Rules, Not Renewables, Might Explain the Iberian Blackout

Summary

On a leafy boulevard in central Madrid on the afternoon of 28 April, half a dozen residents stood in a loose semi-circle on the sidewalk, facing an apartment balcony. A man sat on the balcony with his battery-powered radio, the speaker oriented toward passersby whose mobile phones couldn’t get a signal due to a blackout that had swept Spain and Portugal. Everyone wanted to know the causes of the blackout, which had occurred at 12:33pm, local time. Some speculated it was a foreign attack, while others blamed unstable solar and wind generation, which together comprised 33 percent of Spain’s and 37 percent of Portugal’s electricity generation in 2024.Almost two months after the Iberian blackout, the four official investigations into the cause haven’t yet released their conclusions, and people are still waiting to know the causes of the blackout. Yet academic researchers with access to voltage data, such as electrical engineer Antonio Gómez-Exposito, claim that there may have been sustained overvoltages, in which generating plants sent too high a voltage to the transmission grid, just before the grid’s frequency dropped, which implies a potential issue: poorly distributed reactive power sources. Such sources can help control voltages when renewables send power from the distribution level of the grid up to the transmission level, which is becoming more common as grids add more distributed renewables.In the first days after the blackout, many outlets and experts focused on the frequency of the grid and the need for inertia, which refers to how spinning generators carry physical momentum that makes them slow to change the frequency of the alternating current (AC) they generate. Most equipment on an electrical grid must operate within fairly narrow range of a set frequency. Conventional power plants, such as combined-cycle natural gas or hydroelectric plants, can provide inertia, but newer sources such as photovoltaic solar power do not. So the inertia discourse was in part...