The networker: Europe’s blackout should be a lightbulb moment for future electricity grid planning

On 28 April, at about 10.30 GMT, the electricity grid in Spain and Portugal went down. A sudden outage in part of the Spanish grid caused the country’s interconnection with the French grid to trip like a blown fuse.

This resulted in the two countries’ energy systems to disconnect momentarily, triggering a sudden change in the frequency of the electrical current being delivered, with grim consequences: most of the Iberian peninsula was without power for 10 hours, prompting the Spanish prime minister to declare a state of emergency, but parts of France and Belgium also lost power for a time. It was Europe’s biggest blackout. And it should be a wake-up call for governments everywhere.

Electricity grids are the most complicated large machines in the world – systems into which millions of different units (generators) inject power, which is then distributed to billions of end users. Grids are also the most critical machines societies possess because, when electricity is cut off, suddenly nothing, but nothing works.

If you doubt that, try talking to any one of the 768,000 Irish citizens who were abruptly disconnected by Storm Éowyn in January – some of them for up to 17 days. Or ask Ukrainians, whose grid Vladimir Putin has been trying to destroy since 2022.

In some ways, though, grids are also surprisingly delicate, and therefore potentially fragile. This is because they are synchronous machines: every component part has to be in sync with all the others. How come? Basically, because the electricity they transmit and distribute comes in the form of alternating current, or AC, which periodically reverses direction and changes its magnitude continuously with time.

In Europe, this happens 50 times a second, or at a frequency of 50 hertz, which means that every device on the system has to keep time with that metronome. If it doesn’t, bad things happen very quickly: generators fall out of sync, causing instability and blackouts, electric motors overheat, critical timers run slow or fast, sensitive electronic kit gets damaged and so on.

Up to now, synchronicity has been relatively easy to achieve because most electricity was generated by heating water to make steam, which drives the large rotating generators used in coal, nuclear and oil-powered generating plants.

These turbines can weigh in excess of 100 tonnes and rotate at 3,000rpm or more, so they are basically like huge spinning tops with a lot of inertia, and even if their driving force disappears, they continue to generate electricity for a while. The resulting inertia buys grid controllers the seconds needed to deploy fast-response systems – from gas turbines to batteries – so that frequency stays in range even when a generator trips out.

But we’re now moving into a different world. Addressing the climate crisis means abandoning fossil-fuel generation and moving to electricity produced by renewables. And they don’t come with inertia built in: no flywheels. As one commentator puts it: “Solar panels... directly convert sunlight into electricity without the use of rotating turbines. They are then connected to the grid using electronic inverters, which convert the direct current electricity generated by solar panels into the alternating current that buildings and the grid can use.

“These inverters don’t provide inertia. Instead, they either follow a pre-programmed frequency or mirror the rest of the grid. When the proportion of inverter-based resources versus traditional generators increases, the total physical mass spinning in the system decreases. This means there is less physical momentum to absorb any shocks to the system.”

It also means that we can’t just plug more and more renewables into the grid we’ve got: it has to be extensively reconfigured for the future.

According to one report, just before the blackout happened, solar energy was providing 59% of Spain’s electricity, with wind supplying about 12%, nuclear 11% and gas 5%. This apparently led some people to speculate about whether what happened was a reflection of the dominance of solar energy in the Spanish context.

This seems – to put it mildly – implausible. Spaniards may be short of some things, but sunlight is not one of them. For a full understanding of what happened on 28 April, though, we’ll just have to wait for the publication of the technical inquiry that is under way.

In the meantime, perhaps the most useful product of the blackout might be that the extensive media coverage will have stimulated the public – and politicians – across Europe to start thinking about something critical (and dull) that we have hitherto taken for granted. As the song goes: “You don’t know what you’ve got ‘til it’s gone.”