unit was off-line in order to prevent fouling or silting of the intake structure. W ith the

closed-cycle arrangem ent described above, wher e the intake and disc harge structures are

modified, this would likely not be the cas e and som e pum p ing pow er savings m i ght be

realized.

In m a ny cases, the ne ed f o r addition a l power f o r

the new cir c ulating water pum ps and

f

a ns will req u ire the ins t alla tion of n e w on-s ite, e l ectric a l inf r astruc tur e su ch as m o tor

control centers, transform e rs, switchgear, etc. If this is the ca se f o r this s i te, ple a se

indicate Yes or No and provide a brief descri ption of the nature, size and any difficulties

associated w ith lo cating the equipm en t on the sp readshee t of separately.

Worksheet 10: Fan Pow er

The results in W o rksheet 10 (Fan power) also re quire information about fan size and fan

motor efficiency. Default values for these quantities are displayed on the Worksheet and

can be changed if desired to be tter reflect the situ ation at the individual site or project

designer p r eferences.

21

# 22 The calculations in Worksheet 10 assume that all fans are at full speed whenever the

plant is operating. During some periods of the year, when the unit is at partial load or the

ambient wet bulb temperature is well below desi gn, some operators turn off fans to save

power with little or no e ffect on turbine performance. However, these operating

procedures vary widely from plant to plan t and are not considered in this analysis.

In many cases, the need for additional power for the new circulating water pumps and

fans will require the installation of new on-s ite, electrical infrastructure such as motor

control centers, transformers, switchgear, etc. If this is the case for this site, please

indicate Yes or No and provide a brief descri ption of the nature, size and any difficulties

associated with locating the equipment on the spreadshee t of separately.

Additional maintenance costs

Closed-cycle cooling systems are likely to incur higher maintenance costs than the oncethrough cooling systems which they replace. This is the result of several factors:

The cooling tower itself requi res cleaning, fill and drift elim inator maintenance and, in

some cases, periodic re packing of the tower.

The retrofitted system will have additional circulating water pumps, modified intake

structure, etc. Water treatment may be required for discharge of cooling tower

blowdown. If zero liquid discharg e rules pertain, the costs ca n equal that of the cooling

tower. (This seems unlikely at a site currently on once- through cooling.)

The cost of the additional maintenance in la bor, equipment and chemicals is highly sitespecific. However, a range of independent studies (EPA, Burns, Burns and Micheletti)

have used factored costs ra nging from 1 to 3% of the cooling system capital costs.

Assuming this accounts for approximately 40 % of the ”EASY” estimate on Worksheet 4,

an annual additional maintenance costs may be estimated. This is included in the

summary cost table on Worksheet 14 us ing 2% as an intermediate factor.Worksheet 9: Pumppower calculationsRetrofitProject Cost EstimatesEnter dataPlant:0Automatic calculationUnitNo.CirculatingWaterFlowTowerArrangementLineDia.∆h3∆h4Total HeadPumpPower(gpm)In-line =1;Back-to-back =2ftftftftMW100.00200.00300.00400.00500.00600.00700.00800.00900.001000.00Pumpingpower =(Circ.water flowratex Headrise)/(Pumpefficiency x Motor efficiency)Headrise =∆h1+∆h2+∆h3+∆h4∆h1=Elevationrise fromsumpleveltopumplevel∆h2=Elevationrise frompumptotower site∆h3=Heightoftowerhotwaterdistribution deck∆h4=Headlossthroughcirculating waterlinetotower∆h1,feet5∆h2,feet10∆h3,feet25for in-line arrangement∆h3,feet35forback-to-backarrangmeent∆h4,feetCalculatedassumingcirc.water flowvelocityVelocity,ft/sec9Pumpefficiency0.85Motor efficiency0.9Circ. linelength, ft1,000PumpingPowerCalculationsCalculations:Assumptions:2425Worksheet 10: Fan power calculationsEnterdataPlant:0Automatic calculationUnitNo.NumberofcellsFanPowerMW10.020.030.040.050.060.070.080.090.0100.0Calculations:Assumptions:Fanpower=(Numberofcellsx Fanpower)/Motor efficiencyPowerperfan200Motor efficiency0.9Fan Power Calculations

# Plant perform a nce penalty costs

Retrofitting once-through cooled plants with closed-cyc le cooling generally im poses a

perform a nce penalty on the unit, since the cold water supplied to the condenser from the

cooling tow e r is typically at a higher tem p erature than water that would be withdrawn

from the local natural w a terbody. T h is is a result of the follo wing considerations.

