August 2008 (April 2009 Revision)

DOE/NETL-402/080108 

Water Requirements for Existing and Emerging 

Thermoelectric Plant Technologies 
Disclaimer

This report was prepared as an account of work sponsored by an agency of the 

United States Government. Neither the United States Government nor any 

agency thereof, nor any of their employees, makes any warranty, express or 

implied, or assumes any legal liability or responsibility for the accuracy, 

completeness, or usefulness of any information, apparatus, product, or process 

disclosed, or represents that its use would not infringe privately owned rights. 

Reference therein to any specific commercial product, process, or service by trade 

name, trademark, manufacturer, or otherwise does not necessarily constitute or 

imply its endorsement, recommendation, or favoring by the United States 

Government or any agency thereof. The views and opinions of authors expressed 

therein do not necessarily state or reflect those of the United States Government 

or any agency thereof. 
Water Requirements for Existing and Emerging 

Thermoelectric Plant Technologies 

DOE/NETL-402/080108 

August 2008 

Revised April 2009 

NETL Contact: 

Phil DiPietro 

Office of Systems, Analyses & Planning 

National Energy Technology Laboratory (NETL) 

Prepared by: 

Kristin Gerdes 

Christopher Nichols 

Office of Systems, Analyses & Planning, NETL 

National Energy Technology Laboratory 

www.netl.doe.gov 

 i 
Table of Contents

Executive Summary ........................................................................................................... 1 

1 Background .................................................................................................................. 2 

1.1 Water Usage in Thermoelectric Plants.................................................................. 2 

1.2 Objective .............................................................................................................. 3 

1.3 DOE Water Reduction Effort ............................................................................... 3 

2 Cooling Water Systems................................................................................................ 3 

3 Water Requirements for Power Generation Platforms .............................................. 5 

3.1 Data Sources and Comparison..................................................................................... 5

3.2 Subcritical and Supercritical PC plants...................................................................... 7

3.3 IGCC plants................................................................................................................... 8

3.4 NGCC plants ............................................................................................................... 10

3.5 Nuclear Plants ............................................................................................................. 11

4 Carbon capture and water usage............................................................................... 11 

4.1 Water consumption factors........................................................................................ 13

4.2 Cooling water duty factors......................................................................................... 15

5 Next Steps................................................................................................................... 17 

Appendix A ..................................................................................................................... A-1 

Appendix B ..................................................................................................................... B-2 

References...................................................................................................................... R-1 

 ii 
List of Tables 

Table ES-1. Water consumption and cooling duty factors for thermoelectric power plants.......... 1

Table 3-1. Water intensive processes utilized by different IGCC gasifier designs3 ..................... 10

Table 4-1. Impact of efficiency and water use by CDR equipment on water consumption 

associated with carbon capture for plants using wet recirculating cooling towers...................... 14

List of Figures 

Figure 1-1. Water flow schematic for power plants....................................................................... 2

Figure 2-1. Cooling water system configurations.......................................................................... 4

Figure 2-2. Average total cost and number of cooling systems by type .......................................... 5

Figure 3-1. Water consumption for nuclear and greenfield bituminous coal and natural gas 

thermoelectric power plants utilizing wet cooling towers............................................................... 6

Figure 3-2. Water flow schematic for a greenfield subcritical pulverized coal power plant 

utilizing a wet cooling tower and a wet FGD.................................................................................. 7

Figure 3-3. Water flow schematic for a greenfield supercritical pulverized coal power plant 

utilizing a wet cooling tower and a wet FGD.................................................................................. 8

Figure 3-4. Water flow schematic for a greenfield IGCC plant utilizing a wet cooling tower....... 9

Figure 3-5. Water flow schematic for a greenfield NGCC plant utilizing a wet cooling tower.... 10

Figure 3-6. Water flow schematic for a nuclear plant utilizing a wet cooling tower6 ................. 11

Figure 4-1. Comparison of net plant efficiencies (HHV basis) with and without CDR3.............. 12

Figure 4-2. Comparison of water consumption factors with and without carbon capture for 

greenfield plants using wet recirculating cooling towers – net power basis ................................ 13

Figure 4-3. Comparison of water consumption factors with and without carbon capture for 

greenfield plants using wet recirculating cooling towers – thermal input basis........................... 15

Figure 4-4. Comparison of cooling water duty factors for greenfield plants – net power basis . 16

Figure 4-5. Comparison of cooling water duty factors for greenfield plants – thermal input basis

....................................................................................................................................................... 17

 iii 
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 iv 
Executive Summary 

In light of the critical relationship between power generation and water, it is necessary to 

understand the water-related impacts associated with deployment of the advanced power 

platforms included in the National Energy Technology Laboratory (NETL) research 

program. Table ES-1 shows water consumption and cooling duty factors for several 

power generation platforms, with and without carbon dioxide (CO2) capture. There is 

almost a fourfold increase in water consumption per net kWh between the lowest water 

consuming platform (NGCC) and the highest (Nuclear). Also the addition of CO2

capture and compression increases water consumption by 50% to 90%. Many of the 

advanced power platforms use less water and have a lower increase in water demand 

associated with incorporation of CO2 capture equipment than do current technologies. 

The water consumption factors in Table ES-1 are based on a cooling system in which the 

effluent cooling water from the steam cycle condenser and other water coolers is cooled 

in an evaporative cooling tower and re-circulated. “Consumption” represents water that 

must be made up to account for both evaporation in the cooling tower and a relatively 

small amount that is consumed in unit operations within the generation process. Table 

ES-1 also presents cooling duty factors, or thermal cooling load per kWh of net 

generation. These factors enable one to estimate the impacts of different cooling water 

system configurations (e.g., once-through, wet cooling, dry cooling). The percent change 

with the addition of CO2 capture is different for cooling duty and water consumption 

because cooling duty does not include process water requirements. 

