Tetra Tech, Inc.

10306 Eaton Place, Suite 340 Fairfax, VA 22030 phone 703 - 385 - 6000 fax 703 - 385 - 6007 TO : Paul Shriner and Jan Matuszko, EPA FROM : John Sunda, SAIC and Kelly Meadows, Tetra Tech DATE: April 1 7 , 2009 SUBJECT: Modular C ooling Tower Technology and Costs C losed
- cycle cooling (in the form of However, in estimating compliance costs associated with closed ty picall y onl y considered permanent basins
. Closed
- cycle cooling may also be towers. Modular cooling towers are portable cooling units that can supplement or even replace once
- through cooling water flows at el users of cooling water
. While this over permanent cooling towers does not presentl y have enough technology
. Ty pical Modular Tower Sy stem Much of the technical information below was obtained through correspondence with Blue Stream Services, which has partnered with the modular tower manufacturer Varitech Equipment Company . The services provided b y the vendors primarily involve short and long
- term rentals, especiall y for s ys tems that may require use during only

a portion of the year. 1

1 Although modular units may be purchased, purchase costs were not available. One reason that the vendor may be focusing on temporary and seasonal energy requirements are higher for modular tow ers c towers may be more cost
- effective for systems that would be required for a very long period of time and that are used continuously or for a large portion of the year. 

### MEMORANDUM
10306 Eaton Place, Suite 340

Paul Shriner and Jan Matuszko, EPA John Sunda, SAIC and Kelly Meadows, Tetra Tech , 2009 ooling Tower Technology and Costs cycle cooling (in the form of cooling towers ) is one form of flow reduction However, in estimating compliance costs associated with closed
- cycle cool i ng, permanent ly
- built onsite structures with concrete cold water cycle cooling may

also be achieved through the use of modular cooling Modular cooling towers are portable cooling units that can supplement or even through cooling water flows at el ectric generators and other significant

While this alternative technology offers a number of benefits over permanent cooling towers and could significantly reduce facility

downtime enough information to assess the widespread applicability of this Sy stem Much of the technical information below was obtained through correspondence with Blue Stream Services, which has partnered with the modular tower manufacturer Varitech Equipment Company . The services provided b y the vendors primarily involve short term rentals, especiall y for s ys tems that may require use during only

a portion

Although modular units may be purchased, purchase costs were not available. One reason that the vendor may be focusing on temporary and seasonal
- use systems may be that, as described below, the operating energy requirements are higher for modular tow ers c om pared to permanent towers. As a result, permanent effective for systems that would be required for a very long period of time and that are used continuously or for a large portion of the year. 1 flow reduction
. ng, EPA has structures with concrete cold water

modular cooling Modular cooling towers are portable cooling units that can supplement or even ectric generators and other significant

offers a number of benefits and could significantly

reduce facility

downtime , EPA assess the widespread applicability of this

Much of the technical information below was obtained through correspondence with Blue Stream Services, which has partnered with the modular tower manufacturer Varitech Equipment Company . The services provided b y the vendors primarily involve short
- term term rentals, especiall y for s ys tems that may require use during only

a portion

Although modular units may be purchased, purchase costs were not available. One reason that the vendor use systems may be that, as described below, the operating om pared to permanent towers. As a result, permanent effective for systems that would be required for a very long period of time and2

System Operation M odular cooling towers are typicall y used in e ither a helper mode 2 or a recirculating mode. In the recirculating mode, hot water can be withdrawn directly from the hot water discharge channel, cooled and then returned to the intake channel upstream of the intake pumps or in the intake pump well. The modular tower s ys tem can recirculate all or only a portion of the total cooling s ys tem flow requirements. To recirculate all of the flow, the modular cooling tower pumping rate is matched to the associated condenser cooling water pumping rate through the use of float controls in the intake channel. System Set

- U

p The simplest installation is to withdraw water from the facility ’s effluent channel and pump the water through the towers, where it then flows by gravity to the existing intake channels or cooli ng water pump wells. The upstream portion of the intake can then be blocked off so that the existing recirculation pumps remain functional while intake construction occurs. Other engineering solutions for cooling water pump and piping configurations are possible
. Insome cases, there may be challenges in finding a suitable path for the placement of the temporary cooling water recirculation pipes, but engineering solutions should be available in most circumstances. Modular towers can be installed while the plant is in operation and can be operated on an as - needed basis. The installation can be done quickly ; once the units are trucked in
place, it takes approximately one day per unit to complete the installation. This allows modular towers to be used as a temporary source of cooling water during the period when an intake must be shut down, such as allowing for the retrofit of 316(b) compliance technology
. The Varitech units are transported to the site on a truck trailer bed. In earlier designs prior to this one, the modular units either remained on the truck trailer or were removed using a crane. One advantage of the newer Varitech units is that they can be trucked o nsite, jacked up so that the truck trailer can move out, and then the tower height can be adjusted using built
- in legs that are easily leveled. No crane is necessary , thus reducing mobilization and demobilization costs. These towers require very little s ite preparation as long as the site is moderatel y level. System Design The basic modular cooling tower configuration uses PVC pipes running along the ground to and from the towers, skid
- mounted pumping units that pump water through the towers, and the to wer units themselves. The vendor ty pically provides all the necessary equipment, including pumps, piping, control s ys tem, electrical cable and transformers. The vendor can also provide all necessary services, including engineering design, mobilization/in stallation, contract operation and maintenance, and