1. Cold water f r om a cooling tower is lim ited by the am bient wet bulb te mperature.

Typical tower design s d e live r cold water about 10oF higher than wet bulb at the

“1% wet bulb” design point. 1



# 2. At tim es when the wet bulb is lo wer as it is during colder, dr ie r w eathe r, th e

“approach” to wet bulb is higher than 10oF.

Therefore, the condenser inlet tem p erature with a closed-cycle system is nearly alw a ys

higher than with a once-through cooling system resulting in a corresponding increase in

the condensing tem p erature and the turbine backpressure.

Incre a sed tu rbine ba ckp r essur e le ad s to a high e r unit h eat rate which r e sults in e i ther

reduced MW output at a constant firing rate or a higher firing rate to m a inta in a co nstan t

MW output. In either case, an eco nom i c penalt y is incurred either as lost revenue or

increased fuel cos t

.

An estim ate of the m a gnitude of the perform a nce penalty can be carried out at varying

levels of complexity.

In th e abs e n ce of any ad dition a l inform ation, an annual h eat rate pena lty of 1.5% to 2 % is

consistent w ith a num ber of independent analyses. However, the m a gnitude of the penalty

will vary w ith a num ber of f

actor s. The m o st im portant of these ar e unit ope r a ting

profile, condenser and cooling to wer design, turbine characterist ics and site m e teorology.

The following worksheets indicate the infor m at ion required for a com p r e hensive estim a te

of the perform a nce penalty.

Worksheet 11: Site Sou rce Water a nd Ambient Weather I n formation)

Worksheet 11 (Site sou r ce wate r and am bient weather inform ation) provides tables for

entering inf o rm ation on source water tem p erature and am bient tem p eratu r e and wet b u lb

tem p erature in varying levels of detail. Hour ly data f o r source water data f o r an entire

year is preferred. However, if this level of detail is no t av ailab l e, an a lte rnate tab l e to

provide m a xim u m, average and m i nim u m valu es of source water tem p eratu r e for each

month is provided.

Worksheet 12 , Table A, requests condenser design inf o rm ation, turbine heat rate

inf o rm ation 2 

# and average fuel cost and energy pr ice inform ation. In the absence of

1 

# Th at w e t b u l b te m p er atu r e wh ich is ex ceed e d o n l y 1 % o f th e su mm er ti me ( J u n e thr ough Sep t em b e r )

h our s (

~ 3 0 hou r s /year)



# 26

# 27 condenser design information, the smaller tables to the left of Table A on the Worksheet

will use the indicated default values and th e maximum source water temperature and the

1% wet bulb temperature from Worksheet 11 to calculate a “d esign point” difference in

turbine backpressure between the two cooling systems. Note that Worksheet 11 contains

Table A which can accept condenser design in formation if available. The results

calculated for the design specifications can then be manually substituted for the default

values if desired.

Worksheet 13 (Tables 1 and 2) provide alternate le vels of detail for providing the unit

operating profiles.

The effect of different tower design choi ces can be observed by varying the approach

temperature away from the default value of 10 oF . Limits of 5 oF (larger tower) and 15 oF

(smaller tower) are suggested.

Worksheet 14 (Summary) aggregates all the cost s in expresses them both as an

annualized and a life cost.

