Review of Operational Water Consumption and Withdrawal Factors for Electricity Generating Technologies

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Contract No. DE-AC36-08GO28308

A Review of Operational Water

Consumption and Withdrawal

Factors for Electricity

Generating Technologies

Jordan Macknick, Robin Newmark,

Garvin Heath, and KC Hallett

Technical Report

NREL/TP-6A20-50900

March 2011

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

National Renewable Energy Laboratory

1617 Cole Boulevard

Golden, Colorado 80401

303-275-3000 • www.nrel.gov

Contract No. DE-AC36-08GO28308

A Review of Operational Water

Consumption and Withdrawal

Factors for Electricity

Generating Technologies

Jordan Macknick, Robin Newmark,

Garvin Heath, and KC Hallett

Prepared under Task No. DOCC.1005

Technical Report

NREL/TP-6A20-50900

March 2011

NOTICE

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 herein 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 herein do not necessarily state or reflect those of the United States government or any agency thereof.

Available electronically at

http://www.osti.gov/bridge

Available for a processing fee to U.S. Department of Energy

and its contractors, in paper, from:

U.S. Department of Energy

Office of Scientific and Technical Information

P.O. Box 62

Oak Ridge, TN 37831-0062

phone: 865.576.8401

fax: 865.576.5728

email:

mailto:reports@adonis.osti.gov

Available for sale to the public, in paper, from:

U.S. Department of Commerce

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone: 800.553.6847

fax: 703.605.6900

email:

[email protected]world.gov

online ordering:

http://www.ntis.gov/help/ordermethods.aspx

Cover Photos: (left to right) PIX 16416, PIX 17423, PIX 16560, PIX 17613, PIX 17436, PIX 17721

Printed on paper containing at least 50% wastepaper, including 10% post consumer waste.

iii

Acknowledgments

This work was funded by the U.S. Department of Energy’s (DOE’s) Office of Energy Efficiency

and Renewable Energy (EERE) and Office of Policy and International Affairs (PI). The authors

wish to thank Allan Hoffman and Diana Bauer for their support of this work. We are also

indebted to the following individuals for their thoughtful comments, input, and review of the

document in its various stages: Kristen Averyt, Western Water Assessment (WWA) and the

University of Colorado; Stacy Tellinghuisen, Western Resource Advocates; Timothy Diehl,

U.S. Geological Survey; and Lynn Billman, Elaine Hale, Margaret Mann, Walter Short, and

Daniel Steinberg, NREL. In addition, we would like to thank the participants in the Water for

Energy Workshop who provided valuable input, particularly Christina Alvord and Brad Udall,

WWA and University of Colorado; Mike Hightower and Vince Tidwell, Sandia National

Laboratories; Curt Brown, U.S. Bureau of Reclamation; Margot Gerritsen, Stanford University;

Eric Fournier, UC Santa Barbara; Alex Schroeder, Western Governors’ Association; Ashlynn

Stillwell, University of Texas Austin; Steve Clemmer and John Rogers, Union of Concerned

Scientists; Andrew Wolfsberg, Los Alamos National Laboratory; and Larry Flowers, NREL. We

also wish to thank Mary Lukkonen of NREL for her editorial support.

Executive Summary

This report provides estimates of operational water withdrawal and water consumption factors

for electricity generating technologies in the United States. Estimates of water factors were

collected from published primary literature and were not modified except for unit conversions.

The presented water factors may be useful in modeling and policy analyses where reliable power

plant level data are not available. Major findings of the report include:

• The power sector withdraws more water than any other sector in the United States and is

heavily dependent on available water resources. Changes in water resources may impact

the reliability of power generation.

• Water withdrawal and consumption factors vary greatly across and within fuel

technologies. Water factors show greater agreement when organized according to cooling

technologies as opposed to fuel technologies. Once-through cooling technologies

withdraw 10 to 100 times more water per unit of electric generation than recirculating

cooling technologies; recirculating cooling technologies consume at least twice as much

water as once-through cooling technologies.

• A transition to a less carbon-intensive electricity sector could result in either an increase

or decrease in water use, depending on the choice of technologies and cooling systems

employed. Concentrating solar power (CSP) technologies and coal facilities with carbon

capture and sequestration (CCS) capabilities have the highest water consumption values

when using a recirculating cooling system. Non-thermal renewables, such as

photovoltaics (PV) and wind, have the lowest water consumption factors.

• Federal datasets on water use in power plants have numerous gaps and methodological

inconsistencies. Federal agencies are currently coordinating to improve these data. Water

use factors discussed here are good proxies for use in modeling and policy analyses, at

least until power plant level data improve.

• Impacts of the power sector on freshwater availability can be reduced by utilizing dry

cooling or by using non-freshwater sources for cooling. However, these alternatives are

limited by locally available resources and may have cost and performance penalties.

Improved power plant data and further studies into the water requirements of energy

technologies in different climatic regions would facilitate greater resolution in analyses of water

impacts of future energy and economic scenarios. This report provides the foundation for

conducting water use impact assessments of the power sector while also identifying gaps in data

that could guide future research.

