Energy consumption among Clark Public Utilities customers was 19,632 megawatt hours on Monday, June 28, the third and hottest day of the heat wave, which saw temperatures hit 115 degrees in Vancouver.
An average Monday in late June would draw 12,096 megawatt hours, according to Clark Public Utilities media specialist Dameon Pesanti, meaning the power demand was about 62 percent above normal at the peak of the heat wave.
Clark Public Utilities was able to adjust to the heightened demand, but the incident highlights how a changing climate and extreme weather events are pushing the utility to raise its demand forecasts and tighten its schedule of infrastructure upgrades.
"Our system did extremely well considering the stress it was under, but we're going to probably do a few infrastructure upgrades in the not-too-distant future to be ready for next time," Pesanti wrote in an email.
AC Power
Peak demand during the heat wave was 18 percent greater than the previous peak in 2017. It's unusual for a peak be exceeded by so much, Pesanti said, and unprecedented for it to happen in June.
Clark Public Utilities is normally a winter-peaking utility, meaning its highest-demand days tend to come during the winter heating season. The kind of high demand seen during the heat wave normally only occurs every four or five years during exceptionally chilly weather.
Increased air conditioning usage likely accounts for the vast majority of the extra power use, Pesanti said. Air conditioning is an energy-intensive process, and energy-efficient units tend to be more expensive.
Historically, the Pacific Northwest hasn't had nearly as strong a relationship with air conditioning as the rest of the country, but the gap is closing quickly. A decade ago, roughly 65.6 percent of homes in the Portland-Hillsboro- Vancouver metro area had some form of air conditioning, according to the U.S. Census Bureau's American Housing Survey. By 2019, that figure had risen to 78.6 percent.
Nearly all new homes in Clark County have central air conditioning installed, Pesanti said, and units are an increasingly common addition to older homes. Couple that with Clark County's ongoing housing boom and the result is a much greater potential for hot weather to generate spikes in power demand.
Households often see higher power use in the evening when families are at home, and air conditioning usage is normally part of those regular spikes. But heat waves upend that model, Pesanti said, because when overnight temperatures never fall below the mid-70s, consumers tend to run air conditioning nonstop.
The Weather Factor
Power failures generally come from either supply problems — meaning there's not enough power being generated to meet demand — or distribution problems, where grid infrastructure can't cope with the amount of power being transferred (there's also the possibility of physical damage, such as tree branches falling on power lines).
Mass outages in Texas in February were an example of the former problem — extremely cold weather knocked many of the state's power plants offline.
Tom Haymaker, manager of energy planning and operations at Clark Public Utilities, wrote in a February news release that a failure of that sort would be far less likely in Clark County because our grid is connected to a much bigger network with a wide range of power resources.
The other scenario is the more immediate concern in the Pacific Northwest region. During the heat wave, the Tri-City Herald reported that the Bonneville Power Administration had begun working with utilities in the Tri-Cities area to prepare for possible rolling blackouts to prevent an overload of the transmission system, and the Associated Press reported that several thousand residents in Spokane temporarily lost power on the final day of the heat wave.
Those were situations where peak demand began to bump up against the grid's capacity. Think of a freeway — traffic can get heavier for a sustained amount of time and still keep moving at full speed, but there's an upper limit to how many cars can enter at once before problems arise.
If a grid's peak demand exceeds its capacity, individual components such as wires and transformers will start to fail by overheating and burning out, Pesanti said, knocking out power within local areas. Extreme heat also stresses those systems, exacerbating the risk of burnout.
Under ordinary operating conditions, the utility limits the number of connections to its circuits, essentially keeping additional capacity in reserve to be rolled out during extreme weather events. There's also some redundancy, Pesanti said, allowing operators to find alternate pathways to move power around if the primary or usual circuits are nearing their limits.
There was enough extra capacity to avoid any major issues this time, Pesanti said, but the heat wave and other extreme weather events in recent years have prompted Clark Public Utilities to devote greater attention to the ways in which those events can impact the power grid — both in terms of peak demand and direct physical damage from events such as wildfires.
"What were once thought by many to be mostly one-off events have become common in recent years," Pesanti wrote.
Growth Vs. Efficiency
The total number of residential accounts connected to Clark Public Utilities has been increasing at a rate of about 2.5 percent per year, according to Pesanti, or about 5,200 new customer accounts, each of which represents slightly more than two people on average.
The utility's long-term forecast is a bit lower, pegging the expected growth rate at about 1.5 percent per year for the next five to 10 years.
The growth is partially balanced by Washington's energy codes, which are aimed at reducing energy consumption in new structures. The state's Energy Independence Act also requires major utility providers to meet conservation targets of their own. Clark Public Utilities offers incentives for builders who exceed the energy code standards by at least 10 percent, Pesanti said.
Older homes can also be upgraded with more efficient technology such as LED lighting, low-energy appliances, variable speed heat pumps, smart thermostats, heat pump water heaters and better-insulated windows.
The result is that new homes in Washington are among the most efficient in the country, Pesanti said, which means there's an extent to which utility providers can count on efficiency gains to offset the rise in demand generated by new homes coming online.
"Energy conservation has always been smart business for electric utilities as it allows us to avoid costly system upgrades and constructing or contracting new energy resources," Pesanti wrote.
That's part of why even though the growth rate in terms of new accounts is predicted to be 1.5 percent per year, the utility estimates the growth in total average energy demand will be more like 0.5 percent per year, roughly 2.5 megawatt hours on average.
"Without energy conservation and efficiency, we'd expect those energy demand numbers to be triple," Pesanti wrote.
Balancing Act
Clark Public Utilities produces some energy at its River Road gas turbine plant, but it also buys a lot of wholesale electricity from other providers, most prominently the Bonneville Power Administration. Wholesale power is often purchased months or even years in advance based on forecasted system loads.
The 0.5 percent growth rate is easily manageable, Pesanti said, because the utility's contract with BPA is flexible enough to accommodate both rising demand and more immediate spikes. Still, climate change and extreme weather events play a role in how the forecast process plays out. For example, the utility used to average temperatures from the past 60 years to forecast power demand, but several years ago switched to a model that uses the past 15 years to provide a more accurate estimate of current weather.
The utility makes regular upgrades to accommodate the increased demand, Pesanti said, including installing larger wires and other equipment on primary feeder lines and in some cases new substations, which need to be built when a given area reaches a sufficient level of growth.
Those kinds of projects are completed on a rolling basis, with several years of projects planned at any given time. That's the area where heavy air conditioning usage and other high-demand situations could have an impact on the utility's operations.
"The higher level of electricity usage during the heat event will cause us to take another look at projects that are currently scheduled to be completed in the next several years," Pesanti wrote. "Construction of some of these projects will now be completed sooner."
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