5 lessons from Portugal’s 6-day renewables streak

Years of renewables development set Portugal up for stunning success this fall when the country met all of its electricity needs with renewable sources for six days straight. For five of those days, no fossil fuels had to be burned at conventional power plants to keep the grid humming along.

I recently joined the Weather Channel’s climate-change-focused show Pattrn to talk about Portugal’s clean energy success with hosts Jordan Steele and Stephanie Abrams. A stormy, gusty weather pattern in late October and early November boosted wind power and helped supercharge renewable energy production for Portugal’s 10 million people, but the country’s renewable record is also a sign of things to come.

Here are the five lessons that Portugal’s clean streak teaches us about the broader energy transition.

The grid can handle 100% renewables

At the most basic level, Portugal showed that it’s possible to ramp down fossil fuel generation, operate for days on end with just renewables and then ramp the fossil plants back up when they’re needed again. For a tempestuous moment this fall, those transitions proved seamless, and the lights stayed on, which is vital to maintaining confidence in the shift to carbon-free energy. We learned that this grid, at least, can physically handle 100% renewable operations.

Steady renewables buildout pays off

The fall renewables streak resulted from ideal weather — plus decades of dedicated construction of clean power plants. Portugal’s hydropower dam buildout dates back to the 1970s. The country invested in onshore wind power in the 1990s, and more recently it accelerated solar installations while also preparing for a floating offshore wind expansion to draw power from the turbulent Atlantic seas. Portugal has experienced multiday streaks of high renewables production over the past few years, but with more clean power capacity installed, it was able to go further than ever before.

Diversification of renewable resources is key

A prolonged storm wouldn’t have allowed for a renewable energy record if Portugal relied predominantly on solar power. Instead, the country’s variety of clean resources proved vital to extending the run. Overall, renewables supplied 59% of Portugal’s electricity this year through November; 25% came from wind, 21% from hydro, 7% from solar and 6% from biomass. The late October storm spun the wind turbines and filled reservoirs with water, while the sun still hit drier parts of the country. That weather pattern would have been lousy news for California or Hawaii, where solar is king, but it worked great for Portugal’s clean power portfolio.

Storage is necessary, but it doesn’t have to be lithium-ion batteries

Many people assume that large amounts of energy storage will be necessary to run an electricity system on renewables alone. But Portugal went for six days without a large fleet of battery plants; it lacks any large stand-alone batteries and just has modest capacity of batteries connected to renewable generators. Instead, Portugal used the storage potential of water to its advantage. Hydropower reservoirs provide built-in storage, making it possible to parcel out the voluminous rainfall over time. The country also operates pumped-hydro storage, which uses electricity to lift water up to higher elevations, so it can flow through hydropower generators at a later time. This year, Portugal produced more power from pumped storage than ever before, which the grid operator attributed to the rise in solar production.

Climate goals require doing this all year long

The key question going forward is, as Pattrn host Abrams put it, ​“How do you go from six days to 365 days?” Portuguese leaders aim to stop burning fossil fuels by 2040, and at that point, they can’t hope for ideal weather conditions year-round. But as the diversified renewables buildout continues, production will rise even without the perfect storm. One way to approach the carbon-free goal is to gradually minimize gas combustion over time until it’s no longer needed as a backup source. This sidelining process is already underway: Fossil gas usage in Portugal’s electricity sector fell 42% through November compared to the year before. That helps consumers, because instead of paying to burn imported fossil fuel, they get electricity without fuel costs.