2 The helper mode provides help in c om pliance with 316(a) requirements only, so this application will not be discussed further here.3

removal/demobilization. In short, the vendor can provide all necessary equipment and services with the exception of permitting activities. In many respects, operation and maintenance activities for modular towers will be similar to those for permanent towers, except that these tasks would be performed b y the vendor. One benefit of modular towers is that it will be easier to perform maintenance on the modular units while maintaining generation at near full capacity , since the temporary loss of the flow from one unit at a time represents only a small component of total cooling water flow. In the past, large portable towers generall y ranged in size from 500 ton to 2,000 ton capacities. 3 Recentl y, however, Varitech has begun manufacturing portable 3,000 ton units capable of handling up to 10,000 gpm of cooling water. A typical design flow for these units is 10 MGD or 6,945 gpm (Blue Stream 2008b). These units are the largest portable units available and p rovide the most efficient use of available space. With the use of multiple side
- by
- side tower units, a cooling s ys tem of any size capacity can be assembled. For example, Blue Stream recently worked on a s ys tem for the 2,600 MW Cumberland Plant in Cumberland City , Tennessee , operated b y the TVA (see below) . This plant requires cooling tower flow capacity of 500,000 gpm. In this case, the towers have been installed in a helper tower configuration to eliminate the need to derate (reduce plant generation) during summer source water low
- flow conditions that have been exacerbated by recent drought. The specifications for the 3,000 ton units are: Flow Range: 5,000

– 10,000 gpm Design Flow: 6,945 gpm (10 MGD) Tower Width: 12 ft T ower Length: 50 ft Tower Height: 15 ft excluding ground clearance Fans: 20 direct drive at 15 Hp each Fan Energy

Req.: 300 Hp Shipping Weight: 56,000 lbs Operating Weight: 88,000 lbs Source: Varitech 2008. The towers are constructed of fiberglass
- rein forced plastic, stainless steel, and PVC components to prevent corrosion. The towers contain high efficiency cellular sheet PVC drift eliminators. System Requirements The sy stem requirements are available space for placement of the towers and a route for the piping from the warm water discharge channel to the towers and then from the tower cold water outlet to the intake channel . Each unit is 12 ft wide by 50 ft long and requires a side clearance of 12 ft between units placed side
- by side and 24 to 36 ft between rows

3 Note that in this context a “ton” is a measure of cooling capacity equivalent to 12,000 BTUs/hr.4

to allow for proper air circulation (Blue Stream 2008b). The result is that, for each 10 MGD of design flow volume, an area of approximately 2,000 sq ft i ncluding the side clearance is required. Looking at the tower footprint alone, these 3000 ton units can cool 11.6 gpm/sq ft. The footprint size of the permanent cooling towers derived using the EPRIcost methodology

(as described in Chapter 8 of the TDD) indicates they cool only 3.4 gpm/sq ft. Thus, the modular towers are more compact and should require less space. The reason for this is the higher fan energy requirement (see discussion below) and high efficiency design of the units and fill material. Assuming that the total side clearance for both sides for permanent cooling towers is equal to the tower width, a similarly sized permanent cooling tower would require about 4,000 sq ft. The difference in space requirements may be somewhat less than the factor of 2 that is implied by

the above estimates, since the smaller modular units will have plumes that may

be more prone to recirculation, especiall y if they are placed in arrays of multiple rows and close together using minimum clearance. A 10,000 gp m skid
- mounted pump requires a space of 6 ft by 6 ft (Blue Stream 2008a). Another s ys tem requirement is a power source. The fan energy requirements for modular towers are about 50% higher than the fan energy requirements estimated using EPRI’s methodolog y for a similar design flow. The higher fan energy is part of the modular tower design that allows for the towers to be more compact, taking up less space than permanent towers. A comparison of the total pump and fan energy requirements reported by the v endor to estimates derived from EPRI ’s methodology indicates that the modular towers may require about 70% more electrical energy than equivalent permanent towers to operate. That means that pumping energy requirements may

also be higher for modular tower s. This may be due to the fact that modular towers use multiple pumps and pipes that are smaller in size than those used in permanent towers. The use of smaller pipes and pumps tends to result in greater friction losses and less efficient pump operation. Non

- Wa ter Quality Impacts In general, non
- water quality impacts (e.g., noise, drift, water consumption, plume) should be similar for both modular and permanent cooling towers. Example Installations The largest example facility provided b y the vendor is the 2,600 MW Cumberland Plant in Cumberland City

Tennessee ( operated by

the TVA ). The facility ’s design intake flow ( DIF ) is over 2 billion gallons per day ( BGD ). This plant operat es the towers in a helper mode due to problems with low river flow, whi ch have led to problems in meeting the facility ’s 316(a) discharge limits. Another facility

is the 370 MW WS Lee Steam Station in Anderson County, South Carolina ( operated b y Duke Energy). The facility recentl y purchased modular towers and5

is using them in a recirculating mode to reduce intake flow volume . Existing permanent cooling towers already located onsite are operated in as helper towers; the new modular towers are operated in a recirculating mode during the summer because the river level drops to o far. The modular tower recirculating flow volume is approximately 100,000 gpm , which is close to the facility’s actually intake flow (AIF ). So during the summer , the facility routes the helper tower effluent to the modular towers, recirculating the water back to the intake and thus running water through two sets of towers. Sy stem Costs Table 1 below presents the rental costs and total energy requirements for modular towers (as supplied by the vendor)
. These costs require a minimum rental perio d of four months per year but facilities are only charged for the period the towers remain in use in excess of 4 months each ye ar after that ( i.e., beyond the minimum 4 month rental, a facility is only charged for time the towers are in use; if they are idle, there is no additional fee )
. The rental costs include the tower units, pumps, piping, controls, and maintenance
. These costs do not include items such as site preparation, freight, installation labor, electrical supply

equipment, electricity to operate the pumps and fans , or s ystem removal labor and freight (Blue Stream 2008b). 4 The vendor noted that since the client s are power companies , they usually provide the electrical supply components using their own resources . Table 1 .

