Texas nearly had a total power grid failure. The risks for that doomsday scenario are growing in the West
The February blackouts in Texas put more than 4 million people in the dark and cold, forced millions to boil water and killed dozens who froze, were poisoned by carbon monoxide or even burned to death while trying to stay warm.
As bad as it was, it could have been much worse.
Texas power officials said they were mere minutes from losing control of the grid, a worst-case scenario that could have left nearly the entire Lone Star state without power for weeks.
It's a doomsday situation whose risks are growing, particularly in Western states like Arizona, because of wildfires and extreme temperatures that test the power grid's capabilities.
While recent Arizona power disturbances have been minor compared to Texas this winter and California last summer, those power outages risk not just rolling blackouts that grid operators can control, but a cascading, uncontrolled outage of power.
Something as minor as an inattentive utility worker, or poor communication between neighboring utilities regarding power plant operations could mean the difference between stable, controlled outages and catastrophe.
"If your entire grid turns off, it is very, very difficult to turn it back on," said Kyri Baker, an assistant professor of civil, environmental and architectural engineering at the University of Colorado, Boulder.
A full loss of the power grid is known in the industry as a "black start," where all power plants on the grid go offline and need to reboot. It's rare, but it's also a bigger problem than it may seem because of the way power plants operate.
The U.S. essentially has three distinct power grids; Texas is one of them. The others are the Eastern and Western Interconnections. Officials said the entire Texas grid was threatened by the February freeze.
Arizona is in the Western Interconnection, which has about 80 million people and spans 1.8 million square miles in all or part of 14 states, the Canadian provinces of British Columbia and Alberta, and the northern part of Baja California in Mexico.
Within the Western Interconnection, utilities like Arizona Public Service Co. and Salt River Project maintain their own systems. They are stabilized by connections to other utilities but are not immune to problems like those in Texas.
As Texans learned the hard way, losing power in a somewhat controlled manner with rolling blackouts for even a few days has astronomical consequences. A prolonged outage would be substantially worse, threatening not only exposure to heat and cold but problems with infrastructure like sewer systems that require electric power.
“It is said that electricity is about 5% of the U.S. gross domestic product,” said Brian Cole, general manager of resource management for Arizona Public Service, during a recent update to state regulators. “Well think of it as if we are the first 5%, because if we don’t do our jobs ... the other 95% of GDP doesn’t’ happen."
He explained the importance of avoiding large-scale blackouts.
"Without electricity, there is no gasoline, no electricity for our cars," he said. "There is no cell service, communications, no air conditioning. We found out in Texas there is no water. No heating. No refrigeration for our food. Electricity is not just another commodity. It is at the center of all Arizonans' lives. It is an incredible responsibility we have.”
Arizonans were unaffected by the Texas troubles except for high gas prices paid by utilities.
But just last summer, California blackouts caused by heavy summer power usage — happening at the same time as an Arizona wildfire — caused Arizona utilities to ask customers to curtail usage for the first time in 16 years.
And, a decade ago, a historic cold snap that froze power plants in Arizona, New Mexico and Texas, led to rolling blackouts at Salt River Project for the first time in modern history.
APS hasn't had to use rolling blackouts in recent history but came closest, officials said, in 2004, when a Phoenix-area transformer burned and utilities asked customers to voluntarily conserve power to avoid outages.
Arizona utilities gave their annual update to regulators March 30 regarding the summer forecast.
"We are going to have enough generation resources, fuel supplies and transmission capacity to meet customer demand reliably this summer," Cole said.
But regulators were wary, asking about the worst-case scenarios, such as another wildfire that threatens power lines connecting Arizona to distant power plants on the same day record heat pushes up demand for electricity.
Utility officials said they are well prepared for summer demand, as they do every year. But they are hesitant to say they can handle any situation on the grid that might trigger rolling outages, and any rolling outage threatens worse problems if not handled properly.
Grid failure in AZ: Could a Texas-style grid failure happen in Arizona? Utility officials say not likely
Why more blackouts are likely
As a power grid expert, blackouts are something Baker thinks about a lot these days.
"The situation in Texas and what happened in California last year are bringing resilience more to the forefront of my mind for sure," Baker said.
Baker and other experts warn that rolling blackouts are likely to increase as utilities deal with aging infrastructure, less predictable weather and major disasters like wildfires.
"Summers are getting hotter, we are experiencing issues with the existing grid infrastructure, which is aging, more components are failing, and we are seeing more natural disasters like wildfires," she said. "All of these things together are going to strain the ability to provide consumers with energy. Unfortunately, I think power cuts are going to be a lot more frequent in the next decade."
