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Emission Projections Under NSR Alternatives 

General Concepts 

This paper addresses the emission Implications of New Source Review (MSR) policies. 

These policies will be discussed in the context of their impacts on fossil fu sl fired power 

plants, although the regulations also apply to other source categories as veil. The units 

of key concern are existing coal-fired generators which replace a part or ci>mponent 

and which, in doing so, could increase emissions. The issue is how different policies on 

defining routine maintenance, repair, and replacement (RMR&R) might inl uence 

national emission rates; The policies in question could create either incer tives or 

barriers to improved efficiency, reliability or capacity when actions are taktin during 

maintenance, repair, or replacement of parts at a facility subject to air pollution 

regulation. 

Generally speaking, when parts at a power plant are replaced, they are replaced with 

parts having the equivalent function. In many cases, in the time period between the 

original operation of the power plant, and the point where a part is replaced, technology 

has advanced and better performing parts are now available. Indeed, in some cases, 

exact replacements for the original design are not available. The main rne onanism for 

emissions to be affected is through improvement in unit efficiency, capacity, and 

reliability, as newer parts tend to be more efficient and less prone to malfunction. On a 

regional basis, the primary impact of higher efficiency is to lower emissions, because 

less fuel Is needed to create the same amount of electricity. Changes causing an 

increase in capacity, on the other hand, could lead to greater emissions, because the 

alternative to increased output from existing coal power plants would probably be 

increased construction of new units, which would have lower emissions per kilowatthour generated (whether coal or gas-fired). Improved reliability or availabilily has an 

effect similar to increased capacity if existing plant generation displaces new plant 

generation, as demand for power grows. However, if a change in capacity or availability 

occurred more often, or to a greater degree, at lower emitting coal units tha i at higher 

emitting coal units, then economic dispatching of the inventory of plants could lead to 

lower emissions overall. Given the complexity of the problem, it is difficult tc predict the 

outcome of changes in efficiency, capacity and reliability without the assistance of 

complex computer models. 

These general trends in emissions are not universal. Pollutants which are "capped", 

like sulfur dioxide (S02) under the acid rain program, are not influenced by lliese 

factors. Any reduction or increase In emissions at a particular unit would be adjusted 

for within the emission cap, and regional emissions would remain constant. Nitrogen 

oxides (NOx) present a complex situation, because emissions in most Eastein states 

are capped under the ozone/NOx SIP Call, whereas emissions in other state s are not 

capped. Mercury emissions from existing power plants are currently not regulated, but 

in the future may be subject to a capped limit under a regulatory scheme like the Clear 

Skies Initiative, or they may be uncapped under a Section 112 regulatory sctieme. 
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Emission Projections 

The 0OE/E1A NEMS model was used to evaluate the emissions implications of current 

and alternative NSR approaches. Tables 1 through 3, below, present mc deling results 

for a range of assumptions for efficiency and availability changes which might result for 

an NSR approach which facilitated improvements, versus one which posud barriers to 

such improvements. In each table, the current rules are represented by ihe "Base 

Case" and possible outcomes for modified NSR rules are included as alternative 

scenarios. In this analysis, "capacity" changes are defined as changes which increase 

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Emission Projections 

The DOE/E1A NEMS model was used to evaluate the emissions implications of current 

and alternative NSR approaches. Tables 1 through 3, below, present mc deling results 

for a range of assumptions for efficiency and availability changes which night result for 

an NSR approach which facilitated improvements, versus one which post id barriers to 

such improvements. In each table, the current rules are represented by tlie "Base 

Case" and possible outcomes for modified NSR rules are Included as alternative 

scenarios, in this analysis, "capacity" changes are defined as changes w uch increase 

the amount of fuel which could be utilized above initial design rates for the power plant. 

No increase in hourly fuel use was assumed, due to expectations that physical changes 

at a unit which caused increases in such capacity would be precluded by environmental 

regulation. Results are included for carbon dioxide emissions (expressed as carbon), 

S02, NOx, and mercury. 

