POWER December 2014 - 49

HEAT RATE IMPROVEMENT
■ Remote monitoring. The use of remote
monitoring centers was documented to
improve heat rate 2.5% to 4%.
■ Steam turbine steam path modifications.
EPRI members reported steam turbine
steam path modifications were worth 2%
to 4% heat rate improvements.
■ Cycle alignment. Implementing a cycle
alignment (isolation) program was documented
to be worth at least 0.5% improvement
in heat rate.
■ Capital and maintenance projects. A list
of 57 potential actions and modifications
to improve efficiency was made and evaluated
in detail. While the amount of gains
would be unit-specific, the projected heat
rate improvements ranged from less than
0.1% to over 2% for the various actions
and modifications. One utility applied the
methodology and analyzed a number of
these potential projects for its own specific
fleet, resulting in a projected 5% improvement
in heat rate.
The numerical values presented in this
article may not be additive. They also may
not be achievable or justifiable at every
coal-fired plant. The staffs at many wellperforming
plants have been proactive and
have already implemented some of the previously
discussed improvements (for example,
steam turbine upgrades and remote
monitoring centers), thereby reducing their
potential maximum heat rate improvement
range.
The finances of power generating companies,
both regulated and independent
power producers, are managed prudently,
so any large expenditure must be justified
and/or create a return on investment.
Smaller units consume less fuel, making a
reasonable return on investment difficult
to achieve for expensive modifications.
As mentioned, these units are old and may
have a limited remaining life. Some of
these modifications and actions are quite
costly and require a long period of operation
to realize a return on investment. Such
modifications may not be applicable for
units with a few or unknown years of remaining
projected lifetime.
Finally, management of many coal-fired
plants may be unwilling to attempt many
of these proposed improvements in order
to avoid the possibility of triggering a New
Source Review, which may result in having
to install millions of dollars of additional
emissions controls.
Future Research
Many of the efficiency improvement projects
have been done in parallel, so the individual
effect of each is not well defined. Tests and
analyses could be conducted before and after
future individual modifications are made to
refine the results and reduce the uncertainty
when those modifications are proposed for
other units.
Based on industry data and studies conducted
by EPRI and others, the maximum
achievable heat rate improvement for any
given coal-fired plant is unknown. More detailed
studies to characterize improvements,
taking into consideration constraints like
fuel changes, equipment degradation, design
changes, new environmental controls, and so
forth, are needed to determine the technical
and economic feasibility of the options. Afterwards,
an estimate could be made of the
maximum potential efficiency gains.
While the cost may be high, one could attempt
to implement as many of those modifications
and actions as possible on one unit and measure
the gains realized to provide perhaps the upper
cap of expected heat rate improvement. ■
-Sam Korellis is a principal technical
leader in the Combustion Performance
and Emissions Control R&D group at EPRI.
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POWER December 2014

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