4 Such costs (especially freight) are very site
- specific. Fr eight costs could be $3,000

- $4,000, but can change with fuel costs and distance traveled. GPD GPM Dollars/Month Number of Modular Units Power

Requirement (MW) EPRI Average

Capital Cost EPRI O&M

Costs EPRI Total

Power (MW) 20,000,000 13,889 $120,400 2 1.0 $5,300,000 $25,600 0.58 40,000,000 27,778 $240,800 4 2.0 $10,600,000 $51,200 1.13 60,000,000 41,667 $361,200 6 3.0 $15,900,000 $76,800 1.67 80,000,000 55,556 $481,600 8 4.0 $21,200,000 $102,400 2.22 100,000,000 69,445 $602,000 10 5.0 $26,500,000 $128,000 2.75 120,000,000 83,334 $722,400 12 6.0 $31,800,000 $153,600 3.29 140,000,000 97,223 $842,800 14 7.0 $37,100,000 $179,200 3.83 160,000,000 111,112 $963,200 16 8.0 $42,400,000 $204,800 4.36 180,000,000 125,000 $1,083,600 18 9.0 $47,700,000 $230,400 4.9 200,000,000 138,889 $1,204,000 20 10.0 $53,000,000 $256,000 5.45 220,000,000 152,778 $1,324,400 22 11.0 $58,300,000 $281,600 5.98 240,000,000 166,667 $1,444,800 24 12.0 $63,600,000 $307,200 6.51 260,000,000 180,556 $1,565,200 26 13.0 $68,900,000 $332,800 7.05 280,000,000 194,445 $1,685,600 28 14.0 $74,200,000 $358,400 7.58 300,000,000 208,334 $1,806,000 30 15.0 $79,500,000 $384,000 8.11 320,000,000 222,223 $1,926,400 32 16.0 $84,800,000 $409,600 8.65 340,000,000 236,112 $2,046,800 34 17.0 $90,100,000 $435,200 9.19 360,000,000 250,000 $2,167,200 36 18.0 $95,400,000 $460,800 9.72 380,000,000 263,889 $2,287,600 38 19.0 $100,700,000 $486,400 10.26 400,000,000 277,778 $2,408,000 40 20.0 $106,000,000 $512,000 10.79 1 Each unit consists of a 3,000 ton tower at 6,945 gpm with minimum 4 months rental period 2 Calculated using the EPRI Cooling Tower Calculation Worksheet (EPRI 2007) Source: Blue Stream 2008B System Design Flow Modular Tower Rental1 Permanent Constructed Tower 2 Comparison of Modular and Permanent Cooling Tower Costs and Energy Requirements6

Cost of Modular Towers Compared to Permanent Towers For comparison, Table 1 also includes the capital and O&M costs and the energy requirements for a permanent cooling tower s ys tem , as derived from the EPRI methodology
. A present - value calculation using an interest rate of 5% and the assump tion that the towers will operate for four month s per ye ar indicates that the break
even time period is about 1 4 ye ars (see below for a detailed discussion) . This mean s that if the modular towers are used for 4 months or less each ye ar , the y will be more economical than permanent towers if they are need ed for a period of less than 1 4 ye ars . If the duration of tower operation is extended to 12 months /year, the break
- even time period is less than four years . The break
- even calculation takes into consideration the costs presented in Tables 1 though 4 below ( including estimated cost of energy requirements ), but assumes that the non
- power O&M costs for permanent towers ( Table 1 , Column 7

— EPRI O&M ) are the same for both 4 and 12 months of operation
. The energy costs are a large component of O&M costs
. For permanent towers operated continuously

throughout the year, energy requirements can represent up to 90% of total O&M costs. The results of the break
- even anal ys is demonstrate that modul ar towers may be more financiall y advantageous for facilities that require flow reduction for only a portion of the year and for facilities in which the cooling tower technology will not be needed for the full service
- life of permanent tower s constructed o nsite. Estimation of Costs for Temporary Use During Construction Downtime The temporary

installation of modular cooling towers is an available technology option for minimizin g construction downtime costs
. This approach also has the added benefit of maintain ing generating capacity at base load plants which may be important in regions or time periods where extended facility downtime would be detrimental to maintaining reliable generation
. Below is an estimate of the costs for a ty pical temporary

rental t ower installation
. For each facility with an estimated net downtime period (due to installing a compliance technology

as a result of the proposed rule) , the equations below can be used to estimate the cost of th is downtime technology option
. These costs can then be compared to the lost generation costs of shutting down the generating units
. EPA could then identify

