AVOIDED OPERATING COST
IN THERMAL GENERATING
SYSTEMS
N. CHOWDHURY
Power Systems Research Group
University of Saskatchewan
Saskatoon, Canada
Non-Utility Generation (NUG)
Independent Power Producers
Cogenerating Plants
Type of NUGs
Conventional
Solar
Biomass
Wind
Non-Utility Generation
(1) Dispatchable
Utility maximizes savings
(2) Non-dispatchable
Utility is tied to the NUG schedule
Firm Capacity
Unit Commitment
Capacity Credit
Energy Credit
Non-Firm Capacity
Energy Credit
Operating Cost
Load Profile
Operating Criteria
(1) Deterministic
(2) Probabilistic
Optimum Loading Configuration
Avoided Operating Cost
Optimum operating Cost Without a NUG
Optimum operating Cost With a NUG
All cost figures are evaluated on the
basis of optimum loading schedule
of the generating units that satisfy all
operating and reliability criteria.
Generation Data For the IEEE - RTS
Unit
Type
Unit
Number
Priority
Failure
Size
of
Loading
Rate
(MW)
Units
Order
(f/Yr)
50
4
1-4
4.42
Nuclear
400
2
5-6
7.96
Thermal
350
1
7
7.62
Thermal
155
4
8-11
9.13
Thermal
76
4
12-15
4.47
Thermal
100
3
16-18
7.30
Thermal
197
3
19-21
9.22
Thermal
12
5
22-26
2.98
Thermal
20
4
27-30
19.47
Hydro
50
2
31-32
4.42
Hydro
Running Cost Parameters For the IEEE - RTS
Unit
Type
Unit
Size
Cost Parameters
a
b
c
(MW)
Hydro
50
0.0000
0.50
0.00
Nuclear
400
0.0002
5.34
216.50
Thermal
350
0.0039
8.92
388.20
Thermal
155
0.0066
9.27
206.70
Thermal
76
0.0113
12.14
100.40
Thermal
100
0.0220
17.92
286.20
Thermal
197
0.0030
20.02
301.20
Thermal
12
0.1373
23.27
30.39
Thermal
20
0.1825
37.55
40.00
Load data for the IEEE-RTS
Hour
Load
(MW)
Hour
Load
(MW)
Hour
Load
(MW)
1
2
3
4
1667
1539
1453
1410
9
10
11
12
1710
1881
1923
1945
17
18
19
20
1945
2137
2116
2073
5
6
7
1368
1389
1410
13
14
15
1923
1881
1859
21
22
23
2009
1966
1859
8
1496
16
1859
24
1731
5900
5400
4900
4400
AOC($)
3900
3400
2900
2400
1900
1400
900
100
200
300
400
500
600
Cogeneration energy (MWh)
NEL,
POF=0
NEL,
POF=0.0027
EL,
POF=0
EL,
POF=0.0027
375,500
375,000
374,500
374,000
373,500
373,000
372,500
372,000
371,500
371,000
370,500
100
200
300
400
500
600
Cogeneration energy (MWh)
NEL
POF=0
NEL
POF=0.0027
EL
POF=0
EL
POF=0.0027
4667.80
3746.90
3746.85
3746.80
4667.40
3746.75
4667.20
3746.70
3746.65
4667.00
3746.60
4666.80
3746.55
4666.60
3746.50
1
3
2
4
Number of units
NEL
EL
5
AOC for EL units ($)
AOC for NEL units ($)
4667.60
4650
3730
3710
4600
4550
3670
3650
4500
3630
4450
3610
3590
4400
3570
4350
0.01
3550
0.02
0.03
0.04
Probability of failure
NEL
EL
0.05
AOC for EL units($)
AOC for NEL units($)
3690
373,000
Utility cost with NUG energy ($)
372,800
372,600
372,400
372,200
372,000
371,800
371,600
0.01
0.02
0.03
0.04
Probability of failure
NEL
EL
0.05
Conclusions
Avoided operating cost depends on the
operating criterion.
Optimum loading schedules should be utilized
in the assessment of avoided operating cost.
The technique illustrated in this paper is
simple and straightforward.
The technique can handle deterministic and
probabilistic operating criteria with little
difficulty.