The Western Electricity Coordinating Council, which runs the Western Interconnection, has studied resources in the region and confirmed that at some times of the year, there's little surplus energy to call upon in an emergency.
"Most subregions of the West have some hours of the year when they would be at risk if imports from other areas are limited," said Victoria Ravenscroft, senior policy and external affairs manager at WECC, while updating Arizona regulators in March.
"Our analysis points out there are some vulnerabilities here,” she said.
While careful not to disparage renewable energy, Ravenscroft said that variable resources like solar and wind can magnify supply risks because they are not able to switch on at any time.
And the steady increase of renewables across the West means utilities need to study closely whether their anticipated supplies are reliable at all hours, she said.
"Increasing levels of variable resources drive the issues we see," she said. "We are not saying variable resources are good or that they are bad, we are just pointing out that the variability on the system is changing how we maintain resource adequacy."
Ravenscroft also mentioned that Arizona has normally shared power plants with utilities in the Northwest, as Arizona has the biggest need in summer when air conditioners are humming and the Northwest usually peaks in winter when it's cold there.
But that's changing, and the Northwest is experiencing higher demand in summer, complicating the exchange of power between the regions.
"The days of counting on the Northwest to be cooler and have excess energy to shift down to Arizona when Arizona is really hot are becoming less certain," she said.
Grid requires perfect balancing act
Utilities use rolling blackouts, where they intentionally cut power to portions of their service area, to prevent worse problems on the power grid.
Ideally, rolling blackouts cut power to large blocks of customers for 20-30 minutes to an hour, then "roll" to another area so nobody loses power for too long. In Texas though, there wasn't enough energy available to restore power to those who had it cut for days in some instances.
Grid operators must maintain a near-perfect balance between the number of power customers are drawing with their appliances and the amount of power being fed into the grid by power plants. Too little power and the frequency on the grid will drop, which can cause power plants to shut down to avoid damage.
Too much power at once and the frequency is too high, which also can cause power plants to trip offline.
Texas was caught in the unfortunate situation of having too many power plants shut down because of cold weather to meet demand in the state.
The Texas problems were compounded by the state's isolation from the rest of the country, limiting the power that could be imported, and further worsened by customers trying to use record amounts of power to stay warm in the frigid weather.
While pundits have blamed various types of power plants, Texas had problems across the board. ERCOT officials said that they lost 185 individual power plants during the storm.
Of that, about 28,000 megawatts of capacity was from thermal power plants like coal, gas and nuclear, while 18,000 megawatts was renewables like solar and wind.
Many of the plants were note weatherized to withstand such a cold storm, even though Texas had similar issues a decade earlier and regulators recommended shoring up power plants for such occasions.
'You need power to supply power'
But if Texas utilities hadn't intentionally cut off customers, the imbalanced grid would have caused the remaining power plants to trip offline as well until the whole grid went dark.
That's a major problem.
Utilities practice recovering from so-called "black start" situations, but in reality, U.S. utilities seldom reach that point because getting things restarted is a massive undertaking.
Most power plants actually need power from other power plants to get started and begin making power themselves.
"They can't just immediately start back up, you need power to supply power," Baker said, using an analogy of a car battery that needs a jump start from another battery.
To restart an entire portion of the grid, utilities need a power plant that can start on its own or a connection to a power plant on another grid that can be used to start the first plant.
Arizona has both but hasn't ever needed to perform an actual black start.
Utilities still practice for such a scenario though should they ever need to black start their grid, said Chris Hofmann, SRP director of transmission and generation operations.
Both SRP and APS act as their own "balancing areas" responsible for maintaining power supply and demand on their grids.
"It is really a slow process. You have to open every circuit out there on the grid," Hofmann said. "It can take multiple days to restart."
SRP has contracts with federal hydropower dams to provide energy in a black start scenario and would use that power to restart its gas and coal power plants.
"We drill on this as a region at least once a year," Hofmann said.
Officials use a simulator to work through the black start steps, with APS, SRP and Tucson Electric Power having one such exercise Feb. 26, just after the Texas debacle.
"We all work together to black start our grid and then we try to interconnect to each other," he said.
Do the utilities ever make mistakes in these simulations?
"Absolutely," he said. "I'm not going to say things never happen. They do. Then you start identifying what happened."
The restart needs to be practiced because it's a delicate maneuver. Utilities can't simply start the first power plant. First, they need to ensure that when that plant turns on, demand won't be so high that it will essentially just trip offline immediately. That is done by cutting off connections to customers that would exceed the plant's capacity.
Once that first plant is started up, customers can slowly be added as the plant increases its output, and eventually, the next plant can start, again slowly adding customers to ensure supply and demand are in balance.
Black starts rare, but not unheard of
Actual black starts are rare, but not unheard of in the world.
