Tetra Tech, Inc.

10306 Eaton Place, Suite 340 Fairfax, VA 22030 phone 703
- 385
- 6000 fax 703
- 385
- 6007 DATE: January

15, 2009 TO : Paul Shriner and Jan Matuszko, EPA FROM : Peter Sherman, Tetra Tech and John Sunda, SAIC SUBJECT: Combined Cycle Power Generation Under 316(b) Phase II This memo presents information regarding sy stems , including information cooling water and the number II rule

. Cooling Water Use at Combined Cycle Power Plants Combined Cycle electric power generating s ys tems use a two process. The most common arrangement is a configurat by two combustion gas

- driven turbine turbines then being used to produce steam in a single heat (HRSG). The steam from the HRSG produces electricit y turbine generator. The overall thermal efficiency of combined cycle generating units is 50% to 60%. Conventional coal 40%. Since the combustion turbine component does power generation component produces only about one generated, combined cycle plants 67% reduction) as a similar capacity co 2002). Thus, replacing a conventional steam generation system with a combined cycle generati on sy stem of the same power generation capacit y could reduce cooling water flow by up to 67%. The data in the EPRI consistent with this estimate. 

### MEMORANDUM

10306 Eaton Place, Suite 340

January 15, 2009 Paul Shriner and Jan Matuszko, EPA Peter Sherman, Tetra Tech and John Sunda, SAIC Combined Cycle Power Generation Under 316(b) Phase II This memo presents information regarding the combined cycle electric power production , including information on how combined cycle s ys tems could reduce demand for

the number of combined cycle sy stems potentially subject to the Phase
Cooling Water Use at Combined Cycle Power Plants Combined Cycle electric power generating s ys tems use a two

- stage power generation process. The most common arrangement is a configurat ion where electricity is produced driven turbine

- generators with the hot exhaust gas from these turbines then being used to produce steam in a single heat

- recovery steam generator (HRSG). The steam from the HRSG produces electricit y using a single steam turbine generator. The overall thermal efficiency of combined cycle generating units is 50% to 60%. Conventional coal

- fired plants have a ty pical thermal efficiency

of 36% to
Since the combustion turbine component does not require cooling water and the steam power generation component produces only about one

- third of the total electric energy generated, combined cycle plants should require about a third as much cooling water (i.e., 67% reduction) as a similar capacity co nventional steam

- driven power plant (Micheletti conventional steam generation system with a combined cycle of the same power generation capacit y could reduce cooling water The data in the EPRI study presented below appears to be reasonabl y consistent with this estimate.

1 power production could reduce demand for of combined cycle sy stems potentially subject to the Phase

stage power generation ion where electricity

is produced generators with the hot exhaust gas from these

recovery steam generator using a single steam

- driven turbine generator. The overall thermal efficiency of combined cycle generating units is fired plants have a ty

pical thermal efficiency

of 36% to
not require cooling water and the steam third of the total electric energy require about a third as much cooling water (i.e.,

driven power plant (Micheletti conventional steam generation system with a combined cycle of the same power generation capacit y could reduce cooling water study presented below appears to be reasonabl y2

According to an EPRI report (2002) addressing water and sustainabilit y, 1 combined cy cle electric power facilities withdraw approximately 54% to 60% less water than comparable facilities that do not use combined cy cle technology . In the study , EPRI determined the water withdrawal and water consumption rates per unit of power g eneration for several categories of facilities (See Table 1 below). Although this study focused on water consumption (loss due to evaporation), it also developed water withdrawal data ranges for steam

- based and combined cycle facilities using several t ype s of cooling water sy stems. For the facilities using once

- through cooling s ys tems, the combined cycle sy stem water withdrawal rates were approximately 38%

- 40% of the water withdrawal rates of those facilities using a single cy cle (steam) power generation process. Similarly , for the facilities using cooling towers, the combined cy cle s ys tem water withdrawal rates were approximately