Table ES-1. Water consumption and cooling duty factors for thermoelectric power plantsi

Without CO2

Capture 

With CO2

Capture 

% Change With 

CO2 Capture 

Water Consumption Factors (gallons per MWh net power)*

Nuclear 720 -- 

Subcritical PC 520 990 +90% 

Supercritical PC 450 840 +90% 

IGCC, slurry-fed 310 450 +50% 

NGCC 190 340 +80% 

Cooling Duty Factors (MMBtu per MWh net power)

Subcritical PC 4.7 11 +130% 

Supercritical PC 4.1 9.3 +130% 

IGCC, slurry-fed 3.0 3.7 +20% 

NGCC 2.0 4.2 +110% 

* Based on a cooling water system utilizing wet recirculating cooling towers

 

i

 Factors derived from the NETL Report “Cost and Performance Baseline for Fossil Energy Power Plants 

study, Volume 1: Bituminous Coal and Natural Gas to Electricity”; adjustments described in Appendix A. 

Water Requirements in Emerging Thermoelectric Plant Technologies 1
The factors in Table ES-1 are developed for the purpose of deriving the water-related 

impacts from different power plant deployment scenarios, such as those forecasted by the 

National Energy Modeling System (NEMS) and MarKal models. The body of this report 

presents the calculation methodologies and data sources used to estimate the factors set 

forth in Table ES-1. This information will enable analysts to adjust the factors to 

represent the impact of advanced technologies in the areas of power generation, CO2

capture and compression, and cooling water systems. 

1 Background 

Water, once considered a nearly inexhaustible resource, is increasingly limited, and water 

requirements for electricity production must compete with other demands, such as 

agriculture and sanitation. The 2007 drought in the southeastern U.S. underscored this 

issue with several nuclear power plants in the region reducing their output by up to 50% 

due to low river levels in August 2007.1 Future water-related impacts on the industry 

may also come in the form of regulation. The Environmental Protection Agency is 

developing regulations under §316(b) of the Clean Water Act that will require the 

location, design, construction and capacity of cooling water intake structures to reflect the 

best technology available for minimizing adverse environmental impact. 

1.1 Water Usage in Thermoelectric Plants 

The water-related impacts of fossil fuel thermoelectric power plants are a function of 

(1) the cooling and process water needs, and (2) the system used to provide the cooling 

water. Thermoelectric power plants use water primarily to cool and condense the steam 

used to drive the turbines, with relatively minor amounts of water used for process steam 

make-up and other water-intensive processes, Figure 1.1-1. 

Figure 1.1-1. Water flow schematic for power plants 

Water Requirements in Emerging Thermoelectric Plant Technologies 2
About 43% of existing thermoelectric power plant generating capacity employ a oncethrough cooling water system where water is drawn from a water body, used to condense 

steam, and then returned at a higher temperature.2

 More recently once-through cooling 

water systems have incorporated cooling towers that lower the temperature of the 

discharge water. Further reduction in water withdrawal can be achieved in a recirculating 

system where the bulk of the water is cooled in evaporative cooling towers and reused 

with a lesser amount discharged and made up. A still further reduction in water use is 

possible in dry cooling systems – beneficial for arid regions – that use closed loop air 

cooling thus eliminating losses due to evaporation. 

1.2 Objective 

In December 2006, NETL participated in a Department of Energy (DOE)-wide peer 

review of the analyses that are conducted to show the benefits of the DOE research and 

development portfolio. One of the recommendations from the peer review panel was for 

DOE to consider the water-related impacts associated with advanced thermoelectric plant 

technologies. This report provides the water use factors for use in deriving the waterrelated impacts from different power plant deployment scenarios, such as those 

forecasted by the National Energy Modeling System and MarKal models. 

1.3 DOE Water Reduction Effort 

This report highlights the water-related advantages of advanced power platforms within 

the NETL research portfolio. However, due to the critical relationship between power 

generation and water, NETL has also initiated a research program to specifically develop 

advanced technologies to reduce water consumption by thermoelectric power systems. 

The NETL Existing Plants – Emissions and Capture (EPEC) program contains a diverse 

research portfolio of water projects that have the potential to significantly reduce the 

water-related impacts of thermoelectric plants. The EPEC program focuses on four 

technology pathways: (1) use of nontraditional sources of process and cooling water; (2) 

innovative water reuse and recovery; (3) advanced cooling technologies; and (4) 

advanced water treatment and detection technology. Many of the efforts involve 

integration with existing power plant operations, but are also applicable to advanced 

thermoelectric technologies. More information on the NETL efforts can be found at: 

http://www.netl.doe.gov/technologies/coalpower/ewr/water/index.html

2 Cooling Water Systems 

For a cooling water system, water usage can be described as either consumption such as 

the water evaporated to the atmosphere in a cooling tower or withdrawal which is equal 

to consumption plus any water returned to its source. There are two basic cooling system 

configurations – once-through and recirculating, Figure 2-1. In a once-through cooling 

system, water from an external water source passes through the steam cycle condenser 

and is then returned to the source at a higher temperature with some level of 

contaminants. This system withdraws a significant amount of water, but consumes little 

at the plant site (evaporation may, however, occur after the water is returned to its 

source). To minimize the thermal impact to the water source, a cooling tower may be 

added in a once-through system to allow air cooling of the water (with associated losses 

on site due to evaporation) prior to returning the water to its source. 

