The North American Electric Reliability Corp. should lead development of a new approach to resource adequacy assessments that supplements the traditional loss of load expectation, or LOLE metric, with more granular indicators, according to a Thursday report from the grid watchdog and the National Academy of Engineering.
Traditional resource adequacy models are focused on peak hour conditions and based on a LOLE of 1-day-in-10 years. But LOLE “does not adequately account for the growing risk, over all hours, arising from increased variability and uncertainty caused by the evolving resource mix and increasing demand levels,” according to the report.
The report was produced following a March workshop with NERC and NAE, and sketches out possible new electric reliability criteria for planning resource and transmission adequacy. NERC produces annual assessments of the bulk power system’s reliability, adequacy and associated risks, for upcoming summer and winter seasons as well as a 10-year review.
“There is little doubt that our dependence on electricity as the engine of our economy is increasing at a rapid pace,” Mark Lauby, NERC senior vice president and chief engineer, said in a statement. “As the grid transforms, it is imperative that traditional planning criteria evolve to reflect a new reality in which energy adequacy becomes a critical complementary consideration of resource adequacy when addressing overall system reliability.”
The NERC-NAE workshop resulted in nine “actionable topic areas” the report says can form the basis for an improved approach to resource adequacy. Among them are:
- Development of a multi-metric approach that considers loss of load hours, or LOLH, and expected unserved energy, known as EUE, alongside LOLE;
- A chronological study, piloted by NERC, of the hourly profiles needed to capture inter-hour relationships that could constrain the grid, such as ramping and storage scheduling;
- Calls for NERC to monitor load changes, including those due to electrification, that may lead to shifts in the peak conditions; and,
- Inclusion of “stressed scenarios” in the resource and transmission planning process, and a determination of transmission energy adequacy for stressed resource adequacy scenarios.
Including LOLH and EUE in resource adequacy assessments will help to address unserved energy duration and magnitude, and report event-based statistics, the report said.
Large portions of the North American electric grid are at risk of electricity supply shortfalls during heat waves and other extreme weather events, NERC concluded in its 2024 Summer Reliability Assessment, published in May. The reliability watchdog identified seven areas facing an “elevated risk” of shortfalls due to rising demand, generator retirements and unplanned outages, drought and the potential for low wind performance.
Looking further out, NERC in December said rising peak demand and the planned retirement of 83 GW of fossil fuel and nuclear generation over the next 10 years will create blackout risks for most of the United States.