Table of Contents

List of Figures ............................................................................................................................................ vi

List of Tables .............................................................................................................................................. vi

1 Introduction ........................................................................................................................................... 1

2 Scope and Methods .............................................................................................................................. 2

3 Data Availability and Gaps .................................................................................................................. 5

4 Results: Water Consumption and Withdrawal Factors .................................................................... 6

5 Discussion ........................................................................................................................................... 15

6 Summary ............................................................................................................................................. 17

References ................................................................................................................................................. 18

List of Figures

Figure 1. Operational water consumption factors for electricity generating technologies ............. 7

Figure 2. Operational water consumption factors for geothermal technologies ............................. 8

Figure 3. Operational water withdrawals for electricity generating technologies .......................... 9

Figure 4. Operational water withdrawal factors for recirculating cooling technologies ...............10

List of Tables

Table 1. Water Consumption Factors for Renewable Technologies (gal/MWh) ......................... 12

Table 2. Water Consumption Factors for Non-renewable Technologies (gal/MWh) .................. 13

Table 3. Water Withdrawal Factors for Electricity Generating Technologies (gal/MWh) .......... 14

1 Introduction

Thermoelectric power use has a significant impact on water resources and the power sector is

highly dependent on these water resources; the United States Geological Survey (USGS)

estimated on a national level that 41% of all freshwater withdrawals in the United States in 2005

were for thermoelectric power operations, primarily for cooling needs [1]. The power sector is

thus highly vulnerable to changes in water resources, especially those that may result from

potential climatic changes [2-5]. Increasingly, state agencies in California and New York have

taken policy actions to address the impacts of power plants’ water use and the environmental

impacts of their cooling systems [6, 7]. Furthermore, the 2007 drought in the Southeast exposed

many thermal generators, including Brown’s Ferry nuclear plant, to water-related shut downs

and curtailments due to unlawfully high discharge temperature and shallow or exposed cooling

water inlet locations [8]. Effective integrated energy and water policy planning will require

identifying the individual and cumulative impacts that power plant configurations have on water

resources and the vulnerabilities of specific power plants to changes in water resources. Various

studies have attempted to consolidate published estimates of water use impacts of electricity

generating technologies, resulting in a wide range of technologies and values based on different

primary sources of literature [9-14]. The goal of this work is to consolidate the various primary

literature estimates of water use during the generation of electricity by conventional and

renewable electricity generating technologies in the United States to more completely convey the

variability and uncertainty associated with water use in electricity generating technologies.

Individual water use factors, reported in terms of the volume of water used per unit of electrical

output (gallons per megawatt-hour), are technology and cooling system specific. These water use

factors can be incorporated into energy-economic models to estimate generation-related water

use under different projected electricity portfolio scenarios.

2 Scope and Methods

We evaluate two aspects of water usage: withdrawal and consumption. According to the USGS,

“withdrawal” is defined as the amount of water removed from the ground or diverted from a

water source for use, while “consumption” refers to the amount of water that is evaporated,

transpired, incorporated into products or crops, or otherwise removed from the immediate water

environment [1]. Both water withdrawal and consumption values are important indicators for

water managers determining power plant impacts and vulnerabilities associated with water

resources.

We consider water withdrawals and consumption for the operational phase only. Operational

water use in this study includes cleaning, cooling, and other process-related needs that occur

during electricity generation, such as flue gas desulfurization (FGD) in coal facilities. For the

vast majority of power generation technologies, most of the water used in the life cycle of the

plant occurs during the operational phase, with the exception of non-thermal renewable energy

technologies that do not require cooling systems [9]. In addition, compared to the operational

phase, data for the water requirements of other phases (such as the fuel cycle) are scarce, are

subject to greater definitional boundary differences, and have more site-specific differences.

Also, although the location of the plant is permanent, the locations of the manufacturing or fuel

sources are not permanent. Given this and the continuous local impacts of power plant water use

on water resources during the operational phase, we limit this study to a detailed review of only

the operational water requirements of electricity generating technologies.

The energy technologies addressed here consist of configurations of concentrating solar power

(CSP), solar photovoltaic (PV), wind, biopower, geothermal, hydroelectric, nuclear, natural gas,

and coal technologies. Cooling system technologies considered include wet recirculating

technologies (evaporative cooling towers), once-through cooling systems (open loop cooling),

air-cooled condensing (dry cooling), hybrid wet and dry cooling systems (hybrid cooling), and

pond cooling systems.

Electricity generating technologies use water for different processes, depending on their

configuration. Thermal electricity technologies (e.g., CSP, biopower, coal, nuclear, and natural

gas technologies) generally require water as the working fluid (and as the cooling medium to

condense steam) as part of the Rankine cycle, the thermodynamic process that drives the steam

engine [15]. CSP facilities use water for steam cycle processes, for cleaning mirrors or heliostats,

and for cooling if a cooling tower is used. PV systems require occasional panel washing. Wind

systems require very little water, if any, for cleaning. Biopower facilities use water for cooling

and for steam cycle processing. Upstream water needs for growing energy crops are not

included in this analysis but can be quite substantial (approximately 100 times greater than

operational cooling system needs) and can vary greatly depending on region, crop, and

production methods [16-18]. Geothermal technology configurations (e.g., dry steam, binary, and

flash) can differ greatly in their use of water due to differences in reinjection techniques as well

as vapor temperature and mass [19]. Enhanced Geothermal Systems (EGS) operate similar to

geothermal binary technologies yet also require some additional water for hydraulic stimulation

[19]. Water used in geothermal technologies may come from geothermal fluids, with little to no

impact on local freshwater sources [20]. Over time, however, some geothermal plant efficiencies

may decline and may require outside fresh or brackish water sources, and some technologies

may lower local water tables [19, 21]. Hydroelectric facilities using reservoirs have evaporative

losses resulting from the dammed water [22, 23]. Nuclear, natural gas, and coal facilities use

water for cooling and for steam cycle processes. Coal facilities may also use water for FGD.

Fossil technologies employing carbon capture and storage capabilities will require additional

process water requirements [12].

Estimates of water consumption and withdrawal are displayed irrespective of geographic

location, as many published data do not specify the location or climatic conditions of the plant.

The location of a plant, and its corresponding climatic conditions, can affect its overall efficiency

and thus its water use rate [24-27]. Similar fossil plants utilizing cooling towers may have water

consumption and withdrawal factors that differ by more than 16%, depending on the location in

the United States [28]. Similarly, water consumption factors of CSP plants utilizing cooling

towers may differ by as much as 20% [15]. Inter-annual variations in water intensity are also not

considered for this review. Withdrawal and consumption factors are often reported in terms of

annual averages, yet water intensity of facilities may change by as much as 16% as a result of

diurnal and seasonal variations in temperatures, wind speeds, and humidity levels [28]. Other

factors that may influence water use intensities of power plants that are not considered here

include the age of the plant, the thermal efficiency of the plant, the age of the cooling system,

and the water source [26, 27].