Water Requirements in Emerging Thermoelectric Plant Technologies 3
In a recirculating system, cooling water exits the condenser, goes through a fixed heat 

sink and is then returned to the condenser. This configuration results in relatively low 

water withdrawal, but consumption occurring at the plant site is high relative to a oncethrough configuration. Typical heat sink options for recirculating systems are mechanical 

or natural draft cooling towers and cooling ponds. In cooling towers, the water is cooled 

by the air to near the wet-bulb temperature using the principle of evaporation. Water 

flows over high surface area packing which serves to increase contact time with the air 

and maximize heat transfer. Mechanical draft cooling towers use fans to push or pull air 

through the towers, while natural draft cooling towers utilize large concrete chimneys 

facilitating a natural air current up the tower. While they require less power, natural draft 

towers are extremely large and generally only used at facilities with high cooling water 

requirements. 

Once-Through Recirculating 

Wet Cooling Dry Cooling 

Wet Cooling Tower 

Cooling 

Requirement 

Natural Draft Mechanical Draft 

Cooling Pond Indirect Direct 

Dry Cooling Tower 

Figure 2-1. Cooling water system configurations 

Make-up water to the cooling tower is required to replace the water that evaporates to the 

atmosphere. Evaporation losses are typically the largest contributor to water 

consumption in a cooling tower system and can be estimated based on the cooling water 

flow rate and the cooling water temperature rise. 

As water evaporates in the cooling tower, any dissolved solids that came in with the raw 

make-up water will concentrate. To control the water chemistry and thus avoid scale 

formation and corrosion in the cooling water system, water must be discharged in a 

“blowdown” process. The required blowdown rate is highly dependent on the make-up 

water quality and is often determined based on cycles of concentration – the ratio of 

dissolved solids in the cooling water relative to the make-up water. With poor make-up 

water quality, the maximum allowable cycles of concentration is low requiring a high 

blowdown rate. A mid-range blowdown rate (corresponding to a water quality requiring 

a cycles of concentration of 4) would be one third of the evaporation losses or 25% of the 

total make-up cooling water flow.3

 The water discharged as part of the blowdown 

process may be returned to the original source or sent to a water treatment facility. The 

Water Requirements in Emerging Thermoelectric Plant Technologies 4
quantity discharged (the blowdown) is the primary difference between the raw water 

withdrawal and the water consumption in a wet recirculating cooling tower system. 

When water availability is low, a dry cooling system may be utilized. Dry cooling can be 

either direct or indirect and in each case uses convective heat transfer to provide cooling, 

eliminating evaporation losses. In direct dry cooling systems, the turbine exhaust steam 

enters condenser tubes and is cooled by ambient air. In an indirect system, cooling water 

is used to condense the steam, as in a wet recirculating system. Then the cooling water 

flows through tube bundles that are cooled in a mechanical or natural draft cooling tower. 

Cooling water make-up requirements can be nearly eliminated by use of dry cooling 

systems, but process and steam make-up water requirements are unaffected. 

Wet recirculating systems are roughly 40% more expensive than once-through systems, 

while dry cooling systems are 3 to 4 times more expensive than a wet recirculating 

system.4

 Figure 2-2 shows the average total cost and number of cooling systems for 

fossil/biomass-fueled steam plants in the U.S. for 2005. While most systems currently 

employ once-through cooling, environmental regulations and permitting requirements 

will likely push developers to choose recirculating or dry cooling options in the future. 

19 28 27

182

0

100

200

300

400

500

600

Once through Recirc Cooling

pond

Other (includes dry)

Number of systems

0

50

100

150

200

250

300

Cooling system cost ($/kW)

Number of systems: 1969 and before

Number of systems: 1970 and later

Cooling system cost

Figure 2-2. Average total cost and number of cooling systems by type5

3 Water Requirements for Power Generation Platforms 

3.1 Data Sources and Comparison 

In the 2007 NETL report, “Cost and Performance Baseline for Fossil Energy Plants, 

Volume 1: Bituminous Coal and Natural Gas to Electricity” (NETL Baseline), various 

greenfield thermoelectric plant technologies were designed and costed. Water 

Water Requirements in Emerging Thermoelectric Plant Technologies 5
consumption, while not the primary focus of the NETL Baseline report, was quantified 

for pulverized coal (PC), natural gas combined cycle (NGCC) and integrated gasification 

combined cycle (IGCC) plants. The analysis in Sections 3 and 4 of this report stems 

from these designs.ii For the coal-based platforms, the water use factors are specific to 

bituminous coal. 

Figure 3-1 compares water consumption for six thermoelectric generation platforms using 

the design water consumption values from the NETL Baseline report (coal- and natural 

gas-based systems) and a 2002 EPRI report (nuclear). The units are gallons of water 

consumed per net kWh of generation. All else equal, more efficient platforms will 

consume less water per kWh of net generation. However, other factors such as the steam 

cycle conditions, steam turbine contribution to gross power and process water 

requirements will impact the water usage for each technology. 

0 100 200 300 400 500 600 700

NGCC

Shell IGCC

(Dry fed)

GEE IGCC

(Slurry fed)

Supercritical PC

Subcritical PC

Nuclear

Water Consumption (gal/MWh net)

Gasifier

FGD

Cooling Tower

Figure 3-1. Water consumption for nuclear6

 and greenfield bituminous coal and natural 

gas thermoelectric power plants utilizing wet cooling towers

NGCC and IGCC power plants have lower water consumption due to the fact that around 

2/3 of a combined cycle power plant’s output comes from the combustion turbines which 

require minimal water when compared to the steam cycle. Like PC plants, nuclear power 

generation is all from a steam cycle; however, nuclear plants utilize lower pressure and 

temperature steam, and as a result require more steam and cooling water relative to the 

power produced. 

