The Effects of Greenhouse Gas Limits on Electric Power System

Dispatch and Operations

Miaolei Shao (mxshao@wichita.edu)

Ward Jewell (ward.jewell@wichita.edu)

Department of Electrical and Computer Engineering

Wichita State University

PSERC Tele-SeminarSeptember 2nd, 2008

1

Greenhouse Gas (GHG) Emissions & Electric Power Industry

• United States is the source of 1/4 of the world’s GHG emissions.

• Electric power industry accounts for 38 percent of the nation’s overall carbon dioxide (CO2) emissions and one-third of the overall U.S. GHG emissions.

• 39 states have or are developing State Action Plans specially targeting GHG emission reductions.

-- Regional Greenhouse Gas Initiative (RGGI)

-- California Assembly Bill 32 (AB 32)

2

Electric Power System Features That Impact CO2 Emissions

• CO2 emission factors by type of fuel

• Unit thermal efficiency

• Regional generation mix

• Electricity demand

• Transmission constraints

3

Coal EF Oil EF Gas EF

Bituminous 205 Distillate oil 161 Natural gas 117

Subbituminous 213 Jet fuel 156 Propane 139

Lignite 215 Kerosene 159

Anthracite 227 Petroleum coke 225

Residual 174

Source: S. Goodman, M. Walker, “Benchmarking air emissions of the 100 largest electric power producers in the united states – 2004”, Apr. 2006

CO2 Emission Factors (EF) by Type of Fuel (lb CO2/MBtu)

4

G1 (400 MW coal-fired generation unit)

G2 (400 MW gas-fired generation unit)

P1 = 400 MW

800 MW Load

P2 = 400 MW

400 MW

Bus 1 Bus 2

Two-bus, two-generator power system

CO2 Emission Factors (EF) by Type of Fuel (Cont.)

Heat rate data of 400 MW fossil fired generation units came from “A. J. Wood, B. F. Wollenberg, Power Generation, Operation, and Control, John Wiley & Sons, 1996.”

(346 198) /0.68 /

800

tons htons MWh

MW

CO2 emission factor is 215 lbs/Mbtu for coal and 117 lbs/Mbtu for gas.

5

G1 (400 MW coal-fired generation unit)

Efficiency (400 MW)

Efficiency + 1% Efficiency + 3%

Efficiency (%) 37.9% 38.9% 40.9%

CO2 emissions (tons/h) 345.5 336.7 320.2

CO2 emission reduction (%) N/A -2.5% -7.3%

G2 (400 MW gas-fired generation unit)

Efficiency (400 M)

Efficiency + 1% Efficiency + 3%

Efficiency (%) 35.9% 36.9% 38.9%

CO2 emissions (tons/h) 198.5 193.1 183.2

CO2 emission reduction (%) N/A -2.7% -7.7%

Unit thermal Efficiency and CO2 Emissions

One kilowatt hour (kWh) has a thermal equivalent of approximately 3412 Btu.

6

Regional Generation Mix & CO2 Emissions

G1 (400 MW coal-fired generation unit)

G2 (400 MW gas-fired generation unit)

P1 = 400 MW

600 MW Load

P2 = 200 MW

400 MW

Bus 1 Bus 2

G1 (400 MW coal-fired generation unit)

G2 (400 MW gas-fired generation unit)

P1 = 400 MW

600 MW Load

P2 = 0 MW

600 MW

Bus 1 Bus 2

G3 (400 MW coal-fired generation unit)

P3 = 200 MW

Two-bus, two-generator power system

Two-bus, three-generator power system

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Regional Generation Mix & CO2 Emissions (Cont.)

(G2)(G3)

(G1)(G1)

450

527

450 /0.75 /

600

tons htons MWh

MW

527 /0.88 /

600

tons htons MWh

MW

8

Electricity Demand & CO2 Emissions

G1 (400 MW coal-fired generation unit)

G2 (400 MW gas-fired generation unit)

P1 = 400 MW600 MW Load

P2 = 200 MW

400 MW

Bus 1

Bus 2

Two-bus, two-generator power system

400 MW Load

800 MW Load

P2 = 0 MW

P2 = 400 MW

800

400

600

Load L (MW)

Hours load equals or exceeds L MW

Load-duration curve

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Electricity Demand & CO2 Emissions (Cont.)

