POWER July 2013 - 28

WATER MANAGEMENT
Water Issues Challenge
Power Generators
Drought and competing uses for water continue to challenge power plant operators
worldwide. In response, innovative approaches for reducing water use are
being explored from South Africa to China.
By David Wagman
W
ater is essential to thermoelectric
power generation, but drought
and growing competition for water
from myriad other uses can have major
effects inside the power plant, impacting
operations and, ultimately, reliability.
Consider these recent examples. Dominion's
Millstone nuclear plant in Connecticut
had to shut down a reactor last
August because the water it drew from
Long Island Sound was too warm. In response,
Dominion asked the Nuclear Regulatory
Commission in May this year for
permission to use the seawater at 80F, up
from 75F. A decision is expected in 2014,
following a technical review.
Also last summer, Exelon's two-unit
Braidwood nuclear station near Chicago
needed special permission to operate after the
temperature in its cooling water pond rose to
102F, four degrees above its normal limit.
Elsewhere in the U.S., low water levels on
parts of the Mississippi stalled coal barges
headed to power plants, forcing the U.S.
Army Corps of Engineers to dredge channels
to maintain commercial barge traffic.
Droughts in Europe in 2003 and 2006
forced the shutdown or curtailment of a number
of thermoelectric units. During the 2003
drought, for example, French nuclear opera28
tors
had to shut down as much as 25% of the
country's nuclear fleet.
Drought conditions affect hydroelectric
generation, too. As POWERnews reported
in March, Brazil, which sources 67% of its
power from hydro, has suffered the worst
drought in 50 years, causing dams in the
northeast to fall to 32% of capacity. Both
power generators and electricity consumers
have seen price spikes as a result.
One of the most dramatic examples in the
U.S. is the visibly lower water levels in Lake
Mead and Lake Powell, along the Colorado
River. The light-colored rock in this issue's
cover photo shows how far below historic
levels Lake Mead-which supplies water for
generation at the iconic Hoover Dam near
Las Vegas, Nev.-was in November 2010.
As of mid-May, Lake Powell storage behind
Glen Canyon Dam in Utah was 11,396
thousand acre-feet, around 47% of normal.
Lake Mead storage was 12,887 thousand
acre-feet, or 49% of normal. The April-July
forecast for water flows along the Colorado
River was 3.00 million acre-feet, or around
42% of average. Despite the low levels, the
U.S. Bureau of Reclamation (USBR), which
operates Glen Canyon and Hoover Dams, has
been able to meet its contractual obligations.
However, Ron Smith, USBR acting power
www.powermag.com
Courtesy: NV Energy
manager for the Lower Colorado Region, explained
that lower water levels mean lower
pressure and less generation potential, so the
units have been derated further.
To help address the impacts of lower
lake level on generation at Hoover Dam, the
USBR has installed a " wide-head " turbine
(sometimes called a " low-head " turbine)
on the Nevada side of the dam. N8, as it is
called, is rated at 130 MW but is currently
derated to 115 based on the lake level. " It's
been a very successful installation, " Smith
told POWER, " and the plan is to install
more, " because this type of turbine enables
generation across a wider range of rated
capacity, making for more efficient generation
under low-head conditions.
Growing Water Scarcity
Drought can seem extreme in the U.S., but
a 2011 report from the National Energy
Technology Laboratory (NETL), " Reducing
Freshwater Consumption at Coal-Fired Power
Plants: Approaches Used Outside the United
States, " says that water-short areas can be
more widespread in countries such as China,
South Africa, and Australia. China, for example,
ranks as the world's third-driest country.
The NETL report says that by 2030, China's
annual water demand could reach 216 trillion
POWER | July 2013
http://www.powermag.com
POWER July 2013

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