 

iiThe water requirements associated with each technology that were determined by the NETL Baseline 

report were adjusted based on a more detailed water analysis. The key assumptions related to water 

consumption and withdrawal used in the original study and a description of the subsequent adjustments are 

described in Appendix A. These adjusted factors are utilized throughout this report.

Water Requirements in Emerging Thermoelectric Plant Technologies 6
3.2 Subcritical and Supercritical PC plants 

As the least efficient type of fossil fuel power plant examined here, a subcritical PC plant 

also consumes the most water per kW of power produced. Due to the lower steam 

pressure as compared to a supercritical plant, less energy can be transferred from the 

boiler to the turbine, so more steam flow, and thus more cooling water flow is required to 

generate the same electricity. Schematics highlighting the water flows in a subcritical 

and a supercritical PC plant with a wet FGD unit can be seen in Figure 3-2 and Figure 3-3. 

A PC plant fitted with a wet FGD unit will require make-up water. In an FGD, the flue 

gas enters a large vessel where it is sprayed with a slurry of about 10% limestone and 

90% water. The sulfur in the flue gas and calcium in the limestone create a slurry of 

calcium sulfate (a gypsum). Although much of the water is removed from the gypsum by 

a dewatering process and then recycled, some is contained in the gypsum and must be 

made up. 

Water is also lost from the plant in the form of water vapor in the flue gas. Although 

most of it was generated during combustion or was inherent coal moisture (approximately 

11 wt% for bituminous coal), some of this water is from the FGD system. 

In the steam cycle, the boiler feedwater (BFW) system requires blowdowns and 

subsequent make-up water. Because BFW make-up water is treated to remove 

impurities, the blowdown and make-up rates are not significant compared to the cooling 

water system requirements. 

Water vapor Steam

Turbine

Wet

FGD

Water vapor

Flue gas Steam cycle Cooling water

Boiler

Condenser

Cooling tower

Raw water source (river, lake, ocean, well, municipal system, etc.)

Wet 

gypsum

Cooling 

water 

blowdown:

65-225 

gal/MWh*

FGD 

make-up: 

~70 gal/MWh

BFW 

make-up: 

~10 gal/MWh

Cooling 

tower 

make-up: 

505-665

gal/MWh* BFW 

blowdown

*Range represents cycles of concentration from 3 to 8

Figure 3-2. Water flow schematic for a greenfield subcritical pulverized coal power plant 

utilizing a wet cooling tower and a wet FGD 

Water Requirements in Emerging Thermoelectric Plant Technologies 7
*Range represents cycles of concentration from 3 to 8

Water vapor Steam

Turbine

Wet

FGD

Water vapor

Flue gas Steam cycle Cooling water

Boiler

Condenser

Cooling tower

Raw water source (river, lake, ocean, well, municipal system, etc.)

Wet 

gypsum

Cooling 

water 

blowdown:

55-195 

gal/MWh*

FGD 

make-up: 

~60 gal/MWh

BFW 

make-up: 

~10 gal/MWh

Cooling 

tower 

make-up: 

440-580

gal/MWh* BFW 

blowdown

Figure 3-3. Water flow schematic for a greenfield supercritical pulverized coal power plant 

utilizing a wet cooling tower and a wet FGD

3.3 IGCC plants 

An IGCC power plant’s water profile is significantly lower than either sub- or 

supercritical PC plants as shown in Figure 3-4. This is mainly due to the fact that the gas 

turbine, which requires minimal cooling water, produces around 60% of the plant’s entire 

electrical output. Hot exhaust gas from the gas turbine passes through a heat recovery 

steam generator (HRSG) to drive a steam cycle. It is worth noting that an IGCC’s steam 

cycle operates at a lower pressure than a PC plant’s does (1800 psig, as compared to 2400 

psig for subcritical and 3500 psig for supercritical plants), hence an IGCC plant 

consumes more water per MWh produced from the steam turbine than does a PC plant.iii 

In addition to the use of cooling water for the steam condenser, an IGCC plant has 

cooling requirements for several other gas processing steps. In the air separation unit 

(ASU), cooling water is required to cool compressed air prior to the cryogenic ASU cold 

box. In an IGCC’s acid gas removal (AGR) unit, hydrogen sulfide removal occurs 

through absorption by a chemical or physical solvent that then must be regenerated using 

heat. Cooling water is primarily utilized in the regenerator tower condenser and to cool 

 

iii For the GEE IGCC configuration modeled in NETL’s baseline report, the steam turbine has a capacity of 

299 MW and requires 3,485 gpm of make-up water associated with the condenser, yielding 699 gal/MWh 

gross for just the steam turbine condenser. For the PC plant, the cooling water make-up requirement is 

lower at 555 gal/MWh gross power. However, if the power output of the entire IGCC plant including the 

steam and gas turbines is accounted for, then the GE plant’s cooling water make-up requirement is 271 

gal/MWh gross power. 

Water Requirements in Emerging Thermoelectric Plant Technologies 8
the regenerated solvent. Finally, a relatively small amount of cooling water is required 

for compressor intercoolers in the tail gas treating unit (TGTU). 

Water vapor Water vapor

Syngas Steam cycle Cooling water

Condenser

Cooling tower

Gasifier

HR

SG

BFW

make-up: 

~5 gal/MWh

Cooling 

tower 

make-up: 

275-430

gal/MWh*

Gasification 

process make-up: 

25-55 gal/MWh*

Cooling 

water 

blowdown:

35-145

gal/MWh*

Raw water source (river, lake, ocean, well, municipal system, etc.)