346 /0.87 /

400

tons htons MWh

MW

450 /0.75 /

600

tons htons MWh

MW

544 /0.68 /

800

tons htons MWh

MW

CO2 emission amounts (tons/h)

CO2 emission rates (tons/MWh)

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Transmission Constraints & CO2 Emissions

G1 (400 MW coal-fired generation unit)

G2 (400 MW gas-fired generation unit)

P1 = 400 MW

600 MW Load

P2 = 200 MW

400 MW

Bus 1 Bus 2

G1 (400 MW coal-fired generation unit)

G2 (400 MW gas-fired generation unit)

P1 = 300 MW

600 MW Load

P2 = 300 MW

300 MW

Bus 1 Bus 2

400 MW maximum transmission capability between bus 1 and bus 2

300 MW maximum transmission capability between bus 1 and bus 2

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Transmission Constraints & CO2 Emissions (Cont.)

(G1)(G1)

(G2)

(G2)

450412

450 /0.75 /

600

tons htons MWh

MW

412 /0.69 /

600

tons htons MWh

MW

Transmission congestion help reduce system CO2 emissions?

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CO2 Emission-incorporated Cost Model

2_ 0 1 2( )fuel ij i i i i i iH P k k P k P

2_ 0 1 2( ) ( )fuel ij i j i i i i iF P C k k P k P

2 2

2_ 0 1 2( ) ( )CO ij i CO j i i i i iF P C ef k k P K P

2_ _ _( ) ( ) ( )fe ij i fuel ij i CO ij iF P F P F P

Input-output function

Fuel cost function

CO2 emission cost function

Fuel-emission cost function

2

20 1 2( )( )j CO j i i i i iC C ef k k P k P

13

Fossil-fired Generation Units’ Cost Variation Due to CO2 Emissions

G1 (400 MW coal-fired generation unit)

G2 (400 MW gas-fired generation unit)

• Coal price is 1.90 $/MBtu• CO2 emission factor of coal is 215 lb/MBtu

• Gas price is 3.80 $/MBtu• CO2 emission factor of gas is 117 lb/MBtu

• CO2 price is 30 $/ton

Fuel costs

CO2 emission costsFuel-emission costs

100 200 300 4000

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2x 10

4

Output, P (MW)

Co

sts

($/h

)

100 200 300 4000

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2x 10

4

Output, P (MW)

Co

sts

($/h

)

14

Breakeven Price of CO2

• Gas price is 3.8 $/MBtu

• Breakeven price of CO2 is around 50 $/ton

• Gas price is 5.7 $/MBtu

• Breakeven price of CO2 is around 100 $/ton

Coal price is 1.90 $/MBtu

Coal CO2 emission factor is 215 lb/MBtu

Gas CO2 emission factor is 117 lb/MBtu

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CO2 Emission-constrained ac Optimal Power Flow (OPF)

Objective function

Equality constraints

2_ _ _

1 1

( ) ( ) ( )g gN N

fe ij i fuel ij i CO ij ii i

F P F P F P

1

gN

i Load Lossi

P P P

1

gN

i Load Lossi

Q Q Q

Inequality constraints

i i iP P P i i iQ Q Q

k k kE E E k k k

mn mn mnMVA MVA MVA

Linear Programming

Software used in this research: PowerWorld Simulator

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IEEE Reliability Test System (RTS) • 24 buses

• 38 transmission lines and

transformers.

• a total load of 2850 MW

• a total generation capacity

of 3405 MW

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Case #

Description

Fuel Prices ($/MBtu)System Load (MW) Coal Gas Oil

1Medium fuel price and normal system load

1.88 9.09 12.00 1995

2High fuel price and normal system load

1.95 12.74 16.37 1995

3Medium fuel price and peak system load

1.88 9.09 12.00 2850

4High fuel price and peak system load

1.95 12.74 16.37 2850

Simulation Cases and Description18

0

200

400

600

800

1000

1200

0 50 100 150 200 250 300 350 400 450

Pow

er O

utpu

t (M

W)

CO2 Price ($/ton)

Coal

Gas

Oil

Nuclear

Hydro

70 $/ton 180 $/ton 280 $/ton

080000160000240000320000400000

0200400600800

1000

0 50 100 150 200 250 300 350 400 450

Cost

s ($/

h)

Tota

l CO

2 Em

issio

ns (

tons

/h)

CO2 Price ($/ton)

Total CO2 Emissions (tons/hr) CO2 Emission Costs ($/hr)

Fuel Costs ($/hr) Fuel-Emission Costs ($/hr)

Simulation Results of Case 1• At CO2 price of 70 $/ton, coal and gas power generation start to shift.

• At CO2 price of 180 $/ton, gas power generation almost equals coal power generation.

• At CO2 price of 280 $/ton, major shifting process is finished.

• CO2 emissions decrease from 928 tons/h at CO2 price of 0 $/ton to 514 tons/h at CO2 price of 280 $/ton, a 44.6% reduction.

