emissions from coal in high wind scenarios

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Emissions from Coal in High Wind Scenarios David Luke Oates RenewElec Project Department of Engineering and Public Policy Carnegie Mellon University Advisor: Paulina Jaramillo USAEE Concurrent Session October 11, 2011

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Emissions from Coal in High Wind Scenarios. David Luke Oates RenewElec Project Department of Engineering and Public Policy Carnegie Mellon University Advisor: Paulina Jaramillo USAEE Concurrent Session October 11, 2011. A baseloaded coal unit. A Texas Coal Unit. Source: CEMS 2008. - PowerPoint PPT Presentation

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Page 1: Emissions from Coal in High Wind Scenarios

Emissions from Coal in High Wind Scenarios

David Luke OatesRenewElec Project

Department of Engineering and Public PolicyCarnegie Mellon UniversityAdvisor: Paulina Jaramillo

USAEE Concurrent SessionOctober 11, 2011

Page 2: Emissions from Coal in High Wind Scenarios

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A baseloaded coal unit

Source: CEMS 2008

A Texas Coal Unit

Page 3: Emissions from Coal in High Wind Scenarios

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A coal unit being extensively cycled…

Source: CEMS 2008

Page 4: Emissions from Coal in High Wind Scenarios

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Wind power is intermittent and we can expect more of it

Source: (J Apt 2007)

Aggregated output from 6 turbines • 29 States have RPS• Wind is most likely

source to meet RPS• NREL: 30% energy

from wind is feasible

Page 5: Emissions from Coal in High Wind Scenarios

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PartLoad:Ramping:

What is ‘cycling’?“increased start-ups, ramping and periods of operation at low load levels” (Troy et al. 2010)

Startup:

Page 6: Emissions from Coal in High Wind Scenarios

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Two reasons we should care about cycling:

Costs• Cycling increases cost of

operating a coal unit:– Increased O&M– Increased forced outage

replacement power– Extra fuel costs

• Challenging to quantify costs• One estimate: $15-$225

thousand/cycle

Emissions• Coal units incur emissions

penalties for part-load operation, ramping, and startups

• One estimate for starting up coal suggests a penalty of 100% for CO2, 300% for NOX and 250% for SO2

Sources: (Bentek 2008; Lefton&Besuner 2006; D Lew 2011)

Page 7: Emissions from Coal in High Wind Scenarios

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Research context and objectives

Context• NREL estimated coal cycling

dependence on wind penetration– 1 measure of cycling– no sensitivity based on power

system, fuel mix, etc. • Most studies use very

simplistic emissions models

Objectives• Determine effect of wind

penetration on coal:– Startups– Ramping– Part load operation

• Calculate system-level economic benefits of coal cycling

• Determine emissions implications of coal cycling

Page 8: Emissions from Coal in High Wind Scenarios

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Two Important Data Sources

CEMS• Allows us to determine

emissions impact of cycling• EPA’s Continuous Emissions

Monitoring System• Hourly power output and

CO2, SO2, NOX for electricity units > 25 MW

EWITS• Allows us to model different

wind penetration levels• Eastern Wind Integration

and Transmission Study model results

• Modeled wind power output for thousands of sites across the country

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Three Big Questions:

1. How much coal cycling can we expect to see as wind penetration increases?

2. What is the value to the power system of coal cycling in high wind scenarios?– Determine the system-level economic benefit to

compare with the private cost3. How much does cycling affect emissions of

CO2, NOX, and SO2 from coal units?

Page 10: Emissions from Coal in High Wind Scenarios

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Part 1: Regression Analysis

Overview Independent Variables• Coal output time series• Wind energy

• Goal: What is correlation between wind penetration and cycling?

• Focus on ERCOT• Years: 2007-2010• Weekly Analysis

Cycling Measure Coefficient ± Std. Error R2

Startups (startups/wk/%wind) 1.2 ± 0.2 0.52

Part Load (%Capacity Factor/%wind) -0.3 ± 0.1 0.78

Ramping (%COV coal/%wind) 0.18 ± 0.05 0.81

ConclusionsNeed more sophisticated model to examine emissions

Page 11: Emissions from Coal in High Wind Scenarios

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Part 2: Model Overview“What are the capacities

of each unit and demand for electricity?”