AGR/ASU/TGTU 

Cooling

Gas 

Turbine

Steam 

Turbine

SWS BFW 

Wet blowdown

Waste

*Range represents different gasifier technologies/designs and cooling water cycles of concentration from 3 to 8

Figure 3-4. Water flow schematic for a greenfield IGCC plant utilizing a wet cooling tower

IGCC plants also have water make-up requirements related to the gasification process 

itself. In the gasifier, coal, oxygen and steam are reacted to produce a combustable gas 

called syngas. Each of the different IGCC gasifier designs modeled in the NETL 

Baseline report utilizes water for different sub-processes as shown in Table 3-1. In 

gasifiers marketed by Shell and ConocoPhillips (E-GAS), humidification of the syngas 

stream makes up a large portion of the gasifier’s water demand. Syngas humidification 

along with steam and nitrogen dilution of the syngas aids in minimizing formation of 

NOX during combustion in the gas turbine burner section. The E-GAS and General 

Electric Energy (GEE) gasifiers are slurry fed meaning that water is added to the coal 

prior to gasification. A portion of the water is consumed in the gasification process as it 

is converted to syngas. For these slurry fed designs, molten slag leaving the gasifier is 

quenched in water, then the slurry of water and slag drops out of the stream and is 

disposed of. Although some of the slurry water can be recovered, significant make-up is 

still required. In each of the designs, scrubbing of the syngas with water occurs. 

It was assumed that some process water can be recovered and utilized in other processes 

or otherwise recycled within the system. For example, the quench and scrubber water are 

sent to a sour water stripper (SWS) where the impurities are removed from the water. As 

modeled, a portion of the blowdown from the SWS effluent is recycled to meet other 

process water needs. Filtering or clean up requirements to facilitate this type of internal 

recycle were not evaluated in detail in the NETL Baseline report. 

Water Requirements in Emerging Thermoelectric Plant Technologies 9
Table 3-1. Water intensive processes utilized by different IGCC gasifier designs3

 GEE CoP E-GAS Shell 

Ash Handling 8 8 8

Slurry/Slag Handling 8 8

Quench/Scrubber 8 8 8

Humidifier 8 8

Gasifier Steam 8

Gas Turbine Dilution 8

3.4 NGCC plants 

NGCC plants do not consume water for slurrying or desulfurization and the gas turbine 

generates 65%-70% of the total plant power output. The result is a configuration with a 

low water profile. The NGCC design does, however, consume roughly 25% more water 

relative to power generation from the steam turbine than does a subcritical PC plant, 

despite operating under similar steam conditions. This difference stems from the heat 

source for the BFW heater systems. In the NGCC design, the BFW heating occurs in the 

heat recovery steam generator (HRSG). In the PC design, extraction steam must be used 

for BFW heating. A schematic of a greenfield NGCC plant’s water requirement is shown 

in Figure 3-5. 

Water vapor

Steam

Turbine

Water vapor

Combustion Steam cycle Cooling water

Condenser

Cooling tower

HR

SG

Gas

Turbine

BFW 

make-up: 

<5 gal/MWh

Cooling 

tower

make-up: 

215-285 

gal/MWh*

Cooling 

water 

blowdown:

25-95

gal/MWh*

Raw water source (river, lake, ocean, well, municipal system, etc.)

BFW 

blowdown

Figure 3-5. Water flow schematic for a greenfield NGCC plant utilizing a wet cooling tower 

Water Requirements in Emerging Thermoelectric Plant Technologies 10
3.5 Nuclear Plants 

In a nuclear plant, energy from the decay of uranium heats pressurized water which is 

then used to produce steam in the steam generator (SG). All power produced comes from 

the steam cycle as it does for PC plants. Nuclear plants have a higher cooling tower load 

relative to net power generation. This is because the steam conditions are limited by 

metal brittleness effects from the nuclear reactor thereby reducing efficiency. Figure 3-6

shows the water requirements for a nuclear power plant.

*Cycles of concentration from 5 to 10

SG

Water vapor Steam

Turbine

Nuclear reaction Steam cycle Cooling water

Condenser

Cooling tower

Cooling 

tower 

make-up: 

800-1100

gal/MWh

Cooling 

water 

blowdown:

60-200

gal/MWh*

Raw water source (river, lake, ocean, well, municipal system, etc.)

Pressurized 

Water 

Reactor

Figure 3-6. Water flow schematic for a nuclear plant utilizing a wet cooling tower6

4 Carbon capture and water usage 

The NETL Baseline report designed and costed thermoelectric plants with the capability 

to capture carbon dioxide for each of the fossil energy plant technologies. Based on the 

technologies used in these designs, installing carbon dioxide recovery (CDR) equipment 

increases the water requirement per net power generation of a plant, due both to a 

reduction in the plant efficiency (Figure 4-1) and to the cooling water and process water 

requirements associated with carbon dioxide capture and compression. 

Water Requirements in Emerging Thermoelectric Plant Technologies 11
0%

20%

40%

60%

Plant Efficiency

No CDR

CDR

No CDR 36.8% 39.1% 38.2% 41.1% 50.8%

CDR 24.9% 27.2% 32.5% 32.0% 43.7%

Subcritical PC Supercritical PC IGCC (slurry fed) IGCC (dry fed) NGCC

Figure 4-1. Comparison of net plant efficiencies (HHV basis) with and without CDR

The CO2 recovery method for PC and NGCC plants used in the NETL Baseline study is a 

monoethanolamine (MEA) recovery unit based on the Fluor Econamine FG Plus 

technology. The data presented here are specific to that technology, however, research in 

this area is ongoing and systems with improved efficiency, costs, and/or water balances 

are being pursued. 