• The system fuel costs increase from 18595 $/h at CO2 price of 0 $/ton to 79255 $/h at CO2 price of 280 $/ton, a 326% increase.

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0

200

400

600

800

1000

1200

0 50 100 150 200 250 300 350 400 450

Pow

er O

utpu

t (M

W)

CO2 Price ($/ton)

Coal

Gas

Oil

Nuclear

Hydro

70 $/ton 180 $/ton 280 $/ton

Simulation Results of Case # 1 (Cont.)20

Simulation Results

Case # 1 Case # 2

0

200

400

600

800

1000

1200

0 50 100 150 200 250 300 350 400 450

Pow

er O

utpu

t (M

W)

CO2 Price ($/ton)

Coal

Gas

Oil

Nuclear

Hydro

0

80000

160000

240000

320000

400000

0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400 450

Cost

s ($/

h)

Tota

l CO

2 Em

issio

ns (

tons

/h)

CO2 Price ($/ton)

Total CO2 Emissions (tons/h) CO2 Emission Costs ($/h)

Fuel Costs ($/h) Fuel-Emission Costs ($/h)

0

200

400

600

800

1000

1200

0 50 100 150 200 250 300 350 400 450

Pow

er O

utpu

t (M

W)

CO2 Price ($/CO2)

Coal

Gas

Oil

Nuclear

Hydro

0

80000

160000

240000

320000

400000

0

200

400

600

800

1000

0 50 100 150 200 250 300 350 400 450

Cost

s ($/

h)

Toto

al C

O2

Emiss

ions

(to

ns/h

)

CO2 Price ($/CO2)

Total CO2 Emissions (tons/h) CO2 Emission Costs ($/h)

Fuel Costs ($/h) Fuel-Emission Costs ($/h)

21

70 $/ton 180 $/ton 280 $/ton 130 $/ton 270 $/ton 410 $/ton

Simulation Results (Cont.)

Case # 3 Case # 4

0

200

400

600

800

1000

1200

1400

0 50 100 150 200 250 300 350 400 450

Pow

er O

utpu

t (M

W)

CO2 Price ($/ton)

Coal

Gas

Oil

Nuclear

Hydro

0

200000

400000

600000

800000

1250

1300

1350

1400

1450

1500

0 50 100 150 200 250 300 350 400 450

Cost

s ($/

h)

Tota

l CO

2 Em

issio

n (t

ons/

h)

CO2 Price ($/ton)

Total CO2 Emissions (tons/h) CO2 Emission Costs ($/h)

Fuel Costs ($/h) Fuel-Emission Costs ($/h)

0

200

400

600

800

1000

1200

1400

0 50 100 150 200 250 300 350 400 450

Pow

er O

utpu

t (M

W)

CO2 Price ($/ton)

Coal

Gas

Oil

Nuclear

Hydro

0

200000

400000

600000

800000

1250

1300

1350

1400

1450

1500

0 50 100 150 200 250 300 350 400 450

Cost

s ($/

h)

Tota

l CO

2 Em

issio

n (t

ons/

h)

CO2 Price ($/ton)

Total CO2 Emissions (tons/h) CO2 Emission Costs ($/h)

Fuel Costs ($/h) Fuel-Emission Costs ($/h)

22

80 $/ton 180 $/ton 130 $/ton 260 $/ton

Conclusions

• CO2 emissions from electric power industry are impacted by several power system features; ignoring any of them will incur errors in analysis.

• CO2 emission-constrained ac OPF is a powerful tool that considers all the features that impact CO2 emissions from electric power generation.

• CO2 emission-constrained ac OPF, which can be realized in commercial and educational power system software or developed as stand-alone software, has potential to be utilized for investigating and assessing the effects, including costs and reliability, of GHG limits on electric power industry.

• Simulation results indicate that the effects of GHG limits on electric power system dispatch and operations are sensitive to several factors such as system load levels, fuel prices etc.

• In current high gas price situation, it is quite expensive to reduce CO2 emissions by switching from coal power generation to gas power generation.

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Future ResearchPSERC Project M21: “Technical and Economic Implications of

Greenhouse Gas Regulation in a Transmission Constrained Restructured Electricity Market”

Academic Team Members:

Ward Jewell (lead), Wichita Shmuel Oren, UC BerkeleyChen-Ching Liu, University College DublinYishu Chen, UC Merced

Industry Team Members:

Jim Price, CAISOMariann Quinn, Duke EnergyFloyd Galvan, EntergyMark Sanford, GEJay Giri, AREVATongxin Zheng, ISO-NERalph Boroughs, TVARobert Wilson, WAPAAvnaesh Jayantilal, AREVAJerry Pell, DOESundar Venkataraman, GE Energy

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Thank You

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