                                       

                                  MEMORANDUM



Tetra Tech, Inc.
10306 Eaton Place, Suite 340
Fairfax, VA 22030
phone	703-385-6000
fax	703-385-6007

TO:			Paul Shriner, EPA
FROM:		John Sunda (SAIC) and Kelly Meadows
DATE: 		March 11, 2011

SUBJECT:		Summary of Literature Review and New Developments Concerning Dry Cooling Including Data for Dry Cooling Installations in the U.S.

Alternatives to once-through cooling at power plants and manufacturers can include:
   * Closed cycle wet (evaporative) cooling alone.
   * Closed cycle hybrid wet/dry cooling where both evaporative cooling and indirect dry cooling is employed (e.g., hybrid plume abatement).
   * Closed cycle hybrid wet/dry cooling where both evaporative cooling and direct air cooled condensers are used.
   * Indirect dry cooling alone.
   * Direct air cooled condensers alone.

Except where used in conjunction with wet cooling, indirect dry cooling does not appear to be in use at any power plants in the US. Indirect dry cooling is however, used in numerous applications where it is combined with wet evaporative cooling (aka hybrid wet/dry). Such systems are used for plume abatement and/or for reduction of water consumption.  This memo focuses on the use of dry cooling as a stand-alone cooling system. 

Dry cooling is described and evaluated as a cooling system alternative in Chapter 4: Dry Cooling in the 316(b) Phase I Technical Development Document.  The chapter concludes that dry cooling is not technically or economically feasible for all facilities subject to Phase I and does not represent BTA. Compared to wet cooling, dry cooling would increase air emissions due to the energy penalty, cost more than three times more, and would not significantly reduce impingement mortality or entrainment.

A review of government guidance for European power plants indicates that they have reached a similar conclusion: that dry cooling technologies should only be used where water is in extreme short supply (EU 2001. Environmental Agency UK 2010.) Another report noted that "[c]urrently, dry cooling is used, or viewed as an option of last resort, where water is very costly or limited in availability." (Wolfe 2008).  

The GAO report "Energy-Water Nexus" (GAO 2009) does not focus on consumptive use as an issue for energy production but does include a table of relative withdrawal/ consumption rates for different cooling system types.  It also states that certain important data (including cooling technology and use/consumption by technology) is no longer being collected by USGS or EIA.  The report touches on regulatory compliance issues, as well as space, noise and suitability of technologies; it speaks of facilities balancing the positive and negative tradeoffs of using different power generation and cooling.  It also discusses energy penalties.  The recommendations in the report focus mostly on data collection.

Spray Cooling of Inlet Air for Reduced Energy Penalty

Dry cooling system performance can be enhanced by pre-cooling inlet air using a fine mist spray of water. Cooler air passing though the heat exchanger will result in lower steam turbine backpressures with a corresponding increase in turbine efficiency. System does result in some water consumption but would be used intermittently during periods of high air temperatures with a typical water consumption rate of about 25% of that for wet cooling (Maulbetsch et al 2008).

Comparison of Wet and Dry Cooling Cost

For new power facilities, dry cooling costs can average about 5 times the costs of wet cooling. Multipliers can vary widely based on site-specific conditions and can be as high as 10 times or more the cost of wet cooling. A good analysis of wet versus dry cooling costs can be found in the 2002 EPRI report "Comparison of Alternate Cooling Technologies for California Power Plants" prepared for the California Energy Commission (EPRI 2002). The following text is from the report's abstract:

       "This study defines, explains, and documents the cost, performance, and environmental impacts of both wet and dry cooling systems. A survey of the cooling system literature is provided in an annotated bibliography and summarized in the body of the report. Conceptual designs are developed for wet and dry cooling systems as applied to a new, gas-fired, combined-cycle 500-MW plant (170 MW produced by the steam turbine) at four sites chosen to be representative of conditions in California. The initial capital costs range from $2.7 to $4.1 million for wet systems using mechanical-draft wet cooling towers with surface steam condensers and from $18 to $47 million for dry systems using air-cooled condensers.
       
        Cooling system power requirements for dry systems are four to six times those for wet systems. Dry systems, which are limited by the ambient dry bulb temperature, cannot achieve as low a turbine back pressure as wet systems, which are limited by the ambient wet bulb. Therefore, heat rate penalties and capacity limitations are incurred at some sites depending on local meteorology." (EPRI 2002).

Dry Cooling and California

California doesn't have an explicit requirement that requires dry cooling, but has several regulatory frameworks that make it the de facto policy. The State Water Board issued a policy in the 1970s directing any new power plant to investigate alternative cooling water sources and technologies before they could be permitted to use freshwater in once through cooling. The policy also has the effect of pushing industrial cooling down the priority scale compared to freshwater use, behind municipal, agriculture, and recreation, raising the question of whether there is enough water to satisfy all of these demands. For marine locations, the Coastal Act is applicable, which emphasizes maintaining and restoring coastal resources. Although it does make an exemption for "coastal dependent" industry, the Coastal Commission and the State Lands Commission have made it clear that they will not authorize any new once-through cooling facilities. 

