POWER July 2013 - 29

WATER MANAGEMENT
gallons, one-third of it for industrial demand
driven by thermal power generation. Water
supplies in China for 2030 are estimated at
roughly 164 trillion gallons. As a result, demand
is on track to exceed supply by about
52 trillion gallons in 2030. By comparison,
total water withdrawals in the U.S. in 2005
were 150 trillion gallons.
Reducing water consumption at all
types of steam power plants has been a
worldwide concern for years, sparking
a wide range of efforts to cut water use
Global investment. Efficiency improvements along with supercritical and ultrasupercritical
technologies are gaining favor in countries that face water constraints. Source: NETL
Country
South
Africa
Electricity
generated
by coal
Drivers for reducing freshwater
consumption
85% Abundant coal resources. Coal resources
and power plants are in dry regions.
Approaches for reducing freshwater
consumption
Use efficient supercritical technologies,
dry cooling, advanced control systems,
dry bottom ash handling, and desalination.
Participate in water infrastructure development,
incentives, and water metering.
China
80% Large coal resources, so coal is to be
the dominant fuel for decades. China is
world's third-driest country, and there are
specific policies for reducing freshwater
consumption.
Australia 70% Coal is likely to supply more than half the
total electrical generating capacity through
2035. Many areas are subject to long
drought. Groundwater use is restricted.
India
70% More power is needed than is available.
Coal is expected to remain the dominant
fuel through at least 2050.
Denmark
50% No domestic coal resources.
Germany 49% Coal is to remain a significant power generation
fuel for several years. About half
of coal-fired generation is from low-rank
lignite, and power plants are aging.
Japan
Italy
25% Imports all fuel. It is often difficult to obtain
water from local governments.
13% Coal-fired power generation is to increase due
to coal's lower costs; coal is expected to provide
about one-third of generation as of 2013.
Replace, retrofit small, inefficient plants. Increase
use of supercritical and ultrasupercritical
units. Use dry cooling. Explore integrated
gasification combined cycle (IGCC) technology.
Use desalination at power plants.
Supercritical steam cycles. Dry cooling.
Turbine upgrades. Coal drying. In-plant
water recycling.
Increase efficiency. Use advanced supercritical
steam parameters. Replace/retrofit
old, inefficient plants. Reuse and recycle
wastewater. Research IGCC.
Supercritical and ultrasupercritical plants.
Cogeneration.
Replacement of old, inefficient plants with
new, efficient plants, including ultrasupercritical.
Research into plants with high steam
parameters and new materials. Lignite drying.
Use supercritical and ultrasupercritical
technologies and low-water-consuming
emissions control equipment.
Replace/retrofit old plants with ultrasupercritical
technology.
1. Fourteen gallons of water. NV Energy's 530-MW Walter M. Higgins Generating
Station in Nevada uses a dry-cooling system that enables it to use 14 gallons of water for each
megawatt of power produced. A conventionally cooled power plant might use up to 650 gallons.
Courtesy: NV Energy
while meeting growing demand for electricity
(see table).
Steam-electric plants in the U.S. account
for around 40% of the nation's freshwater
withdrawals. Much of that water is returned
to its source, however. That leaves actual
net consumption for power generation at
around 3% of the nation's overall freshwater
consumption.
Much of the net consumption stems from
evaporation and drift losses from cooling
systems. Research published by the Electric
Power Research Institute (EPRI) suggests
that water use rates at plants with closedcycle,
wet cooling systems might not be
sustainable in some locations as thermal
discharges from once-through cooling face
increasing regulatory scrutiny. Some plants
already operate under water use restrictions
or are being required to install water-conserving
technologies. What's more, siting
new capacity can be difficult due to water
supply constraints.
The net result is that cooling and water
treatment technologies to reduce water consumption,
the use of reclaimed water, and the
reuse of internal water and even wastewater
streams are gaining traction in the generation
sector. (See also " New Coal Plant Technologies
Will Demand More Water " in the POWER
archives at powermag.com.)
For example, NV Energy's Walter M.
Higgins Generating Station in southern
Nevada (Figure 1 and the photo at the top
of this story) is a 530-MW combined cycle
power plant that uses two Westinghouse
501FD combustion turbines and an Alstom
STF30C steam turbine. The plant entered
service in 2004 and, unlike conventional
power plants, uses a six-story-high dry
cooling system. Similar to a car radiator,
40 fans (each 34 feet in diameter) condense
the steam and cool plant equipment. The
plant uses 14 gallons of water for each
megawatt produced. By contrast, a conventionally
cooled power plant of similar size
might use as much as 650 gallons of water
per megawatt. The Higgins Station also
saves water by reusing " gray water " from
three nearby casinos.
NV Energy is one of the most experienced
generators in the U.S. when it comes to dry
cooling. Its 1,102-MW Chuck Lenzie Station,
30 miles north of Las Vegas, ranks as one of
North America's largest dry-cooled power
plants. The plant includes two side-by-side
power production blocks outfitted with GE
7FA combustion turbines. The exhaust from
the four turbines produces steam for two GE
D-11 steam turbines. As part of its water use
strategy, the Lenzie station also uses a water
clarifier system that recaptures and recycles
about 75% of the process water.
July 2013 | POWER
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POWER July 2013

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