The cause of the initial drop that led to the catastrophic cascade of events is unclear, though a collapse in Spain’s solar power system was certainly involved. Data from Spanish grid operator Red Electrica shows that on Monday solar generation dropped at 12:30 p.m. from around 18 GW to just under 5 GW by 1.35 p.m., so this accounted for the vast majority of the overall drop. But it remains unknown why this occurred or why it caused the entire system to collapse so rapidly.
One possible contributor is the lack of so-called 'grid inertia' as a result of the relatively small share of nuclear and fossil fuel generation in Spain's power mix. Inertia is the kinetic energy created by the rotation of spinning generators. In the case of a sudden loss of power, this provides a temporary supply of energy that can help maintain grid frequency, thus acting as a shock absorber. Inverter-based wind and solar power, which generated just under 70% of Spain's total electricity at the critical moment on Monday, does not involve physical rotation and therefore inertia could not compensate for the sudden loss of power.
An obvious short-term solution to avoid a repeat of the blackout would be to maintain a higher baseload of rotating power generation. Over the long term, however, power systems will need to invest heavily in battery capacity to store electricity as well as technologies for synchronising the grid that are critical to maintaining the 50 Hz frequency.
In theory, this should be doable, as battery costs have declined sharply in recent years and are being deployed at scale around the world.
But all this would still require heavy investments. While spending on new solar capacity reached around $500 billion last year, investment in grids was only at around $400 billion, becoming bottlenecks for the energy transition, according to the International Energy Agency.
While this outage might be unprecedented on the continent, European governments cannot say there were no warning signs.