Certain aggregations of fuel technology types and cooling system types were made to facilitate

analyses. Nuclear technologies include pressurized water reactors and boiling water reactors.

Coal technologies make no distinction between wet, dry, and no FGD. For recirculating cooling

technologies, no distinction is made between natural draft and mechanical draft cooling tower

systems. All pond-cooled systems are treated identically. Pond-cooled systems can be operated

in manners that resemble both recirculating systems and once-through systems as well as in

hybrids of these technologies [29]. Different configurations and operating practices of pond-

cooled systems can lead to widely different reported water withdrawal and consumption values.

No distinction is made between water types, which may include freshwater (surface and

groundwater), saline water, or municipal waste water. In 2005, 71% of thermoelectric water

withdrawals were from freshwater sources [1]. Saline withdrawals are primarily concentrated in

California, Florida, and the coastal Northeast, with the rest of the country relying on freshwater.

Data sources include published academic literature, state and federal government agency reports,

non-governmental organizations’ reports, and industry submissions to government agencies for

permitting procedures. Estimates of national average water use intensity for particular

technologies, estimates of existing plant operational water use, and estimates derived from

laboratory experiments were considered equally. Certain sources report ranges of water

consumption and withdrawal factors in place of specific values. If traceable individual case

studies form the basis for the range given, the individual values are included as independent

estimates within the set of estimates that are statistically analyzed. If a range is given and the

underlying data points are not given, then the midpoint of that range is used for calculating an

average value, and the high and low extremes are used for determining extreme ranges. This

method of addressing ranges may lead to a bias toward data sources reporting explicit cases and

may also underestimate actual water use at facilities, as it was observed that the midpoint of the

range of extremes are in general less than values reported from individual facilities. This review

did not alter (except for unit conversion) or audit for accuracy the estimates of water use

published. Because estimates are used as published, considerable methodological inconsistency

is inherent, limiting comparability. We report minimum, maximum, and median values for fuel

technology and cooling system combinations in tables and additionally show 25

and 75

percentile data in figures. Due to the wide range of values reported from a small number of

sources, median values may differ significantly from mean values. Upon request, raw data are

available from the authors.

3 Data Availability and Gaps

Although the power sector is the largest user of water in the nation, national statistics on the

consumption and withdrawal rates of individual power plants are characterized by

inconsistencies and scarcity [30]. Power sector water use data on a national level are collected

by two federal agencies, the USGS and the U.S. Department of Energy’s Energy Information

Administration (EIA). The USGS reports water withdrawals for thermoelectric power

production by county and sector every five years; water consumption values for thermoelectric

power production were last reported for 1995 [31]. These data are collected by state agencies that

do not always utilize the same methods or definitions in determining water withdrawals [1].

EIA provides official energy statistics on an annual basis, and EIA Form 923 reports, among

other data, annual water withdrawal, discharge, and consumption rates in Schedule 8D, providing

similar definitions of withdrawal and consumption as the USGS [29]. However, data are not

entirely comprehensive and have omitted nuclear facilities and some natural gas combined cycle

technologies [32]. Additionally, the quality of data is also of concern with power plants reporting

data; many of the power plants report water withdrawal and consumption values that are far

below or above detailed engineering studies of water use in power plants considered in this

review. The National Energy Technology Laboratory compiled water use data in their 2007 Coal

Power Plant DataBase [33]. However, this database is limited by the data availability and

quality of EIA datasets. No similar public database has been developed for natural gas or

nuclear generating facilities.

Detailed engineering studies and more general assessments of water use at individual

thermoelectric power plants are uneven in their treatment of fuel technologies and cooling

systems. For example, water consumption data for coal, natural gas, nuclear, and parabolic

trough CSP facilities using a wet recirculating cooling system are relatively abundant. Fewer

studies are available addressing water withdrawals for all technologies or water consumption for

once-through, pond, and dry-cooling systems. Very little data exist for dedicated biomass,

geothermal, and power tower CSP facilities.

Additionally, boundary conditions of water use studies are not always clear or consistent; some

sources only report aggregated operational water usage, whereas other reports include water use

by individual processes. However, the particular processes included in disaggregated studies may

not be equivalent; the inclusion of FGD water requirements in coal facilities is one example

where its explicit or implicit consideration is inconsistent across datasets. Geothermal facilities

add an additional layer of complexity, as often cooling processes can make use of geothermal

fluids rather than freshwater; some sources exclude geothermal fluids from calculations whereas

others include geothermal fluids. Estimates of evaporation from hydropower reservoirs are

complicated by the multiple uses of reservoirs (e.g., water supply, recreation, and flood control)

and the different methods of allocating evaporation to electricity production [22, 23].

Hydropower estimates are reported according to the allocation methods utilized in the published

reports, which allocate all reservoir evaporation to power production.

4 Results: Water Consumption and Withdrawal Factors

The cooling system employed is often a greater determinant of water usage than the particular

technology generating electricity, both in terms of water consumption (Figures 1 and 2) and

water withdrawal (Figures 3 and 4). Once-through cooling technologies withdraw 10 to 100

times more water per unit of electric generation than cooling tower technologies, yet cooling

tower technologies consume at least twice as much water as once-through cooling technologies.

Water consumption for dry cooling at CSP, biopower, and natural gas combined cycle plants is

an order of magnitude less than for recirculating cooling at each of those types of plants.

