Column by Jacob Østergaard, Professor and Head of Division, DTU Wind. Published in Politiken on 02.07.25.
At the end of April, Southern Europe went dark and the media went into a frenzy. An almost 24-hour blackout caused chaos in cities such as Madrid, Barcelona, and Lisbon - and journalists around the world all wanted answers to the same question: How could this happen?
The answer I could give to the media who asked was: “We don’t know”. Not the most exciting answer, I know, but the right one nonetheless. Yet the media began a desperate search for a better one.
For example, according to Reuters, the Portuguese grid operator REN stated that the incident was due to an atmospheric phenomenon with extreme temperature fluctuations. The statement was reported by media outlets around the world, but later withdrew it because REN denied making the statement.
In the Danish trade media Økonomisk Ugebrev, you could read a different view. Here, Morten Springborg - whose expertise lies in economics and energy investments - stated that the collapse was due to an overly ambitious energy policy for wind and solar energy roll-out. According to Springborg, this has led to a lack of system resilience, and he concludes that a solar and wind-based energy system is as stable as “a house of cards in a storm”.
The conclusion is severely lacking in nuance and evidence, and together the examples reflect a sad trend: When the topic is complex and we need answers instantly, the media helps to spread speculation and misinformation that is impossible for ordinary people to navigate.
This is serious for two reasons:
1. In an age of misinformation everywhere, it’s no less important for the media to be the guarantor of verified information.
2. The climate crisis won’t wait. Spreading unsubstantiated fears about wind and solar energy risks delaying the green energy transition, which will affect us all.
What’s left is a responsibility to clean up—and show the way. No one has taken on that responsibility yet, so I’d like to do so.
What we know
Going back to the blackout, it was difficult to pinpoint a single trigger because the exact cause can only be found by analysing thousands of pieces of data in depth.
That work has now begun, and on 17 June we learned more: The Spanish government released a report investigating the cause of the widespread breakdown - and it is neither atmospheric phenomena nor a lack of resilience from renewable energy sources.
According to the report, the blackout in Spain was linked to inadequate regulation of the electrical voltage in the grid. The inadequate regulation resulted in extraordinarily high voltages.
To prevent damage to the electrical installations, the integrated protection systems in both power plants and solar plants disconnected the devices from the grid. The disconnection reduced the ability to control the high voltage and—in a sequence of unfortunate reactions—led to the total collapse that blacked out the entire Iberian Peninsula.
The inability to regulate the electrical voltage in the grid was due to a number of factors, according to the analyses. First, several of the central power plants that were supposed to regulate the voltage were not functioning optimally. Second, an important power plant in southern Spain was reported down the night before the blackout. Third, a solar farm delivered an insufficient response. And fourth, there were prior fluctuations in the European system that helped destabilize the voltage.
Finally, several solar plants disconnected too quickly in relation to the rules, several large consumers did not comply with the technical rules for connecting to the grid, and the report also states that wind and solar plants are not currently required to regulate voltage in the grid, even though it is technologically feasible.
Based on this information, I find it important to emphasize that the outage cannot be attributed to one specific cause. Instead, it should be seen as a chain reaction of technical factors that show how hyper-complex a system we’re dealing with. The system crosses European borders, so a failure in one part of the system can quickly affect large areas with multiple countries.
What we can learn
If we are to draw one important lesson from the blackout in Southern Europe, it is the need for a much greater understanding of the energy system as a whole.
This need is further exacerbated by the fact that the electrical characteristics of the energy system will change in the future as we transition to a system based on wind turbines and solar cells. Renewable energy sources operate on completely different
terms than current power plants, and preventing future blackouts requires knowledge of how to create an optimal interaction in the system.
The good news is that we can build into wind turbines and solar panels the features needed to control and regulate the electrical voltage in the grid, for example. Through digital solutions, the devices can be controlled so that the overall system is both robust and stable.
To get there, however, we need to shift the focus from the individual technologies that can be commercialized to the interaction of the overall digital control. Specifically, through a digital simulation tool that is an exact replica of the future renewable energy system, you can study the system in real time and learn how it reacts to different disruptions.
This gives us knowledge about cause and effect that we can use to design an energy system that is robust to external influences. Not only can it put us ahead of events and prevent blackouts like the one in Southern Europe. It can also restore security in Europe.
