COMBUSTION TURBINE

EFFICIENCY IMPACTSKate Corcoran

GRO Fellow

EPA GRO FELLOWSHIP

The GRO Fellowship Program is administered by the National

Center for Environmental Research (NCER) in EPA’s Office of

Research & Development (ORD)

The Fellowship supports students during their junior and senior

years of undergraduate study and includes support for an

internship at an EPA facility during the summer of their junior year.

GOALS OF INTERNSHIP

Gain familiarity with the CAA Prevention of Significant

Deterioration permitting program for GHG emissions

Gain experience with a variety of EPA air pollution permit

technical programs and in how air pollution is generated and

controlled

Study the efficiency impacts for combustion turbine technology

related to GHG permitting to provide a comparative analysis of

EPAs BACT determinations and ISO conditions for electric

generation projects located in Texas

INTERNATIONAL STANDARD

OPERATING (ISO) CONDITIONS

Ambient Temperature at 59.0ºF

Relative Humidity at 60%

Ambient Pressure at Sea Level

SIMPLE CYCLE RULES OF THUMB

Ambient Temperature: 0.4% reduction in power output per 1°F

increase in ambient temperature above 59°F, and a

proportionate increase in heat rate. The opposite holds true for

decreasing temperatures.

Site elevation: 3.3% reduction in power output per every 1,000-ft

increase in site elevation above sea level. Heat rate is

unaffected.

COMBINED CYCLE RULES OF THUMB

Ambient temperature: 2.5% reduction in power output per 10°F

increase in ambient temperature above 59°F, and a

corresponding increase with decreasing temperatures. 0.5%

impact on heat rate (up and down, respectively) per 10°F

change in air temperature from 59°F.

Site elevation: 3.3% reduction in power output per every 1,000-ft

increase in site elevation above sea level. Heat rate is

unaffected.

CO2 EMISSION CALCULATIONS

The equation for estimating CO2 emissions as specified in 40 CFR 75.10(3)(ii) is:

𝑊𝐶𝑂2=𝐹𝑐 ×𝑈𝑓 ×𝑀𝑊𝐶𝑂2

Where:

WCO2= CO2 emitted from combustion, tons/hour

MWCO2= molecular weight of CO2, 44.0 lbs/mole

Fc = Carbon-based Fc-Factor, 1040 scf/MMBtu for natural gas or site-specific Fc factor

Uf = 1/385 scf CO2/lb-mole

CO2 EMISSIONS CALCULATIONS (CONT)

𝐶𝑂2 TPY = [(CTHC*CTO) + (STHC*STO)] *𝑊𝐶𝑂2 )/2,000

Where:

WCO2= CO2 emitted from combustion, tons/hour

CTHC = CT Heat Consumption, MMBtu/hr

CTO = CT Operation, hrs/yr

STHC = ST Heat Consumption, MMBtu/hr

STO = ST Operation, hrs/yr

REFERENCES FOR DATA COLLECTION

DATA COLLECTION - Snapshot

Company Name City County Turbine ModelTemp Max

(F)Temp Min

(F)Temp Mean

(F)Elevation

(m)CT

hrs/yrST

hrs/yrDuct

burning?CT heat consump

MMBTU/KWHST heat consump

MMBTU/KWH

CT Power Output

MW

ST Power Output

MWBACT Limit

lb CO2/MWH

Tenaska Roans Prairie Partners, LLC Shiro GrimesGE 7FA.05, 7FA.04,or S GT6-5000F(5) 79.8 54.4 67.1 107 2920 n/a No

Option 1 (Siem): 2441Option 2 (GE(5)): 2378Option 3 (GE(4)): 2198 n/a

Option 1 (Siem): 231Option 2 (GE(5)): 212Option 3 (GE(4)): 176 n/a

Option 1 (Siem): 1334Option 2 (GE(5)):1310Option 3 (GE(4)):1321

Southern Power Company Cushing Nacogdoches Siemens F(5) 76.9 54.1 65.5 125 2500 n/a No 2146 n/a 232 n/a pending

