Batteries Not Included
Grid Scale Batteries are Long Overdue, Recent Blackouts are just the beginning.
The Spanish Blackout: A Case Study in the Risks of Inadequate Grid Storage
The Spanish blackout of April 28, 2025, should serve as a stark warning of what happens when power grids are not adequately adapted to manage intermittent renewable energy. Without sufficient deployment of grid-scale battery storage, such failures are likely to recur—not only in Spain, but in other high-renewable jurisdictions like Texas, which have already experienced similar disruptions.
This event was one of the worst blackouts in European history, affecting nearly 55 million people across Spain, Portugal, and parts of southern France. It disrupted railways, telecommunications, and businesses for up to 23 hours. Spain—renowned for its sunshine and wind resources—has one of the highest renewable penetration rates in the world. As of early 2025, 56.9% of Spain’s electricity came from renewables, according to Red Eléctrica de España (REE) the Spanish grid company, with 23.2% from wind and 17% from solar.
Timeline of the Blackout
While a full investigation is ongoing, Spanish authorities and energy experts have released a preliminary reconstruction of the sequence of events:
Initial Trigger (12:32:57 PM): A sudden generation loss of 2.2 GW occurred in southwestern Spain, possibly due to a power plant or transmission failure. The grid momentarily stabilized.
Second Event (1.5 seconds later): A subsequent generation loss was accompanied by low-frequency oscillations—a deviation from the European standard of 50 Hz.
Interconnector Failure (3.5 seconds later): The Spain–France interconnector tripped, cutting off the Iberian Peninsula from the broader European grid.
Cascading Collapse: Automatic protection mechanisms disconnected a massive 15 GW of Spanish generation (around 60% of total supply) and 5 GW in Portugal. The collapse included nuclear, coal, solar, and wind generation, leading to a full system outage—a phenomenon known locally as "el cero" (the zero).
Contributing Factors
1. High Renewable Penetration with Low Inertia
At the time of the blackout, Spain was sourcing an estimated 70–80% of its electricity from renewables. With fewer traditional spinning generators (e.g., coal, gas), the grid had low mechanical inertia, making it more vulnerable to frequency disturbances.
2. Inadequate Voltage Control
A government report released in June 2025 blamed REE and private generators for failing to manage grid voltage. Thermal plants—paid to absorb excess voltage—underperformed, exacerbating instability.
3. Poor Grid Management and Planning
Experts cited insufficient scheduling of thermal reserves during peak renewable output. Control systems may not have been adequately calibrated for such high levels of renewable input.
4. Overvoltage and Reactive Power Deficiency
Sustained over voltages from large-scale renewable plants overwhelmed parts of the grid. The lack of sufficient reactive power support contributed to the failure.
5. Limited Interconnectivity
The Iberian Peninsula has limited high-voltage connections to France. Once the France interconnector tripped, Spain and Portugal were electrically isolated, amplifying the crisis.
6. Aging Infrastructure and Nuclear Phase-Out
Spain’s grid has struggled to keep up with the rapid expansion of renewables, with underinvestment in grid upgrades. Meanwhile, Spain’s nuclear phase-out (slated for 2035) reduced baseload capacity—four reactors went offline during the blackout, and three were already under maintenance.
7. Political and Operational Shortcomings
The crisis exposed weaknesses in grid oversight, including REE’s crisis response and broader political coordination.
How Grid-Scale Batteries Could Have Helped
Properly deployed grid-scale battery systems could have significantly mitigated—or even prevented—the extent of the blackout by addressing the specific vulnerabilities Spain experienced:
1. Synthetic Inertia and Frequency Regulation
Problem: Low inertia and a 0.5 Hz frequency drop triggered automatic shutdowns.
Battery Solution: Batteries can provide synthetic inertia—responding to frequency deviations within milliseconds. Unlike gas plants, they don’t require warm-up time and could have instantly stabilized the grid.
2. Voltage Control and Reactive Power Support
Problem: Over-voltages from renewables destabilized transmission lines.
Battery Solution: Grid-forming inverters in advanced battery systems can dynamically manage voltage and reactive power, unlike traditional fossil fuel generators.
3. Preventing Cascading Failures
Problem: The loss of 15 GW overwhelmed the system and tripped protection protocols.
Battery Solution: Battery systems could have acted as buffers—discharging stored energy rapidly to fill gaps. A 2–4 GWh system could have covered the initial 2.2 GW loss, allowing grid operators critical response time.
4. Accelerating Black Start Capability
Problem: Grid restoration took 23 hours and relied on slow-to-start hydro and gas plants. Nuclear was unavailable.
Battery Solution: Batteries can initiate black start sequences much faster than conventional sources—helping bring the grid back online in hours rather than a full day.
5. Managing Renewable Surpluses
Problem: Excess solar generation during midday contributed to over-voltages and grid imbalance.
Battery Solution: Batteries can absorb surplus energy, minimizing curtailment and overgeneration issues—especially important when pumped hydro capacity is maxed out.
Limitations and Cost Considerations
While battery systems could have made a significant difference, they are not a complete substitute for traditional grid stability mechanisms:
Cost: Deploying enough storage to replace lost generation (e.g., 10–20 GWh to offset a 15 GW drop) would cost $3–6 billion at ~$300/kWh.
Scale: Grid-forming inverters are promising but remain largely untested at the multi-GW scale Spain requires.
Complementarity: Many experts argue that batteries must work alongside thermal reserves, flexible gas plants, and upgraded grid infrastructure to be fully effective.
Conclusion
The April 2025 Spanish blackout wasn’t caused by renewable energy—but by a grid that was not yet equipped to manage its variability. It exposed deep systemic weaknesses in grid design, management, and investment planning.
Grid-scale batteries could have:
Stabilized frequency and voltage during the initial seconds of the crisis
Prevented cascading failures by rapidly supplying lost power
Enabled faster black start recovery
Managed renewable surpluses and curbed over-voltage
As renewable penetration accelerates worldwide, the lesson is clear: batteries must no longer be treated as an optional add-on—but as a foundational component of modern grid architecture.