the facilities that could benefit economically from employing this option and adjust the downtime costs accordingl y. Each project will have a minimum cost associated with installation and demobilization costs plus rental costs (minimum four months for Blue Stream)
. The decision to utilize modular towers to reduce downtime costs will be somewhat dependent on whether the estimated lost generati on costs for the net downtime period exceeds the total cost for tower rental by

a large enough margin to make it economically worthwhile
. Lo st generation costs will also be dependent on both the downtime duration and facility ’s capacity utilization rate ( CUR) during the downtime period
. Due to the installation and minimum rental period costs, this technology will likely be more attractive to facilities that expect longer downtime requirements and a high CUR during the outage
. The decision to use temporary cooling towers may not be limited to just economic7

considerations for the facility, as the need to maintain minimum regional generating capacity and the cost of replacement power generation may also factor into the decision. Table 2 presents the estimated one
- time installation and demobilization costs that are not covered b y the vendor rental costs
. The total costs apply to all applic ations regardless of duration
. The shipping, installation, power supply, demobilization, an d other costs not covered b y the vendor fees are derived using the assumptions below:

 Freight

– transportation costs per tower ( each way) is $6,000 including shipping of towers and ancillary

equipment.  Installation labor

– installation time of one day per tower is assumed to require six persons for two 8
- hr shifts per tower.  Demobilization labor
- same as for installation.  Labor Rate
- $50/hr ($38/hr in 2002 adjusted for inflation to 2009).  Site Preparation
- assumed as $4,000 per unit ( estimate based on B PJ).  Electrical hookup

– material and labor cost is assumed to be $20,000 per unit ( estimate based on BPJ).  Allowance

– additional costs equal to 50% of total for above items (freight, labor, site preparation, and electrical) to account for all other costs
.  Power

– cost estimate for power to operate pumps and fans are based on a CUR of 85% and an average wholesale power cost of $65/Mwh. Table 2

GPD GPM Freight Two Way Mob/Demob.

Labor Site Preparation Electrical Total Fixed Costs Excluding Rental* 20,000,000 13,889 $24,000 $9,600 $8,000 $40,000 $122,400 40,000,000 27,778 $48,000 $19,200 $16,000 $80,000 $244,800 60,000,000 41,667 $72,000 $28,800 $24,000 $120,000 $367,200 80,000,000 55,556 $96,000 $38,400 $32,000 $160,000 $489,600 100,000,000 69,445 $120,000 $48,000 $40,000 $200,000 $612,000 120,000,000 83,334 $144,000 $57,600 $48,000 $240,000 $734,400 140,000,000 97,223 $168,000 $67,200 $56,000 $280,000 $856,800 160,000,000 111,112 $192,000 $76,800 $64,000 $320,000 $979,200 180,000,000 125,000 $216,000 $86,400 $72,000 $360,000 $1,101,600 200,000,000 138,889 $240,000 $96,000 $80,000 $400,000 $1,224,000 220,000,000 152,778 $264,000 $105,600 $88,000 $440,000 $1,346,400 240,000,000 166,667 $288,000 $115,200 $96,000 $480,000 $1,468,800 260,000,000 180,556 $312,000 $124,800 $104,000 $520,000 $1,591,200 280,000,000 194,445 $336,000 $134,400 $112,000 $560,000 $1,713,600 300,000,000 208,334 $360,000 $144,000 $120,000 $600,000 $1,836,000 320,000,000 222,223 $384,000 $153,600 $128,000 $640,000 $1,958,400 340,000,000 236,112 $408,000 $163,200 $136,000 $680,000 $2,080,800 360,000,000 250,000 $432,000 $172,800 $144,000 $720,000 $2,203,200 380,000,000 263,889 $456,000 $182,400 $152,000 $760,000 $2,325,600 400,000,000 276,000 $480,000 $192,000 $160,000 $800,000 $2,448,000 *Includes 50% allowance to account for all other costs. Costs are in 2008 Dollars System Design Flow Installation and Demobilization Costs

Calculated Installation and Demobilization Costs8

Table 3 presents the tower rental costs based on the data in Tables 1 and 2 and includes the total costs for a rental duration of up to 16 weeks, the weekl y rental costs for periods exceeding 16 weeks, and power cos ts which are shown separatel y . Note that the tower rental costs already include tower O&M for labor and materials, with the exception of the cost of p ower to operate pumps and fans.Table 3

The total downtime for all cost modules range s from <4 weeks to 15 weeks, with the exception of installing cooling towers at nuclear facilities which has a relatively hi gh downtime value of 32 weeks
. In the 2004 Phase II rule , the total downtime values were converted to net downtime by subtracting 4 weeks of routine maintenance d owntime. 5 A second possible approach to consider downtime is to use facility
- specific data to calculate facility
- specific estimated routine maintenance durati ons ranging from 1 to 8 weeks
. Using this approach, the calculated net downtime periods for any facility c ould range from 0 to 14 weeks
. Since both of these approaches would yield outages that are less than the minimum four
- month (16 weeks) rental period, the minimum cost will apply to most technology

modules at non
- nuclear facilities
. The only variable cost is the power to operate the pumps and fans.