2 

# A manufacturer-supplied heat rate curve would be preferable to these poin t values if available.28Worksheet 11: Site source water and ambient temperature dataEnterdataPlant:0AutomaticcalculationWater SourceDate/TimeTemperature, FMonthMaximum, FAverage, FMinimum, FSourcewater temperature1/1/060:00JanuaryYearlymaximum,F1/1/061:00FebruaryYearlyminimum,F1/1/062:00MarchYearlyaverage,F1/1/06 3:00AprilAmbienttemperature1/1/064:00MayYearlymaximum,F1/1/065:00JuneYearlyminimum,F1/1/066:00JulyYearlyaverage,F1/1/06 7:00AugustAmbient wetbulb1/1/068:00September1%wet bulb, F1/1/069:00OctoberYearlyminimum,F1/1/0610:00NovemberYearlyaverage,F1/1/06 11:00December1/1/0612:00Annual0 #DIV/0!01/1/0613:001/1/0614:001/1/0615:001/1/0616:001/1/0617:00MonthMaximum,FAverage, FMinimum, F1/1/0618:00January1/1/0619:00February1/1/0620:00March1/1/0621:00April1/1/0622:00May1/1/0623:00June1/2/060:00JulyAugustSeptemberOctoberNovemberextend forfull yearDecemberAnnual72#DIV/0!0Wet bulbtemperaturedataSITEINFORMATIONSourcewatertemperature dataAmbienttemperature dataWorksheet 12: Cooling system and unit design informationPlant:0EnterdataAutomatic calculationMax.source watertemperature,F0Unit123 45Steamcondensing temperature,F27Condenserdesign specs.Turbinebackpressure,inHga0.3Coolingwaterflow,gpm00000Steamflow, lb/hrHeatload,Btu/hr1%wetbulbtemperature,F0Waterinlettemp.,FSteamcondensingtemperature,F37Waterexittemp.,FTurbinebackpressure,inHga0.3Steamcondensing temperature,FSteamcondensingpressure,inHgaEfficiency/heatratepenaltiesOutput@design backpressureOutput@designbackpressure+1inHgaRange,F20Output@designbackpressure +2 inHgaTTD,F7Approach,F10Fuelcost,$/MMBtu5Powerprice,$/MWh35EconomicfactorsDefaultvaluesCooling towerdesignassumptionsOnce-throughcooling(basedonDefaultvaluesbelow)Once-throughcooling(basedonDefaultvaluesbelow)Condenserdesign assumptionsTableA---UNITDESIGN/OPERATINGINFORMATION(If available--otherw2930Worksheet 13: Unit operating profile; (Table 1---preferred)UnitOperatingProfileDataPreferred:Hourlypowerlevel foreachunitforcorresponding period assourcewaterandambienttemperature data(See Table 1)Minimum:Monthly energyoutput(MWh)foreachunitfor same year as source water andambienttemperaturedata(See Table 2)Unit1Unit2Unit3Unit4Unit5MWMWMWMWMW1/1/060:001/1/061:001/1/062:001/1/063:001/1/064:001/1/065:001/1/066:001/1/067:001/1/068:001/1/069:001/1/06 10:001/1/06 11:001/1/06 12:001/1/06 13:001/1/06 14:001/1/06 15:001/1/06 16:001/1/06 17:001/1/06 18:001/1/06 19:001/1/06 20:001/1/06 21:001/1/06 22:001/1/06 23:001/2/060:00extendfor fullyearTable1HourlyPower Level--ByUnitDate/Time31Worksheet 13: Unit operating profile;(Table 2---minimum)Unit1Unit2Unit3Unit4Unit5add'l unitsMWhMWhMWhMWhMWhJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecemberTable2Monthly EnergyOutput--ByUnitMonthWorksheet 14: SummaryMaintenanceHeatratepenalty$ $$MW$/yr$/yr$/yr$$$$$$EasyAverageDifficultEasyAverageDifficultEasyAverageDifficult1 $0$0$00.00$0$0$0$0$0$0$0$0$02 $0$0$00.00$0$0$0$0$0$0$0$0$03$0$0$00.00$0$0$0$0$0$0$0$0$04$0$0$00.00$0$0$0$0$0$0$0$0$05$0$0$00.00$0$0$0$0$0$0$0$0$06$0$0$00.00$0$0$0$0$0$0$0$0$07$0$0$00.00$0$0$0$0$0$0$0$0$08$0$0$00.00$0$0$0$0$0$0$0$0$09$0$0$00.00$0$0$0$0$0$0$0$0$010$0$0$00.00$0$0$0$0$0$0$0$0$0CapitalCostOperatingPowerUnitNo.Annualized CostPresentValue--LifeCostSUMMARYINFORMATION32