Spain, Portugal seek answers following massive power outage

Sánchez launched a government investigation into the cause of the five-second event that knocked out 15 gigawatts—the equivalent of a 60 percent drop in demand—across Spain and Portugal. The incident was actually two interruptions in power, the first of which Spain’s grid could recover from, but the second of which resulted in more damage progressing to the point of interruptions from France’s electrical system, the Associated Press reported.

Even though the outage happened in seconds, it took almost 23 hours for the grid to return to normal; and experts say that determining the cause of the event could take up to six months.

“We will find out what happened in those five seconds,” Sánchez promised while also cautioning industry experts and the general public from jumping to conclusions. Sara Aagesen, Spain’s energy minister, has asked power companies to provide data for “every millisecond during those five seconds,” according to Reuters.

There has been plenty of finger-pointing this week in the absence of clear answers about the cause of the outage, which possibly was due to the need for inertia on the grid, best provided by thermal sources like nuclear, coal, or natural gas. Here’s a closer look:

Reliance on renewables: Many were quick to assign blame to Spain’s and Portugal’s recent large increase in solar and wind generation sources, which occurred under the prime minister’s direction. Sánchez was quick to fire back, saying, “It wasn’t a problem of an excess of renewables,” adding that people drawing such a conclusion are “either lying or showing their ignorance,” Bloomberg reported.

As of 2023, wind power supplied 22 percent and solar contributed 15.1 of Spain’s overall energy mix, according to the International Energy Agency. Spain’s five operational nuclear plants account for 20 percent of electricity used across the Iberian Peninsula—but leaders there are looking to phase out all nuclear output by 2035.

According to Red Eléctrica (REE), Spain’s part-state-owned utility, just before the system crashed the largest contributors to the grid were as follows: 53 percent solar, 11 percent wind, and 15 percent from a combination of nuclear and natural gas. The BBC reported a slightly different breakdown at the time of the event: roughly 60 percent solar, 12 percent wind; and 11.6 percent nuclear.

But it’s safe to say Spain and Portugal were heavily reliant on renewable power sources at the time.

“This type of thing is caused by grid instability and tends not to happen when you have more baseload like nuclear on the grid,” said Seth Grae, chair of the American Nuclear Society’s International Council and chief executive of Lightbridge Corporation. “The more your sources on the grid are intermittent, the greater the risk.”

“But anyone who claims to have a lot of information will be jumping the gun,” Grae added.

If it plays out that the reliance on renewables had a hand in this blackout, this event could be used as a warning against other countries relying too heavily on these intermittent energy sources. As reported by the Telegraph, a lack of inertia was probably a major contributor to the blackout, which is a direct result of a reliance on renewable generation. This blackout in Spain is an example of what Meredith Angwin, author of Shorting the Grid: The Hidden Fragility of Our Electric Grid and longtime nuclear advocate who spent her career in science and research, calls the “fatal trifecta," that is, an overdependence on renewables, just-in-time natural gas, and imports from your neighbors. Spain’s grid is clearly a prime example of this trifecta, led by an overdependence on renewable energy.

Grid instability: While there are many technical and political nuances surrounding electrical grids in different countries, one overarching reality is that grids are sensitive to an imbalance in energy provided versus consumption.

Discussions of intermittent renewable sources over the years have focused on the nonstable nature of power being produced from wind or solar as the power output is dependent on the weather. There is more to it than that, as explained by Grady Hillhouse, an author, civil engineer, and science communicator widely known for his educational video series Practical Engineering.

In an article and corresponding YouTube video from Hillhouse, he explained how connecting solar power to the electrical grid is actually much more complicated than people realize and creates issues more than just weather intermittency for power production. In short, stable grids require a delicate balance between electricity supply and demand and require generators to produce power at certain frequencies.

Hillhouse looked at a 2022 trip on the Texas electrical grid that led to a massive drop in solar power production due to inverter-based resource behavior, revealing vulnerabilities in how renewable energy integrates with the grid. He explained how solar power is difficult for the electrical grid because it relies on inverter-based resources (IBRs), which behave very differently from traditional power plants. Unlike nuclear or gas generators that produce stable power with built-in inertia, solar panels produce direct current (DC) that must be converted to alternating current (AC) using inverters. The inverters lack physical inertia, so they can’t help to stabilize grid frequency during sudden power losses to allow grid operators time to react—as what happened in Spain where the interruption lasted less than 5 seconds before the grid collapsed.

Back to Spain: Like in Hillhouse's example of Texas, at the time of the interruption, Spain was relying heavily on solar power. Meredith Angwin confirmed this possibility in a conversation with Nuclear News. She noted that all the data is not in yet, so making a conclusion as what was to blame is difficult. “Although one factor is that the Spanish grid was running very heavily on IBRs. These types of generators don’t supply inertia to the grid, which means the grid is more likely to have a big interruption from a relatively small fault.” This seconds-long interruption was enough to cause the blackout.

What about nuclear? Spain’s planned phase-out of nuclear power, announced in December 2023, could have contributed to this week’s outage, said Yolanda Moratilla, chair of the Energy and Natural Resources committee at the Engineering Institute of Spain.

“This event was unprecedented in Europe” and may never be fully explained, she told the Anadolu news agency. But Moratilla said she has been warning the government of outage risks for a while now, since the country’s phase-out of coal and reduction in nuclear leaves the grid too reliant on combined-cycle natural gas units to fill in when solar and wind don’t deliver enough energy.

Sánchez on Tuesday criticized nuclear as “no more resilient than other sources” and said heavier reliance on nuclear energy would have led to a “much slower” recovery, because nuclear plants also went off line early in the outage and took longer than other sources to get back up to full power.

But the difference is that the nuclear power plants were shut down as a safety precaution due to loss of off-site power and had to ascend their large power loads gradually back onto the grid. When a grid has a stable, steady source of baseload power—nuclear, for example—it is less reliant on intermittent, unpredictable sources of power, making the chance of a massive outage (and the need to voluntarily shut down power plants) far less likely. In terms of nuclear safety during the event, operators took precautionary measures. Only four of Spain’s five operating reactors were on line at the time of the blackout and proactively shut down due to loss of off-site power. Spain’s Nuclear Safety Council said Monday it had activated its emergency response organization.

Clearly, nuclear power is more of an asset as a baseload power source than a load-following option for national grids. Depending on how the details emerge of the causes of the blackout, this event could become a clear example of the need to maintain a diverse balance of power sources, like nuclear along with renewable sources instead of relying heavily on intermittent sources.