Figures 1 through 3 show NOx emission changes overtime for the same hypothetical 

changes in unit availability and heat rate (efficiency). These results reflecl extreme 

scenarios, and actual outcomes are likely to fall short of the potential amis ;lon 

reductions and Increases presented (perhaps by about one-half). Mftlgatlrg factors 

include the ability of source owner/operators to avoid new source review by "netting 

out", the likelihood that modest improvements in these parameters could bn» made at 

existing unite without triggering NSR, and the possibility that potential imprcivement 

rates would not be achieved in practice. Attachments 1 and 2 present greater detail on 

the technologies assumed and the mechanisms by which changes in efficiency and 

availability would manifest in annual emissions. 

Table 1. 

Parameter 

2010 

Coal Generation (billion kJlowatthours) 

[•^i»rr_T^TTTn^ffiii»ffl»^?.,r_iirriTii:irn____________________i 

Avg. Efficiency - Coal (percent) 

Carbon Emissions (minton metric tons) 

Sulfur Dioxide Emissions (million tons) 

Nitrogen Oxicty Emissions (million tons) 

Mercury Emissions (tons) 

2020 

Coal Generation (billion kllowatthours) 

Coal Consumption (quadrillion Btu) 

Avg. Efficiency - Coal (percent) 

fi^,!!OT^1^rfl7af_T_ll^____iTm3 

Sulfur Dioxide Emissions > million tons) 

Nitrogen Oxide Emissions (million tons) 

Mercury Emissions (tons) 

Base Case 

2215.2 

22.8 

33.2% 

688.8 

9.7 

4.0 

43.7 

2423.2 

24.7 

33.d% 

790.i. 

8.9 

4.2 

44.0 

10/0* 

2231.7 

20.7 

36.0% 

634.4 

9.7 

3.7 

41 .£ 

2484.3 

&.1 

37.0% 

75-7.6 

8.9 

3.9 

42.2 

Scenario 

10/2 "" 

2271.1. 

21.:» 

38.89! i 

639; 

9.7 

3.(1 

41.1 

2612.1 

23.2 

37.0% 

745.7 

8.9 

3.9 

42.7 

' 

10/5*" 

2336.6 

21.6 

36.9% 

647.6 

9.7 

3.6 

42.8 

2600.5 

24.0 

36.9% 

759.4 

8.9 

4.0 

43.2 

Scenaho 10/0 assumes 10% improvement In heat rate and no change in availability. 

Scenario 10/2 assumes 10% improvement In heat rate and 2% in availability. 

Scenario 10/5 assumes 10% improvement in heat rate and 5% in availability. 
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Table 2. 

Parameter 

2010 

Avg. Efficiency - Coal (percent) 

Carbon Emissions (million metric tons) 

Sulfur Dioxide Emissions (million tons) 

Coal Generation (billion kilowatthours) 

Coal Consumption i1

PTTTT-miTmr-C ' T 

Nitrogen Oxide Emissions (million tons) 

Mercury Emissions (tons) 

2020 

Coal Generation (billion kilowatthours) 

Coal Consumption (quadrillion Btu) 

Avg. Efficiency- Coal (percent) 

Carbon Emissions (million metric tons 

Sulfur Dioxide Emissions (million tons! 

Nitrogen Oxide Emissions (million tons) fc 

Mercury Emissions (tons.' 

Base Ga$a 

2215.2 

22.8 

33.2% 

886.8 

4.0 

« T 

2423.2 

24.71 

33.5% 

790.2 

8.9 

T 2 

MS. 

1W0 

2235.0 

19.6 

39.0% 

TOM 

"3§ir 

2489.0 

21.8 

39.0% 

7753 

8.9 

3.7 

Scenario 

40.5 

lie 

22! 0.3 

.!0.0 

39 5%" 

~8lX3" 

4iJ!3 

252:181 

. Zi:.1 

38.-l%i 

«iS" 

HI'S 

4i57 

Scenario 15/0 assumes 15% improvement in heat rate and no change in availability. 

Scenario 15/2 assumes 15% improvement in heat rate and 2% In availability. 

Scenario 15/5 assumes 15% improvement in heat rata and 5% in availability. 

15/5' 

2343.8 

IBS 

39.0% 

619.6 

9.7 

3.7 

ITU 

2616.1 

2 2J 

38.9% 

730.5 

8.9 

3.9 

4Z2I 

Table 3. 

