POWER April 2012 - 56

WATER MANAGEMENT
to usage. Many projects have inventoried
these sources, tested the waters, investigated
impediments to use, and explored treatment
methods to increase usage.
" Alternative water sources continue to replace
freshwater usage for cooling for power
plants, and this is probably the biggest trend
in water management in the power sector, "
Carney said. " Although no specific projects
can be cited, it is likely that many of the
NETL projects on alternative sources have
assisted in this implementation. "
For example, Nalco Co., working with
NETL, recently completed testing of a prototype
electrodeionization (EDI)/scale inhibitor
that would allow more alternative water
sources to be used. Carney pointed out that
" although the EDI process is not commercialized
yet, they did have improvements to scale
inhibitors for calcite, gypsum, and silica that
will be used at power plants. "
Another successful technology, not yet
used commercially, is a flue gas drying process
that was demonstrated at the pilot scale
by Lehigh University, Carney said. The condensing
heat exchangers dealt with the acid
environment in the flue gas, and calculations
show that they are cost-effective when the
recovered heat is used to preheat boiler feedwater.
The recovered water could be used to
replace 10% to 33% of required cooling water.
The process may also be used to dry flue
gas for carbon capture applications.
Another recent NETL project Carney
mentioned is the prototype Air2Air Water
Conservation Cooling Tower that was constructed
by SPX Cooling Technologies at the
San Juan Generating Station in New Mexico
(Figure 7). It was tested from 2008 through
2009 and provided cooling for 35 MW of
power production.
The tower saved 18.5% of the water lost in
cooling at this location with no degradation
of thermal performance on the condenser and
no freezing problems. Carney said, " depending
on climate, this technology could save
10% to 25% of the water lost to evaporation
from cooling towers. "
The commercial product arising from this
work is called the ClearSky Plume Abatement
Tower; it can be viewed at www.spxclearsky
.com. Carney pointed out that, although the
technology is currently marketed as plume
abatement, some customers are interested in
it due to the water savings.
Although not a part of this prototype tower,
it is possible to collect the water that is condensed,
which is very clean and nearly pure,
resulting in an inexpensive, low-energy water
treatment method, Carney explained. With the
technology's current configuration, the water
just flows back into the tower and replaces
withdrawals and decreases the amount of salty
56
blowdown water that needs to be discharged.
Additional improvements to Air2Air Technology
will be finished in 2012.
" Currently, NETL is receiving no funding
for power plant water issues, " Carney said.
" Funding for thermoelectric power plant cooling/water
management was discontinued in
2009, and the remaining projects will wrap
up shortly. The research focus for the Existing
Plants Program has shifted to carbon capture.
There is some research now in the carbon sequestration
program for water usage. "
New Initiatives to Promote
Sustainable Water Usage
Recently, the U.S. government made some
moves nationally to deal with water scarcity,
and state governments also have taken
action, especially in arid areas and those
that are most heavily affected by freshwater
shortages, Markhoff said. Areas such as the
Southwest, including California, currently
have very serious demands on their water
supplies and have already taken measures to
require zero liquid discharge at power plants.
He emphasized: " As the dynamics change
throughout the rest of the country in the
coming years, however, we expect eventual
changes in policy and more stringent requirements
to appear in other states as well. "
Technology solutions exist to overcome
challenges related to water scarcity, according
to Kemp. The key challenge is economics and
understanding what solution will best balance
water, economics, and environmental factors
for a specific plant in a specific location. Options
include air cooling technology, similar to
what was deployed by Pacific Gas & Electric
for its Gateway Generating Station in Antioch,
Calif. The Gateway plant's dry cooling
technology uses 97% less water and produces
96% less discharge than a conventional water
cooling system and avoids the use of river water.
Kemp added that hybrid systems that use
a combination of dry and wet cooling are another
technology option.
" There is no free lunch, however, " Kemp
said. " The cooling technologies that use less
water are more expensive to install, reduce
the performance efficiency of the generating
technology, and end up increasing fuel consumption
and greenhouse gas emissions per
MWh generated. "
An area of potential growth in the U.S. is
the use of recycled or reclaimed water. Kemp
pointed out that " this is used in other parts
of the world, particularly Singapore, with tremendous
success. The Calpine power generation
station in Mankato, Minn. is also a good
example of the benefits of using recycled water
for cooling thermal power stations. "
Eberts also has some strong opinions
about what future steps need to be taken in
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POWER | April 2012
the U.S. to deal with increasing challenges
related to water availability. " First and foremost,
we must increase education and awareness
about the true value of water, " he said.
" We need to start making positive steps toward
cost recovery for water treatment and
water transmission infrastructure and not be
reliant on subsidies that are reliant on public
will. We need to continue to invest in our
water infrastructure. History shows us that it
is better to plan, maintain, and invest, rather
than wait until a crisis to act. Delaying and
deferring could result in paying two to three
times more for infrastructure than what it
would have cost under a reasonable and
planned schedule. "
Eberts said that state and federal governments
need to recognize the value of water
and the need for investment in our country's
buried infrastructure. He added that " state-tostate
regulations for water varies widely-we
need more consistency for water use when
siting power plants. "
Likewise, Byers pointed out that from an
environmental regulatory standpoint, the nation
as a whole would benefit from a more
coordinated and comprehensive national
policy that balances the goals of improving
water quality and stemming water scarcity.
7. A cool way to conserve water. The
prototype Air2Air Water Conservation Cooling
Tower that was constructed by SPX Cooling
Technologies at the San Juan Generating Station
in New Mexico in collaboration with the
National Energy Technology Laboratory is on
the left. It is larger and has no plume, as compared
with the existing cooling towers on the
right. It was tested from 2008 to 2009 and
provided cooling for 35 MW of power production.
The ambient temperature was 27F with
a relative humidity of 65% when this photograph
was taken. Source: National Energy
Technology Laboratory
http://www.spxclearsky http://www.powermag.com
POWER April 2012

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