Environmental Engineering Reference
In-Depth Information
ERCOT publishes wind, coal, nuclear, natural gas, and hydroelectric gener-
ation data on a 15-minute basis. In addition, hourly generation and emissions
data are available through the CEMS system. Both the ERCOT 15-minute
data and the CEMS 60-minute data were utilized to determine the emission
implications of cycling units due to wind generation.
The same methodology was used for calculating emission implications of
wind in ERCOT as was used in the PSCO analysis with one exception. Due
to the availability of the 15-minute generation data, wind event details can be
calculated more precisely. For the ERCOT analysis, a wind event was defined
as an instance during which a 10% or greater dip in coal generation coin-
cided with an increase in wind energy generation. The frequency of cycling
events in ERCOT is captured within this section along with a case study
covering a 1-day period.
Frequency of Coal and Gas Cycling
Coal plants in the ERCOT system are cycled based on wind generation. The
8-day example shown in FigureĀ  2.19 illustrates the mechanism. Every day,
as wind increases between 9:00 p.m. and 5:00 a.m., coal generation dips. On
some days, such as November 9 and 10, coal generation drops significantly,
but even on days of limited wind such as November 8, wind appears to push
a small amount of coal generation offline.
12,000
Nuclear
Coal
Gas
Wind
Hydro & Other
10,000
8,000
6,000
4,000
2,000
-
Nov 5
Nov 6
Nov 7
Nov 8
Nov 9
Nov 10 Nov 11 Nov 12
Source: CEMS, BENTEK Energy
FIGURE 2.19
Cycling of coal plants as wind generation increases, November 5-12, 2008.
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