Avg. Efficiency - Coal (percent) 

Carbon Emissions (million metric tons 

Parameter 

2010 

Coal Generation (billion kilowatthours) 

Coal Consumption (quadrillion Btu) 

Sulfur Dioxide Emissions (million tons 

Nitrogen Oxide Emissions (million tons) 

Mercury Emissions (tons) 

2020 

Coal Generation (billion kilowatthours) 

Coal Consumption (quadrillion Btu) 

Avg. Efficiency - Coal (percent, 

Carbon Emissions (million metric tons) 

(percent) 

ffiion metrh 

Sulfur Dioxide Emissions (million tons) 

Nitrogen Oxide Emissions (million tons) 

Mercury Emissions (tons! 

Base Case 

2215.2 

22.8 

"35-2%* 

688.8 

"97 

4.0 

43.7 

2423.2 

"237 

33.5%, 

790.2 

8.9 

__u 

311 

"W 

£cenai 

2222.81 

21.7 

34.9% 

860.7 

9.7 

3.9 

42.9 

2457.4 

"2-T8 

35.2% 

765.3 

9.0 

4.0 

3_d 

to 

2264. 

22.1 

35.0% 

666. 

9,7 

3.8 

"33T3 

2489.2 

24.1 

35.2% 

771.0 

9.0 

TT 

43.7 

' Scenario 5/0 assumes 5% improvement in heat rate and no change in availability. 

** Scenario 5/2 assumes 5% improvement in heat rate and 2% in availability. 

*** Scenario 5/5 assumes 5% Improvement In heat rate and 5% in availability. 

5/5 •5K 

2328.8 

22.7| 

34.9% 

676.7 

4.0 

44.0 

2570.3 

24.9 

35.2% 

783.9 

8.9 

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Conclusions 

For capped pollutants, like S02, NSR policy will have no impact on future emissions. 

For uncapped, or partially capped pollutants, a policy that facilitates Improvements in 

efficiency and reliability as parts are replaced will tend to reduce national amissions. 

For the pollutants and scenarios examined in this analysis, emissions declined by a 

moderate amount (typically 3-7%) in ail scenarios except one, compared lo a baseline 

case in which such improvements in plants were prohibited under NSR pcilicy. The one 

scenario in which some emissions Increased (by up to 1%) combined a wry high 

increase in availability with a low Improvement in efficiency. This scenario is not 

considered a likely outcome from NSR regulatory changes (see discussion of likely 

availability changes In Attachment 1), but Is included for completeness. 
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Attachment 1 

Unit Availability For Coal-fired Power Plants 

Data on the causes of power plant outages is maintained by the North American 

Electric Reliability Council (NERC), and much of tiiis data is accessible at their website 

(www, nerc.eom/~aads/_. The top 25 causes of outages at coal units for tte period 

1996-2000 are presented In the table below. 

NERC GADS Data 

Principal causes of outages or derating at coal units, 1996-2000. 

