One recent autumn afternoon, I watched the Atlantic gusts collide with the
cliffs that rise above Nazar�, Portugal. Rain pelted down, and the world-
renowned swells rose into walls of water that even the most death-defying
surfers reach only via Jet Ski. For me, this looked like a rained-out,
late-season beach getaway, but for the sliver of Iberia that is Portugal,
it looked like a bright future. That weekend, the nation of 10 million ran
on nothing but wind, solar and hydropower.

As it turned out, those rainy, blustery days were just a warmup. Portugal
produced more than enough renewable power to serve all its customers for
six straight days, from October 31 to November 6.

�The gas plants were there, waiting to dispatch energy, should it be
needed. It was not, because the wind was blowing; it was raining a lot,�
said Hugo Costa, who oversees Portugal for EDP Renewables, the renewables
arm of the state utility, which was privatized in 2012. ?�And we were
producing with a positive impact to the consumers because the prices have
dropped dramatically, almost to zero.�

To hit Paris Agreement climate goals by 2050, nations need to run their
grids without carbon emissions not just for three or six days, but year-
round. A handful of countries already do this, thanks to generous
endowments of hydropower, largely developed well before the climate crisis
drove investment decisions for power plants. Others score highly on
carbon-free power thanks to big fleets of nuclear plants.

Portugal falls into a different, more relatable bucket: It started its
decarbonization journey with some legacy hydropower, but no nuclear
capacity nor plans to build any. That meant it had to figure out how to
cut fossil fuel use by maximizing new renewables.

How did Portugal make this happen? It committed to building renewables
early and often, pledging a 2050 deadline for net-zero carbon emissions in
2016, several years before the European Union as a whole found the
conviction to take that step. Portugal�s last coal plants shut down in
2022, leaving (imported) fossil gas as the backstop for on-demand power.

�The key conclusion, in my opinion, is that it shows that the Portuguese
grid is prepared for very high shares of renewable electricity and for its
expected variation: We were able to manage both the sharp increase of
hydro and wind production, and also the return to a lower share of
renewables, when natural-gas power plants were requested again to supply
some of the country�s demand,� said Miguel Prado, who covers Portugal�s
energy sector for Expresso newspaper.

The task ahead for Portugal�s grid decarbonization is to reduce and
ultimately eliminate the number of hours when the country needs to burn
gas to keep the lights on. Leaders want gas generation, which made up 21%
of electricity consumption from January through October, to end completely
by 2040.

To reach its climate goals, Portugal has focused on diversification of
renewable resources; instead of depending primarily on wind, water or sun,
it blends each into the portfolio and finds ways to make them more
complementary. The country�s power companies are now chasing major
additional offshore wind opportunities, expanding solar installations and
repowering older onshore wind projects to get more out of the best
locations.

Anatomy of a six-day clean energy streak
After the overthrow of the authoritarian Estado Novo dictatorship in 1974,
the newly formed state utility Energias de Portugal constructed a series
of hydroelectric dams on the once-wild rivers that rushed from the eastern
mountains to the western coast. The company built its first onshore wind
projects in the 1990s, when solar simply couldn�t compete economically,
and solar installations have only recently started to catch up.

That�s why the gray skies didn�t hurt overall renewable production during
the country�s recent record-setting stretch, as they would have in, say,
California or Hawaii. The wind and hydro were cranking, and that�s what
mattered.

Any milestone in the rapidly evolving clean energy sector should come with
specific parameters. So what exactly did the Portuguese grid accomplish
earlier this month?

The six-day record refers to the 149 consecutive hours in which ?�energy
from renewable sources exceeded the industrial and household consumption
needs across the country.� The country�s previous record for that metric
was 131 hours (a little over five days), achieved in 2019. That doesn�t
mean that fossil fuel plants weren�t operating � just that the overall
renewable generation more than met customer needs.

But Portugal also just set a national record for meeting the entire
electricity system�s needs ?�without resorting to conventional thermal
power generation.� This gas-free stretch started Halloween night and ran
for 131 consecutive hours, about 5 days, nearly tripling Portugal�s
previous record of 56 hours straight in 2021. And for 95 of those
consecutive hours, Portugal exported clean electricity to Spain, because
it consistently had more than it needed � again without burning gas.

That trendline is the thing to watch. Renewables-friendly weather will
come and go, and shoulder months are ripe for renewables to outpace
consumer demand because heating or cooling needs are lower than in the
summer and winter. But the last time Portugal had ideal conditions for a
renewables record, it only lasted one-third as long without burning gas.
As more wind and solar capacity comes online, Portugal expands its arsenal
for running entirely on renewables.

This particular week stood out, but it exemplifies a historic shift in
energy sources. Natural-gas use for Portugal�s electricity production fell
39% year-over-year for the period from January to October, according to
REN. That brought overall gas use to its lowest level since 2006.

Portugal has made grid decarbonization perfectly tangible for itself. To
reach its climate goals, it needs to take the playbook from this one week
in November and run it for longer periods of time, until eventually it
doesn�t even need gas on standby. And it has to do so even in the parts of
the year when the winds and the rain don�t lash the off-season traveler
who�d heard so much about a climate reminiscent of Southern California.

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Next steps for grid decarbonization
Portugal�s clean energy accomplishments today build on several decisions
made in the past: The country chose to invest in new hydropower capacity,
and 18 years ago, it ran a large-scale wind auction, Prado noted.

�It was also important that the country didn�t go to a massive investment
in solar capacity when the technology was still expensive,� he explained.
?�Now Portugal is facing a huge demand of developers to build new PV
utility-scale plants, as well as a big demand for decentralized solar
projects, taking advantage of a low-cost technology to increase the share
of renewable energy in the years to come.�

The country still has a steep task ahead to hit its national target of 85%
renewables by 2030, Prado added. Major challenges include slow permitting
processes and the complexities of balancing ecological impacts with the
need for cleaner power.

One way to mitigate delays in permitting new plants is to refurbish old
ones.

Portugal has limited landmass to work with, and the best onshore wind
sites are already taken, Costa said. But early projects still run 500-
kilowatt turbines, while new turbines can produce 6.2 megawatts. Thus,
swapping an old turbine for a new one could unlock 12 times the existing
capacity. EDP Renewables is doing this strategically to increase
production at times when projects aren�t hitting their full export levels;
such upgrades produce more clean power throughout the year without
necessitating grid investment to handle surges of power.

EDP Renewables is also investigating hybrid power plants, which combine
wind and solar at the same location.

�If we combine wind and solar, what we see is that there is a big
complementarity,� Costa said. ?�Typically, when we have wind blowing, we
don�t have sun. And when we have sun, typically we don�t have that much
wind.�

Grouping developments like that dilutes the fixed costs of construction,
making them ?�more rational, economics-wise,� Costa said. In other words,
developers can save money compared to building the same resources in
separate locations.

Portugal currently has no large stand-alone battery storage plants, though
some batteries sit alongside solar or wind projects. The storage built
into the hydropower networks has sufficed until now to balance swings in
other forms of generation. But as renewables push ever higher in their
share of electricity production, the need to rapidly store and discharge
power will call for more batteries, Costa said.