Environmental Engineering Reference
In-Depth Information
created at the Pawnee and Cherokee plants. The Arapahoe, Hayden, and
Comanche plants showed small NO
X
savings.
PSCO Case Study Conclusions
The case studies in this section conclude that cycling coal-fired facilities to
compensate for intermittent must-take energy sources results in inefficient
operation during the cycling event and for hours afterward. This inefficiency
results in severe degradation of emission savings at best and net additional
emissions in many cases. Variable generation sources such as stored energy
and natural gas facilities are necessary on systems that utilize intermittent
energy sources to fully realize emission savings.
ComparisonofPSCOandERCOTSystems
To gain a better understanding of the impacts of wind events on coal-fired
generation and validate the findings relative to the PSCO territory, this section
examines coal cycling in the Electric Reliability Council of Texas (ERCOT)
system. ERCOT and PSCO have aggressively pursued wind generation in the
past decade due to legislative goals and incentives. Wind power is a must-
take resource on both systems, but is curtailed more often at ERCOT because
resources are much larger and can create reliability problems when the system
is fully generating. Finally, both systems are dispatched by central operators
that attempt to utilize as much wind generation as possible without disrupt-
ing reliability standards. More important than these similarities, however,
are the distinctions. ERCOT has far larger gas-fired generation capacity and
requires publishing of detailed wind generation data that, when combined
with CEMS data, enables precise definition of wind events, thus facilitating a
better understanding of the emission implications of wind use.
Wind,Coal,andNaturalGasInteractionsinERCOTSystem
This section examines the interactions of wind, coal, and natural gas in the
ERCOT region of Texas as a means of further validating the results found in
the PSCO territory. It will demonstrate that while ERCOT's scale of wind, gas
and coal operations is larger than in PSCO's territory, the result is the same.
Since the wind blows at night when gas generation is relatively low as a per-
cent of total generation, coal plants are cycled, producing more SO
2
, NO
X
, and
CO
2
than would have been the case had those coal plants not been cycled.