5 Based on EPA’s site visits, 4 weeks is a typical outage period for many facilities. GPD GPM Total Minimum Costs for Tower Rental Up to 16 Weeks including Installation/ Demobilization Tower Rental

Additional Weeks (Dollars/Week) Number of

Modular Units Power

Requirement (MW) Estimated Weekly

Power Costs (Dollars/week) 2 20,000,000 13,889 $604,000 $30,100 2 1.0 $3,285 40,000,000 27,778 $1,208,000 $60,200 4 2.0 $6,570 60,000,000 41,667 $1,812,000 $90,300 6 3.0 $9,855 80,000,000 55,556 $2,416,000 $120,400 8 4.0 $13,140 100,000,000 69,445 $3,020,000 $150,500 10 5.0 $16,425 120,000,000 83,334 $3,624,000 $180,600 12 6.0 $19,710 140,000,000 97,223 $4,228,000 $210,700 14 7.0 $22,995 160,000,000 111,112 $4,832,000 $240,800 16 8.0 $26,280 180,000,000 125,000 $5,436,000 $270,900 18 9.0 $29,565 200,000,000 138,889 $6,040,000 $301,000 20 10.0 $32,850 220,000,000 152,778 $6,644,000 $331,100 22 11.0 $36,135 240,000,000 166,667 $7,248,000 $361,200 24 12.0 $39,420 260,000,000 180,556 $7,852,000 $391,300 26 13.0 $42,705 280,000,000 194,445 $8,456,000 $421,400 28 14.0 $45,990 300,000,000 208,334 $9,060,000 $451,500 30 15.0 $49,275 320,000,000 222,223 $9,664,000 $481,600 32 16.0 $52,560 340,000,000 236,112 $10,268,000 $511,700 34 17.0 $55,845 360,000,000 250,000 $10,872,000 $541,800 36 18.0 $59,130 380,000,000 263,889 $11,476,000 $571,900 38 19.0 $62,415 400,000,000 276,000 $12,080,000 $602,000 40 20.0 $65,700 1 Each unit consists of a 3,000 ton tower at 6,945 gpm with minimum 4 months rental period 2 Based on w

holesale power cost of $65/Mw h and fan/pump power utilization of 90%. Costs are in 2008 Dollars System Design Flow Fan and Pump Power Modular Tower Rental 1 Modular Tower Costs9

The costs shown in Table 3 were plotted against the recirculating flow rate and the data were fitted to straight lines
. Table 4 presents cost estimation equations derive d from this data
. Equations for O&M costs for pump and fan energy are presented in both megawatts at full capacity

and in dollars per week assuming that the ene rgy usage will be 85% of full capacity over the operating period and the average wholesale cost of electricity is $65/Mwh. 6 Table 4

Additional Cost In formation The rental fee is charged only for the months the towers are used; the equipment can stay onsite the remainder of the year at no extra charge
. Thus, installation/demobilization costs can be amortized over the entire rental contract period
. As a result, modular cooling towers are often rented for periods of several years or more . Another bene fit is that rental towers can be financed through the facility ’ s operating budget, thus avoiding the time
- consuming planning and approval requirements for such a major capital expenditure as a cooling tower. Modular towers may

be capable of producing cold er water than permanent cooling towers, which in turn could offset a portion of the extra power requirements through a reduction in the turbine efficiency energy penalty . The vendor stated that the modular towers had an approach of 7 to 10  F , while the E PRIdocumentation specified an approach of 10  F for permanent towers (Blue Stream 200 9 )
. The approach is the difference between the temperature of the cold water exiting the tower and the wet bulb temperature of the air and thus, towers with lower approa ch values will produce colder water. The modular tower cited here is designed to be efficient and compact and accomplishes this , in part , by using a higher fan power and thus may produce colder water. Cooling t owers can be designed with different approach values , generall y ranging from 5 to 15  F with 10  F being a typical design value. In general , a tower with a lower approach will cost more and in the case of permanent towers will be larger in size
. The 316(b) Phase I Rule based cooling tower c osts on a vendor
- supplied tower sizing factor

6 Either approach could be used in the economic analysis, but using megawatts would be the most accurate. Generally speaking, the relative magnitude of the O&M cost component is equal to about 1/3 of the mo nthly tower rental costs. Modular Cooling Tower Costs Equation Constant Units Total Costs ?16 Weeks (TC 16 ) TC 16= DIF(gpm) x Constant 43.527 Dollars Added Weekly Costs for >16 Weeks TC wk = DIF(gpm) x Constant 2.169 Dollars/week Variable O&M - Pump & Fan Power (OM MW) OM MW= DIF(gpm) x Constant 0.0000700 MW Variable O&M - Pump & Fan Power (OM $$ )* OM $$ = DIF(gpm) x Constant 0.6707 Dollars/week* Energy Penalty -Heat Rate (EP) EP=MWS x Constant 0.02 MW MWS = Total facility steam generating capacity * Based on assumed power cost of $65/Mwh and 85% power utilization Costs are in 2008 Dollars Cost Equations f or Modular Cooling Towers10

