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WECC Simulation Highlights Extreme Weather Risk 10 Years From Now

A new study from the Western Electricity Coordinating Council provides recommendations to help stakeholders prepare for extreme winter weather events.

The study, Year 10 Extreme Cold Weather Event, evaluated the potential impacts of an extreme cold weather event on the reliability of the electric power system 10 years in the future.

It found vulnerabilities in the electric power system in the Western Interconnection with respect to natural gas supplies, battery storage charging regimes, and transmission flows.

The study extrapolated data from the extreme cold weather event that occurred between December 21 and December 26, 2022, and brought very low temperatures, heavy snow, and high winds to much of the United States and parts of Canada.

In the simulation, WECC applied the system conditions of the 2022 event to its 2032 Anchor Data Set, a stakeholder-vetted compilation of load, resource, and transmission information. With that data as a baseline, WECC changed its input assumptions to model a similar storm in 2032.

The simulation mimicked the 2022 event load shape for 2032, while increasing load by 10 percent, doubling the forced outage rates of thermal generation, decreasing the output of wind and solar generation, and limiting natural gas availability by 15, 25, and 35 percent. No other changes were made to the 2032 resource mix or transmission topology.

WECC reported that the study yielded three observations. First, natural gas generation would be necessary to continue serving load during the modeled extreme cold weather event.

If all natural gas generators remained online, no load shedding occurred, but natural gas derates would result in load shedding, which highlighted the power system’s dependence on natural gas generation during extreme weather events. That dependence is a compound risk because cold weather events can affect the natural gas system, WECC noted.

Secondly, WECC observed that the timing of unserved load was heavily influenced by battery charging schedules. Charging batteries in the morning for discharge later in the day, for instance, can increase morning load and shift unserved load to the morning peak, the study said.

WECC noted, however, that its energy storage model optimizes a 24-hour cycle that requires the batteries to charge and discharge each day, which may not reflect actual practices of charging and discharging over multiple days and skew results by shifting unserved load to the morning peak.

The simulation also found there were hours, such as during the 35 percent natural gas derate scenario, when unserved load occurred even though batteries were being discharged.

WECC said the simulation also showed that transmission flowed from south to north more frequently in the extreme weather events, which WECC said was “noteworthy” and may signal “a more substantial change in transmission use patterns, particularly during widespread extreme events.”

Based on the observations derived from the study, WECC made three corresponding recommendations:

  • Stakeholders should closely monitor natural gas availability under extreme cold conditions and maintain datasets for studying extreme weather conditions and its impact to the natural gas system and correlate that data with electric system data to facilitate weather event studies;
  • WECC should implement software enhancements to enable multi-day battery storage cycling to more realistically analyze storage operation, dispatch, and commitment during extreme cold weather; and
  • WECC and industry should model new transmission projects under various system conditions to evaluate the effect on transmission use and flows and should explore the reliability implications of reverse of flows on major WECC transmission paths.
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