To meet the specifications of the Econamine process, a polishing scrubber simultaneously 

cools the flue gas and reduces the SO2 concentration to less than 10 ppmv. The gas then 

contacts the MEA, which absorbs the CO2. The CO2-laden MEA is then steam-heated to 

release the CO2. The MEA is recovered and reused, and the carbon dioxide is cooled and 

compressed for shipment. Overall, the CDR facility involves a number of subprocesses 

which collectively require a significant amount of cooling water. This includes flue gas 

cooling, water wash cooling, absorber intercooling, reflux condenser duty, reclaimer 

cooling, the lean solvent cooler, and CO2 compression interstage cooling. At the same 

time, however, the cooling water requirements associated with the steam turbine 

condenser are reduced slightly relative to the power from the steam turbine as low 

pressure extraction steam is routed to the MEA regenerator condenser. In addition, a 

portion of the cooling water that is evaporated is offset by collecting water that condenses 

as the CO2 is cooled and compressed. In a plant without CDR equipment, this water 

would generally leave the stack as water vapor. 

For IGCC plants, a high level CO2 recovery will require a water-gas shift reactor and a 

physical-absorption based scrubber. The water-gas shift reactor increases the CO2 and 

hydrogen concentration in the syngas stream by converting carbon monoxide to CO2 and 

hydrogen by the addition of steam over a catalyst bed. CO2 is then removed from the gas 

stream using a two-stage Selexol process. The greater concentration of CO2 in the IGCC 

process allows use of this physical-solvent. This results in less of an increase in cooling 

water requirements compared to the chemical solvent used in the Econamine process for 

PC and NGCC plants. The remaining increase in cooling duty is due to an increase in the 

ASU cooling requirements and the addition of CO2 compressor intercoolers. 

Water Requirements in Emerging Thermoelectric Plant Technologies 12
4.1 Water consumption factorsiv

Utilizing the design conditions and assumptions of the NETL Baseline report, water 

consumption factors (net of the blowdown from the cooling water system) for each of the 

plant technologies with and without CDR equipment were developed. Raw water 

withdrawal factors which show the entire volume of water withdrawn for cooling water 

and process use is provided in Appendix B. 

Figure 4-2 compares the water consumption relative to net power generation. In the PC 

and NGCC cases, water consumption per net generation increases by 90% and 76%, 

respectively, with the addition of CO2 capture. The bulk of the increase is from higher 

cooling tower load related to the utilization of the cooling water-intensive chemicalabsorption CO2 recovery method at the back end of the power plant. In the IGCC slurry 

fed case, CO2 recovery occurs prior to combustion so the water consumption factor 

increases by only 46%. More than half of this increase is due to water-intensive 

processes in the gasifier and in the water gas shift (WGS) process. 

0

200

400

600

800

1,000

Water Consumption

 (gal/MWh net)

Cooling Tower

FGD

WGS

Gasifier 

Total 517 985 452 844 309 452 295 475 192 338

Cooling Tower 449 884 392 759 290 355 243 355 192 338

FGD 68 101 59 86

WGS 52 49

Gasifier 19 45 53 71

No CDR CDR No CDR CDR No CDR CDR No CDR CDR No CDR CDR

Subcritical PC Supercritical PC IGCC (slurry fed) IGCC (dry fed) NGCC

Figure 4-2. Comparison of water consumption factors with and without carbon capture for 

greenfield plants using wet recirculating cooling towers – net power basis 

The reason for increases in cooling water consumption per net power generation is a 

combination of the reduction in efficiency and the additional cooling water and process 

water for CDR equipment. Table 4-1 shows the total increase in water consumption for 

carbon capture and breaks it down into the expected water increase due to the lower 

efficiency of the carbon capture platform and the increased water usage due to additional 

cooling and process water for CDR processes. 

 

iv See Appendix A for key information on the basis for these factors. 

Water Requirements in Emerging Thermoelectric Plant Technologies 13
Table 4-1. Impact of efficiency and water use by CDR equipment on water consumption 

associated with carbon capture for plants using wet recirculating cooling towers 

Plant Type Impact of Efficiency Impact of Water Use 

by CDR Processes 

Total Increase in 

Water Consumption 

for Carbon Capture 

 Increase in Water Consumption Due to CO2 Capture, gal/MWh net (%)

Subcritical PC 247 (48%) 221 (43%) 468 (90%) 

Supercritical PC 198 (44%) 195 (43%) 393 (87%) 

IGCC (slurry fed) 54 (18%) 89 (29%) 143 (46%) 

IGCC (dry fed) 84 (28%) 96 (32%) 180 (61%) 

NGCC 31 (16%) 114 (60%) 146 (76%) 

Figure 4-3 shows the water consumption factors on a HHV thermal input basis which 

essentially removes the impact of the efficiency reductions and only concentrates on the 

water use by the CDR equipment. On this basis, most of the increase in water 

consumption for the IGCC cases is due to process water usage including the addition of 

the steam for the WGS reaction and water demand associated with gasifier operation. 

The change in water consumption associated with the cooling water system for the IGCC 

cases is primarily due to compression cooling. 

This information is also useful if policy and economic considerations point to the 

implementation of carbon capture for existing PC or NGCC plants. Should a plant be 

retrofitted with CDR equipment, the net power output of that plant would be reduced and 

thus the increase in water consumption for that specific plant would not increase by the 

90% or 76% quoted above. For example, for an existing subcritical PC plant based on 

the design used in this evaluation, the water consumption assuming a constant coal feed 

rate would increase by 30% or require roughly 16 gallons of additional make-up water 

per MMBtu of thermal input (HHV). This additional requirement is almost entirely for 

the cooling tower load. As a result, if a particular plant has maximized its water draw, 

the additional water requirements are only associated with the cooling tower load and 

could thus be achieved with conversion to recirculating or the addition of a dry cooling 

system. 

