Environmental Engineering Reference
In-Depth Information
TABLE 2.5
Summary of Calculations of Estimated and Actual Emissions of SO
2
, NO
x
, and CO
2
via Methods A, B, and C
SO
2
(lb)
NO
x
(lb)
CO
2
(ton)
Method A
September 22 emission rates (per MWhr
generated)
0.0305
0.0320
0.0110
Actual stable emissions generated 8 p.m.-3 a.m.
48,370
50,778
17,457
Estimated stable emissions generated 8 p.m.-3
a.m.
41,900
43,986
15,122
Saved [additional] emissions
6,470
6,792
2,335
Method B
September 22 emission rates (per MWhr
generated)
0.0350
0.0320
0.0110
September 28 emission rates (per MWhr
generated)
0.0345
0.0361
0.0112
Actual emissions generated 8 p.m.-3 a.m.
48,370
50,778
17,457
Stable day emissions (no wind) generated
8 p.m.-3 a.m.
47,430
49,580
15,356
Saved [additional] emissions
940
1,198
2,101
Method C
September 22 emission rates (per MWhr
generated)
0.0350
0.0320
0.0110
September 28 emission rates (per MWhr
generated)
0.0345
0.0361
0.0112
Actual emissions generated 8 a.m.-3p.m.
160,646
167,926
52,010
Stable day emissions (no wind) generated
8 p.m.-3 a.m.
131,823
150,909
53.969
Saved [additional] emissions
[28,823]
[17,017]
1.686
NO
X
, and 410 tons or 2.2% of CO
2
would have been avoided. The use of wind
generation in a manner that forced PSCO to cycle Cherokee added signifi-
cant emissions from the Cherokee plant on July 2, 2008. Additionally, assum-
ing that the same quality of coal was used throughout the event, cycling the
plant also required PSCO to burn approximately 22 tons more coal than it
would have burned if the plant had not been cycled.
Figure 2.11 also shows how important the definition of event duration is
to the estimated impact. If the narrow 3:00 to 7:00 a.m. definition is used,
the impact of cycling is considerably smaller. However, this definition does
not consider the longer term difficulties of recalibrating the emission con-
trols after a significant cycling event which, as we have seen, can result in
increased emissions over several hours. Clearly the longer term perspective
involves the most appropriate means to measure these impacts.