The Gateway project in Antioch and the Willow Pass facility nearby (http://www.energy.ca.gov/sitingcases/willowpass/) are located in the Sacramento/San Joaquin Delta, where water use is a major issue. Both are new facilities. There are several threatened & endangered species present in the area, likely contributing to the conclusion that dry cooling is the most appropriate technology. 

It is widely recognized that dry cooling is the primary option for new facilities except in those locations where reclaimed water is available. Few facilities even attempt to apply for new once-through or wet cooling permits anymore. The bottom line is that for new facilities, dry cooling is technologically and economically competitive with wet cooling when factoring in environmental compliance issues. 

Dry Cooling and New York

In the past 10 years, six power generation systems were installed with dry cooling in the state of New York.   Outside of New York City, these include:
   *  The new 350 MW combined cycle Caithness Long Island Energy Center 
   * The new 1,080 MW combined cycle Athens Power station. 

In the New York City area, air-cooled condensers are favored by siting authorities. New York City area facilities include:
   * A 500 MW combined cycle plant constructed by Astoria Energy LLC adjacent to the existing Charles Poletti Plant came online in 2006. The Charles Poletti Plant was closed in January 2010.
   * A second 500 MW combined cycle plant will be constructed adjacent to the existing Astoria Energy LLC facility is planned to come online in 2011.
   *  The Astoria Energy Center, a 500 MW combined cycle plant located one mile from the Charles Polleti Plant constructed on the site of an old oil terminal. 
   * The KeySpan Corp's 250-MW combined cycle expansion at the existing 2,160 MW facility at Ravenswood completed in 2004 was space constrained requiring the dry cooling system to be located on the roof.
   * The Astoria Repowering Project is a project currently under development that will replace 31 existing simple cycle turbines with a capacity of 600 MW with four new combined cycle units with a proposed capacity 1,040 MW.

Disadvantages of Dry Cooling in a Retrofit

1.	Cost effectiveness. Increasing flow reduction from 95% to 99% does not significantly reduce impingement mortality or entrainment reduction in relation to wet cooling towers, especially when dry cooling costs many times more.
2.	Efficiency. Total energy penalties can double for dry cooling versus wet cooling, although the gap may be less in colder climates. With dry systems, the dry bulb temperature is the governing variable as opposed to wet systems (which depend on wet bulb temperature). Since dry bulb is always greater than wet bulb (can be equal at 100% saturation) and dry systems have a narrower cooling range, dry systems will always have higher steam condensing temperatures than wet. 
3.	Configuration. There are two options in a dry system: air cooled condensers (ACC) and indirect. ACC operates like a car radiator in that the system is a sealed loop that exhausts steam from the turbine directly to the radiator fins where it is condensed and returned to the boiler. The ACC configuration is limited because, ideally, the ACC is placed close to the turbine exhaust point in order to maintain the necessary pressure through the system. The indirect dry system places a heat exchanger between the turbine exhaust point and the cooling tower. Water or some other fluid circulates between the tower and the surface condenser. This is less efficient than an ACC and requires a larger tower, increasing the energy penalty. An indirect system is also limited in terms of distance (although not as much as an ACC) since pressure must be maintained through the sealed loop. Indirect systems are the only plausible configuration for retrofits at power plants and many manufacturers since they already have a surface condenser in place. Retrofitting to an ACC would require substantial modifications to the system, approaching the cost and complexity of a repower.
4.	Unprecedented. There is no evidence that any facility has ever done a retrofit to dry cooling. Recognizing that technology options are different for new and existing facilities, it is difficult to make the case for dry cooling's feasibility since there are no known case studies anywhere in the world.


Summary of Dry Cooling Installations in the US

Both GEA and SPX have been the main suppliers of large dry cooling systems (both direct and indirect cooling systems) in the US.  However, when asked about indirect cooling installations in the US, a GEA representative said that that they are not aware of any installed in the US and that their Hungary office supplies indirect dry cooling systems.

Attachment A presents a list of direct air-cooled condensers installations from 1968 to 2010 provided by GEA Power Cooling, Inc.  This list includes 61 installations in the US with 20 installed from 2000 to 2009.  Only six (15%) of the 41 projects prior to 2000 had generating capacities of 100MW or greater.  Whereas 13 (65%) of the 20 from 2000 to 2009 had generating capacities of 100MW or greater. Thirteen of the recent 20 were combined cycle plants, four were coal-fired and the remaining three were waste-to-energy and cogeneration plants. 