Indeck Wharton, LLC Danevang WhartonGE 7FA.05

or Siemens SGT-5000F(5) 79.95 58.93 69.45 21 2500 n/a No 2054 n/a 216.6666667 n/aOption 1 (GE): 1276

Option 2 (Siem): 1337

Invenergy Thermal Development LLC Goldsmith Ector GE 7FA.03 78.18 51.1 64.65 957 2500 n/a No 1611.48 n/a 165 n/a 1393

NRG Tx Pwr LLC (PH Robinson Sta) Bacliff Galveston GE 7E 76.8 62.46 69.73 5 1752 n/a No 921.67 n/a 65 n/apending/ ap withdrawn

proposed in ap: 1450

Golden Spread El. Coop. - Antelope Sta. Abernathy Hale GE 7FA.05 70.03 44 58 1024 4572 n/a No 1940.74 n/a 202 n/a 1304

Guadalupe Power Partners LP Marion Guadalupe GE 7FA.04 79.9 56.55 68.25 197 2500 n/a No 1788.82 n/a 165 n/a 1268

Lon C. Hill LP Corpus Christi NuecesGE 7FA.04, or

Siemens SCC6-5000F 81.01 63.54 72.26 2 8760 8760 Yes 2412.8 670Option 1 (GE): 183

Option 2 (Siem): 240 260 900

City of Austin - Sand Hill En. Ctr. Del Valle Travis GE 7FA.04 79.33 55.98 67.65 148 8760 8760 Yes 1911.6 681.5 173.9 189 930

Southern Power Company Trinidad Henderson Mitsubishi J model 75.9 53.8 64.9 92 8760 8760 Yes 3214 402 ? ?pending

proposed in ap: 922

Victoria WLE LP Victoria Victoria GE 7FA.04 80.56 60 70.3 29 8760 4375 Yes 1816 483 182.684 92.5 940

NRG Texas Pwr LLC (Cedar Bayou) Baytown ChambersGE 7FA-05 or Siemens F(5)

or M 501GAC 77.4 59 68.2 7 8760

Option 1 (GE): 3500Option 2 (Siem): 3500Option 3 (MHI): 3200 Yes

Option 1 (GE): 2101.2Option 2 (Siem): 2337.6Option 3 (MHI): 2586.1

Option 1 (GE): 523.1Option 2 (Siem): 606.3Option 3 (MHI): 632.5 264 ? pending

NRG Texas Pwr LLC SR Bertron La Porte HarrisGE 7FA-05 or Siemens F(5)

or M 501GAC 79.1 59.66 69.35 6 8760

Option 1 (GE): 3500Option 2 (Siem): 3500Option 3 (MHI): 3200 Yes

Option 1 (GE): 2101.2Option 2 (Siem): 2337.6Option 3 (MHI): 2586.1

Option 1 (GE): 523.1Option 2 (Siem): 606.3Option 3 (MHI): 632.5 264 ? pending

Tenaska Brownsville Partners LLC Brownsville Cameron MHI 501 GAC 82.9 65.4 74.185 10 5200 5200 Yes 2903 250 274 336 914

Pinecrest Energy Center LLC Lufkin Angelina

GE 7FA.05 orS GT6-5000F(4)

S GT6-5000F(5) 77.25 54.2 65.7 95 8260 8260 Yes

Option 1 (GE): 2861Option 2 (Siem(4)): 2764Option 3 (Siem(5)): 3110 750

Option 1 (GE): 215Option 2 (Siem(4)): 205Option 3 (Siem(5)): 232 271

Option 1 (GE): 942Option 2 (Siem(4)): 909.2Option 3 (Siem(5)):912.7

La Paloma Energy Center Harlingen CameronGE 7FA.04

or SGT6-5000F(4) or (5) 82.9 65.4 74.185 12 8260 8260 Yes

Option 1 (GE): 1230.6Option 2 (Siem(4)): 1626

Option 3 (Siem(5)): 1584.2 750

Option 1 (GE): 183Option 2 (Siem(4)): 205Option 3 (Siem(5)): 232 271

Option 1 (GE): 934.5Option 2 (Siem(4)): 909.2Option 3 (Siem(5)):912.7

Calpine/Deer Park Energy Center LLC Deer Park Harris Siemens 501F 79.1 59.66 69.35 8 8760 8760 Yes 1852.17 725 180 200 920