The 10-state area covered by the RC West reliability group, which covers 42 separate grids including in Arizona, has never had one.
Even the massive Northeast blackout of 2003 that knocked out power to about 50 million people and lasted four days, didn't cascade through the entire Eastern grid. Though it did create energy "islands" that had to be reconnected to the functioning portions of the grid. And portions of Canada had rolling blackouts for weeks after that event.
An actual black start was necessary for the Australian state of South Australia in September 2016 after a wind storm, though the isolated portion of the grid had only about 1.5 million people living there. That's a fraction of the state of Arizona, let alone ERCOT or the Eastern and Western power grids in the U.S.
Even this relatively small black start didn’t go perfectly. The first two power plants intended to provide energy into the state to restart their power plants were not available that day.
But officials were able to get some outside power into the state nonetheless, and by midnight that day, 80-90% of customers had power restored.
Palo Verde plant would be priority
Utilities have a set order for turning on power plants in Arizona in an actual black start.
For APS, one of the first priorities in a black start is to restore electric service from the grid to the Palo Verde Generating Station nuclear plant west of Phoenix.
The nuclear plant has backup power sources including batteries and generators, but grid power is preferred to keep the water pumps cooling the nuclear fuel at the plant, said Sarah Kist, general manager of transmission and distribution operations and maintenance for APS
"You need a really stable grid to bring Palo Verde online," she said. "It is important to get offsite power to Palo Verde quickly to make sure all the safety systems have enough power to operate properly."
APS has two designated power sources to jump-start its grid in a black start: Glenn Canyon Dam and the gas-fired Ocotillo Power Plant in Tempe, which recently was rebuilt with diesel generators that can start the plant without an external power source.
Utilities keep extra power on hand
Utilities strive to avoid blackouts of any kind by always having more power on hand than they expect customers to need.
APS operates with a 15% reserve margin in summer, meaning it has more electricity available from power plants that it can call upon at a moment's notice.
But there is a cost to that preparation, as customers pay the expense of the reserve even though they aren't usually dipping into that power. APS keeps a 12% margin in non-summer months, though because demand is lower outside of summer it usually has more resources it could call to action those months.
SRP likewise maintains a reserve of 14-15% for peak hours, with as much as 20% during other parts of the year.
And if the entire region is expected to have tight supplies, SRP will increase its reserves, spokesman Scott Harelson said.
The Western Interconnection also has reserve sharing groups so interconnected utilities can pool their reserves.
Utilities base the reserve on complex forecasts of customer usage based on history and, importantly, weather forecasts.
“Forecasting load is a science and an art,” said Cole, from APS.
But those forecasts are getting more challenging. Resource constraints in the Southwest are "real," Cole said, especially with nuclear plants closing in California.
And the weather is getting less predictable.
For every 1 degree the summer temperature rises in Arizona, APS needs an additional 150 megawatts of capacity from power plants, which is equal to a small gas generator, Cole explained. So a day that's 5 degrees hotter than expected requires five more gas units to start up than forecast.
Cole said that when California initiated rolling blackouts in summer 2020, Arizona was one failed power plant or power line away from also needing rolling outages.
"The demand for energy in the region just simply exceeded supply," he said. "Each company and state claimed their own energy to serve their own customers. Some companies ran short."
APS didn't run short, but if there was a problem at any of its power plants during those few hot summer days, there was nowhere in the region it could have turned for help, he said. Utilities in all the surrounding states were maxed out, he said.
"We feel good going into the summer but I don’t want to leave you thinking there are no risks," he said.
With consumers returning to normal work routines as the COVID-19 pandemic wanes, power demand could be higher than forecast, he said. And extreme weather is a perennial threat.
“Another extreme heatwave could cause loads to be much higher than we are planning for,” he said.
Utilities look for additional solutions
Baker said that as power demand gets less predictable to forecast, utilities should look at additional ways to methodically cut power, rather than jump to rolling blackouts.
Both APS and SRP have programs where business and some residential customers can volunteer to have power reduced when demand is high to reduce strain on the grid. Baker says these programs are likely to get more popular.
"There are probably smarter ways of doing power cuts, instead of cutting power to a whole distribution grid," she said. "You could just cycle homes that have power cuts or maybe smaller portions of the distribution grid."
Some customers have resisted the idea of a utility selectively controlling their power or even thermostats. Baker says such programs serve a larger public good.
"This could help prevent some multi-day outages on the grid," she said. "It would help people keep their homes cool or hot if they are doing more granular power cuts."
Reach reporter Ryan Randazzo at ryan.randazzo@arizonarepublic.com or 602-444-4331. Follow him on Twitter @UtilityReporter.
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