Heat Dome

The heat dome.

The extreme heat dome that roasted the Pacific Northwest in late June and into early July brought record-shattering temperatures, caused tragic deaths numbering in the hundreds, literally melted some public infrastructure and left indelible memories with all of us who experienced it.

It also tested the region's electric system, which, with limited exceptions and despite some on-the-edge conditions, kept power flowing to customers in the dangerously hot weather.

Officials of four Northwest utilities outlined their heat-dome experiences at the Aug. 6 Pacific Northwest Utilities Conference Committee board of directors meeting. I found their stories worth sharing, and followed up with them and associates for this column.

They recounted new peak-load numbers, along with preparations for the heat, measures to address it, impacts on their systems, and internal and external communications. They also discussed issues raised by this event, along with lessons learned for a climate-changing future that may bring similar or even-more-scorching weather to the region.

Record-Setting Loads

The four utilities—Avista Utilities, Benton PUD, Clark Public Utilities and Idaho Power—all broke prior summer or overall peak-load records during the extended heat.

Avista hit its all-time system peak of 2,381 MW on June 29, a few megawatts above its all-time winter peak and 140 MW higher than the prior summer record, according to Scott Kinney, director of energy supply. He noted Spokane recorded three straight days above 105 degrees, and parts of its service territory exceeded 110. And nighttime lows only dropped to the mid-70s, "very warm for us."

Benton's total system load maxed out at 490 MW on June 29, smashing the previous high from July 2020 of 437 MW, reported GM Rick Dunn. That new record came during a four-day streak of daily high temperatures reaching or exceeding 110. His utility serves a large summer irrigation load and also has been adding new customers (mainly residential) at a significant clip, including about 1,000 in 2020. "What our system hadn't seen yet . . . was enough super-hot consecutive days to reveal a loss of diversity event that might drive our demand to a higher point," he said.

Clark recorded a new summer peak of 1,016 MW on June 28—besting the previous summer record of 863 MW in 2018—on a day in which temperatures at nearby Portland International Airport hit a mind-boggling 116. Tom Haymaker, Clark's manager of energy planning and operations, noted Clark's winter peak is slightly more than 1,100 MW, but the seasonal gap has narrowed significantly and "we're . . . giving some thought as to whether we're a dual-peaking utility now."

Idaho Power peaked at 3,751 MW on June 30, 9.5 percent above its previous all-time record load, reported COO Adam Richins. He shared a slide showing the IOU exceeded its previous peak in each of nine consecutive hours on both June 29 and 30, from 2 to 11 p.m. Richins said Idaho Power typically peaks in late June or early July with a large irrigation load during that period (700 MW to 800 MW), and in addition early summer 2021 brought "a perfect storm in terms of heat and drought and [customer] growth" of close to 3 percent annually in recent years.

Heat Preparations

These (and other) utilities had some advance warning of this potentially severe heat wave, and thus some time to prepare.

Avista, for example, "started preparing for summertime conditions . . . about a month before the heat event," said Kinney, adding the utility was at that time more concerned about market liquidity for the third quarter, and specifically August, based on forward market prices.

Among other actions, Avista minimized planned maintenance outages on its transmission and distribution systems, informally reached out to larger customers about voluntary load-shedding (it lacks demand response programs), checked its hydro licenses for emergency capabilities and reviewed its energy curtailment plan. Those were "all helpful as we got into" the heat dome, said Kinney.

Shortly before the hottest temperatures arrived, Avista adjusted some distribution-system feeders in anticipation of specific areas of stress, according to Kinney and Mike Magruder, director of system operations and planning. And on the morning of June 28, Kinney said, the system operations team stopped any T&D maintenance outages.

Clark—which Haymaker said is a customer of The Energy Authority for services that include daily and real-time forecasting and prescheduling real-time trading—was watching the approaching heat "pretty intently," he said, adding, "The real challenge we had was without any temperatures like that ever in the historical record, it's hard to know where your saturation level is with regards to air conditioning."

Haymaker said Clark has experienced minimal load growth in recent years, but significant growth in new customers, with nearly every new home equipped with air conditioning. "We have an idea of how many air conditioners there are," he said. "You don't get a sense of how they're really used until you have a significant event like this."

