Revisiting the 2021 Texas Winter Storm

Prologue

Just over 6 months ago Texas experienced one of the most intense winter storms on record. It was cold, there was a lot of snow in places that don’t normally receive snow, but the story really revolved around the infrastructure, specifically, the failing of the power grid. And just last week the Federal Energy Regulatory Commission posted several findings from their upcoming report, spoiler alert: It’s not good. Summer is winding down — and thankfully it was a mild one by Texas standards — and winter is not too far off in the future. In a changing climate researchers predict these ‘end-member’ weather events will occur more frequently, and since history is the best educator, let’s take another look.

What happened

This past February, Texas experienced some of the coldest sustained temperatures on record. As many read in the news, this caused an unprecedented failure of Texas’ electrical grid, causing 4 million people to be without electricity at its peak. A cavalcade of problems resulted, ranging from municipal water systems failing, evacuations of hospitals, and most tragically, loss of life.

This article aims to focus on the data and shed light on what happened and when. But first, a few bits of information that will make it all easier to understand:

1. Texas’ power grid (which covers 90+% of the population in Texas) is not connected to the national grid.
2. ERCOT — the Electrical Reliability Council of Texas — manages the flow of electricity from producers to regional consumers (for example, Austin Energy, my power provider), who in turn control the flow to individual customers (for example, me).
3. Texas’ power grid is built to thrive in the summer. It gets hot here, really hot, and for a really long time. During the winter months, some of our power generation capacity goes offline because it just isn’t (normally) needed. Much of that generation takes weeks to months to bring back online.

The storm

The cold weather began sweeping into the state on 10 Feb. In Austin, we had some freezing rain, blustery winds and falling temperatures. Schools closed because the roads were unsafe, but by and large, the grid held up. This first storm was a typical Texas winter front that we see maybe one or two times a year: windy, temps in the 20s, and a little ice.

The real hammer dropped on Valentine’s Day. In Austin, we started the day just below freezing (31°F at midnight) with temperatures dropping steadily all day to 14°F 24 hours later. It warmed up briefly into the low 20s but then dropped to 6°F by the morning of 16 Feb. This pattern, albeit with differing magnitudes and timing, was repeated throughout the state. On the morning of 15 Feb., Austin Energy customers began receiving calls that their power would be rolled, which means turned off for ~45 minutes and then back on for 15 minutes, to keep the grid from overloading yet allowing people to stay somewhat warm. However, in Austin and throughout the state, those who were rolled off were not rolled back on — for days.

Figure 1: A timeline of February storm in south-central Texas. Source: https://www.weather.gov/media/ewx/wxevents/ewx-20210218.pdf

It was not only cold, but it was cold for a long time. Austin Bergstrom airport recorded a temperature of 32°F or below for 164 hours (previous record was 112 hours)! Austin set a record for the coldest February temperature ever (6°F). Keep in mind that Austin is two times closer to the Tropic of Cancer than North Dakota!

Figure 2. Temperature readings at the international airports in Dallas-Fort Worth (DFW), Austin, and Houston.

The number of records eviscerated by this cold snap is quite impressive. The snowfall totals were unlike anything we’ve seen in decades. Austin received close to eight inches, just east of DFW received six and north of Houston — quite near the Gulf of Mexico — received up to four inches. Del Rio (a town on the Rio Grande) recorded almost a foot of snow, beating its previous record by nearly 10 inches!

Figure 3: Snowfall on the morning of 15 Feb. as seen from my garage. By the end of the day, my kids had converted the exersaucer seen on the curb to a sled. Texans are gonna Texas.

At one point, the entire state of Texas was under a winter storm warning.

Figure 4: NOAA weather advisories on 14 Feb. 2021. Source: https://www.weather.gov/media/ewx/wxevents/ewx-20210218.pdf

Considering the magnitude of the cold, combined with its duration and the fact that much of Texas’ power generation is not generally winterized, it’s easy to see how and why things failed so catastrophically.

Failure to generate power

Figure 5: Four major sources of ERCOT power generation compared to total power generated. Major drops in in power generation occurred in the early morning hours of 15 Feb.

The proverbial wheels fell off at 2 a.m. on 15 Feb. Natural gas wellheads in the Permian Basin froze up. These failures, in conjunction with failures at coal-fired power plants, caused a 16% drop in statewide power generation. Three hours later, nuclear power dropped by 28% (2% of total statewide power generation). These failures, coupled with an additional 2–3% statewide power generation drop due to frozen wind turbines, meant that Texans woke on 15 Feb. to some of the coldest statewide temperatures ever and with 20% less power. By the time temperatures rebounded statewide five days later, Texas had lost nearly 40% of its generation capacity (a peak of ~68 kMW on 14 Feb. and a min of ~42 kMW on 17 Feb.).

Figure 6: Temperatures at DFW, Austin, and Houston with power generation by type. Check out that Solar signal!

When we look at the power generated versus the load on the system in the JMP graph above, you can see the problems that led to Texas coming within less than five minutes of losing its entire grid. It was at the time of the two downward spikes on the early morning of 15 Feb. (Figure 7) that, statewide, the grid’s frequency dropped dangerously below 60 Hz. Experts hypothesize that 4 minutes and 37 seconds longer at that low frequency would have fried ERCOT’s entire network, taking weeks to months to bring it back online. (The Generation data was preliminary at publication time, which likely explains why the Total Generation minus Total Load is negative for so many days in Figure 7).

Figure 7: Power Load matched Power Generation nearly step for step. Large drop-offs in Load on 15 February were caused by loss of generation, not lower power usage.

How did we fare?

We were fortunate. We maintained electricity throughout the ordeal, and while we had to boil water for five days, we never completely lost water pressure. Maintaining our utilities made it possible for us to open our home up to friends without power (which translated to six adults, 11 kids, two dogs, and no COVID!) for four days.

Many in Austin and across Texas were much less fortunate. Reports of deaths caused by the outages have trickled in. Jackson, MS, which received weather that was nearly as intense from the same storm, was without water for a months! One hopes that the new regulations enacted as a result of this utility failure will be enough when this inevitably happens again.

Data presented above is available at JMP Public.

A version of this post appeared in the JMP Blog.