POWER September 2014 - 52

WATER
2. Electricity market under with-regulation conditions that reduce capacity.
Lost capacity means different, more-expensive units operate, leading to generation
cost increases (the difference between the red and blue lines) and changes in emissions.
Source: Veritas Economic Consulting LLC
■ Baseline supply ■ With-regulation supply
90
80
70
60
50
40
30
20
10
Less expensive to operate
the new equilibrium, a less-efficient unit is
operating and the cost of meeting electrical
load increases by the shaded area between the
red and blue lines. The closed unit no longer
has stack emissions, but there are increased
emissions from the fossil-fueled plant(s) that
make up the lost generation.
Implications of Compliance via
Cooling Tower Retrofit
As just explained, increased production costs
arise from capacity losses due to a plant cloMore
expensive to operate
Generating units
sure. However, similar effects occur whenever
a unit's net capacity is reduced. This is the case
any time a cooling tower is operated because of
electricity requirements for pumps and fans.
Based on a " 1% of capacity " rule of thumb
for mechanical draft tower electricity requirement,
a 1,000-MW unit converting to closedcycle
cooling would require 10 MW that would
previously have been supplied to the grid.
Extended outages for conversions could
have particularly significant production cost
implications. Considering emissions impacts,
outages like shutdowns lead to reduced
on-site emissions for fossil-fueled units and
increased emissions from fossil-fueled units
making up lost generation.
These outages are expected to be more
extensive for nuclear plants due to extensive
underground piping and safety considerations.
Unlike fossil plants, nuclear plants do not create
stack emissions, and there is no on-site
emission reduction. Operating pumps and
fans are effectively an auxiliary electrical load
requiring replacement generation from off-site
fossil sources that do create emissions.
An additional important effect arises from
cooling tower energy penalties. According to
the EPA, the energy penalty arises from " slightly
lower generating efficiency attributed to higher
turbine backpressure when the condenser is not
replaced with one optimized for closed cycle operation
when retrofitting existing units. " When
discussing this topic, the rule notes the EPA's
concerns regarding " increased air emissions associated
with additional fuel usage due to the
energy penalty when retrofitting to cooling towers
related to human health, welfare, and global
climate. " This effect occurs because many oncethrough
power plants were situated and designed
to take advantage of naturally cold water. Colder
cooling water is important for thermal generation
because it increases unit efficiency. Closedcycle
conversions would cause these units to use
warmer closed-cycle cooling water and would
Gas-Turbine HRSG
BEST SUITED
FOR GAS
TURBINES UP
TO 120MW.
FOLLOW A LEADER
52
14 H.P. Vent Silencer
15 H.P. Steam Drum
H.P. Steam Outlet
4 H.P. Superheater
5 H.P. Evaporator
2 Duct Burner
1 Distribution Grid
18 Stack
17 L.P. Steam Drum w/ Integral Deaerator
16 L.P. Vent Silencer
6 C.O. Catalyst
9 H.P. Evaporator
3 Observation Port
7 Injection Grid
8 S.C.R.
10 H.P. Economizer
11 L.P. Superheater
L.P. Superheater Outlet
L.P. Evaporator 13
DA. Pre-Heater 12
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POWER September 2014

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