Authorities in Spain and Portugal are still investigating the cause of the worst blackout in their nations’ histories. But the massive power failure follows years of risky renewable energy campaigns that have severely weakened the power grid on the Iberian Peninsula.

Millions of Spaniards and Portuguese were left without power April 28 when power failed in both nations as well as, briefly, in parts of southern France. Spain’s government declared a state of emergency and deployed an extra 30,000 police and military law enforcement officers to the streets.

“The electricity system was hit by a dramatic power generation loss in southwestern Spain,” according to Red Eléctrica de España, the country’s grid operator. The loss was around 15 gigawatts in as little as five seconds, amounting to about 60% of total electricity supply. The majority of the country’s solar generation is located in Southwestern Spain.

Although early reports have avoided pointing fingers at the nation’s solar installations, energy experts note that dependence on wind and solar power makes such failures far more probable. “A lack of inertia was probably a major contributor to the blackout,” Nuclear Newswire pointed out, “which is a direct result of a reliance on renewable generation.”

Many critics of net-zero policies are quick to point out that less than a week before the blackout, Spain boasted that it was generating 100% of its power from “renewable” energy sources. When that announcement was made, the Spanish solar market was already in freefall, with major developers tripping over themselves to sell their solar holdings that have proven to be structurally unprofitable. In an even more hubristic gesture, Spain earlier in April had finalized plans to close all of its nuclear plants. Headlines like Bloomberg’s “Spain’s Nuclear Shutdown Set to Test Renewables Success Story” have aged poorly.

While we await an official announcement of the precise causes and nature of the blackout, it is still possible to highlight the underlying vulnerabilities that made the event likely. This is important because Spain has travelled further down the path to net-zero and decarbonization than the state of Michigan is following.

We don’t know which straw broke the camel’s back, but one look at the camel’s diet reveals that he is chronically underfed.

The underlying problem is an oft-overlooked reliability attribute: Grid inertia. Energy reporter Robert Bryce explains grid inertia by comparing electricity to water:

Just as the local water utility uses its pumps to deliver tons of water at high pressure and volume to its customers, the electric utility uses spinning generators — think of them as electron pumps — to push huge volumes of electrons (water molecules), at high pressure, into the local grid. The key difference between the water grid and the electric grid is that the water grid is far simpler. For instance, if the pressure in the water grid drops, it only means that customers must spend a little more time filling up their coffee pots or swimming pools. On the electric grid, voltage (again, think water pressure) must be kept stable regardless of how many customers are using electricity... The grid must be continually tuned so that electricity production and electricity usage match. Matching generation and consumption helps assure that voltage on the grid stays at near-constant levels. If voltage fluctuates too much, blackouts can occur.

The important thing is to ensure frequency is as close as possible to the desired level (50Hz in Europe, 60Hz in North America).

Grid inertia is a result of the mechanical inertia of turbines and generators (tightly wound copper coils surrounding electromagnets) that are propelled by the energy produced by boiling water in a coal, nuclear, or combined-cycle natural gas plant. (This earns them the technical title of “synchronous generators.”) Wind turbines do provide a minimal amount of grid inertia, but studies have shown that their support is ineffective. Solar panels, on the other hand, have zero grid inertia because they have no mechanical inertia.

For this reason (among others), multiple studies conclude that high penetration of wind and solar around the planet represents a growing threat to grid inertia and stability. One study concludes that “the practical upper limit for renewables is around 40% of total electricity generated.”

The authorities in Portugal emphasize “anomalous oscillations” on their high-voltage lines — oscillations which, on a well-balanced grid with plenty of inertia, would be far less likely to cause any higher-impact events. (Portuguese sources blame “induced atmospheric vibration.”)

Variable generation, like wind and solar, has not yet been definitively tagged as the source of the blackout. However, an honest look at the situation demonstrates that Spain and Portugal’s heavy reliance on variable wind and solar played the key role in last week’s blackout.

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