Calpine - Channel Energy Center Pasadena Harris Siemens 501F 79.1 59.66 69.35 9 8760 8760 Yes 1852.17 475 180 200 920

7 Simple Cycle

11 Combined Cycle

SIMPLE CYCLE

BACT limits in permits: 1268 – 1393

Average: 1317

BACT limits at ISO: 1099 – 1484

Average: 1222

Average % difference: 7.2%

0

200

400

600

800

1000

1200

1400

1600

TRPP LLC (1) TRPP LLC (2) TRPP LLC (3) Indeck (1) Indeck (2) Invenergy GSEC

lbs

CO

2/M

WH

Simple Cycle

BACT Limit in Permit BACT Limit at ISO

SIMPLE CYCLE RULES OF THUMB

Biggest impact on efficiency: high temperatures

All turbines experience power output reduction and heat rate

increase in the 4.41 – 8.38% range, at an average of 7.35%

Elevation has little effect on power output, ranging from

reductions of 0.02 - 3.38%, averaging 1.15%

COMBINED CYCLE

BACT limits in permits: 900 – 942

Average: 915

BACT limits at ISO, 8760 hrs: 728 – 889

Average: 748

Average % difference: 10.7%

Combined cycle

calculations are much less straightforward than simple

cycle calculations!

R6 issued permits contain a 10-

12% compliance margin

(design margin, performance

margin and degradation

margin) that results in a higher

BACT limit than ISO BACT limits.

0

100

200

300

400

500

600

700

800

900

1000

Lon C. Hill

LP (1)

Lon C. Hill

LP (2)

Austin

Energy

Victoria

WLE LP

Pinecrest

EC LLC

(1)

Pinecrest

EC LLC

(2)

Pinecrest

EC LLC

(3)

La

Paloma

EC (1)

La

Paloma

EC (2)

La

Paloma

EC (3)

Calpine

Deer

Park

Calpine

Channel

lbs

CO

2/M

WH

Combined Cycle

BACT Limit in Permit BACT Limit at ISO, 8760 Operating hrs/yr

COMBINED CYCLE ASSUMPTIONS

Combined cycle calculations have more variables than simple cycle

calculations, which make them more complex, and thus combined

cycle calculations should be made on a case by case basis.

Variables:

Duct burning

Different configurations

Hours of operation

Case by case example:

Austin Energy:

• Both the CT and ST operate at 8760 hrs/yr,

with duct burning

BACT Limit in permit: 930 lbs CO2/MWH

BACT Limit at ISO: 849.3 lbs CO2/MWH

% difference: 8.7%

COMBINED CYCLE RULES OF THUMB

Biggest impact on efficiency: high temperatures

All turbines experience power output reduction in the 4.23 – 5.98% range, at an average of 5.13%

Elevation has little effect on power output, ranging from reductions of 0.01 – 0.49%, averaging 0.13%

Temperature, high and low, has little effect on heat rate

The combined cycle is less affected by changes in ambient temperature and pressure than the simple cycle across the board.

RESULTS SUMMARY

Simple Cycle BACT limits are 7.2% different than estimated ISO

BACT limits.

Combined Cycle BACT limits are 10.7% higher than estimated ISO

BACT limits.

The Simple Cycle limit calculations are more accurate than the

Combined Cycle because less assumptions are required.

The largest impact on power output and heat rate for all turbines

in this data set was high ambient temperatures.