From Climate Etc.

by Russ Schussler (Planning Engineer)

On April  28^th Spain, Portugal and parts of France suffered a major grid outage. A formal evaluation will likely be released at a later date cataloging many of the contributing factors and system deficiencies. Unfortunately, such reports often provide more confusion than clarity, as they tend to prioritize the triggers for system outages over the underlying causes. Post hoc it is easy to look at the vast data available and construct favored narratives about how the outage might have been avoided. This piece will look at “advance” warnings that point to the true cause of the blackout in Spain, Portugal and parts of France.

Core Insight: It has long been predicted that replacing conventional synchronous generators, which rotate together with the grid, with asynchronous inverter-based resources like wind, solar, and batteries will increase the risk of blackouts. Grid planners recognize that unanticipated adverse events—such as line outages, generator trips, substation failures, and major faults—will continue to impact power grids. Their challenge is to ensure the grid is robust enough to withstand and recover from such disturbances without major consequences. Proponents of wind, solar, and batteries may attempt to attribute blackouts to the adverse events that triggered the outage, rather than to flaws in the underlying system. This is akin to blaming an automobile’s brake failure on the conditions that necessitated sudden braking, rather than on the failure of the braking system itself. While lessons learned may help mitigate risks from adverse events, such occurrences cannot be entirely eliminated from grid operations. Reducing the risk of blackouts depends on enhancing grid robustness.

My Warnings and Predictions

My May 7, 2015 posting, Transmission planning: wind and solar noted the following:

The grid is built upon and supported by heavy rotating machinery. Synchronous spinning generators combine with power lines and loads to make up complex electro-mechanical machine that must maintains stability. Stability refers to the ability of the system to stay in synchronism, balance loads and generation and maintain voltages following system disturbances. Intermittent generation (wind/PV solar) does not rotate in synchronism with the grid. As such they do not have performance characteristics that support the grid as well as synchronously rotating generators (hydro, coal, gas, nuclear plants) do. The system must be able to ride out power imbalances caused by faults and outages. Greater penetrations of non-synchronous generators (inverters used for PV Solar and Wind) tend to make the system, all else equal, less stable….

The power grid does not always operate as planned. Extreme weather, unanticipated outages and a host of other factors can result in the system operating somewhere outside of planned conditions. Generally, the system is robust enough to handle most departures without problems. For more severe departures from planned conditions the re-dispatch of generating resources is a major tool for the system operators. As the amount of intermittent generation increases, this tool will become blunted from a lack of qualifying capable dispatchable resources…. …. There are suggestions that intermittents could better mimic conventional generation, but it would incur significant costs. …. Building a surplus of renewable resources to sit idle waiting to back each other up and respond as needed is economically implausible at this time.

Greater penetration of renewable resources will limit the options available to operators while at the same time increasing uncertainty around expected generation patterns. To accommodate such uncertainty the choices are to: 1) increase grid costs and infrastructure, 2) limit the operational flexibility of the grid, 3) increase generation costs through backup generation resources or 4) live with increased risks and degraded reliability. Likely all four are and will continue to occur to some extent as the penetration of intermittent resources increases.…

(W)hen intermittent resources only make up a small percentage of total system generation, the adverse impacts are masked by the margin and robustness built into the system… As penetration levels rise and renewables replace non-intermittent conventional units, they will have major impacts upon grid costs and reliability.

The next year in January of 2016 I elaborated on those points in a piece entitled Renewables and grid reliability. It’s worth a full read, but I will reference the key points here:

• There has been a high value placed on having an extremely reliable bulk grid as the costs and consequences of bulk grid outages are severe
• The bulk grid supports and is supported by conventional rotating generators (Coal, natural gas, hydro, nuclear, biomass) which provide “Essential Reliability Services” (ERSs)
• Wind and solar provide increased reliability risks because they are new changing technologies, they are intermittent and they do not as readily provide ERSs
• Current high levels of reliability depend upon experience gained over time through the gradual adoption of new technologies
• Wind and solar can be made to provide approximations of ERSs, but that requires significant increased costs and reduced generation output
• Because of the complexity of impacting factors and the high level of reliability maintained for the US grids, systemic degradation of the reliability of the grid is hard to detect and measure
• The amount of renewable penetration that can be accommodated will vary from area to area and power system to power system – There is not a single answer
  • Because conventional resources produce an abundance of ERSs, accommodation of low levels of renewables may be accomplished with negligible risks
  • Because current renewables do not provide adequate ERSs high penetration levels provide significant risks
  • Between the above two levels there is a gap of (wicked?) uncertainty.
• For assessing grid reliability, the maximum penetration of wind and solar during times of stress is the key number not the “average” contribution of wind and solar
• Increased penetration of such asynchronous resources, all else equal, will likely adversely impact bulk grid reliability
• As the penetration level of asynchronous generation increases this will either increase cost, limit operational flexibility, degrade reliability or most likely result in a combination of all three factor

A decade ago, major power systems were still sufficiently robust, so the risks from emerging problems were minimal at the time. The above statements warned that such concerns would eventually arise if trends continued. At low levels of penetration, the additional risks were small, but as penetration increased, the risks grew exponentially. By the time of this posting, Wind and Solar Can’t support the Grid in December of 2024 the existing risks had become clear:

 Unlike conventional rotating generation, wind and solar do not readily supply inertia and other essential reliability services. As penetration of  wind and solar resources increase, grid reliability decreases. The challenges of increasing wind and solar increase exponentially as you increase their share of generation. Policy makers, academics and others seeking to increase wind and solar are focusing on the wrong problems (intermittency) and failing to study the real operational problems inherent in inverter based generation from wind and solar.

On February 19 of this year in this post Unraveling the Narrative Supporting a Green Energy Transition, I outlined the major issues by addressing the misleading and false claims of the “green energy narrative” through bullet-point rebuttals. The points about inverter-based generation are particularly worth reviewing for those seeking more detail. After considering these factors and analyzing reviews of grid outages, it became clear that wind and solar were significantly degrading grid reliability in many areas, and much was being done to conceal this fact. I felt confident that upcoming grid outages would be linked to high penetration of wind and solar.

When an outage occurs, you can always choose to point a finger at any of the multiple things that went wrong. (#44, #26)   Some traditional fossil fuel technology will always be included in the set of things that were not right. (Loss of just renewables doesn’t usually cause big problems because apart from energy, they don’t support the system while in service.) For various reasons, advocates insist the finger should be pointed away from renewables (and the gap in needed system support) and at the conventional technology that was not perfect when the outage occurred. It’s critical to note that conventional technology is never perfect across a large system, however we were able to make reliable robust systems that could easily accommodate such imperfections. But now the presence of less dependable resources and inverter-based energy makes systems far less robust, even during times when those problematic resources are working well. It’s  a near sure bet the next large grid outage will be largely caused by problems associated with high levels of wind and solar penetration, whether those resources are available during the outage or not.

Major Outages Following my Posting

Since my February 19, 2025 prediction was published, two major blackouts have occurred. The first, six days later, left 98% of Chile without power. Limited reliable information is available about the Chilean outage, which was caused by a 500 kV line outage. Although Chile has significant hydro resources, many were offline, and the system relied heavily on wind and solar at the time. The system collapsed due to “unwanted activations” of electronic and special protection systems. At best, the issue likely stemmed from the learning curve associated with the complex protection schemes required for wind and solar generation. Our experience with conventional technology has developed over decades, so glitches with newer systems are expected. However, with accelerated efforts to integrate large amounts of newer technology, more such glitches are likely. A more serious concern is whether the complexity and challenges of high levels of asynchronous inverter-based generation are, as warned, inherently overwhelming.

More information is available about the blackout impacting Spain and Portugal. Two large solar installations tripped offline, followed by the loss of an interconnection to France. This created a generation shortfall that caused the system frequency to drop dangerously. Large amounts of asynchronous resources (wind and solar) disconnected from the system in response to the frequency drop, leading to the system’s collapse.