SYSTEM/COMPONENT CAUSE 

AVG NO. OC C 

PER UNIT-YR 

0.43 

0.33 

0.21 

0.57 

0.32 

4.95 

1.83 

1.16 

0.92 

1.63 

2.67 

0.7 

0.96 

6.44 

0.62 

0.57 

0.20 

0.48 

3.89 

0.39 

0.53 

0.56 

0.51 

0.02 

0.32 

AVERAGE MWH 

PER UNIT-YR 

83,199 

00.766 

41,527 

40,013 

37,735 

35,785 

30,202 

22.949 

19,642 

19,809 

17,237 

15.695 

14,959 

13,821 

13.549 

13,138 

10.475 

10,337 

9,689 

9,207 

8,005 

7,930 

7,571 

7.502 

7,298 

AVERAGE MW 

PER OUTAGE 

193,623 

185,529 

196,080 

70,047 

116,539 

7^2 3 

16.439 

19,738 

21,386 

10,645 

6^455 

22,336 

15.604 

2,146 

21,969 

23,097 

36,353 

21.454 

2,489 

23,397 

15.126 

14,463 

14,713 

324,107 

22,465 

MAJOR BOILER OVERHAUL 

SOOT BLOWERS - STEAM 

MAJOR TURBINE OVERHAUL 

PULVERIZER OVERHAUL 

BOILER INSPECTIONS 

PULVERIZER MILLS 

FURNACE WALL LEAKS 

FEEDWATER PUMP 

PULVERIZER INSPECTION 

ELECTROSTATIC PRECIPITATOR PROBLEMS 

OTHER PULVERIZER PROBLEMS 

HIGH PRESSURE HEATER TUBE LEAKS 

BOILER, MISCELLANEOUS 

OPACITY- FOSSIL STEAM UNITS 

FIRST REHEATER LEAKS 

REDUCED POWER TO AVOID SLAI3/FOULING 

ESP FIELD OUT OF SERVICE 

SECOND SUPERHEATER LEAKS 

PULVERIZER FEEDERS 

BURNERS 

PULVERIZER MOTORS AND DRIVE 3 

FIRST SUPERHEATER LEAKS 

ELECTROSTATIC PRECIPITATOR F OULING 

SERVICE WATER PUMPS AND MOTORS 

CIRCULATING WATER PUMPS 

Grouping these problems by power plant section, it can be seen that about 75% are 

due to failures in the boiler or pulverizers, 17% due to turbine repair, and 7% due to 

parasitic power units (ESP, pumps, motors). 

The incidence of such problems has decreased over the past two decades, oven 

though the average age of these power plants has increased, due to improved 
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maintenance practices by plant operators. The figure below shows the average coal 

power plant availability (defined as the hours the unit could deliver power in a year, 

divided by the hours in a year, expressed as a percentage) since 1982. 

Note that the rate of improvement in availability has dropped from about 0.5% per year 

Coal Unit Availability (NERC) 

1M2 19B4 1886 1988 1B80 1882 1984 1896 1998 2000 2002 

in the early 1980's to 0.1% per year in the late 1990's. This is believed attributable to 

physical limits on average fleet availability. These trends would suggest tha' even 

aggressive programs to improve availability cannot improve performance more than 1% 

(cumulatively) between 2000 and 2010. Hence, average availability might be expected 

to rise from 86% to 87% by 2010. In the absence of a rigorous methodology to 

attribute the portion of this future improvement to actions which would be considered 

"routine maintenance, repair and replacement" versus non-routine actions subject to 

permit restrictions or new source review limitations, one half of the increase :x>uid be 

assumed to be constrained by current NSR policy. 

Given the uncertainty In predicting a change In availability, a range ofchanges was 

modeled using the NEMS modeling system. Even though less than a 1 % increase in 

availability is expected, a range of 0 to 5% increase was modeled. An overview of the 

NEMS system Is available at 

http://tonto.eia.doe.aov/FTPROOT/forecastino/OS812000.pdf. 
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Attachment 2 

Potential for Efficiency Improvements At Existing Coal-Fired Power Plants 

The average efficiency of the US fleet of coal-fired power plants was 33% in 2000, 

which equates to a heat rate (fuel energy needed to generate one kilowati -hour of 

power) of 10,240 Btu/kwh. Possible measures to improve this efficiency have been 

investigated in recent years due to interest in fuel savings, as well as in time greenhouse 

gas emissions reduction (i.e., C02) which would accompany such a performance 

improvement. For example, see Integrating Consultancy - Efficiency Stan:lards for 

Power Generation. Australian Greenhouse Office, Jan. 2000; Review of Potential 

Efficiency Improvements at Coal-Fired Power Plants. Perrin Quaries Associates, Inc., 

for Clean Air Markets Division, USEPA, April 2001; Increasing Electricity Availability 

From Coal-Fired Generation In the Near-Term. The National Coal Council, May 2001. 

The Department of Energy is currently studying such measures. Preliminaiy results 

from the DOE effort have highlighted several promising options, as indicated in the 

table below. 

Table 2.1 

Technology 

Turbine reblading 

% Efficiency 

Improvement 

5-10% 

Concept 

Energy management 

Intelligent soot blowing 

Distributed Control System 

controls 

Generator exciter 

replacement 

Condenser enhancement 

Overall improvments 

1-6% 

1-2% 

0.5-2% 

1-2% 

1% 

Replace existing turbine blade sections and 

seals with more efficient computer-based 

designs. 

Replace current power plant eontro: system with 

real-time performance monitoring and 

adjustment of chemical feed rates, mir flow, 

steam temperatures, outage maintenance 

against a theoretical model. 

