On 28 April 2025, a significant power outage affected millions of people in Spain and Portugal. As the investigation into the causes of this blackout unfolds, several technical insights have emerged that are worth discussing within the 4TU.Energy community.
Initial findings and causes
According to a recent article in The Guardian (see link below), the blackout was caused by multiple technical failures rather than a cyber-attack or sabotage. The Spanish government commissioned an expert report that attributed the outage to the network's inability to control grid voltage, leading to a chain reaction of disconnections. The report highlighted voltage instability and oscillations in the system, which ultimately resulted in a catastrophic power loss.
Grid interconnections and stability
A notable aspect of the power grid in Spain and Portugal is the limited number of connections to the rest of Europe, with only two interconnections located in the Pyrenees. This limited connectivity made it challenging to stabilize the grid during the outage. As prof. Han Slootweg of TU Eindhoven pointed out to the Dutch broadcaster NOS in April, the lack of robust interconnections can lead to overloading of high-voltage lines, causing a cascade of failures (see link below).
A lack of inertia in the system
Prof. David Smeulders, scientific director of 4TU.Energy and professor of Energy Technology at Eindhoven University of Technology, provided valuable insights into the incident back in April. He emphasized the need to view the power grid as a large balancing act. When a part of the grid fails, it must be compensated immediately to maintain stability.
Prof. Smeulders also pointed out the challenges posed by the rapid fluctuations in solar power generation. Unlike traditional power plants, solar panels can stop generating electricity almost instantaneously when clouds pass over, leaving little reaction time for grid operators to compensate. This lack of inertia in the system is one of the significant challenges of integrating renewable energy sources into the grid.
Addressing the Challenges
In addition to improving technical difficulties with the grid, the article in The Guardian mentions that the Spanish government's expert report recommended strengthening supervision and compliance to better manage future voltage fluctuations.
The Path Forward
The power outage in Spain and Portugal serves as an important reminder of the complexities involved in managing modern power grids, especially as we increasingly rely on renewable energy sources. It underscores the need for continued research and innovation in grid stability, interconnections, and energy storage solutions.
As members of the 4TU.Energy community, we are at the forefront of addressing these challenges. Let us continue to collaborate and share our expertise to build a more resilient and sustainable energy future.
🌐 The Guardian article 17 June 2025
🌐 NOS article (in Dutch) 29 April 2025
🌐 David Smeulders appeared as a guest on the talk show Eva, hosted by Eva Jinek, on 29 April 2025. The segment featuring him starts at 3 minutes in (in Dutch)
📸 Picture credit: Anton Dmitriev via Unsplash