Water Requirements in Emerging Thermoelectric Plant Technologies 14
0

10

20

30

40

50

60

70

80

90

100

Water Consumption

per HHV Thermal Input

 (gal/MMBtu)

Cooling Tower

FGD

WGS

Gasifier 

Total 55.7 71.8 51.8 67.4 34.6 43.1 35.5 44.5 28.6 43.2

Cooling Tower 48.4 64.4 45.0 60.5 32.5 33.8 29.2 33.2 28.6 43.2

FGD 7.3 7.4 6.8 6.8

WGS 4.9 4.6

Gasifier 2.1 4.3 6.3 6.7

No CDR CDR No CDR CDR No CDR CDR No CDR CDR No CDR CDR

Subcritical PC Supercritical PC IGCC (slurry fed) IGCC (dry fed) NGCC

Figure 4-3. Comparison of water consumption factors with and without carbon capture for 

greenfield plants using wet recirculating cooling towers – thermal input basis

4.2 Cooling water duty factorsv

The water consumption factors for the cooling requirements described above can only be 

applied to wet recirculating cooling towers. Knowing the cooling duty associated with 

the cooling water systems for plants with and without CO2 capture allows application of 

this data to once-through or dry cooling systems. Utilizing the design cooling duty from 

the NETL Baseline report for various processes within the plants, factors for cooling 

water duty per net power generation and per coal feed rate were developed as shown in 

Figure 4-4 and Figure 4-5. 

The cooling water duty follows a similar pattern to the water consumption factors with 

the increase related to CO2 capture for NGCC and PC plants being far greater than for the 

various IGCC cases. For PC and NGCC plants, the increase in the cooling tower load is 

primarily due to the cooling needed for the amine process with some increased load due 

to CO2 compressor intercoolers. The condenser duty actually decreases with the addition 

of CDR equipment both per net power and relative to the coal feed rate. The reason for 

this decrease is that a portion of the steam from the steam turbine is routed to the 

Econamine system and condensed in the solvent regenerator reboiler. 

For the IGCC cases, a significant portion of the additional water consumption associated 

with CDR capability is due to the gasifier and WGS process, so the cooling tower load 

increase is less significant than the overall water consumption increase. The minor 

increase in additional cooling system load is due to the reduced efficiency of the CDR 

 

v

 See Appendix A for key information on the basis for these factors. 

Water Requirements in Emerging Thermoelectric Plant Technologies 15
configuration, additional cooling load on the AGR unit and the addition of CO2

compressor interstage coolers. Again this information can be used to evaluate the cooling 

water needs for retrofitting an existing PC or NGCC plant with CDR equipment with the 

added flexibility to evaluate dry and once-through cooling systems. 

0

2

4

6

8

10

12

Cooling Water Duty

 (MMBtu/MWh net)

CO2 comp intercool

Econamine

Miscellaneous

ASU & TGT intercool

AGR

Condenser

Total 4.7 10.7 4.1 9.3 3.0 3.7 2.5 3.7 2.0 4.2

CO2 comp intercool 0.39 0.36 0.25 0.22 0.13

Econamine 6.13 5.54 2.91

Miscellaneous 0.10 0.15 0.09 0.14 0.03 0.04 0.03 0.04 0.04 0.04

ASU & TGT intercool 0.36 0.49 0.27 0.43

AGR 0.10 0.32 0.14 0.32

Condenser 4.58 4.00 3.99 3.27 2.53 2.61 2.09 2.69 1.97 1.08

No CDR CDR No CDR CDR No CDR CDR No CDR CDR No CDR CDR

Subcritical PC Supercritical PC IGCC (slurry fed) IGCC (dry fed) NGCC

Figure 4-4. Comparison of cooling water duty factors for greenfield plants – net power 

basis

Water Requirements in Emerging Thermoelectric Plant Technologies 16
0.0

0.2

0.4

0.6

0.8

1.0

Cooling Water Duty 

per HHV Thermal Input

 (MMBtu/MMBtu)

CO2 comp intercool

Econamine

Miscellaneous

ASU & TGT intercool

AGR

Condenser

Total 0.50 0.78 0.47 0.74 0.34 0.35 0.30 0.35 0.30 0.53

CO2 comp intercool 0.03 0.03 0.02 0.02 0.02

Econamine 0.45 0.44 0.37

Miscellaneous 0.01 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.01 0.01

ASU & TGT intercool 0.04 0.05 0.03 0.04

AGR 0.01 0.03 0.02 0.03

Condenser 0.49 0.29 0.46 0.26 0.28 0.25 0.25 0.25 0.29 0.14

No CDR CDR No CDR CDR No CDR CDR No CDR CDR No CDR CDR

Subcritical PC Supercritical PC IGCC (slurry fed) IGCC (dry fed) NGCC

Figure 4-5. Comparison of cooling water duty factors for greenfield plants – thermal input 

basis

5 Next Steps 

To extend and improve the factors presented here, the following next steps are 

recommended: 

• Refine the water consumption and withdrawal factors presented here with a 

specific focus on water requirements. Process simulations will be used as 

necessary. 

• Develop water consumption and withdrawal factors for an integrated gasification 

fuel cell (IGFC) platform. 

• Develop water consumption and withdrawal factors for plant designs with oxyfuel combustion. 

• Develop water consumption and withdrawal factors for low rank coal for each of 

the coal-based platforms. 

• Develop factors for solid residuals for each of the coal-based platforms. 