Figure 1. Operational water consumption factors for electricity generating technologies

IGCC: Integrated gasification combined cycle. CCS: Carbon capture and sequestration. CSP: Concentrating solar power. Whisker ends represent

maxima and minima. Upper and lower ends of boxes represent 75

and 25

percentile, respectively. Horizontal lines in boxes represent medians.

Figure 2. Operational water consumption factors for geothermal technologies

EGS: Enhanced geothermal systems. Whisker ends represent maxima and minima. Upper and lower

ends of boxes represent 75

and 25

percentile, respectively. Horizontal lines in boxes represent

medians.

Figure 3. Operational water withdrawals for electricity generating technologies

IGCC: Integrated gasification combined cycle. CCS: carbon capture and storage. Whisker ends represent maxima and minima. Upper and lower

ends of boxes represent 75

and 25

percentile, respectively. Horizontal lines in boxes represent medians. Recirculating cooling withdrawal

values are also shown in Figure 4.

Figure 4. Operational water withdrawal factors for recirculating cooling technologies

IGCC: Integrated gasification combined cycle. CCS: carbon capture and storage. Whisker ends

represent maxima and minima. Upper and lower ends of boxes represent 75

and 25

percentile,

respectively. Horizontal lines in boxes represent medians.

Water consumption factors for renewable (Table 1) and non-renewable (Table 2) electricity

generating technologies vary substantially within and across technology categories. The highest

water consumption factors for all technologies result from the use of evaporative cooling towers.

With the exception of hydropower, pulverized coal with carbon capture and CSP technologies

utilizing a cooling tower represent the upper bound of water consumption, at approximately

1,000 gal/MWh of electricity production. The lowest operational water consumption factors

result from wind energy, PV, and CSP Stirling solar technologies and natural gas combined cycle

facilities that employ dry cooling technologies. Water withdrawal factors for electricity

generating technologies show a similar variability within and across technology categories

(Table 3). The highest water withdrawal values result from nuclear technologies, whereas the

smallest withdrawal values are for non-thermal renewable technologies. Consistent with

literature, withdrawal factors for CSP, wind, geothermal, and PV systems are assumed to be

equivalent to consumption factors.

Table 1. Water Consumption Factors for Renewable Technologies (gal/MWh)

Fuel Type Cooling Technology Median Min Max

Sources

PV N/A Utility Scale PV 26 0 33 3 [10, 34, 35]

Wind N/A Wind Turbine 0 0 1 2 [11, 36]

CSP

Tower

Trough 865 725 1,057 17 [10, 34, 37-46]

Power Tower 786 740 860 4 [34, 39-41]

Fresnel 1,000 1,000 1,000 1 [47]

Dry

Trough 78 43 79 10 [38, 42-44]

Power Tower 26 26 26 1 [48]

Hybrid

Trough 338 105 345 3 [42, 47]

Power Tower 170 90 250 2 [47]

N/A Stirling 5 4 6 2 [34, 49]

Biopower

Tower

Steam 553 480 965 4 [49-51]

Biogas 235 235 235 1 [52]

Once-through Steam 300 300 300 1 [50]

Pond Steam 390 300 480 1 [50]

Dry Biogas 35 35 35 1 [51]

Geothermal

Tower

Dry Steam 1,796 1,796 1,796 1 [10]

Flash (freshwater) 10 5 19 3 [19, 20, 49]

Flash (geothermal fluid) 2,583 2,067 3,100 2 [53]

Binary 3,600 1,700 3,963 3 [10, 54, 55]

EGS 4,784 2,885 5,147 4 [10, 51, 54, 55]

Dry

Flash 0 0 0 1 [51]

Binary 135 0 270 2 [19, 51]

EGS 850 300 1,778 2 [19, 51]

Hybrid

Binary 221 74 368 1 [56]

EGS 1,406 813 1,999 2 [51, 56]

Hydropower N/A

Aggregated in-stream and

reservoir

4,491 1,425 18,000 3 [22, 23]

Most geothermal facilities can use geothermal fluids or freshwater for cooling.

Table 2. Water Consumption Factors for Non-renewable Technologies (gal/MWh)

Fuel Type Cooling Technology Median Min Max

Sources

Nuclear

Tower Generic 672 581 845 6 [10, 14, 27, 50, 57]

Once-

through

Generic 269 100 400 4 [27, 50, 57, 58]

Pond Generic 610 560 720 2 [27, 50]

Natural

Gas

Tower

Combined Cycle 198 130 300 5 [13, 34, 50, 57, 59]

Steam 826 662 1,170 4 [10, 14, 49, 60]

Combined Cycle with CCS 378 378 378 1 [59]

Once-

through

Combined Cycle 100 20 100 3 [50, 57, 60]

Steam 240 95 291 2 [10, 49]

Pond Combined Cycle 240 240 240 1 [57]

Dry Combined Cycle 2 0 4 2 [50, 57]

Inlet Steam 340 80 600 1 [49]

Coal

Tower

Generic 687 480 1,100 5 [10, 14, 27, 50, 58]

Subcritical 471 394 664 6 [13, 57, 59, 61]

Supercritical 493 458 594 6 [13, 57, 59, 61]

IGCC 372 318 439 7 [13, 59]

Subcritical with CCS 942 942 942 1 [59]

Supercritical with CCS 846 846 846 1 [59]

IGCC with CCS 540 522 558 3 [59]

Once-

through

Generic 250 100 317 4 [10, 27, 50, 58]

Subcritical 113 71 138 3 [57]

Supercritical 103 64 124 3 [57]

Pond

Generic 545 300 700 2 [27, 50]

Subcritical 779 737 804 3 [57]

Supercritical 42 4 64 3 [57]

Table 3. Water Withdrawal Factors for Electricity Generating Technologies (gal/MWh)

Fuel Type Cooling Technology Median Min Max

Sources

Nuclear

Tower Generic 1,101 800 2,600 3 [27, 50, 57]