“How much power does each unit produce every hour?”

“How much CO2, NOX and SO2 are produced?”

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UCED model capacity mix is comparable to PJM

Source: NEEDS 2006

PJM 06167 GW

Model168 GW

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

OTHERHYDRONUCWINDNGSTEAMNGCTNGCCSUBPCBIT

Capa

city

Frac

tion

Page 13: Emissions from Coal in High Wind Scenarios

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Unit Commitment and Economic Dispatch (UCED) Characteristics

Costs• Fuel• Startup• Shutdown• Reserve commitment• Wind curtailment

Constraints• Supply = Demand• Minimum Generation• Capacity• Ramp rate• Min up / Min down• Reserve requirement

Page 14: Emissions from Coal in High Wind Scenarios

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UCED Characteristics Continued

• Minimizes total cost of meeting demand• Hourly Dispatch• Perfect Information• Daily dispatch, iterated through 1 year• Solved using Mixed Integer (Linear)

Programming

Page 15: Emissions from Coal in High Wind Scenarios

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Emissions Model Rationale

• Many analyses assume constant emissions factors

• This method does not adequately account for emissions associated with startup/shutdowns or ramping

• Coal units incur emissions penalties for part-load operation, ramping, and startup

Sources: (Katzenstein& Apt 2009; D Lew 2011; Bennett &McBee 2011)

Page 16: Emissions from Coal in High Wind Scenarios

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Higher emissions rate during startup

Source: CEMS

NOx emissions from a coal unit

Power output (MW)

NO

x em

issio

ns (k

g/m

in)

Note: I’m going to eliminate the coloring

Page 17: Emissions from Coal in High Wind Scenarios

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Base Case: Validation

PJM 2006 UCED Jan 06 UCED Jun 060%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

OtherWindHydroGasCoalNuclear

Perc

enta

ge o

f tot

al re

sour

ce

Reference Model January Model June

Page 18: Emissions from Coal in High Wind Scenarios

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Base Case: PJM Resource Use

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Next Steps: Comparative Scenario Analysis

No Cycling Constraints

Low Cycling Constraints

Moderate Cycling Constraints

No Added Wind

Base Case $ / CO2 / NOX / SO2

$ / CO2 / NOX / SO2

$ / CO2 / NOX / SO2

5% Wind $ / CO2 / NOX / SO2

$ / CO2 / NOX / SO2

$ / CO2 / NOX / SO2

$ / CO2 / NOX / SO2

10% Wind $ / CO2 / NOX / SO2

$ / CO2 / NOX / SO2

$ / CO2 / NOX / SO2

$ / CO2 / NOX / SO2

Page 20: Emissions from Coal in High Wind Scenarios

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Policy Implications

Gives a clearer picture of how coal units behave with renewables

• Renewable Portfolio Standards– Given that coal cycling occurs, how much emissions benefit do we see

from RPS?• Electricity Market Structure

– Given that cycling produces private costs and (maybe) social benefits, do we need to change the way we pay operators of coal units?

Page 21: Emissions from Coal in High Wind Scenarios

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Acknowledgments

• CEIC, RenewElec for financial support• Paulina Jaramillo for a great deal of guidance• Todd Ryan, Allison Weis for countless

discussions• Bri Matthias-Hodge and NREL Wind

Technology Center for help building my UCED model

Page 22: Emissions from Coal in High Wind Scenarios

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References• Apt, J, 2007. The spectrum of power from wind turbines. Journal of Power

Sources.• Bennett, P. &McBee, B., 2011. The Wind Power Paradox. pp.1–58.• D Lew, G.B.A.M.M.N., 2011. Does Wind Affect Coal? Cycling, Emissions, and

Costs (Presentation), National Renewable Energy Laboratory (NREL). pp.1–21.• Energy, B., 2008. How Less Became More: Wind, Power, and Unintended

Consequences in the Colorado Energy Market,• Katzenstein, W. & Apt, Jay, 2009. Air Emissions Due To Wind And Solar Power.

