Winter Storm Elliott stressed regional electric grids across the U.S. in different ways
Energize Weekly, January 18, 2023
Winter Storm Elliott, the bomb cyclone with freezing temperatures and blizzard conditions that swept across the U.S. east of the Rockies, sparked a wave of outages with its impacts varying from regional grid to regional grid.
On Dec. 23, a cold front moved across the country boosting the demand for both natural gas heating and electricity. Regional infrastructure and grids had trouble meeting the demand leading to widespread rolling blackouts.
On Christmas Eve, an estimated 1.6 million customers were without power, according to PowerOutage.us.
In the wake of the episode the Federal Energy Regulatory Commission (FERC) and the North American Electric Reliability Corp. (NERC) opened a joint inquiry into bulk power operations to determine the cause of the spate of outages.
In announcing the investigation, the agencies said that while most outages were due to weather impacts on local distribution systems, bulk power – the wholesale provision of electricity – was also “significantly stressed.”
“The effects of Winter Storm Elliott demonstrate yet again that our bulk power system is critical to public safety and health,” FERC Chairman Richard Glick said in a statement. The joint inquiry, Glick said, will allow the agencies “to dig deeper into exactly what happened so we can further protect the reliability of the grid.”
There were pronounced differences in how the storm affected regional grids, according to an analysis by energy market consultant BTU Analytics.
“This surge in regional demand met well-worn constraints in supply, causing gas prices to rapidly rise from Transco Zone 5 in North Carolina all the way to the Algonquin Citygate in Massachusetts,” BTU Analytics said.
In New England, there was a knock-on effect as home heating demands for natural gas impacted electricity generation. In the last five years, three gigawatts (GW) of natural gas-fired generation capacity has been added to the ISO New England grid, bringing the total gas-fired capacity to 20 GW.
But as the storm hit and home heating demand rose, even as electricity demand remained average, power providers were forced to switch to other fuels – primarily fuel oil.
On Dec. 24, 41 percent of all ISO New England electricity generation was being provided by fuel oil, almost 6 GW. In 2021, fuel oil made up about 1 percent of generation.
“Such a large shift in the fuel mix away from natural gas immediately resulted in an enormous increase in power sector emissions, as the overall carbon intensity of ISO-NE generation rose over fourfold across the span of just two days,” energy analyst Joe Warner wrote in the BTU Analytics assessment.
New England power providers burned an estimated 31.5 million gallons of oil during the December cold snap. About 28 million gallons have been or are set to be replaced, according to ISO New England.
In Tennessee and the Carolinas, a different dynamic played out as most homes are heated by electricity rather than natural gas or fuel oil. Across the region, 70 percent of households depend on electric heating compared to 17 percent in ISO New England states, according to a 2020 U.S. Energy Information Administration survey.
“When bitter cold descended into the southern United States and businesses and residences switched on their electric heaters to stay warm, a sudden and rapid ramp in electricity demand followed, pushing total load to record highs,” BTU Analytics said.
The prime electricity suppliers – Duke Energy and the Tennessee Valley Authority (TVA) – ramped up generation and struggled to maintain adequate reserve margins. On the morning of Dec. 22, gas-fired power generation reached 22 GW, more than double the demand two days earlier.
Both generators were forced move to emergency load-shedding and rotating outages.
The PJM Interconnection, the grid operator for all or parts of 13 mid-Atlantic and Midwestern states and the District of Columbia, also had to take conservation measures to avoid blackouts as a significant portion of its generation capacity failed.
Dec. 23 started with about 12,000 megawatts (MW) of generation down and that grew to 34,000 MW on Dec. 24 and eventually reaching 46,000 MW out of service.
The PJM Interconnection has launched a probe to determine why so much generating capacity failed and why power providers could not meet their obligations.
“In addition to the load shedding in Tennessee and the Carolinas, multiple energy emergencies were declared and new demand records were set across the continent’’ Jim Robb, NERC president and CEO, said in a statement. “This storm underscores the increasing frequency of significant extreme weather events – the fifth major winter event in the last 11 years – and underscores the need for the electric sector to change its planning scenarios and preparations for extreme events.”