Once-through Generic 44,350 25,000 60,000 4 [27, 50, 57, 58]

Pond Generic 7,050 500 13,000 2 [27, 50]

Natural

Gas

Tower

Combined Cycle 253 150 283 6 [12, 13, 50, 57, 59]

Steam 1,203 950 1,460 2 [49, 60]

Combined Cycle with

CCS

496 487 506 2 [12, 59]

Once-through

Combined Cycle 11,380 7,500 20,000 2 [50, 57]

Steam 35,000 10,000 60,000 1 [49]

Pond Combined Cycle 5,950 5,950 5,950 1 [57]

Dry Combined Cycle 2 0 4 2 [50, 57]

Inlet Steam 425 100 750 1 [49]

Coal

Tower

Generic 1,005 500 1,200 4 [27, 35, 50, 58]

Subcritical 531 463 678 7 [12, 13, 57, 59, 61]

Supercritical 609 582 669 7 [12, 13, 57, 59, 61]

IGCC 390 358 605 11 [12, 13, 35, 59]

Subcritical with CCS 1,277 1,224 1,329 2 [12, 59]

Supercritical with CCS 1,123 1,098 1,148 2 [12, 59]

IGCC with CCS 586 479 678 6 [12, 59]

Once-through

Generic 36,350 20,000 50,000 4 [11, 27, 50, 58]

Subcritical 27,088 27,046 27,113 3 [57]

Supercritical 22,590 22,551 22,611 3 [57]

Pond

Generic 12,225 300 24,000 2 [27, 50]

Subcritical 17,914 17,859 17,927 3 [57]

Supercritical 15,046 14,996 15,057 3 [57]

Biopower

Tower Steam 878 500 1,460 2 [49]

Once-through Steam 35,000 20,000 50,000 1 [50]

Pond Steam 450 300 600 1 [50]

5 Discussion

Despite methodological differences in data, general trends can be observed and broad

conclusions can be drawn from the breadth of data collected. A transition to a less carbon-

intensive electricity sector could result in either an increase or decrease in water consumption per

unit of electricity generated, depending on the choice of technologies and cooling systems

employed. Non-thermal renewable technologies, such as wind and PV systems, consume

minimal amounts of water per unit of generation. However, the highest water consumption

factors considered in this study, excluding geothermal and hydroelectric facilities, which can

have high water intensities but also have important caveats, are low-carbon emitting technologies

that utilize cooling towers: pulverized coal with carbon capture technologies and CSP systems.

Decisions affecting the power sector’s impact on the climate may need to include water

considerations to avoid negative unintended environmental consequences on water resources.

This can be addressed by integrated energy and water policy planning, as the availability of

water in certain jurisdictions may limit the penetration of these technologies and cooling system

configurations.

Freshwater use impacts can be reduced by utilizing dry cooling or by using non-freshwater

sources as a cooling medium. Initial work suggests that the performance penalty for CSP

facilities switching from wet cooling to dry cooling results in an annual reduction in output of

2%–5% and an increase in the levelized cost of producing energy of 3%–8%, depending on local

climatic conditions [15]. Using national averages, the annual performance penalty for switching

from wet cooling to dry cooling for nuclear plants is 6.8%, combined cycle plants 1.7%, and

other fossil plants (including coal and natural gas steam plants) 6.9% [62]. Further efforts are

needed to evaluate performance and cost penalties associated with utilizing dry or hybrid cooling

systems for fossil fuel facilities using carbon capture technologies. Utilizing reclaimed water,

such as municipal wastewater, is another approach that could lessen the impact of the power

sector on freshwater resources and wastewater treatment facilities. The legal and physical

availability of municipal wastewater, especially in rural areas, may be a limiting factor to its

widespread usage, and the cost and performance penalties of utilizing such sources must be

investigated further [63].

The choice of cooling system may play an important role in the development of our future

electricity mix. Differences between cooling systems can have substantial environmental impacts

on local water resources [64-66]. Employing wet cooling technologies (i.e., once-through and

cooling tower technologies) imposes an inherent tradeoff between relatively high water

consumption and relatively high water withdrawals, which has important implications for

regional cooling system policies and regulations. A reduction in withdrawals (but a

corresponding increase in consumption) may benefit a watershed that has an abundance of water

but may lead to concerns in an area that is already lacking water. A shift away from, for

example, once-through cooling systems in coastal areas that withdraw saline water, to inland

recirculating systems such as cooling towers that primarily consume freshwater, will impact

watersheds and water availability differently depending on local conditions. The use of

alternative cooling technologies may serve as an energy security benefit for utilities and

communities, given uncertainties in future scenarios of water availability and expected

vulnerabilities for power plants [4, 5]. Reduced levels in bodies of water, or substantial increases

in the temperature of these bodies of water, may require thermal power plants to run at lower

capacities or to shut down completely, as was seen in France in 2003 [67]. Utilizing dry cooling

or non-freshwater sources avoids some of the risks associated with these drought and climate

change scenarios.

Accurate estimates of water use in individual power plants, and the effect of this water use on a

regional scale, will be elusive until more studies are conducted for the variety of technologies

and cooling systems currently in operation along with those expected to be developed and

deployed. Furthermore, calibration of these values on national and regional scales will remain

challenging until methods for collecting and evaluating data by federal agencies has improved.

Nonetheless, certain conclusions regarding the overall impact power plants have on water

resources can be drawn on regional levels from existing water use data.

Further studies with consistent boundary conditions and methods are necessary to develop water

consumption and withdrawal estimates for certain technologies and cooling systems to fully

understand reasons for variations in data that are not attributable to climatic factors or technology

vintages. To better understand how cooling system and technology system decisions will be

made in the future, analyses using energy-economic models will require improved data on water

availability and regional water use factors. Existing data collected from federal agencies are

currently inconsistent and incomplete [30]. However, in 2009, the U.S. Government

Accountability Office released a report calling for improvements in federal agency water data

collection in power plants; EIA is currently working with the USGS and other federal agencies to

improve the scope and quality of its data collection [30]. Such efforts should improve the

availability of power plant specific data and the ability to calibrate model estimates.