38%

- 46% of the water withdrawal rates of those facilities using a single cy cle power generation process. The facilities using combined cy cle technology and cooling towers had the lowest overall cooling water withdrawal rate.
Table 1. EPRI Report Data on Average Water Withdrawal and Consumption Based on Cooling Design Fuel Prime Mover Cooling System Water Withdrawal

(gal/MWh) Water

Consumption (gal/MWh) Fossil/biomass/waste Steam Once through 20,000 to 50,000 ~ 300 Fossil/biomass/waste Steam Cooling pond 300 to 600 300

- 480 Fossil/biomass/waste Steam Cooling towers 500 to 600 ~ 480 Nuclear Nuclear steam Once through 25,000 to 60,000 ~ 400 Nuclear Nuclear steam Cooling pond 500 to 1100 400

– 720 Natural gas/oil Combined cycle Once through 7500 to 20,000 ~ 100 Natural gas/oil Combined cycle Cooling towers ~ 230 ~ 180 Natural gas/oil Combined cycle N ot specified ~ 0 ~ 0 Coal/petroleum residuum Combined cycle Cooling towers ~ 380 ~ 200
Source: Water & Sustainability (Volume 3): U.S. Water Consumption for Power Production

— The Next Half Century, EPRI, Palo Alto, CA: 2002. 1006786
Currently , most combined cy cle generating sy stems use natural gas or fuel oil as the fuel source (t ypical new facilities use natural gas)

. The use of natural gas also results in the lowest air emissions of commonly used fuels

. The 2009 EIA Energy Outlook (earl y release) projects that natural gas (55%) and renewable sources (22%) will provide most of the 255 gigawatts of generating capacity projected to be added between 2007 and 2030. A new technology in the developmental stage called Integrated C oal Gasification Combined Cy cle (IGCC) uses coal a s the fuel source. These sy stems first convert coal to a gas and then use the gas to generate electricity in a similar manner as conventional combined cy cle s ys tems. Due to the energy requirements of the additional processes, the

1 Water & Sustainability (Volume 3): U.S. Water Consumption for Power Production

— The Next Half Century, EPRI, Palo Alto, CA: 2002. 1006786.3

thermal efficiency

of IG CC sy stems is not quite as high as for conventional combined cy cle, but may

reach up to 50%. Similarly , flow reduction isn’t quite as high

- IGCC sy stems us e 20

- 50% less water compared to a conventional (non

- combined cy cle) coal power station of similar s ize (CCSD 2008). There are currently

two IGCC plants operating in the US and both have been in operation since the mid 1990s and thus are included in EPA’s Phase II plant database. These are the Tampa Electric Power Station's 250 MW Polk I I GCC plant that went online in 1996 (EIA Plant ID #7242) and the Wabash River Repower IGCC project that went online in 1995 (EIA Plant ID #1010). IGCC is a relativel y new technology and, as such, has presented issues of reliability , cost, and water pollution in earl y applications. It is too earl y for this to be considered a mainstream technology

. Single

- cy cle power plants using gas, oil or coal as a primary fuel can be retrofitted with a heat recovery

steam generator (HRSG) that makes combined

- cy cle operations pos sible. Ty pically , combined

- cy cle retrofitting involves retiring the original boiler and replacing it with a gas turbine. The original steam turbine and feedwater heaters are usually retained. Such retrofitting enables a power producer to increase its el ectrical output without building entirely

new facilities because of the increased thermal efficiency of combined cy cle technology

. Impediments to such retrofits include the capital costs, as well as the higher cost (relative to coal) and availability of n atural gas as fuel

. Use of Combined Cycle Power Generation in Phase II The information presented in Tables 2 and 3 below summarize available DOE EIA data for steam generating units at Phase II facilities. The generating capacity data summarized is for generating units that use steam as a prime mover in the generating process and generating units that are coupled with such units. These include the following prime mover codes:

 ST

- steam turbine that is not combined cycle;
 CT

- combustion turbine compon ent of combined cy cle;
 CA

- steam turbine component of combined cy cle;
 CS

- combined cy cle generator driven by both steam turbine and combustion gas turbine. In this analy sis, total combined cy cle generating capacity is calculated by

summing the nameplate capacit y for all operating facility generating units with prime movers CS, CA, and CT. The generating capacity for the steam turbine