of $30/gpm for a cooling tower with an approach of 10  F and a sizing factor of $50/gpm for a tower with an approach of 5  F
. 7 (USEPA 200 0 ) Thus, based on these sizing factors, it is estimated that a reductio n of the approach from 10  F to 5  F w ould result in an increase in capital costs for a permanent tower of approximately 67%. It is estimated that a 1.0  C reduction in the cooling water temperature can decrease the heat rate of a thermal power plant b y 5 Kcal/KWh
. 8 (National Productivity Council of India (NPCI) 2009) Using this factor, a coal
- fired plant with a heat rate of 9,000 BTU/KWh (thermal efficiency = 37.9%) would increase its output by 0.12% for each 1.0  F reduction in cooling water temperat ure during warmer periods of the years . Another anal ys is of a theoretical pressurized water nuclear reactor predicted that an increase in cooling water temperature by 1.0  C would decrease output by 0.45%
. (Durmayaz and Sogut 2006) This is equivalent to a change in output of 0.25% for a 1.0  F change in cooling water temperature , or roughl y double the NPCI
- based estimate
. Note that an approach of 5  F is generally considered the lower limit for tower design , due to the fact that the tower size will incre ase exponentially as the approach decreases, resulting in greatl y diminishing returns in terms of perform ance versus costs. The quality

of the water being circulate d through the towers (e.g., concentration of suspended of solids) may affect the type of tower fill that can be used , which can in turn affect the efficiency

of the tower and the approach value
. The modular towers use a film fill that is more susceptible to plugging and fouling than splash fill. Film fills come in different designs that can be tailored to the water quality
. If the water contains solids or is susceptible to biofouling that could plug the smaller holes /channels , then a fill with larger holes/channels must be used , which will reduce the efficiency of the tower. Applicability

f or 316(b) Modular cooling tower systems would be most useful for projects requiring a temporary source of cooling water during major repairs or construction at existing once
- through intakes and cooling tower sy stems, such as during the downtime associated with retrofitting a new intake technology or closed
- cycle cooling s ys tem (although there are limitations on the latter, as discussed below). The modular towers would be available to those facilities with sufficient space for the towers and where the exis ting cooling water pumps and pump wells or intake channels can be blocked off (see Figure 1). 9 Modular towers require somewhat less space than permanent towers and, s ince the modular cooling towers consist of many individual units, they

can also be placed in configurations

7 These factors were then scaled up using factors for additional cost components such as installation, etc., but the relative ratio of total capital costs should be similar. 8 These estimates of the effect of cooling water temperature on plant output are presented as specific examples found in literature. Most technical sources are reluctant to provide a quantitative estimate of this sort because the actual effect will vary depending on the turbine system design and the specific operating conditions. 9 In Figure 1 , a sheet pile wall was used to block off the intake canal to ensure that returned water was recirculated, essentially eliminating the withdrawal of intake water with the exception of make
- up water. M ake
- up water was withdrawn from the discharge canal.11

that allow for efficient use of available space, including space that might not otherwise be useful for conventional multi
- cell cooling towers. 10 Potential Sites for Modular Towers Modular towers may

provide a significant reduction in downtime and the associated costs at some facilities. In some cases, especiall y those where the interruption period is fairl y long or if the facility is a baseload facility, the downtime costs (due to lost generation) can be much higher than the tower rental costs, resulting in substantial overall savings for the project when modular cooling towers are used. As described in Chapter 8 of the Technical Development Document (TDD), EPA estimated that 100% of normal generating revenue will be lost during net c onstruction downtime; 11 however, in cases where modular towers are compatible with site conditions, this is likely an overestimate for facilities with long downtime periods, since it does not consider modular towers as an available cost
- saving option. The actual downtime costs would simply be the modular cooling tower rental costs for the period, including mobilization/demobilization costs. Modular cooling towers are also useful at facilities that are subject to periodic interruptions or reductions in the quantity of water withdrawn for cooling purposes, and can be a cost
- effective option for facilities that require supplemental cooling or flow reduction for onl y a portion of the year. 12 Limitations on Applicability This technology

is most appropriate for compliance technologies that involve major modifications to the intake structure or relocation of the intake inlet. There are limitations regarding the use of modular cooling towers at nuclear facilities and in conjunction with the installation of new coo ling towers
. At nuclear plants, the service water may be pumped from a combined service water and condenser cooling water intake, or it may be from a separate intake. Nuclear facilities have more stringent safety requirements for the service water s ys tem than for the condenser cooling water sy stem. The service water s ys tem is considered part of the emergency

and safety s ystem, which has very rigorous certification requirements regarding the manufacturing, installation, and maintenance of each component.

10 On e option for facilities that have tight space constraints is to place all or a portion of the tower units or pum ps on floating barges. Of course, use of barges may be limited by factors such as conflict with waterbody navigation or poor suitability of the adjacent waterbody for barge use. Figure 2 shows how mo dular towers can be laid out in a variety of configurations that may provide for more efficient use of space and use of space that might not be suitable for typical multi
- cell permanent towers. 11 For many facilities, EPA assumed that construction would be performed during a facility’s regularly scheduled maintenance outage (normally four weeks). 12 As described below , rental costs for multi
- year tower rental are assessed only for the period they are use d each year. Eventually, after many years, the total cost of tower rental will exceed the cost of permanent towers. The time that it takes to reach this point is much longer if towers are used for only a portion of the year than if they are used year
- round.12