Frequency control is an essential reliability service supported by rotating machines with inertia. Such machines would have limited the frequency drop and helped the system recover from the excursion. More load shedding based on automatic underfrequency protection could have delayed the collapse and possibly saved the core grid. Inverter-based generation exacerbated the collapse and did little to prevent it. This collapse resembles one in South Australia caused by a lack of inertia.

What Are They Saying About This Outage?

Remarkably, many are focusing on the problems caused by a lack of inertia and the challenges of inverter-based generation. The core issues driving this blackout are clearer than in most cases.

Predictably, others are deflecting blame from wind and solar. The Spanish Prime Minister blamed Induced Atmospheric Vibration (IAV) for introducing frequency oscillations, claiming extreme weather caused corona discharge, which created electrohydrodynamic (EHD) forces. These forces allegedly caused low-frequency oscillations that worsened the situation. IAV may have triggered outages or aggravated the situation, but as noted, there will always be triggers stressing the system. The system should have been robust enough to withstand this disturbance, but it wasn’t due to lower levels of inertia.

Reuter’s advises, Don’t blame renewables. Blame “management of renewables”.  They suggest more conventional generation or devices like synchronous condensers should have been online to support the system—effectively admitting that Wind and Solar Can’t Support the Grid. Undoubtedly, other system components were also malfunctioning. As I mentioned earlier, a thorough review will provide data that can be shaped into narratives to deflect attention from the root causes.

An expert from Madrid argues that the triggering event wasn’t an N-1 event (where the system loses its single most impactful element) but an N-2 event (a double contingency). He does not blame inertia, as the system isn’t required to have enough inertia to survive an N-2 event. He suspects one of the events was caused by RoCoF relays, which interrupt generation when frequency changes rapidly. Note that frequency problems tied to low inertia caused the loss of solar facilities and the system collapse.

I may not have heard his best arguments fully and correctly and they may be refined further. He likely knows more about the technical specifics of the occurrence than I do, but I suspect our differences are more philosophical then technical. He seems to be saying that: 1)  the system performed outside the bounds of study protocols, 2) the causes of the two events leading to the double contingency are unclear (though RoCoF variations may have caused one), and 3) since the event was outside study criteria, low inertia isn’t to blame.

I counter that system planning was insufficient. Systems should remain stable across many N-2 events, as many double contingencies have less severe consequences than the worst N-1 event. This N-2 event doesn’t seem particularly severe compared to potential N-1 events. Moreover, both RoCoF issues and large frequency deviations are worsened by low inertia and mitigated by higher inertia. This blackout has the fingerprints of low inertia everywhere.

How Should We Define the Cause of Blackouts?

Consider the Suzuki Samurai, a popular automobile in the 1980s with a stability problem: it frequently tipped over. Proponents of these vehicles pointed out that rollovers were often accompanied by sharp turns, adverse conditions, road grading, unanticipated obstacles, or the behavior of other vehicles. Despite these complicating factors, Samurais were much more likely to tip over than other cars due to their tall, narrow body, high center of gravity, and short wheelbase. These characteristics made the car nimbler in off-road situations, particularly at slower speeds. Proponents could argue that if other cars drove more slowly and were equally nimble, Samurais wouldn’t need to swerve as much, reducing rollovers. Sweeping changes to perfect the world—such as ensuring all roads are well-graded, lowering speed limits, or preventing dogs and children from running into the road—could theoretically eliminate the Samurai’s problems. Similarly, calls to “modernize the grid and its operations” so wind and solar can perform without causing problems are overly idealistic. The Samurai needed to be safe in less-than-optimal conditions that drivers might encounter. Likewise, the grid must be robust enough to survive many issues claimed to “cause” blackouts. Trying to improve the world while making the Samurai’s base narrower and raising its center of gravity is a fool’s errand, as are efforts to eliminate grid problems so wind and solar can function without conventional generation.

