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The Effects of Greenhouse Gas Limits on Electric Power System
Dispatch and Operations
Miaolei Shao ([email protected])
Ward Jewell ([email protected])
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
7
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
9
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)
10
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
11
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?
12
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 $/MBtu
Coal CO2 emission factor is 215 lb/MBtu
Gas CO2 emission factor is 117 lb/MBtu
15
CO2 Emission-constrained ac Optimal Power Flow (OPF)
Objective function
Equality constraints
2_ _ _
1 1
( ) ( ) ( )g gN N
fe ij i fuel ij i CO ij ii i
F P F P F P
1
gN
i Load Lossi
P P P
1
gN
i Load Lossi
Q Q Q
Inequality constraints
i i iP P P i i iQ Q Q
k k kE E E k k k
mn mn mnMVA MVA MVA
Linear Programming
Software used in this research: PowerWorld Simulator
16
IEEE Reliability Test System (RTS) • 24 buses
• 38 transmission lines and
transformers.
• a total load of 2850 MW
• a total generation capacity
of 3405 MW
17
Case #
Description
Fuel Prices ($/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 $/ton, a 326% increase.
19
0
200
400
600
800
1000
1200
0 50 100 150 200 250 300 350 400 450
Pow
er O
utpu
t (M
W)
CO2 Price ($/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.
23
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
24
Thank You
25