He attributed the 150 MW jump in Clark's new peak load virtually all to air conditioning demand in the unprecedented heat (the prior Portland high temperature was 107, which was 9 degrees lower than it hit June 28).

Weathering the Heat

As the severe late-June heat blanketed the Northwest, none of the four utilities found issues accessing power supplies, although market energy came at a price.

"I think we were a little bit surprised how liquid the market was," said Kinney.

He noted the extreme heat mainly centered over the Northwest, so regional resources weren't in unusually high demand elsewhere in the West, although you "had to pay a premium for it."

Average peak power prices at the Mid-Columbia and California-Oregon Border hubs were above $100/MWh from June 25 to June 29, and topped $300/MWh on June 28, according to NewsData's Western Price Survey.

Clark, meanwhile, leaned on its 248-MW-capacity natural gas-fired River Road Generating Plant. Even though its output dropped slightly because the hot air reduced its efficiency, the plant "ran like a champ," said Haymaker. "And I think given its location [in Clark County] it's a pretty important resource to have . . . in those times of stress."

He added, "It was a pretty extreme event, and we were out purchasing additional power supplies," and even though it "was expensive, it was available. And we didn't get a sense of any particular stress or panic in the wholesale market."

Benton is a BPA Slice/Block customer, and likewise was in the market during the heat dome, for as much as 200 MW in some hours, according to Dunn. "Our hedging strategy worked very well, in spite of the big temperature increases and price spikes," he said. "We were well-positioned with swaps" and went into summer long in heavy load-hour power in anticipation of high market prices.

Nonetheless, these utilities faced specific challenging circumstances as the acute heat enveloped their systems.

Idaho Power's Richins identified transmission access as a vital concern for his utility. He said its hardest day meeting loads came June 28, more so than on its peak-load day of June 30, because of lower transmission availability in the Northwest. "We're importing 10 percent of energy during peak times; we need to rely on the transmission," he said, noting that on June 28 Idaho Power "imported a fair amount" of power via non-firm transmission.

More generally, Richins said, Idaho Power transmission access is "pretty constrained everywhere" in terms of direction. He said the utility finds the Northwest market typically more liquid and with lower prices, and Idaho Power also has more transmission available, compared to southerly markets, notably including California.

For Avista, the heat dome especially stressed its distribution system. Kinney and Magruder reported some transformers on June 28 were well above 95 percent loading, and two feeders exceeded their 100 percent operating limit. Standard practice in such circumstances "is to drop load in order to protect the equipment," said Magruder, describing it as "very localized to specific equipment that was basically at its limit."

Avista reported a total of 18,012 unique customer outages on June 28 and 29; some customers experienced multiple outages, according to Casey Fielder, senior communications manager.

Benton, which gets 200 MW of its 272 MW of total contracted capacity from BPA (per its website), relies on the BPA transmission system, which according to Dunn faces potential reliability concerns in the Tri-Cities area under peak-loading summer conditions.

(BPA spokesman Doug Johnson elaborated to me that the BPA system has five major transmission paths into the Tri-Cities area, and if one goes out, contingency plans are in place for the other four in the event of another unplanned outage; those plans include the potential for load shedding. He also said BPA is "fully aware" of transmission issues in the growing Tri-Cities area and plans projects to strengthen the local system in 2022-2025.)

Dunn said BPA had shared with Benton "specific load levels" that prompt concerns, and "this heat dome event blew through that by a substantial margin." He said BPA on the morning of June 28 informed Benton and other local utilities to be on guard.

In the end, he said, "We're very glad it worked out and we didn't have a problem" with the system.

Dunn also singled out nearby 603-MW-capacity Ice Harbor Dam on the lower Snake River as a valuable resource specifically for the Tri-Cities grid, especially in a situation such as late June when every megawatt mattered. BPA has long said that in summer peak periods, Ice Harbor in particular "would be available to help with afternoon peaks in the summertime," he said.

[Ahead: A look at other utility measures, utility internal and external communications, and implications and lessons learned from the heat dome will appear in the Sept. 24 issue (No. 2023).]

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