April 29th,  2025

A major blackout across Spain and Portugal has brought new attention to an important question: how do we ensure power grid stability as we transition to renewable energy?

On April 28, millions were affected as electricity supplies across Spain and Portugal were disrupted. Traffic lights failed, trains stopped running, airports temporarily closed, and mobile networks became unreliable. Authorities declared a state of emergency, urging citizens to limit travel and communications while efforts to restore power got underway.

At the time of the outage, over 60% of Spain’s electricity was being generated by renewable sources — primarily solar and wind. Spain has been a leader in renewable energy adoption, with green power making up around 56% of its total energy production on average.

While renewable energy is essential for reducing carbon emissions and building a sustainable future, the events in Spain highlight a key technical challenge: managing grid stability when a large share of electricity comes from variable, non-inertial sources.

Why Grid Stability Matters

Traditional power plants — such as coal, gas, and hydroelectric — generate electricity using heavy rotating machines that naturally stabilise the grid. They provide something called inertia, which acts as a buffer against sudden changes in frequency or voltage.

In contrast, solar panels and wind turbines generate power electronically, without this mechanical inertia. This can make grids more sensitive to fluctuations, especially when renewable energy dominates the system without enough backup infrastructure in place.

According to grid operators, the Spanish blackout was linked to atmospheric vibrations and extreme temperature variations, which caused anomalous oscillations in the high-voltage network. As different regions drew varying amounts of power for cooling, parts of the grid experienced mismatched frequencies and voltages, triggering a cascade of equipment failures and outages.

Some experts have noted that while temperature fluctuations can affect grids, the relatively mild weather (around 22°C) raises questions about whether grid resilience was a bigger factor — particularly with such a high percentage of solar generation active at the time.

What This Means for Renewable Energy Transition

The blackout does not undermine the vital importance of renewable energy. Instead, it shows that moving towards net zero requires modernising the grid, not just changing the sources of generation.

Key strategies for a resilient green energy future include:

Energy storage solutions: Batteries and other technologies can supply fast-reacting support to smooth out fluctuations.

Grid-forming inverters: Advanced inverters can help mimic the stabilising effects traditionally provided by fossil fuel generators.

Backup dispatchable generation: Systems such as hydroelectric, biogas, or green hydrogen can provide flexible support during periods of volatility.

Smarter grid management: Using real-time data, predictive analytics, and flexible demand-response measures to maintain balance.

Spain’s recent achievement of running its entire grid on renewable energy earlier this month is a landmark milestone — and these events highlight the need to build on that success with continued investment in resilience and innovation.

The path to a cleaner energy future is clear, but it must be supported by robust infrastructure and careful planning to ensure that renewable power is both sustainable and reliable for generations to come.