6 Summary

We reviewed primary literature for data on water withdrawal and consumption factors for

electricity generation in the United States and have consolidated them in this study. These

detailed water consumption and withdrawal factors can be utilized in energy-economic and

transmission planning models to better understand the regional and national impacts on water

resources for various electricity future scenarios and can inform policy analysis at a national and

local level. Improved power plant data gathered on a regional level and further studies into the

water requirements of existing and emerging technologies (such as carbon capture technologies)

are necessary to assess the water impacts of a developing decarbonizing economy in more detail.

References

1. Kenny, J.F.; Barber, N.L.; Hutson, S.S.; Linsey, K.S.; Lovelace, J.K.; Maupin, M.A.

Estimated Use of Water in the United States in 2005. U.S. Geological Survey Circular

1344. Reston, VA: USGS, 2009; p. 52.

2. Vörösmarty, C.; Green, P.; Salisbury, J.; Lammers, R. "Global Water Resources:

Vulnerability from Climate Change and Population Growth." Sci.; Vol. 289 (5477),

2000.

3. Bates, B.C.; Kundzewicz, Z.W.; Wu, S.; Palutikof, J.P. Climate Change and Water.

Technical Paper of the Intergovernmental Panel on Climate Change. Geneva,

Switzerland: IPCC, 2008.

4. Dai, A. "Drought Under Global Warming: A Review." Wiley Interdiscip. Rev.: Clim.

Change; Vol. 2, 2010; pp. 45–65.

5. National Energy Technology Laboratory (NETL). Water Vulnerabilities for Existing

Coal-fired Power Plants. DOE/NETL-2010/1429. Pittsburgh, PA: National Energy

Technology Laboratory, 2010.

6. California State Lands Commission. Resolution by the California State Lands

Commission Regarding Once-through Cooling in California Power Plants. Proposed

April 13, 2006.

7. New York State Department of Environmental Conservation. Best Technology Available

(BTA) for Cooling Water Intake Structures. Proposed March 4, 2010.

8. NETL. Impact of Drought on U.S. Steam Electric Power Plant Cooling Water Intakes

and Related Water Resource Management Issues. DOE/NETL-2009/1364. Pittsburgh,

PA: National Energy Technology Laboratory, 2009.

9. Fthenakis, V.; Kim, H.C. "Life-cycle Uses of Water in U.S. Electricity Generation."

Renew. Sustain. Energy Rev.; Vol. 14, 2010; pp. 2039–2048.

10. Gleick, P. Water in Crisis: A Guide to the World's Fresh Water Resources. New York:

Oxford University Press, 1993.

11. Inhaber, H. "Water Use in Renewable and Conventional Electricity Production." Energy

Sources, Part A; Vol. 26, 2004; pp. 309–322.

12. NETL. Cost and Performance Baseline for Fossil Energy Plants-Volume 1: Bituminous

Coal and Natural Gas to Electricity Final Report. DOE/NETL-2007/1281. Pittsburgh,

PA: National Energy Technology Laboratory, 2007.

13. NETL. Power Plant Water Usage and Loss Study. 2007 Update. Pittsburgh, PA:

National Energy Technology Laboratory, 2007.

14. Western Resource Advocates (WRA). A Sustainable Path: Meeting Nevada’s Water and

Energy Demands. Boulder, CO: Western Resource Advocates, 2008.

15. Turchi, C.; Wagner, M.; Kutscher, C. Water Use in Parabolic Trough Power Plants:

Summary Results from WorleyParsons’ Analyses. NREL/TP-5500-49468. Golden, CO:

National Renewable Energy Laboratory, 2010.

16. Stone, K.C.; Hunt, P.G.; Cantrell, K.B.; Ro, K.S. "The Potential Impacts of Biomass

Feedstock Production on Water Resource Availability." Bioresour.Technol.; Vol. 101,

2010; pp. 2014–2025.

17. Berndes, G. "Bioenergy and Water—The Implications of Large-scale Bioenergy

Production for Water Use and Supply." Global Environ. Change; Vol. 12, 2002; pp.

253–271.

18. Berndes, G. "Future Biomass Energy Supply: The Consumptive Water Use Perspective."

Int. J. Water Resour. Dev; Vol. 24, 2008; pp. 235–245.

19. Clark, C.; Harto, C.; Sullivan, J.; Wang, M. Water Use in the Development and

Operation of Geothermal Power Plants. ANL/EVS/R-10/5. Argonne, IL: Argonne

National Laboratory, 2011.

20. Kagel, A.; Bates, D.; Gawell, K. A Guide to Geothermal Energy and the Environment.

Washington, DC: Geothermal Energy Association, 2007.

21. Bradbury, D. "Californian Groups Clash Over Geothermal Water Use." Bus. Green;

2009.

22. Gleick, P. "Environmental Consequences of Hydroelectric Development: The Role of

Facility Size and Type." Energy; Vol. 17 (8), 1992; pp. 735–747.

23. Torcellini, P.; Long, N.; Judkoff, R. Consumptive Water Use for U.S. Power Production.

NREL/TP-550-33905. Golden, CO: National Renewable Energy Laboratory, 2003.

24. Miller, B.A.; Alavian, V.; Bender, M.D.; Benton, D.J.; Ostrowski Jr., P.; Parsly, J.A.;

Shiao, M.C. "Integrated Assessment of Temperature Change Impacts on the TVA

Reservoir and Power Supply Systems." Hydraulic Engineering: Saving a Threatened

Resource—In Search of Solutions: Proceedings of the Hydraulic Engineering Sessions at

Water Forum ’92; 1992; pp. 563–568.