Replace current soot blowing systen with 

"smart" systems, which can reduce iiteam use 

for soot blowing by 30%. 

Automate manual adjustment of air registers, 

burner tilt, fan power, etc., using an <iptimal 

computer "smart" system. 

Replace current mechanical exciter v,ith a more 

efficient solid-state system. 

Replace condenser with a larger unit lo reduce 

back pressure and make steam turbii e more 

efficient. 

8-17% (Numbers are not additive due to soma 

overlapping improvements, and possible 

double-counting.) 

In general, these improvements all improve the efficiency of steam conversion to 
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electricity, or reduce parasitic power consumption within the power plant. Such 

improvements in efficiency produce more power for the same amount of < nergy 

consumed, and therefore do not increase emissions, in and of themselves;;. However, 

two larger scale issues must also be considered. 

First, if the increase in efficiency also improves the unit's economics, then the unit might 

be dispatched (used) more, while other units are used less. It is likely thai: voluntary 

efficiency improvements would improve unit economics. To further evaluate this 

situation, emission changes at a midwestem power pool for were evaluated for a range 

of hypothetical efficiency improvements in coal-fired, units. Four hypothetical NGCC 

generating units were "added" to the system to reflect a future scenario in vhich a 

broader mix of coai and gas-fired units would probably exist. The analysis found that 

only a very large change in efficiency (13.5%, or greater) would be likely to change the 

relative dispatching of coal units with generically different units, such as nalural gasfired or nuclear units, and that even at such high levels of efficiency improvement, the 

net effect was a reduction in emissions of 3-4%. (10/19/2001 email from V. Koritarov, 

ANL, to D. Carter, USDOE) It would be reasonable to expect some shifting in 

dispatching between other coal units, if all the units were not comparably improved, 

Such a change could result in an increase in emissions if higher emitting units were the 

subject of efficiency improvements. However, given emission caps for sulfur dioxide, 

caps in certain states for nitrogen oxides, and a tendency by power plant operators to 

achieve optimal performance (both efficiency and emissions) at their "flagship" units, it 

seems much more likely that units receiving the greatest efficiency upgrade.; would be 

the cleaner units. Under these circumstances, efficiency improvements of the type 

cited above would reduce emissions. In other words, if one expects a 10% overall 

improvement in efficiency at coal units, efficiency improvements of 12% might occur at 

the lowest emission units, and improvements of 8% at the highest emitting t lits. This 

behavior would lead to significant emission reductions in periods of "off-pea.:" 

generation, which includes the major portion of the year. However, this type of behavior 

is difficult to model and was not simulated in the model runs by ANL or EIA. 

The second larger scale-Issue is that of demand growth. The growth in electricity 

demand over the next decade is projected to be greater than expected growth in 

electricity production due to efficiency Improvements at coal-fired power plan Is. 

Another way of looking at this is that almost all additional generation which ccmes from 

efficiency improvements would be power not needed from new generators. Elecause 

the efficiency improvements are at existing coal units, whereas new generaticin over the 

next decade will be dominated by much lower emitting natural gas combined i:ycle 

units, one might suppose that the efficiency improvement would result in increased 

emissions overall. However, this is not the case. As long as the increased ptiwer 

production does not require additional coal consumption (which is the case for these 

efficiency improvements), then the resulting net emissions will be lower than tie total 

emissions for "unimproved" coal plants and "super-clean" natural gas plants. 

Most, but not all of the efficiency improving technologies cited in Table 2.1 reflect 

replacement components. This Is Important to note because some NSR policies might 
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apply differently to replacement parts versus new components added to a slant for the 

sole purpose of Improving efficiency. 

Given the expanding suite of efficiency improving technologies, and growing interest in 

reducing greenhouse gas emissions through efficiency improvements, It is reasonable 

to project overall efficiency improvements, in the absence of NSR constraints, as large 

as10-15%. Such a range Is much larger than conventional wisdom, which is perhaps 

shaped by expectations under the current NSR policy, and the absence of efficiency 

incentives related to climate change concerns. To cover a broad range of possible 

improvements, a range of 5% to 15% was examined using the NEMS modeling system. 

TOTAL P.10