While PJM experienced some of its highest peak loads ever during the late January winter storm, it overestimated load, with relatively high load forecasting errors, RTO officials told the Operating Committee.
PJM’s Paul Dajewski told the Operating Committee on Feb. 5 that while operations were strained during the Jan. 24-27 storm, named “Fern” by The Weather Channel, load did not quite reach the forecasted peaks and the RTO maintained reliability.
“We were able to operate through this period reliably; we did have sufficient generation reserves; we were able to serve our loads; we were able to serve our exports,” Dajewski said, adding that PJM provided emergency energy sales to neighboring regions.
PJM saw an instant peak load of 140,049 MW on Jan. 29 at 8:05 a.m. and two new top 10 hourly integrated peaks of 139,046 MW on Jan. 29 and 138,479 MW the following day. It noted that the data are preliminary.
Dajewski said there was a lot of uncertainty with preparing for the storm, owing to the duration of the freezing temperatures, pipeline flexibility, fuel storage, generators running into emission limits, load forecast accuracy, and the interplay between when gas resources are committed and when they purchase fuel from pipelines.
PJM asked that generators cut short maintenance outages between Jan. 25 and Feb. 2, reducing some transmission constraints. The RTO declared a long-duration extreme event, so fuel-limited resources were required to signal when they have 32 hours or less of fuel inventory, rather than the standard 16-hour notice.
The load forecast error was high between Jan. 26 and 29, peaking with an 8% over-forecast on Jan. 27. PJM’s Joseph Mulhern said temperatures were not quite as low as expected and that it’s possible the RTO’s modeling did not properly account for building closures. PJM said that it is difficult to predict the number of buildings that will close because of the weather, as the decisions are based on subjective, location-specific factors.
Stakeholders expressed surprise that building closures would contribute to load falling gigawatts below the forecast. Mulhern said PJM is exploring the issue further.
Transmission constraints and limited ramp capability drove $797.6 million in uplift costs, mostly in balancing operating reserve charges. There were $577.9 million in make-whole costs, $98.2 million in lost opportunity costs and $121.6 million in day-ahead operating reserve charges assigned. PJM is working on a more detailed breakdown of the make-whole costs for stakeholders.
Conservative operations were used to secure advance commitments, which PJM’s Brian Chmielewski said contributed to the make-whole costs. Pre-emergency load management was called in the BGE, Dominion and Pepco zones Jan. 25 for localized transmission constraints, and maximum generation, load management and low-voltage alerts were issued for Jan. 27.
PJM’s Brian Fitzpatrick said gas pipelines performed “very well,” with only one compressor station failing and 1,500 MW of generation interrupted. Winterization efforts on gas production appear to have led to a decrease in reduced output during winter events, with 5% production lost in Appalachia and 9% across the country. Nonetheless, spot prices were some of the highest he has seen, reaching $300/MMBtu on some interfaces.
Even with actual load coming in below forecast, Fitzpatrick said there was a lot of concern in the gas market about the duration of the storm, high loads and potential scarcity.
“That inherent fear in the market drove those prices,” he said.
PJM received Department of Energy waivers under Section 202(c) of the Federal Power Act to operate 39 units totaling 5.2 GW past environmental permit limits for 1,035 hours. The department also invoked a lesser used 202(c) provision to make backup generation available, but those units were not dispatched. (See Wright Ready to Use Emergency Powers to Dispatch Backup Generation During Winter Storm.)
PJM’s Joe Ciabattoni said the day-ahead bid period was extended on Jan. 26 and 27 because of issues running credit checks on market participants. It took longer for staff to accept bids because of the number of offers exceeding $1,000, triggering the automatic offer verification process.
A severe cold snap Jan. 16-21 preceded the storm, but it was much easier for the RTO to manage, with no emergency actions taken. The generation fleet performed well, and no emergency procedures beyond cold weather advisories or alerts were required. Load peaked at 135,121 MW on Jan. 21 at 7:40 a.m. with no load management deployed.
While all pipelines enforced the restrictions in their tariffs, there was no drop-off in production, and fuel remained available and relatively affordable for dispatched units. No advance commitments were made in preparation.
