POWER August 2011 - 66

PLANT OPERATION & MAINTENANCE
ity commission case filing for a cost of operations
recovery claim. Table 1 illustrates
the general range of cycling costs included
in that specific claim and contrasts common
rules of thumb with hard data. Table 2 summarizes
the estimated cycling costs for a 500MW
conventional coal-fired plant developed
as part of a recently completed cycling study.
The estimates developed using the approach
described in the following sections were several
times larger than customers' estimates.
Cost-of-Cycling Estimates
The Intertek-Aptech staff has developed
two approaches to developing cycling cost
estimates, such as the one summarized in
Table 2, so that results can be compared and
validated: the top-down estimate and the bottom-up
estimate. Unit- and plant-specific information
and industry data on similar units
are also used in these analyses.
Top-Down Estimates. Top-down estimates
use historical unit operating data and
historical cost data to determine the costs of
cycling operations (hot, warm, and cold starts
and shutdowns; load following; and ancillary
services such as regulation and ramping). Fundamentally,
we take wear and tear costs and
other cycling-related costs and statistically
Tips from the Cycling Experts
■ Understanding the true cost of operating a
plant under all potential operating scenarios
is vital to a successful cycling plant.
■ Both the equipment and operating procedures
are key factors in managing the
cost of cycling.
■ Cycling at the lowest possible ramp rate
that satisfies system needs or economics
will often reduce the damage rates.
Cycle at a fast rate only when really
necessary, as it is costly.
■ Operators of all cycling plants need to
pay special attention to water chemistry
and transients.
■ Low-impact or cost cycling will require
targeted equipment modifications for a
plant originally designed to operate in
baseload mode.
■ Develop startup and shutdown procedures,
and ensure that operators adhere
to them, so that desired operating reHDS
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determine the costs of cycling using detailed
multivariable regression techniques that examine
cost versus total cycling damage.
sults are achieved and are repeatable.
■ Perform a comprehensive cost-of-cycling
study to develop a specific set of costjustified
modifications and target cycling
countermeasures with a known payback.
■ Many items identified in the cost-of-cycling
study can be implemented immediately
and at low cost, such as revised
operating procedures or control system
modifications.
■ Employ a cost-monitoring system, such
as Intertek-Aptech's COSTCOM (Cost
Control of Operations and Maintenance
or Cost COMmunication) real-time software,
to alert operators when the plant
is using a damaging ramp rate or operating
mode, and then display real-time
costs to operators.
■ Keep offline time short and the equipment
hot to reduce cold starts, especially with
the boiler/heat recovery steam generator.
The first step to determining operating
costs is to examine the actual validated
plant maintenance costs, primarily found in
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66
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POWER | August 2011
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POWER August 2011

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