Obtaining certification for a new technology can be a rather involved process with no guarantee that the technology will become certified. During intake construction downtime, the intake no longer functions as a cooling water source and thus, when modu lar towers are used during construction downtime to replace this cooling water, they

become the sole source. For this reason, it is unlikely that modular towers would be considered for situations where they would become at any time during plant operation the sole source of cooling water for the service water s ys tem at a nuclear facility
. At nuclear facilities where the condenser cooling water has a separate intake, the installation of modular towers would still be required to meet rigorous seismic and f ire control requirements. Even if these requirements were met, there may be a perception of modular towers as a “temporary technology” that could influence the Nuclear Regulatory Agency ’s decision to permit such a technology application. For the reason s discussed above, modular towers are not likely to be used as an alternate cooling water source to keep a nuclear plant operating during construction activities. It may , however, be possible to use them in situations where they function as an alternate s ource of cooling water where once
- though operation can be maintained as a backup, provided the technology

can meet the technical requirements. For facilities installing new (permanent) cooling towers, modular towers are also unlikely to prove useful. In order for modular towers to be used as an alternate source of cooling water during the construction downtime, space must be available for the towers and piping for both the permanent and modular towers. This essentially doubles the space required; most fa cilities would be unlikely to have this much available space. Implications for EPA ’

s Engineering Costs One difficulty of incorporating this potential construction cost
- saving option into the compliance technology

economic anal ys is is that there is insuff icient information to determine for which facilities and construction projects this technology would be viable. The primary

obstacle that may

limit the technology

viability is the availability

of sufficient space to place the modular cooling towers. However, this technology should be viable for more facilities than conventional permanent cooling towers because modular towers require somewhat less space and also allow for more flexibility in the placement of individual units, including the availability of alternatives such as placing some or all of the units on barges. Conventional cooling towers are generally too large to be installed on floating barges. In general, limitations on the availability of sufficient space for modular towers will be greatest at facilities that are located in higher density urban areas, where there is insufficient available space within the plant property boundaries as well as there being no undeveloped land adjacent to the plant that could be purchased and used for siting coo ling towers.13

Also, the elevation of the available land is an important consideration. Optimal locations for cooling towers should be at elevations that are not much higher than those of the generating unit condensers to ensure that pumping costs are ec onomicall y acceptable. Summary of Advantages and Disadvantages The advantages and disadvantages of modular c ooling towers (as compared to permanent cooling towers) are summarized below. Advantages include:

 Can be more economical than permanent towers where requirements for use are temporary or seasonal  Can be installed quickly  Can be installed with minimal site preparation  Can be installed without use of explosives that might be necessary for permanent tower concrete basins  May be available to more facilities because they require less space than conventional cooling towers  Can be installed in almost any configuration  Can be installed on barges  Can be used to provide temporary suppl y of cooling when ex isting i ntake is being modified  Rental cost includes e quipment maintenance and repair  Can be paid for using facility operating budget Disadvantages include:

 Economic benefit over permanent towers diminishes or disappears as period of use per ye ar or number of ye ars in use increase  Energy

requirements ( and thus operating costs ) are h igher than for permanent towers Analy sis The CUR at which the plant would have otherwise been operating during the downtime is an important factor in determining whether the lost generation cost would be high enough to justify using this technology

option during construction downtime
. To analyze how capacity utilization could affect this decision, the lost generation costs and total tower rental costs were calculated and then comp ared for different CUR values and different net downtime durations in weeks
. The typical generating capacity associated with each recirculating flow rate was calculated using the average cooling water requirement of 707 gpm per MW
. Lost revenue was assum ed to be $45/Mwh, based on an assumed wholesale value of $65/Mwh minus an assumed fuel cost of $20/Mwh
. The tower costs and lost generation costs were then calculated for different downtime durations in weeks14

and CUR values in increments of 10%
. The data were then reviewed to determine the minimum number of weeks for assumed CUR values at which the lost generation cost exceeded the tower rental costs. 13 Using an assumed value for cooling water requirements of 707 gpm/MW, a facility requiring 400 MGD of recirculating cool ing water (last row in Tables 1
- 3) would generate approximately

400 MW of electricity

at full power. Lost generation costs for the loss of 400 MW of electric power generation are estimated to be approximate $18,000/hr using the assumed value for lost revenue of $45/ MWh
. This is equivalent to a loss of $2.4 million dollars per week if the capacity utilization rate (CUR) is 80%
. Using this example, at $65/MWh, a reduction in the approach of 1.0  F (increase in efficiency of 0.12%) will increase revenue b y $3,120/hr or $419,000 per week at 80% CUR. Table 5 presents the results of the anal ys is and indicates that the use of temporary cooling towers to reduce downtime costs will not likely be cost
- eff

ective for construction projects with net downtime durations of less than 6 weeks for facilities with a high CUR during the downtime period
. Nor would temporary towers be economical for facilities with CUR values of <40% for the range of estimated constru ction downtime durations for most of the technology

cost modules considered by EPA
. Since most facilities would likely schedule the construction downtime to coincide with a period of time where power demand is lower, the CUR during the downtime period wil l likely be lower than the annual average CUR for the plant. Table 5

13 The lost revenue cost estimates derived here are intended only for obtaining a rough estimate of which ty pes of facilities would be likely to use such towers and for what minimum downtime periods would the use of rental towers be expected to be economical. Actual lost revenue costs are derived in the economic analysis using a much more detailed plant
- specific approach. Note that the relative costs of the towers compared to lost generation were generally the same regardless of the size of the system ( i.e., the DIF). CUR During Rental Period Breakpoint

(Weeks) 20% See Note* 30% 14 40% 11 50% 9 60% 7 70% 6 80% 6 90% 5 * Uneconomical - monthly tower costs almost equal to lost generation BreakPoint - When Lost Generation Cost Exceeds Rental Cost15