- only category is calculated by summing the nameplate capacity for all facility

generators with prime mover ST. The generating unit nameplate capacit y is obtained from the EIA 2006 generator database. A review of the 2006 EIA generator data indicates that 44 (8%) of the population of 525 facilities in the Phase II database operate combined cycle generating units. Table 2 presents the estimated number of facilities in the Phase II universe that operate various combinations of the different ty pes of steam generating units. The estimated numbers are4

extrapolated from data for the population of 525 facilities in the database to the total universe of 536 facilities using facility sample weights. The combined cycle component of those facilities with both ty pes of steam generating units ranges from 22% to 95%. The 2006 EIA generator database indicated that the steam ge nerating units for six of the plants currentl y included in the Phase II database (Table 2 weighted total = 7) were permanentl y retired. It is possible that the cooling water withdrawal rate for these plants may no longer be large enough (i.e., >50 MGD) fo r them to be considered as in

- scope Phase II facilities.
Table 2. Estimated Number of Facilities in

the Phase II Universe by Steam Generation Type Steam Generation Ty pe Estimated Number

of Facilities Steam Turbine Only 484 Combined Cycle Only 20 Both Steam Turbine and Combined Cycle 25 No Steam (mostly

gas turbines)* 7 Total Universe

- All Plants 536
*T hese plants operated steam turbine generating units in 2000 and the plants are still in operation but have since retired all steam turbine generation units. Table 3 lists the population of facilities in the Phase II database that operated combined cy cle generating units in 2006. The table presents total combined cy cle generating sy stem nameplate capacity for generating units with the prime movers CT, CA, and CS in the 2006 EIA generator database. Table 3 also shows the proportion of total steam generating capacity

(sum of ST, CT, CA, and CS) that is comprised by the combined cy cle generating s ys tem.5 Table 3 . Population of Facilities in the Phase II Database with Combined Cycle Generating Units

3 900 34% 201 185 100% 260 1398 50% 399 227 100% 400 604.3 35% 533 654 100% 612 1644 100% 613 1042.4 100% 620 2720 95% 643 619.7 65% 658 30 22% 675 126.5 100% 676 369 38% 689 247 83% 693 58 37% 862 647.3 100% 1007 328 100% 1010 305 26% 1404 226 48% 1588 1744.4 74% 1595 253.6 100% 1904 325 53% 2079 306.8 34% 2406 1186 77% 2465 24.6 49% 2493 360 50% 2539 893.1 100% 2708 102 24% 2951 247 25% 3236 515 100% 3295 547.8 85% 3527 126 100% 3631 189.6 88% 3797 446.6 25% 3804 613 33% 4040 579 100% 6042 1224.6 41% 6043 2448.5 59% 6112 742.6 100% 7242 326.3 100% 10617 107.8 100% 10745 1848.6 100% 54785 192.6 100% 54914 322 100%

Combined Cycle Nameplate Capacity (MW) EIA Facility Code Percent of Total Steam Capacity6

References Micheletti, W. Burns, J. Emerging Issues and Needs in Power Plant Cooling S ys tems. www.netl.doe.gov/publications/proceedings/02/EUW/Micheletti_JMB.PDF CCSD. Cooperative Research Centre for Coal in Sustainable Development

. IGCC Power Generation Fact Sheet. Accessed on December 19, 2008 at website: http://www.ccsd.biz/factsheets/igcc.cfm Wabash River Energy

L td . Wabash River Coal Gasification Repowering Project

- Final Technical Report. August 2000. Accessed at website: http://www.netl.doe.gov/technologies/coalpower/cctc/cctdp/bibliograph y/ demonstration/ pdfs/wabsh/Final%20_Report.pdf U.S. Department of Energy (U.S. DOE). Energy

information Administration (E IA). Form EIA

- 860 Database (2006). Generator Database.