Water Requirements in Emerging Thermoelectric Plant Technologies 17
Appendix A 

Key assumptions in the 2007 NETL baseline report: 

- Raw water makeup is assumed to be provided 50% by a publicly owned treatment 

works and 50% from groundwater 

- Cooling water circulation and losses were determined using the following: 

o Design ambient wet bulb temperature of 51.5 oF to achieve a cooling water 

temperature of 60 oF (8.5 oF approach) 

o Cooling water temperature range of 20 oF 

o Evaporative losses of 0.8% of the circulating water flow rate per 10 oF of 

range 

o Drift losses of 0.001% of the circulating water flow rate 

o Blowdown rates = evaporated losses / (cycles of concentration – 1) 

 Mid-range cycles of concentration of 4 was used (measure of water 

quality) 

- Blowdown from other processes in the plant were assumed to be routed to the cooling 

water system, backing out makeup water, as follows: 

o PC and NGCC cases with CO2 capture: condensed water resulting from the 

cooling and compression of CO2 (for non CO2 capture cases, this water leaves 

with the flue gas)vi

o All cases: the boiler feedwater blowdown is routed to the cooling water 

system 

- Note that cooling water and process water requirements will vary significantly with 

process conditions such as temperature 

Adjustments to water requirements detailed in the 2007 NETL baseline report: 

- In the baseline report, for the PC and IGCC cases, an engineering estimate for 

miscellaneous cooling duty requirements of 100 MMBtu/hr was added (75 MMBtu/hr 

for the NGCC cases). This number was adjusted in this analysis as follows: 

o PC cases: assumed to be 55 MMBtu/hr for the subcritical no CO2 capture 

cases and was scaled based on coal feed rate for all other PC cases 

o IGCC cases: assumed to be 20 MMBtu/hr for the GEE IGCC no capture case 

and was scaled based on coal feed rate for all other IGCC cases 

o NGCC cases: assumed to be 20 MMBtu/hr for both cases 

- In the baseline report, cooling duty associated with the ASU and the TGTU 

intercoolers was documented, but not utilized in determining the cooling water 

circulation rate. The cooling duty and associated cooling water requirements were 

added for these processes in this analysis. 

 

vi Note that this was a significant change between the May 2007 report and the Revised August 2007 report 

Water Requirements in Emerging Thermoelectric Plant Technologies B-1
Appendix B 

Below are the raw water withdrawal factors corresponding to the discussion in Section 4. 

This analysis incorporates all water withdrawn for various uses in the plant. 

0

200

400

600

800

1,000

1,200

1,400

Raw Water Withdrawal

 (gal/MWh net)

Cooling Tower

Boiler Feedwater

FGD

WGS

Gasifier 

Total 667 1,326 582 1,142 406 571 376 593 256 471

Cooling Tower 590 1,213 515 1,044 382 469 320 468 254 468

Boiler Feedwater 8 12 8 12 5 5 4 5 2 3

FGD 68 101 59 86

WGS 52 49

Gasifier 19 45 53 71

No CDR CDR No CDR CDR No CDR CDR No CDR CDR No CDR CDR

Subcritical PC Supercritical PC IGCC (slurry fed) IGCC (dry fed) NGCC

Figure B-1. Comparison of raw water withdrawal factors with and without carbon capture 

for greenfield plants using wet recirculating cooling towers – net power basis

0

20

40

60

80

100

120

Raw Water Withdrawal

per HHV Thermal Input

 (gal/MMBtu)

Cooling Tower

Boiler Feedwater

FGD

WGS

Gasifier 

Total 71.9 96.6 66.7 91.1 45.5 54.3 45.3 55.6 38.1 60.2

Cooling Tower 63.7 88.4 59.0 83.3 42.9 44.6 38.5 43.8 37.7 59.8

Boiler Feedwater 0.9 0.9 0.9 0.9 0.5 0.5 0.4 0.5 0.4 0.4

FGD 7.3 7.4 6.8 6.8

WGS 4.9 4.6

Gasifier 2.1 4.3 6.3 6.7

No CDR CDR No CDR CDR No CDR CDR No CDR CDR No CDR CDR

Subcritical PC Supercritical PC IGCC (slurry fed) IGCC (dry fed) NGCC

Figure B-2. Comparison of raw water withdrawal factors with and without carbon capture 

for greenfield plants using wet recirculating cooling towers – thermal input basis 

Water Requirements in Emerging Thermoelectric Plant Technologies B-2
References 

 

1

 Energy Velocity Suite, Nuclear Regulatory Commission Outage query. 

http://www1.ventyx.com/velocity/vs-overview.asp

2

 National Energy Technology Laboratory (NETL), “Estimating Freshwater Needs to Meet Future 

Thermoelectric Generation Requirements” Report DOE/NETL-400/2008/1339, Revised September 2008. 

http://www.netl.doe.gov/technologies/coalpower/ewr/pubs/2008_Water_Needs_Analysis-Final_10-2-

2008.pdf 

3

 National Energy Technology Laboratory (NETL), “Cost and Performance Baseline for Fossil Energy 

Power Plants study, Volume 1: Bituminous Coal and Natural Gas to Electricity” Report DOE/NETL2007/1281, Revised August 2007. 

http://www.netl.doe.gov/energy-analyses/pubs/Bituminous%20Baseline_Final%20Report.pdf

4

 R.Tawney, Z. Khan, J. Zachary (Bechtel Power Corporation), “Economic and Performance Evaluation of 

Heat Sink Options in Combined Cycle Applications”, Journal of Engineering for Gas Turbines and Power, 

April 2005, Vol. 127. 

5

 U.S. Department of Energy, Energy Information Administration (EIA). Form EIA-767: Annual SteamElectric Plant Operation and Design Data. 2005 data. 

http://www.eia.doe.gov/cneaf/electricity/page/eia767.html

6

 Electric Power Research Institute (EPRI), “Water & Sustainability (Volume 3): U.S. Water Consumption 

for Power Production – The Next Half Century”, Palo Alto, CA: 2002. 1006786. 

Water Requirements in Emerging Thermoelectric Plant Technologies R-1