As winter approaches, concerns about the reliability of the electric grid in the southern United States have been raised, especially after the rolling blackouts experienced last year.
The North American Electric Reliability Corporation’s (NERC’s) 2023–2024 Winter Reliability Assessment (WRA) released earlier this month provides a comprehensive view of the potential challenges and readiness of the bulk power system (BPS) for the upcoming winter season.
This assessment is a crucial tool for informing industry leaders, planners, operators, and regulatory bodies about the potential risks and necessary actions to ensure reliable power supply during the winter months.
Focus on the South
One of the key findings of the WRA is the risk of insufficient electricity supplies during peak winter conditions.A significant portion of the North American BPS, including areas in the southern United States, is at risk because of prolonged cold snaps that can lead to high generator outages and increased demand, particularly from electric heating systems, according to the report.
The Midcontinent Independent System Operator region, which has seen an increase in available resources through new wind and natural-gas-fired generation, remains vulnerable to extreme cold-weather events, particularly in its southern areas.
These events can cause high generator outages due to inadequate weatherization or insufficient natural gas fuel supplies, such as was seen during outages in 2022 just before Christmas.
Similarly, the regions covered by PJM Interconnection, SERC-East, and SERC-Central are also at risk of energy emergencies during severe cold-weather events.
Despite having adequate resources for normal winter conditions, these regions’ generators are susceptible to decreases in capacity and outages under extreme conditions.
The assessment also highlighted the critical role of generator fuel supplies, particularly natural gas, in ensuring winter electricity demand is met.
The interconnected nature of the natural gas and electric systems means that disruptions in one can have significant effects on the other.
Last Winter
Winter Storm Elliott, which struck in December 2022, was a “once-in-a-generation storm” that brought unprecedented challenges in particular to southern portions of the country serviced by federal energy utility the Tennessee Valley Authority (TVA).The storm affected most of the eastern continental United States, bringing heavy snowfall, high winds, and freezing rain, causing widespread travel disruptions and power outages.
Despite these preparations, the storm’s speed, its intensity, and the resulting conditions exceeded the TVA’s forecasts and efforts.
The TVA system experienced its coldest average temperature since February 1996, with lows in major cities such as Nashville and Memphis dropping to 1 degree F. Energy demand surged, resulting in the highest 24-hour electricity demand supplied in the TVA’s history on Dec. 23, 2022, according to the report.
The TVA team worked to increase generation and meet the soaring demand. This involved dispatching units that weren’t previously in service and executing day-ahead, real-time, and emergency purchases.
Despite these efforts, the TVA faced significant challenges. Of its 232 generating units, 38 were negatively affected, mostly because instrumentation froze. This resulted in the TVA’s nuclear and hydro assets, which weren’t affected by the extreme weather, playing a crucial role in supporting energy demand during the event.
NERC Recommendations
NERC states that coal, another vital fuel for electricity generation in winter, also faces challenges. Although generator owners report fewer coal supply issues than they had last winter, there are concerns about coal transportation, particularly in areas affected by drought conditions that could restrict coal availability and affect generator output, according to the report.
Another area of concern is the growing complexity in load forecasting during winter, the report says. The electrification of the heating sector and the increase in variable solar power resources add to the unpredictability of electricity demand, making it challenging to accurately forecast and plan for peak demand conditions.
Recommendations by the agency include reviewing seasonal operating plans, implementing cold-weather preparations, monitoring fuel supplies, and being prepared for potential reserve deficiencies.
Additionally, regulators are encouraged to support grid operators with environmental and transportation waivers and public appeals for energy conservation.
Events such as winter storms Uri in 2021 and Elliott in 2022 have underscored the need for improved cold-weather preparedness and coordination between generator owners and operators and BPS operators, the agency added.
The assessment stresses the importance of planning and coordination to address the various challenges that could affect the reliability of the electric grid in the southern United States during the winter to keep customers warm.
