Spain suffered a massive power outage on 28 April that forced demand to drop by almost two-thirds in a matter of moments. The cascading effects of the subsequent blackout swept across to Portugal, leaving the entire Iberian peninsula in the dark. The exact cause of the incident remains unclear, but it had an immediate and significant impact on Spain and Portugal, and raised broader questions regarding grid stability and energy policy across Europe. So, what led to this event? And how can Spain stop it from happening again?
Spain’s power landscape
Spain is currently aiming to phase out fossil fuel and nuclear generation in favour of renewables, with a target for the latter to make up 74pc of total power output by 2030.
Some market participants have pointed to an over-reliance on renewables in Spain as a potential contributing factor to the outage. Traditional thermal generation spins large turbines, building up kinetic energy, meaning when there are sudden changes in grid frequency they will continue to spin for a short while, allowing fast-acting reserves to deploy. Intermittent renewables such as wind and solar do not behave in this way, making a renewables-heavy generation mix less resistant to sudden changes in frequency. While the exact cause of the blackout remains unclear, Spain’s transmission system operator REE has suggested a sudden loss of generation as a possible trigger, which would have caused a drop in frequency.
The blackout began at 12:33 local time. In the 15-minute period leading up to this, the two largest sources of thermal generation — gas and nuclear — made up 5.6GW of national output, almost a quarter below the 7.3GW April average for the same time period. Low-inertia solar power was at 19.1GW, or around 60pc of Spain’s generation mix, at that time — well above the 14.7GW April average for the same 15-minute period.
Many sources of generation have built-in protection mechanisms, designed to automatically disconnect them from the grid in the case of a sudden change in frequency and prevent equipment damage. This can have a domino effect, in which many generating sources disconnect in rapid succession, leading to outages. As Spanish households lost power, so too did the country’s nuclear plants, causing them to automatically shut off as part of standard security procedures.
Systemic concerns
While a lack of inertia may have contributed to the cascading failure that followed, grid operators ordinarily have many systems in place to maintain grid stability in extreme circumstances, including ancillary services and control reserves. One growing technology with an almost immediate response time is battery energy storage systems (Bess). But Spain has little Bess capacity to offer, with just 25MW, lagging far behind its 500MW target for 2025.
And Spain’s position as an energy island — with only roughly 3GW of connection to France — may have made the situation more difficult to manage, although simultaneously preventing the fault from spreading further. A smaller grid means perturbations have a proportionally bigger impact on grid frequency. In 2020, REE noted that inertia in the Spanish system was 50pc lower than in the continental grid, and the stability of its frequency was “considerably worse”. But France was able to cut its electrical connection to Spain for roughly an hour, which may have prevented the outage from spreading further. The inertia of French nuclear plants attenuated the frequency perturbations as they rippled out from Spain, avoiding the impact spreading further afield, according to nuclear association Sfen.
Looking forward
Spain will now navigate a tense political climate searching for a blackout scapegoat. Once authorities establish a cause for the blackout, the country will undoubtedly be left with decisions to make. The relevant authorities must establish measures to prevent this happening again. What remains less clear is how Spain reacts to increased scepticism regarding renewables integration and the energy transition, which could require more serious political upheaval in the coming years.
Spain’s commitment to phase out nuclear power by 2035 was already a controversial topic, and the blackout has brought the question back to the fore. Utility Endesa’s chief executive Jose Bogas repeated his concerns over the plans the day after the blackout, suggesting it might "prove imprudent to abandon a zero-emissions technology which is safe and competitive", with the outage “highlighting the importance of the guarantee of power supply”. Nuclear advocates have long argued the technology’s use case as a stable base-load provider, and recent events are likely to provide supporters with further ammunition.
At a European level, increasing interconnectedness is an essential goal to mitigate the intermittency of renewable output, with each region of the continent supplying others in times of surplus, and receiving support in times of dearth.
But as the Nordic countries have learnt as a result of high prices in Germany increasing costs for their own consumers, stronger connection to a sick neighbour spreads contagion. A meeting between French and Spanish energy ministers to discuss increasing interconnection was on the agenda at the London IEA energy security conference last week. One project is already in the works, with two more under consideration, to increase Spain’s cross-border transmission capacity to 8GW.
One bad day seems unlikely to divert the juggernaut of EU policy that has promoted interconnectedness throughout this century, initially to improve market efficiency, and latterly to afford the continent security of supply. Europe's grids have successfully handled ever-increasing quantities of intermittent renewables in recent years. And this week's events may yet prove to be just another of the rare but almost impossible to avoid failures of a complex and generally highly dependable system, which grid operators keep on line with very little downtime through constant actions that receive little publicity.
But policy makers may have a new worry in the back of their minds — do they really want to hitch themselves to neighbours whose weakness may bring down their own grids?
Authors:
James Doran, Market Reporter European Electricity
Rhys Talbot, Associate Editor European Electricity
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