It has been nearly two months since Winter Storm Elliott, which brought extreme cold conditions to most of the United States, causing energy emergencies across the country and electricity outages for 1.5 million households, including rolling blackouts throughout the Southeast. While some local outages were caused by downed or frozen power lines, many were caused by shortages in power supply and frozen instrumentation, including the rolling blackouts experienced by TVA in Tennessee and Duke Energy in North Carolina. These issues also ailed other regional grids, but did not lead to rounds of rolling blackouts like those experienced in the Southeast.
Now that the snow has settled from the storm, federal and state regulators can apply some lessons that were learned. Most importantly, wind energy and interregional transmission were integral to keeping the lights on for regions experiencing energy shortages and limiting the extent of blackouts in other areas. Furthermore, RMI analysis suggests that more wind energy and interregional transmission could have potentially prevented some of the rolling blackouts experienced in the Southeast during this storm.
Wind Energy Was Abundant and Widely Shared
Renewables performed well across the country during Winter Storm Elliott, specifically in the regional electricity grids SPP, MISO, and PJM. Wind in these regions steadily generated electricity through the storm and experienced fewer forced outages than fossil fuel resources due to the extreme cold. In PJM, for example, preliminary data suggests that coal and gas plants were responsible for 87 percent of the forced outages on December 24, with gas plants representing a disproportionately large portion (70 percent).
A major grid savior that prevented widespread blackouts across the eastern United States was the transmission network connecting different regional energy systems, which allowed energy to be moved to where it was needed. Inter-regional transmission is critical to allow the sharing of existing resources in, tight conditions improving grid reliability. Winter Storm Elliott made this perfectly clear: during the storm, energy originating from as far north as Canada was used across the country when fossil fuel generators were experiencing outages due to the extreme cold. Had TVA, Duke, and other regions experiencing tight grid conditions not been able to access imports from their neighbors through transmission, blackouts would have undoubtedly been far more widespread.
Regions in the Southeast that experienced blackouts during Winter Storm Elliott also experienced strong wind conditions that would have been ripe for additional wind generation had there been more wind turbines installed, shown in the chart below. Surface-level wind speeds at airports across North Carolina, for example, were recorded as high as 33 miles per hour, well above the range of wind speeds needed to generate power at wind turbines. Yet, Tennessee and North Carolina have lagged and occasionally outright opposed building new wind resources, and in 2021, wind energy in Tennessee and North Carolina represented only 0.04 and 0.4 percent of each state’s total net generation, respectively.
While wind was strong during Winter Storm Elliot, that will not necessarily be the case in every winter storm. In the face of extreme winter weather, a diversity of resources (including wind power from other regions supplied through adequate transmission) is essential to ensure that the lights stay on and to minimize the risk of blackouts when one type of generator is unable to deliver, like gas was during this recent winter storm.
Limited Transmission Meant Wasted Renewables
Although energy was successfully shared through the existing transmission network, that network is stretched to its limits, and as a result, excess energy, specifically wind energy, was curtailed (i.e., wasted). While wind resources may be abundant locally, if excess wind generation cannot be stored or sent to other regions that need it, it will be curtailed. That’s what happened during blackouts in the Southeast during Winter Storm Elliot — the central United States had an abundance of wind energy that could not be utilized in regions experiencing energy shortages and blackouts due to insufficient transmission.
At one point while TVA was experiencing blackouts on December 23, SPP alone experienced about 3 GW of wind curtailments, shown below. That 3 GW of wasted wind power is more energy than what can be produced at TVA’s largest coal plant, the Cumberland Fossil Plant, which is planned to be retired and replaced in 2026. Had this energy been available, it could have alleviated the Southeast’s shortage, both in terms of magnitude and duration, and kept the lights on for more households during the extreme cold.
Beyond alleviating outages, additional transmission could have provided significant financial benefit for utilities and consumers. New analyses have found that additional interregional transmission during Winter Storm Elliott could have created nearly $100 million in benefits, and that potential savings resulting from interregional transmission investments have never been higher.
Learning from This Event
Ongoing investigations from NERC, FERC, and state commissioners will provide additional insight into what exactly went wrong and what utilities can do to ensure a more reliable grid in the face of extreme winter weather. Until then, federal and state regulators can consider the following insights:
A diverse set of carbon-free resources (including transmission, renewable energy, battery storage, energy efficiency, and demand flexibility) are integral to maintaining grid reliability during extreme winter weather. To avoid the risk of relying on a single type of resource to ensure adequate energy supply, state regulators and policymakers need to ensure and at times require that a diverse set of resources are being considered in utility resource planning and reliability planning.
The US grid today is too fragmented, and more interregional transmission can both improve grid reliability and save ratepayers money. Federal regulators at FERC should consider requiring both a minimum amount of energy transfer capability between regional grids and a robust interregional planning process as it considers options to improve interregional transmission planning.
We can get more out of our existing transmission system today by implementing additional solutions that make it more efficient, such as reconductoring, dynamic line ratings, and other grid-enhancing technologies (GETs). These technologies can quickly and affordably increase the renewable energy uptake on the grid, which is even more valuable during tight grid conditions. Both state policymakers and FERC should be thinking about GETs and ways to get the most out of our existing grid infrastructure.
Achieving a reliable energy grid during periods of extreme winter weather is no easy feat, but reflecting on past storms can provide valuable insights about what needs to be done to ensure a more resilient and reliable grid in the face of extreme winter weather. Doing so will help ensure that when the temperature drops in the future, nobody has to worry if the power will stay on.
By Ashtin Massie, Sarah Toth. © 2023 Rocky Mountain Institute. Published with permission. Originally posted on RMI.
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