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Incorporating Wind into a Natural-gas Turbine Baseload Power System Increases NOx and CO2 Emissions from the Gas Turbines

CMU - FUTURE ENERGY SYSTEMS: EFFICIENCY, SECURITY, CONTROL

Warren Katzenstein and Dr. Jay Apt

warren@cmu.eduapt@cmu.edu

March 11th, 2008

22

Today I will discuss

• Background and Motivation• Research Question• Approach

– Actual wind data– Actual emissions data from two types of natural-gas turbines

• Model Construction– General Electric LM6000 turbine– Siemens-Westinghouse 501FD turbine

• Results• Implications

3

Renewables Portfolio Standards

State Goal

☼ PA: 18%¹ by 2020

☼ NJ: 22.5% by 2021

CT: 23% by 2020

MA: 4% by 2009 +1% annual increase

WI: requirement varies by utility; 10% by 2015 goal

IA: 105 MW

MN: 25% by 2025(Xcel: 30% by 2020)

TX: 5,880 MW by 2015

☼ AZ: 15% by 2025

CA: 20% by 2010

☼ *NV: 20% by 2015

ME: 30% by 200010% by 2017 - new RE

State RPS

☼ Minimum solar or customer-sited RE requirement* Increased credit for solar or customer-sited RE

¹PA: 8% Tier I / 10% Tier II (includes non-renewables)

HI: 20% by 2020

RI: 16% by 2020

☼ CO: 20% by 2020 (IOUs)*10% by 2020 (co-ops & large munis)

☼ DC: 11% by 2022

DSIRE: www.dsireusa.org September 2007

☼ NY: 24% by 2013

MT: 15% by 2015

IL: 25% by 2025

VT: RE meets load growth by 2012

Solar water heating eligible

*WA: 15% by 2020

☼ MD: 9.5% in 2022

☼ NH: 23.8% in 2025

OR: 25% by 2025 (large utilities)5% - 10% by 2025 (smaller utilities)

*VA: 12% by 2022

MO: 11% by 2020

☼ *DE: 20% by 2019

☼ NM: 20% by 2020 (IOUs)10% by 2020 (co-ops)

☼ NC: 12.5% by 2021 (IOUs)10% by 2018 (co-ops & munis)

ND: 10% by 2015

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Intermittent Power

Time

Power

1 Hour 2 Hour

5

Research Question

Does operating one or more gas turbines to fill in intermittent wind power result in increased NOx and CO2 emissions compared to full-power steady-state operation of natural-gas turbines?

6

Approach

+

+

+

1

2

n

=

Firm PowerVariable PowerCompensating Power

Time

Power

Gas

Wind

7

Approach

Wind Power Output

Calculate Power Leveland Ramp Rate Needed

GT’s Control and Regression Map

GT Emissions Model

+-

Error

Calculated Emissions

Ideal Fill Power

Realized Fill Power

8

Objective Function for Baseload Plant

9

Calculating Pollutant Mass Emissions of Baseload Plant

10

0 0.5 1 1.5 2 2.50

10

20

30

40

50

60

70

80

90

Time (hours)

Pow

er (M

W)

Data Slice from Output of Two Wind Farms in Pennsylvania

Wind Data Obtained

• Wind Data– Output of 3 existing

wind farms• Eastern• Southern Great

Plains• Central Great

Plains– 1 to 10 seconds

resolution– 32 total days of data– From anonymous

source

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Gas Turbine Data Obtained• NOx emissions & heat

rate for 7 CTs & 1 NGCC– 1 minute resolution– Ranges from 38 days of

data to 135 days of data– CTs are LM6000s– Have

• Gas flow (HSCFH)• Load (MW)• NOx ppm and lbs• NOx ppm corrected to

15% O2

• O2 %• Heat rate (mBtu/hr)

– From anonymous source

90 95 100 105 110 115 1200

5

10

15

20

25

30

35

40

45

50

Time (hours)

Pow

er (M

W)

Data Slice of Power Output of LM6000 Data Obtained

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GE LM6000 – Rated 40-45MW

Source: www.sealegacy.com Oct. 4th, 2007

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CO2 Emissions vs Power for LM6000

(idle)

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0 5 10 15 20 25 30 35 40 45 50-20

-15

-10

-5

0

5

10

15

20

Power (MW)

Ram

p R

ate

(MW

/Min

)

