The recent blackout that left millions of citizens in the Iberian Peninsula in the dark has rekindled the debate on the role of renewable energy in ensuring the security of electricity supply. With the incident of April 28, 2025, Spain and Portugal experienced one of their largest energy crises, the causes of which are still being unraveled and generating controversy at both the technical and political levels.
Although power was restored within a few hours to most of the network, the incident has exposed structural vulnerabilities. in the national electricity system. While research progresses, the focus has been on renewable energy, which has been criticized for its difficulty in providing stability compared to traditional sources such as nuclear or thermal.
What happened during the April 28 blackout?
At about 12:32 p.m., a An electrical collapse disconnected the peninsula from the European system., leaving millions of users without electricity in Spain, Portugal, and parts of southern France. According to Red Eléctrica de España (REE), there was a sudden drop in photovoltaic generation, with losses of 15 gigawatts of power in just five seconds in the southwest of the peninsula, which brought down the rest of the system in a matter of moments.
The outage coincided with a high presence of renewable sources on the grid, especially solar and wind.At that time, more than 60% of Spain's electricity came from renewable sources. However, experts and organizations such as the Renewable Foundation emphasize that the massive disconnection was a consequence, not necessarily the trigger, of the crisis.
Initial hypotheses pointed to a possible cyberattack or extreme weather events; however, both REE and European and Portuguese authorities They ruled out computer sabotageOther analyses suggest that the cause was a combination of power line failures, poor interconnection with France, and the complexity of managing a grid dominated by renewable energy.
The debate on the stability of renewable energies
The difficulty of renewables in providing inertia and robustness to the grid has been the subject of discussion In the days following a blackout, conventional sources such as nuclear, thermal, or hydroelectric plants provide a natural mechanical inertia that helps dampen fluctuations and maintain grid frequency. Renewable energy sources, on the other hand, are typically connected through electronic systems that do not directly provide this stability, making them more vulnerable to sudden changes in demand or supply.
Experts consulted emphasize the need for storage systems and advanced control technologies (such as Power Oscillation Damping, POD) to cushion fluctuations. However, Much of the renewable energy park in Spain still lacks these devices., since its adoption is not yet mandatory for new installed capacity.
Various technical analyses agree that the Spanish system was operating with an adequate safety margin., provided there is sufficient conventional backup. Furthermore, REE typically limits the injection of renewables to maintain stability in the face of potential risks. The massive shutdown of solar and nuclear power plants was, in part, an operational response to the frequency drop and loss of synchronization, rather than the root cause of the crisis.
The phenomenon of low inertia is exacerbated when the grid relies on many renewable plants without sufficient conventional input. This, coupled with the limited interconnection with Europe (barely 3-5% of installed capacity, well below the EU target), prevents the import of sufficient energy to rebalance the grid in critical situations. The Iberian Peninsula remains an “electric island”, especially vulnerable to collapses of this type.
Technical and human factors: What went wrong?
In the preliminary investigation, it has been detected that The automatic disconnection of solar and nuclear power plants occurred when the grid frequency decreased. beyond safe limits. This response, anticipated by protocols, prevented major damage to infrastructure, but worsened the domino effect that led to the total blackout.
Many experts point to the lack of infrastructure modernization, the limited presence of energy storage systems, and the slowness in incorporating advanced control technologies as key areas to address. Likewise, the Lack of coordination protocols and effective communication between operators, technicians and organizations also influenced the difficulty in anticipating and managing the emergency.
Some Red Eléctrica technicians warn that current regulations do not yet require the widespread implementation of systems like the POD in renewable energy parks, which makes it difficult to cushion fluctuations in the face of serious disturbances. On the contrary, the phasing out of conventional sources such as nuclear and gas could, according to several reports, reduce the system's resilience if the transition is not accompanied by appropriate technical measures.
The CNMC and Redeia analysis already warned about the risks of a renewable-dominated system without sufficient backup infrastructure, especially on days of low demand and high solar production, as occurred on the day of the blackout.
Institutional responses and initiatives for the future
President Pedro Sánchez announced the creation of a commission of inquiry to clarify the causes of the ruling. and demanded the collaboration of all electricity companies to adopt improvements and guarantee supply. In parallel, the European Union and ENTSO-E (European Network of Transmission Operators for Electricity) have already established expert panels to develop recommendations and strengthen the resilience of interconnected systems.
For their part, the Iberian and French network operators worked on the creation of “electric islands” and in the progressive restoration through flows from France and Morocco, activating crisis protocols unprecedented in the region.
The blackout has served as a reminder of the need to accelerate investments in international interconnections, energy storage, and technological adaptations for efficient management of renewables on the grid. Organizations such as Greenpeace, the Renewable Foundation, and Ecologists in Action insist that the energy transition must not be halted, but must be accompanied by modernization to incident testing, increased storage capacity, and regulations that ensure the technical balance of the grid.
Beyond the exact causes, this incident has highlighted The challenge of combining the commitment to clean energy with the obligation to guarantee a secure and stable supplyThe move toward a 100% renewable system will continue, but episodes like this demonstrate the importance of strengthening the grid, investing in storage solutions, and adjusting regulations so that the integration of renewables doesn't compromise the reliability of the Spanish electricity system.