POWER May 2011 - 60

THE FUTURE OF COAL
■ Determine fleet baseline performance.
Baseline performance data is presented for
key performance metrics, including plant
age, heat rate, and capacity factor. For
ease of presentation, plants were grouped
into five-year age " bins. "
■ Develop reasonable predictions. Using the
baseline performance as a starting point, I
analyzed dozens of alternative plant configurations
and historic performance. One
particular database query seems to present
good information for estimating potential
plant closures.
Characterize the Fleet
The U.S. coal-fired fleet consists of 1,105
units with a nameplate capacity of 342.733
GW, according to the Burns & McDonnell
database. Because plant age is often cited as
a reason for retirement, it's useful to examine
the fleet's age. Figure 1 illustrates the age of
each unit in the database, calculated as the
difference between 2011 and the year it began
commercial operation.
The average age of all units is 42.5 years,
the MW-weighted age is 37.1 years, and
the capacity factor-weighted age is 40.0
2. Coal fleet fuel use. Over 86% of the
coal fleet burns either a bituminous or a subbituminous
fuel. Source: POWER and Burns
& McDonnell
Lignite 3%
Other
12%
Subbituminous
29%
Bituminous 56%
years. The MW-weighted age tells us that
the average size of new power plants has
been increasing over the past few decades.
The capacity factor-weighted age tells us
that the capacity factor of newer plants is,
on average, higher. No matter how you cut
the numbers, the fleet continues to age-
although we shouldn't mistake age alone
as representative of the economic life of a
power plant.
The database includes many useful metrics
that describe interesting characteristics
of the fleet, including type of coal used (Figure
2), boiler manufacturer (Figure 3), and
boiler type (Figure 4).
As discussed earlier, classification of combustion
byproducts is currently under intense
review by the EPA, and new cooling water
intake structure rules were proposed in late
March. We can also characterize the number
of units that these two rules may impact (Figures
5 and 6) by examining metrics that I'll
return to later.
Determine Fleet Baseline
Performance
Three metrics were selected to describe the
3. Coal fleet boiler manufacturers.
Source: POWER and Burns & McDonnell
Riley/Babcock
Power 9%
Other
12%
Foster Wheeler
115%
CE/Alstom 39%
Babcock & Wilcox
30%
performance of the current fleet of coal-fired
plants. The first is the average size of plants
constructed over time (Figure 7). Interestingly,
the glory days for building very large central
station plants was the 1960s, especially
for those first supercritical plants, ranging up
to 1,300 MW.
Given that these large plants remain vital
baseload resources, it's no wonder that the
capacity factor-weighted age of the fleet is
40 years. Although the number of plants constructed
and placed into operation over the
past 10 years has fallen short of predictions,
their average nameplate rating increased significantly.
The
average capacity factor illustrates that
plants under 40 years old are the backbone
of the baseload fleet; as a plant hits about the
50-year milestone, operation appears to shift
to more load-following or cycling operation,
as suggested by decreasing capacity factors
(Figure 8). For comparison, the overall average
fleet capacity factor is approximately
62%. However, 455 plants (not including
recently commissioned ones, for which capacity
factor information was not available)
reported an annual capacity factor of 70% or
higher.
The average size of plants over 40 years
of age is 400 MW. Average plant heat rate,
as expected, generally improved in recent
years (Figure 9). Plant heat rate is difficult
to determine for some plants, so the Burns &
McDonnell database does have a few plant
heat rate gaps (81% of the plants reported).
Nevertheless, the trends and averages presented
here remain instructive.
Develop Predictions
Predictions must be scenario-based, given
the current regulatory uncertainty. That
means that unit-based decisions using specific
company economic modeling, independent
system operator dispatching decisions,
and other regional grid issues are ignored,
4. Coal fleet boiler design. Source:
POWER and Burns & McDonnell
Vert-ceiling 2%
Fluid bed 3%
Unknown 6%
Cyclone 7%
Opposed 19%
Other 7%
T-fired 37%
unknown 11%
Wet 11%
Other or
Pond or
canal 10%
Dry 78%
Front 20%
Tower, forced
14%
Other
14%
60
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POWER | May 2011
Once-through,
fresh 44%
Tower,
induced
9%
5.Coal fleet bottom ash handling.
Source: POWER and Burns & McDonnell
6. Coal fleet cooling water source.
Source: POWER and Burns & McDonnell
Once-through, salt 3%
Tower, natural 6%
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POWER May 2011

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