The blackout on Monday, April 28, was a gray swan event. It was an unexpected event that made us aware of our enormous dependence on electricity, but it was on the radar as a possibility. The electricity grid operator itself, Red Eléctrica de España (REE), declared the blackout exceptional and completely extraordinary, but in February, in its parent company Redeia's annual report to the National Securities Market Commission, it had already warned investors that the high penetration of renewable energy (in 2024) in the grid would affect the electricity supply. According to REE, this was a probable risk in the short and medium term that would lead to an imbalance between generation and demand. Furthermore, in 2023, REE itself and the National Commission on Markets and Competition had already warned of a risk of a blackout due to overvoltage (with a greater energy flow than the transmission grid can handle). Furthermore, REE had indicated that it did not have sufficient tools to prevent grid tensions. Well, ruling out a cyberattack, this appears to be what happened on April 28th, shortly after 12:30 p.m., when photovoltaic plants were disconnected, causing the frequency to drop below 50 Hz and increasing voltage, destabilizing the grid. The firewalls didn't work, and France disconnected shortly after. The result was a "fuse trip," and 15 gigawatts of generation (approximately 60% of the electricity being consumed) were suddenly lost.
A stable electricity grid requires the rotational inertia (the physical momentum) of traditional turbines (hydroelectric, nuclear, or gas) to dampen fluctuations. A sufficient amount of synchronous backup power is needed to cope with a disturbance (which can come from either a drop in consumption or generation, because the system requires instantaneous equality between supply and demand). Following the incident, REE, which is responsible for managing and operating the electricity transmission grid and ensuring its continuity of supply, has implemented more gas-fired combined cycle plants, at a higher cost, and fewer renewables, to avoid a repeat of the blackout.
The conclusion from the crisis is that grid resilience must be strengthened with a balance of renewable and traditional sources and with possible technical improvements such as the introduction of synthetic forms of inertia. This means more investment. Renewables, in addition to being fundamental to environmental objectives, give us greater independence from fossil fuel producers (and from those from autocratic countries or those that appear to be moving towards autocracy) and generate electricity at lower costs (in Spain, electricity prices have recently been below European ones). However, the integration of renewables poses significant challenges because they require large investments, but when they predominate, the wholesale market price can often be zero or negative. The question, then, is how to finance investments in renewables, and also in the necessary traditional backup energies. Good market design is needed to overcome this problem. For example, auctions to supply green energy can play an important role. A complementary alternative is to enhance battery-based energy storage, where technological advances are still lacking for this to be implemented on a large scale, and to promote pumped hydropower. The latter takes advantage of excess generation above demand to pump water uphill as potential energy to be transformed into kinetic energy when needed.
Another stabilizing element is the integration of European electricity markets. The Iberian Peninsula (Portugal also suffered the blackout because we are in the Iberian market) is an energy island given its weak connection to France, which is not interested in competing with Spanish electricity. During the crisis, we exported electricity to France. We hope the blackout will spur interconnection.
The president of REE (and former Minister of Housing under President Rodríguez Zapatero) stated in 2021 that there was "no risk of a blackout" because the Spanish electricity system was "the best in the world, the safest and most advanced." Perhaps the most cautious people should purchase the kit survival recommended by the European Commission.