A 2016 post entitled Renewables and grid reliability explained:

 I will share a planning secret. We don’t really think that the specific outage and the specific conditions which were identified in the study will actually occur and the system will be “saved” by that particular fix. We have learned over time that planning that way results in a system that is sufficiently robust so that system operators can sufficiently recover when unanticipated events happen across variety of circumstances. Planners will model the new technology as best they can, but if adoption of new technology is rapid, they will not have the needed experience behind them to justify confidence in the models.

Low inertia and the fact that many inverter-based generation resources tripped offline during the frequency excursion caused the blackout. While it’s true that without the triggering event, no outage would have occurred, systems cannot be designed to avoid all serious unanticipated events. Power systems should however survive most rare, once-in-fifty-year events, whether anticipated or not.

If low inertia (among other issues with asynchronous inverter-based generation) makes N-2 outages and cascading events more likely, planning criteria must change. If the many models for dispersed inverter-based generation are collectively less accurate than considerably fewer models for large central generating stations, planning must change.   If the protection schemes are grossly more complicated and prone to failure, planning must change. All this will increase costs and complexity and incur more failures in meantime directly attributable to wind, solar, and batteries. Proponents might ask, “We never had to plan for N-2 events before; why now?” The answer is simple: these changes are necessary to maintain reliability. RoCoF, mentioned earlier, is a newer metric developed solely due to high penetration of inverter-based generation, as detailed in ENTSO-E’s Inertia and Rate of Change of Frequency. RoCoF “protection” contributed to this blackout. It cannot be overemphasized that adapting to increased inverter-based generation will complicate planning, raise costs, and create more opportunities for failures.

The Evidence of Increasing Risk has been here a Long Time

The January 2014 posting,  Renewables and grid reliability, included a graphic from NERC (North American Electric Reliability Corporation). This figure showed the system response to a 2,750 MW generation trip in actual and forecast years, based on additions of asynchronous resources. The chart clearly illustrates that the system responds less favorably each year as the amount of  inverter-based resources (shown in parentheses) increases.

This same trend emerged in Spain and Portugal. It’s no surprise that the risk of blackouts grew as inverter penetration increased. In fact, a similar outage occurred in the Spanish system in2021, but higher inertia levels at the time prevented a disaster.

Increased penetration of asynchronous inverter-based generation degrades several metrics critical for system reliability. Grid experts have long been aware of these issues but have struggled to effectively reach and convince key audiences. The charts, data, and explanations may be clear, but most people won’t heed the message until they face a harsh wake-up call.

Conclusions

Proponents have long dismissed predictions that increased wind and solar use will raise costs and reduce reliability. Despite calculations on paper suggesting that large-scale integration of wind and solar is cheaper, real-world evidence shows they increase costs. Despite claims about reliability, previous outages have demonstrated the potential for wind and solar to heighten blackout risks. Pressure has been applied to frequently to distract from the real issues and real-world impacts.

It cannot be emphasized enough: the grid must be robust enough to survive major contingencies in an imperfect world. We must stop listening to those who, after an outage or blackout, insist the problem was unexpected events on the grid rather than the fact that grid reliability has been degraded by increased penetration of inverter-based generation.

Similarly, those who claim that wind, solar, and batteries can be made to support the grid more effectively must be challenged to acknowledge their current real-world capabilities and set reasonable expectations for future performance. Making inverter-based generation perform well enough to support a grid is a complex and extremely challenging problem.

Reuters’ suggestion to “not blame renewables, but rather the management of renewables” is particularly infuriating. Grid managers, tasked with maintaining stability, have been ignored for far too long. Grid and generation decisions are often driven by political rather than engineering considerations. The challenges of using and managing inverter-based generation have been acknowledged for years. Blaming those struggling to manage what’s been thrust upon them, while excusing renewables, is blatantly unfair.

Wind and solar have a place, but their appropriate levels vary by region based on current and foreseeable capabilities, not unrealistic hopes. Hopes for the future are admirable, but there’s a vast gap between what might one day be possible and what is practical and proven today. Reliable electricity is too critical to depend on unproven technology.

The recent blackout should serve as a wake-up call for policy makers. If it doesn’t, more events will follow, with increasingly severe consequences.

Note: Thanks to Chris Morris for edits, ideas and discussions around this topic.