Attachment B presents a list of direct air-cooled condensers installations in the US from 1968 through 2006 from all vendors provided to EPA by EPRI.  This list includes 73 facilities. When the six recent (2006 through 2009) facilities on the GEA list are added, the total becomes 79 facilities.

Table 1 provides the distribution of dry cooling installations and total capacity by state and region from 2000 through 2009 based on the 79 installations from both the GEA and EPRI lists. Based on the combined data approximately 74% of the total steam capacity was installed in the period from 2000 through 2009. As can be seen in Table 1, the greatest concentrations of dry cooling capacity are located in the northeastern and southwestern regions of the US.


                                    Table 1
Number and Total Capacity of Dry Cooling Condenser Systems Installed from 1968 through 2010 by State
                                    Region
                                     State
                             Number of Facilities
                           Total Steam Capacity MWe
                           Total Steam Capacity MWe
                              Northwestern States
                                      AK
                                       3
                                      80
                                     1,443

                                      MT
                                       1
                                      42


                                      WA
                                       3
                                      306


                                      WY
                                       6
                                     1,015

                             North Central States
                                      MN
                                       2
                                      61
                                      120

                                      MI
                                       1
                                       9


                                      IL
                                       2
                                      10


                                      IA
                                       1
                                      40

                              Northeastern States
                                      CT
                                       2
                                      305
                                     4,124

                                      MA
                                      11
                                     1,485


                                      ME
                                       2
                                      100


                                      NJ
                                       3
                                      429


                                      NY
                                      13
                                     1,288


                                      PA
                                       3
                                      438


                                      RI
                                       1
                                      80

                              Southwestern States
                                      AZ
                                       1
                                       3
                                     3,777

                                      CA
                                       7
                                      558


                                      CO
                                       2
                                      900


                                      NM
                                       1
                                      148


                                      NV
                                       5
                                     1,050


                                      TX
                                       3
                                      880


                                      UT
                                       1
                                      200


                                      HI
                                       1
                                      38

                              Southeastern States
                                      MS
                                       1
                                      350
                                      755

                                      VA
                                       2
                                      325


                                      WV
                                       1
                                      80

                                     Total
                                       
                                      79
                                    10,220
                                    10,220
                                       
References

EU. European Commission. Integrated Pollution Prevention and Control (IPPC).
Reference Document on the application of Best Available Techniques to Industrial Cooling Systems. December 2001.
http://eippcb.jrc.es/reference/cv.html

GAO. Energy-Water Nexus: Improvements to Federal Water Use Data Would Increase Understanding of Trends in Power Plant Water Use October 2009
GAO-10-23
http://www.gao.gov/new.items/d1023.pdf

Environmental Agency UK. "Cooling Water Options for the New Generation of Nuclear Power Stations in the UK." 2010.

Electric Power Research Institute. Comparison of Alternate Cooling Technologies for California Power Plants Economic, Environmental and Other Tradeoffs. Prepared For:
California Energy Commission. February 2002
500-02-079F
http://www.energy.ca.gov/reports/2002-07-09_500-02-079F.PDF

"Astoria Energy Project Queens, NY SCS Energy LLC. Taking Modularization To The Next Level." Combined Cycle Journal, Fourth Quarter 2006.
http://www.scsenergyllc.com/ccjournal.pdf

Ravenswood Expansion
http://www.emersonprocess.com/home/library/articles/ccj/ccj03q4_ravenswood.pdf

Air Resources Group, LLC. Astoria Repowering - Draft Environmental Impact Statement EIA. April 16, 2010
http://www.nrgenergy.com/news-center/astoria/pdf/Binder%20I%20--%20DEIS/01%20DEIS.pdf

Riverkeeper. "Comprehensive Survey and Investigation of Dry Cooling Systems to Reduce I and E." (in P2 Docket)

Wurtz, W. SPX Cooling Technologies Inc. and Peltier, R. PhD PE. "Air-Cooled Condensers Eliminate Plant Water Use. Power Magazine. September 15, 2008. 
http://www.powermag.com/water/Air-cooled-condensers-eliminate-plant-water-use_1361.html

Wolfe, J.R., Phd, PE, Limno-Tech. "Costlier, Scarcer Supplies Dictate Making Thermal Plants Less Thirsty." Power Magazine January 15, 2008.
http://www.powermag.com/issues/features/105.html

Maulbetsch, J.S, DiFilippo M. N., Zammit K. D. "Spray Cooling for Performance Enhancement of Air-Cooled Condensers." EPRI Advanced Cooling Workshop. August 9, 2008. http://mydocs.epri.com/docs/AdvancedCooling/PresentationsDay2/7_070908%20Spray%20Enhance%20Presentation%20Day%202_Zammit.pdf



                                 Attachment A
                    GEA Air Cooled Condenser Installations
                             (See pdf Attachment)
                                       

                                 Attachment B 
                  Air Cooled Condenser Installations from EPRI
                                       