LM6000 NOx Emissions as a Function of Power Level and Ramp Rate

0

0.2

0.4

0.6

0.8

1

1.2

Model Construction - Regression AnalysisN

Ox

Em

itted (lbs/min)

15

Region 4

Region 2

Region 1

Region 3

Idle Power

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Siemens-Westinghouse Combined-Cycle Turbine – Rated 200 MW

www.summitvineyardllc.com

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Operating Limit Constraint

Operating Limit Constraint

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CO2 Emissions vs Power for SW 501FD

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Siemens-Westinghouse - Regression Analysis

0 20 40 60 80 100 120 140 160 180 2000

0.5

1

1.5

2

2.5

3

3.5

Power (MW)

NO

x E

mitt

ed (l

b/m

in)

GE Document GER-3568G

Results

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0 0.5 1 1.5 2 2.50

10

20

30

40

Time (hours)

Pow

er L

evel

s (M

W)

Wind + CT Operating Parameters

Ideal Fill PowerWind PowerActual Fill Power

0 0.5 1 1.5 2 2.5-20

-10

0

10

20

Time (hours)

Ram

p R

ate

(MW

/min

)

Ramp Rates

Results (1) – LM6000

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Expected Emission Reductions Calculation

⎥⎥⎦

⎤

⎢⎢⎣

⎡

∗

−∗= +

nPenetratioWindMMM

NaturalGasTotal

GasNatuarlWindTotalral GasTotal,Natu

,

,100ReductionEmissionExpected

%1005.0)5.01(

100ReductionEmissionExpected,

=⎥⎥⎦

⎤

⎢⎢⎣

⎡

∗−

∗=NaturalGasTotal

ral GasTotal,Natu

MM

Example Calculations

If Wind Penetration is 0.5, then expect MTotal, Wind + NaturalGas = 0.5·MTotal,NaturalGas

If Wind Penetration is 0.3, then expect MTotal, Wind + NaturalGas = 0.7·MTotal,NaturalGas

%1003.0)7.01(

100ReductionEmissionExpected,

=⎥⎥⎦

⎤

⎢⎢⎣

⎡

∗−

∗=NaturalGasTotal

ral GasTotal,Natu

MM

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Expected Emissions ReductionEastern Wind Farm

6,400 lbs1,500 lbs-240%± 250%

NOx

6,968 tons732 tons76%± 1%

CO2

501FD (NGCC, DLN)

1,595 tons176 tons80%± 1%

CO2

8,300 lbs290 lbs29%± 4%

NOxLM6000 (CT)

Mass Emitted by Wind + NG

Emissions Reduced

Expected Emissions Reduction

Turbine

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Expected Emissions Reduction

-530% + 150% - 5%

-600% + 100% -75%

-240% ± 250%

NOx

78.9% ± 0.1%

76.8% ± .2%

76% ± 1%

CO2

501FD (NGCC, DLN)

77% ± 1%

77% ± 1%

80% ± 1%

CO2

31% ± 4%

21% ± 3%

29% ± 4%

NOxLM6000 (CT)

Central Great Plains

Southern Great Plains

EasternWind Farm

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Generating Smaller Wind Data Sets

1000 min

(16.6 hrs)

+1 min

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Implications• 1 MWh of wind energy does not eliminate 1 MWh of emissions• Impacts

– Clean Air Interstate Rule (CAIR)• Significant penetration of wind power will make it harder for

CAIR to achieve emission reduction goals– Emission displacement studies

• Overestimating the amount emissions are displaced by wind– Life Cycle Analyses

• Don’t account for wind’s effect of decreasing emission efficiencies of conventional generators

– Technology• Not all gas turbines are equally suitable for pairing with wind• R&D program to improve emissions of heavily cycled gas

turbines

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AcknowledgementsAllen Robinson, Cliff Davidson, Lester Lave, Mitchell Small

Anonymous resource for power plant emissions data,

Anonymous resource for wind data

Funding CEICNETL CIT Dean’s Fellowship

Warren Katzensteinwarren@cmu.edu

Dr. Jay Aptapt@cmu.edu

Questions?

Renewable Portfolio Standard which would require

electric utilities to obtain 15 percent of their electricity

from wind, solar, or biomass energy by 2020

– NYTimes June 15th, 2007

RPS dsireusa.org C.A.I.R epa.gov

LA Smog Apt