Table 6 presents a comparison of estimated downtime costs for a 400 MW and a 1000 MW power plant , assuming two different capacity utilization rates : one for a baseload plant (80%) an d one for an intermediate load plant (60%) . The net downtimes are based on EPA estimates for cost modules 4, 7, 12, and 14 , and are associated with relocation of intakes to a submerged offshore location
. These net downtimes are the net values after subtracting out a four
- week concurrent scheduled maintenance downtime event. Table 6 shows that downtime cost for longer durations can be reduced substantially by use of modular towers, especially at baseload facilities
. The last column is the break
- even point for these examples , similar to that shown in Table 5
. Table 6 Comparison of Estimated Downtime Costs for Use of Modular Tower Versus Plant Shut Down

As an example of the potential benefits of a lower tower design approach value , if the example 400 MW facility in row one of Table 5 is used along with the 0.12% (output increase /1.0  F) factor described above, the effect of reducing the cold water temperature by 1.0  F would be to increase plant revenue by up to $3,8 00,000 for the nine
- week period if this were to occur during a period of continuously elevated air temperatures
. Note that the benefit of increased generating efficiency is only available during periods when the wet bulb temperature is high enough to result in a turbine back
- pressure that is well above the design back
- pressure of the turbine. Conclusions In summary , modular towers are a technology that offers a potentially

significant reduction in facility

downtime related to compliance with the proposed rule
. Facilities that are able to install the modular towers may actually face no downtime at all, which would eliminate a significant component of the costs of the proposed rule and replace it with the smaller, temporary cost of modular tower rentals
. (See the Environmental and Economics Benefit Analysis for a discussion of the role of downtime costs in EPA’s estimation of national economic impacts.) However, EPA is not able to estimate how many facilities would be able to employ these modular towers, nor has it attempted to estimate the overall cost savings o f using them
. As a result, EPA has not adjusted its national cost estimates to include the use of modular cooling towers. Plant Size Design Intake Flow 1 CUR2 Net

Downtime 3 Downtime Co sts - Lost Revenue for Plant Shut Down 4 Modular

Tower Rental Modular

Tower Power Costs 5 Downtime

Total Cost Using Modular Towers Downtime Cost

savings for Using Modular Towers Percent

Reduction in Downtime Costs Break

Even NetDowntime MW MGD % Weeks Dollars Dollars Dollars Dollars Dollars % Weeks 400 407 80% 9 $21,800,000 $12,200,000 $1,600,000 $13,800,000 $8,000,000 37% 5.7 400 407 60% 9 $16,300,000 $12,200,000 $1,200,000 $13,400,000 $2,900,000 18% 7.4 1000 1018 80% 10 $60,500,000 $30,500,000 $4,300,000 $34,800,000 $25,700,000 42% 5.8 1000 1018 60% 10 $45,400,000 $30,500,000 $3,200,000 $33,700,000 $11,700,000 26% 7.4 1 Estimate based on average of 707 gpm/MW 2Capacity Utilization Rate During Downtime 39-10 Weeks is the net downtime for cost modules 4, 7, 12, and 14 4Based on CUR and net revenue loss of $45/MWh 5Based on CUR and power cost of $65/MWh16

References Blue Stream Inc ., Richard Brister
. Telephone contact record by John Sunda, SAI C
. Regarding technical requirements and costs of modular cooling towers
. May 30, 2008 a . Blue Stream Inc
. Email from Richard Brister to John Sunda, SAI C
. Re: Requ est for Modular Cooling Tower Cost Information In Support of EPA 316(b) Rule
. M ay 30, 2008 b
. Blue Stream Inc
. “Estimated Cooling Cost Chart” (attachment to May 30, 2008 email from Richard Brister to John Sunda, SAI C). Blue Stream Inc ., Richard Brister
. Telephone contact record by John Sunda, SAI C
. Regarding technical requirement s and costs of modular cooling towers
. June 10, 2008c. Blue Stream Inc ., Richard Brister
. Telephone contact record by John Sunda, SAI C
. Regarding modular tower energy requirements and approach
. March 25, 2009. Durmayaz, Ahmet and Sogut, Oguz
. Influence of Cooling W ater Temperature on the E fficiency

of Pressurized
- W ater Reactor Nuclear
- P ower Plant
. International Journal of Energy Research
. Vol. 30 No. 10. pp 799
- 810
. 2006. National Productivity

Council of India (NPCI)
. Guide Book 3

– Energy Efficiency in Electric Utilities
. Chapter 7

– Cooling Towers
. No Date
. A ccessed on March 25, 2009 at website: http://www.em
- ea.org/Guide%20Books/book
3/Chapter%203.7%20Cooling%20Tower.pdf
. EPA
. 316(b) Phase I

– Proposed Rule
. Economic and Engineering Anal ys es of the Proposed Rule
. Appendix A
. August 2000. EPRI
. Tower Calculation Worksheet
. September 17, 2007. Varitech Equipment Company
. Fact Sheet : VTECT
- ID3000 Portable Cooling Tower ( equipment specifications )
. A ccessed on May 30, 2008 at website: http://www.rentalcoolingtowers.com/product
- specifications.htm17

Figure 1. Intake Canal with Sheet Pile Wall, Forming a Closed Loop System18

Figure 2 . Example of Flexible Configuration