25. Giusti, E.; Meyer, E. Water Consumption by Nuclear Power Plants and Some

Hydrological Implications. U.S. Geological Survey Circular 745. Reston, VA: USGS,

1977.

26. Yang, X.; Dziegielewski, B. "Water Use by Thermoelectric Power Plants in the United

States." J. Am. Water Resour. Assoc.; Vol. 43, 2007; pp. 160–169.

27. Dziegielewski, B.; Bik, T. Water Use Benchmarks for Thermoelectric Power Generation.

Research Report of the Department of Geography and Environmental Resources.

Carbondale, IL: Southern Illinois University, 2006.

28. Huston, R. An Overview of Water Requirements for Electric Power Generation. Water

Management by the Electric Power Industry. Gloyna, E.; Woodson, H.; Drew, H., eds.

Austin, TX: University of Texas Center for Research in Water Resources, 1975.

29. Energy Information Administration (EIA). Form EIA-923 Power Plant Operations

Report Instructions, OMB No. 1905-0129, U.S. Department of Energy, 2011.

30. U.S. Government Accountability Office (GAO). Improvements to Federal Water Use

Data would Increase Understanding of Trends in Power Plant Water Use. GAO 10-23.

Washington, DC: U.S. Government Accountability Office, 2009.

31. Solley, W.; Pierce, R.; Perlman, H. Estimated Use of Water in the United States in 1995.

U.S. Geological Survey Circular 1200. Reston, VA: USGS, 1999.

32. EIA. Form 906/920/923: Utility, Non-utility, and Combined Heat And Power Plant

Database. 2007 Monthly Time Series. Washington, DC: U.S. Energy Information

Administration, 2010.

33. NETL. 2007 Coal Plant Database. Pittsburgh, PA: National Energy Technology

Laboratory, 2007.

34. Leitner, A. Fuel from the Sky: Solar Power’s Potential for Western Energy Supply.

NREL/SR 550-32160. Golden, CO: National Renewable Energy Laboratory, 2002.

35. Meridian. Energy System Emissions and Materiel Requirements. Report to U.S.

Department of Energy, Alexandria, VA: Meridian Corporation, 1989.

36. American Wind Energy Association. AWEA Estimate Based on Data Obtained in

Personal Communication with Brian Roach, Fluidyne Corp., 1996.

http://archive.awea.org/faq/wwt_environment.html#How%20much%20water%20do%20

wind%20turbines%20use%20compared%20with%20conventional%20power%20plants.

Accessed November 17, 2010.

37. Cohen, G.; Kearney, D.; Drive, C.; Mar, D.; Kolb, G. Final Report on the Operation and

Maintenance Improvement Program for Concentrating Solar Plants. SAND99-1290.

Albuquerque, NM: Sandia National Laboratories, 1999.

38. Kelly, B. Nexant Parabolic Trough Solar Power Plant Systems Analysis-Task 2:

Comparison of Wet and Dry Rankine Cycle Heat Rejection. NREL/SR-550-40163.

Golden, CO: National Renewable Energy Laboratory, 2006.

39. Sargent & Lundy. Assessment of Parabolic Trough and Power Tower Solar Technology

Cost and Performance Forecasts. NREL/SR-550-34440. Golden, CO: National

Renewable Energy Laboratory, 2003.

40. Stoddard, L.; Abiecunas, J.; Connell, R.O. Economic, Energy, and Environmental

Benefits of Concentrating Solar Power in California. NREL/SR-550-39291. Golden, CO:

National Renewable Energy Laboratory, 2006.

41. Viebahn, P.; Kronshage, S.; Trieb, F.; Lechon, Y. Final Report on Technical Data, Costs,

and Life Cycle Inventories of Solar Thermal Power Plants. 502687. Rome, Italy: New

Energy Externalities Developments for Sustainability Project, 2008; pp. 1–95.

42. WorleyParsons. Beacon Solar Energy Project Dry Cooling Evaluation. Report No.

FPLS-0-LI-450-0001. North Sydney, Australia: WorleyParsons, 2009.

43. WorleyParsons. Analysis of Wet and Dry Condensing 125 MW Parabolic Trough Power

Plants. Report No. NREL-2-ME-REP-0002-R0. North Sydney, Australia:

WorleyParsons, 2009.

44. WorleyParsons. Material Input for Life Cycle Assessment Task 5 Subtask 2: O&M

Schedules. Report No. NREL-0-LS-019-0005. North Sydney, Australia: WorleyParsons,

2010.

45. WorleyParsons. Parabolic Trough Reference Plant for Cost Modeling with the Solar

Advisor Model. North Sydney, Australia: WorleyParsons, 2010.

46. Kutscher, C.; Buys, A. Analysis of Wet/Dry Hybrid Cooling for a Parabolic Trough

Power Plant. Golden, CO: National Renewable Energy Laboratory, 2006.

47. DOE. Concentrating Solar Power Commercial Application Study: Reducing Water

Consumption of Concentrating Solar Power Electricity Generation. Report to Congress.

Washington, DC: U.S. Department of Energy, 2009.

48. Brightsource_Energy. Application for Certification, Volumes I and II, for the Ivanpah

Solar Electric Generating System. Submitted to California Energy Commission Docket

Unit. Application For Certification (07-AFC-5), August 31, 2007.

49. California Energy Commission (CEC). 2007 Environmental Performance Report of

California’s Electrical Generation System. California Energy Commission Final Staff

Report. Sacramento, CA: California Energy Commission, 2008.

50. Electric Power Research Institute (EPRI). Water and Sustainability (Volume 2): An

Assessment of Water Demand, Supply, and Quality in the U.S.-The Next Half Century.

Technical Report 1006785. Palo Alto, CA: Electric Power Research Institute, 2002.