Environmental Science & Technology, 43(2), pp.253–258.• Lefton, S.A. &Besuner, P., 2006. The Cost of Cycling Coal Fired Power Plants.

Coal Power Magazine, (Winter 2006), pp.16–19.• Troy, N., Denny, E. & O'Malley, M., 2010. Base-Load Cycling on a System With

Significant Wind Penetration. Power Systems, IEEE Transactions on, 25(2), pp.1088–1097.

Page 23: Emissions from Coal in High Wind Scenarios

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End

Page 24: Emissions from Coal in High Wind Scenarios

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EWITS Data Use

• Average power available: 43 GW

• 30% of PJM peak demand

Locations of EWITS Sites near PJM region

Page 25: Emissions from Coal in High Wind Scenarios

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EWITS data doesn’t match Kolmogorov below 3 h

Source: Todd Ryan

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Fleet Selector

• DESCRIBE OPTIMIZATION

Page 27: Emissions from Coal in High Wind Scenarios

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NREL suggests cycling increases with wind penetration

Source: Western Wind and Solar Integration Study, NREL, 2010, p. 153

Operating Level:

No Wind 10% Wind 20% Wind30% Wind

Page 28: Emissions from Coal in High Wind Scenarios

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Timeline

Accomplished• Integrate data sources• Select representative fleets

from available sources• Build CO2 emissions models• Implemented working UCED

Before January• Implement forced/unforced

outages• Perform sensitivity on

reserve requirements, fuel mix

• Build NOX and SO2 emissions models

• Run scenarios varying wind penetration and cycling constraints

Page 29: Emissions from Coal in High Wind Scenarios

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Use of Hourly Data

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Reserve Requirements

3+1• Carry 1% of peak load for regulation is

reasonable for modest penetration• Or Regulation equal to stddev of 10-min net

load changes

Page 31: Emissions from Coal in High Wind Scenarios

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Startups and Wind Penetration

0 5 10 15 20 25 30 350

5

10

15

20

25

30

35

40

45

50

Wind Energy Penetration [%]

Incr

ease

in C

oal S

tart

ups [

%]

NOT ACTUAL DATA

Page 32: Emissions from Coal in High Wind Scenarios

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System Costs and Startups

40 50 60 70 80 90 100 1100

5

10

15

20

25

30

35

# of Coal Startups

Incr

ease

in S

yste

m C

ost [

%]

Slope: $/startup

NOT ACTUAL DATA

Page 33: Emissions from Coal in High Wind Scenarios

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Anticipated Sensitive Parameters

• Reserve rules– Contingency reserve margin– Regulating reserve margin

• Fuel Mix– Amount of coal

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Ramp Rate Definition

• Output of each unit approximated by discontinuous stepwise curve

• Ramp rate approximated by change in power output from hour to hour (MW/h)

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DETAIL ON OPTIMIZATION METHOD

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Base Costs and Constraints

• Show all costs and constraints

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Fleet Selector

• Problem 1: data on every unit in power systems not available

• Problem 2: want to be able to test different fuel mixes

• Problem 3: many differences between units of the same fuel type

• Solution: program to match distributions of size and heat rate to reference system

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Results summary for a particular wind penetration

Cost CO2 NOX SO2

Startups (200±50) $/start (10±3) t/start (10±3) t/start (10±3) t/start

Energy produced below 50% capacity

(100±20) $/MWh (15±4)t/MWh (15±4)t/MWh (15±4)t/MWh

Ramping (10±3) $/MW (5±2) t/MW (5±2) t/MW (5±2) t/MW

NOT ACTUAL DATA

Page 39: Emissions from Coal in High Wind Scenarios

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Average vs. incremental HR

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Base Case: Validation ContinuedPJM 06 UCED

Mean CO2 output emissions rate [t/MWh]

0.94 0.92

Startups / month 24 22

Ramping distance[MW/month]

3000 3250

Energy produced below 50%[MWh/month]

1000 1250

*Note that uncertainties are not yet available and will be included in final results

NOT ACTUAL DATA