ETL 1110-2-550
30 May 97
b. The unit capacity values represent the
R = unit's equivalent forced outage rate,
investment cost associated with delivering the
percent
replacement capacity with the most likely thermal
alternatives. The /kW-year capacity value is
e = 2.718
based on a mix of coal-fired steam plants, gas-fired
b. Using this equation, effective load carrying
combined cycle plants, and gas-fired combustion
turbine plants, weighted by the Energy Information
capabilities (ELCC's) can be developed for each
Administration's projections of future capacity
unit size and each forced outage rate associated with
additions nationwide. The Corps usually obtains
the different proposed rehabilitation measures or
these values from the FERC, although they can be
plans. Ratios of ELCC are developed by dividing
developed from data published by the Electric
the ELCC for a proposed measure by the ELCC for
Power Research Institute (EPRI) and other sources.
the capacity value developed by FERC. The ratios
of ELCC can then be applied to the unit capacity
values to estimate the gain in capacity benefits that
D-14. Increase in Capacity Benefits
apply to the proposed rehabilitation measure or
Realized by Increased Availability
plan. The capacity values, as developed by FERC,
already include a factor which accounts for the
a. Although improving the electrical-
average availability of a typical hydropower unit
mechanical reliability of hydroelectric generating
compared with a thermal generating unit. For the
units clearly increases the peak load-carrying capa-
example study, assume that the $ 95/kW-year
bility of the units, it has proven difficult to quantita-
FERC capacity value is based on a typical hydro
tively estimate the benefits realized from this gain.
unit availability of 93 percent, and the availability
However, a relationship of generating unit average
of the units in their existing condition is 91 percent.
availability to effective load-carrying capability has
Assume that the turbine runner replacement
been developed.
increases the availability to 93 percent, and adding
the generator rewind increases it to 95 percent.
ELCC = C - {M * ln[(1 - R) + (R * eC/M)]}
These availability values would be obtained from
reliability studies.
where
c. While these capacity value adjustments are
ELCC = effective load-carrying capability of
small, they apply to the entire dependable capacity
unit, MW
of the plant, so they result in substantial benefits.
Table D-2 summarizes the calculation of the
C = rated capacity of that unit, MW
increase in capacity unit values based on the ELCC
ratios. The table also provides total benefits
M = system characteristic (typically,
attributable to both the increases in dependable
3 percent of total system capacity),
capacity and increases in reliability.
MW
Table D-2
Increase in Capacity Benefits
Case
Dependable Capacity
Capacity Value
Total Benefits
Incremental Benefits
MW
$/kW-year
(
||content||
,000)
(
||content||
,000)
Existing
185
93
17,200
--
New Runners
190
95
18,050
850
+ Rewind
226
97
21,900
4,700
D-8
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