51. EPRI; DOE. Renewable Energy Technology Characterizations. EPRI Topical Report-

109496. Palo Alto, CA: EPRI, 1997.

52. Mann, M.; Spath, P. Life Cycle Assessment of a Biomass Gasification Combined-Cycle

System. TP-430-23076. Golden, CO: National Renewable Energy Laboratory, 1997.

53. Layton, D. "Water-related Impacts of Geothermal Energy Production in California's

Imperial Valley." 1979 Annual Meeting of the Geothermal Resources Council. CONF-

190906--18. Livermore, CA: Lawrence Livermore Laboratory, 1979.

54. Kozubal, E.; Kutscher, C. "Analysis of a Water-cooled Condenser in Series with an Air-

cooled Condenser for a Proposed 1-MW Geothermal Power Plant." Trans. - Geotherm.

Resour. Counc.; Vol. 27, 2003.

55. EERE. Geothermal Technologies Program: Geothermal FAQs. Washington, DC: U.S.

Department of Energy Office of Energy Efficiency and Renewable Energy, 2006.

56. Kutscher, C.; Costenaro, D. Assessment of Evaporative Cooling Enhancement Methods

for Air-Cooled Geothermal Power Plants. NREL/CP-550-32394. Golden, CO: National

Renewable Energy Laboratory, 2002.

57. NETL. Estimating Freshwater Needs to Meet Future Thermoelectric Generation

Requirements. DOE/NETL-400/2009/1339. Pittsburgh, PA: National Energy Technology

Laboratory, 2009.

58. Hoffmann, J.; Forbes, S.; Feeley, T. Estimating Freshwater Needs to Meet 2025

Electricity Generating Capacity Forecasts. Pittsburgh, PA: National Energy Technology

Laboratory, 2004; pp. 1–12.

59. NETL. Cost and Performance Baseline for Fossil Energy Plants-Volume 1: Bituminous

Coal and Natural Gas to Electricity-Revision 2. DOE/NETL-2010/1397. Pittsburgh, PA:

National Energy Technology Laboratory, 2010.

60. Feeley, T.J.; Green, L.; Murphy, J.T.; Hoffmann, J.; Carney, B.A. Department of

Energy/Office of Fossil Energy’s Power Plant Water Management R&D Program.

Pittsburgh, PA: National Energy Technology Laboratory, 2005; pp. 1–18.

61. NETL. Existing Plants, Emissions and Capture – Setting Water-Energy R&D Program

Goals. DOE/NETL-2009/1372. Pittsburgh, PA: National Energy Technology Laboratory,

2009.

62. Environmental Protection Agency (EPA). Clean Water Act, in Section 316b. Chapter 3,

U.S. Environmental Protection Agency. 2009.

63. EPRI. Use of Degraded Water Sources as Cooling Water in Power Plants. Technical

Report 1005359. Palo Alto, CA: Electric Power Research Institute, 2003.

64. Carter, H.; Schubel, J.; Wilson, R. "Thermally Induced Biological Effects Caused by

Once-through Cooling Systems: A Rationale for Evaluation." Environ. Manage.; Vol. 3,

1979; pp. 353–368.

65. Laws, E. Aquatic Pollution. 3rd edition. Hoboken, NJ: John Wiley and Sons, Inc, 2000.

66. Reynolds, J.Z. "Power Plant Cooling Systems: Policy Alternatives." Sci.; Vol. 207, 1980;

pp. 367–372.

67. Poumadère, M. "The 2003 Heat Wave in France: Dangerous Climate Change Here and

Now." Risk Anal.: An Off. Publi. Soc. Risk Anal.; Vol. 25, 2005; pp. 1483–1494.

F1147-E(10/2008)

REPORT DOCUMENTATION PAGE

Form Approved

OMB No. 0704-0188

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources,

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this bur

den estimate or any other aspect of this

collection of information, including suggestions for reducing the burden, to Department of Defense, Executive Services and Communications Directorate (0704-

0188). Respondents

should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it do

es not display a

currently valid OMB control number.

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.

1. REPORT DATE (DD-MM-YYYY)

March 2011

2. REPORT TYPE

Technical Report

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

A Review of Operational Water Consumption and Withdrawal

Factors for Electricity Generating Technologies

5a. CONTRACT NUMBER

DE-AC36-08GO28308

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

J. Macknick, R. Newmark, G. Heath, and KC Hallett

5d. PROJECT NUMBER

NREL/TP-6A20-50900

5e. TASK NUMBER

DOCC.1005

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401-3393

8. PERFORMING ORGANIZATION

REPORT NUMBER

NREL/TP-6A20-50900

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

10. SPONSOR/MONITOR'S ACRONYM(S)

NREL

11. SPONSORING/MONITORING

AGENCY REPORT NUMBER

12. DISTRIBUTION AVAILABILITY STATEMENT

National Technical Information Service

U.S. Department of Commerce

5285 Port Royal Road

Springfield, VA 22161

13. SUPPLEMENTARY NOTES

14. ABSTRACT (Maximum 200 Words)

Various studies have attempted to consolidate published estimates of water use impacts of electricity generating

technologies, resulting in a wide range of technologies and values based on different primary sources of literature.

The goal of this work is to consolidate the various primary literature estimates of water use during the generation of

electricity by conventional and renewable electricity generating technologies in the United States to more completely

convey the variability and uncertainty associated with water use in electricity generating technologies.

15. SUBJECT TERMS

water consumption; water withdrawal; electricity generating technologies; geothermal; thermoelectric power; cooling

systems; energy-economic model

16. SECURITY CLASSIFICATION OF:

17. LIMITATION

OF ABSTRACT

18. NUMBER

OF PAGES

19a. NAME OF RESPONSIBLE PERSON

a. REPORT

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

Unclassified

19b. TELEPHONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98)

Prescribed by ANSI Std. Z39.18