Spain is about to face the challenge of a "black start"
119 comments
·April 29, 2025Animats
justlikereddit
The groundwork for the blackout will inevitably come back to a buildout and reliance of renewable sources that do not have spinning mass that can do frequency synchronization.
There are costly means to compensate for the lack of spinning baseload but actually building these devices have been neglected, to no ones surprise.
Tade0
Why would you need a spinning mass when you have an inverter which can produce a range of frequencies and outputs and it all boils down to coordination?
Looking at power generation reports it's the plants relying on inertia (like nuclear) which were disconnected and haven't been reconnected since:
abe_m
At the time I'm writing this, there appears to be about equal (hydro + gas) = (solar + wind). It appears they are running a significant portion of the grid with high inertia generators.
In a control system when you have an actuator that is much more responsive than the load, you can get into instable operating regimes where. On a small scale, when you are setting up servo motors, there is an inertia matching ratio for stability. In some of the systems I set up it was 10:1 load inertia:motor inertia. If you exceed that, you end up with elasticity between the motor and load that the motor can locally be above set point, and the control tells the motor to slow down, while the load has not yet reached set point. The motor is then too slow, and the control tells it to go faster, and you get the motor oscillating around the speed of the load.
On the grid you can have similar elasticity. An inverter many km away can get too far ahead in the AC cycle, then when that signal reaches the local inverter, the local inverter slows down, but the remote inverter has already slowed down, and by the time that slower wave gets to the local inverter, it is already too slow, and so the local inverter starts to speed up. If you get the frequency "right" you can end up with a positive feedback loop. With a high inertia rotating generator, the system is damped and slow enough to respond you don't change set point faster than the signal can propagate.
atwrk
Not my area of expertise, but I think this is wrong? Modern PV inverters used in rooftop solar could easily start frequency synchronization autonomously, but are regulated to not do that autonomously in (at least) parts of the EU.
More importantly, according to the REE, PV played a mayor role in the current and successful black start.
justlikereddit
How?
If the power is out, do you imagine that all the load that is out there disappears too?
If I'm in a blackout and put my multimeter into the grid socket, will the measurement be something that my local inverter can drive an AC load through with no problems?
And if that's not possible, how do we get an AC wave out to my 5000 local solar panel neighbors? And if we don't get any carrier wave to synch it to, then how do all these thousands of individual inverters decide on the unison synchronization necessary to all start jumping together?
And if they try and fail, will all the connected load accept a graceful out of synch mixed power noise at 0-220v until things properly latch together?
The problem isn't like playing a sine tune of acoustic sound that's merely audible to your local neighbor, who can dial in his own tune, and then daisy chaining this until it matches on a grid sized level.
tenthirtyam
I've always wondered why we can't just have a "master" power station transmit a 50Hz signal modulated at, say, 50MHz. Then all the other station simply sync to that, including small scale such as domestic PV etc.
Then depending on how out-of-sync a given station is with the signal, they ramp production up or down accordingly.
Is the problem here that there is inadequate or slow feedback to the supply side regarding load and therefore you'd end up with under-voltage?
Bjartr
That's more or less how it works. Knowing what 50hz is and how out of sync a generator is is easy. AFAIK, the problem is one of inertia, both electrical and mechanical. A generator is a spinning mass, the more load on the generator, then the slower it turns. How fast it turns decides the frequency of power it generates. Say you get your generators running at 50hz at night, and then during the day it gets hot and thousands of AC units get turned on. Now your generators are running at 40hz.
It's not about getting the generator to spin at 50hz, it's about getting it to spin at 50hz under dynamic load. Most generators are mostly fixed speed I think for the sake of efficiency, so the mechanism the grid has to regulate the frequency of power is largely by controlling the number of generators running at any given time, and how much of the grid is connected to them. Ramping up and down based on the current observed frequency of the grid is exactly how this all works. However it's more complicated because what if two or more power stations see a low frequency grid and decide to ramp up more generators? Well now the grid frequency is too high. If they them respond to that by ramping down, it'll go too low. Rinse and repeat and you get undesirable frequency oscillation, so there needs to be more communication across the grid than just responding to the locally observed frequency.
Connect a stopped, or sufficiently out of phase generator to a full scale power grid and the puny thousands of pounds of metal that make up a generator are going to get ripped apart by the sheer inertia of the power grid forcing it to match speed and phase in an instant. This is also a problem when attempting to connect two isolated grids, of they're too out of phase with each other, catastrophic physical damage will occur.
tomatotomato37
Unfortunately that pretty much just leaves solar panels, as wind/hydro/concentrated solar/geothermal all rely on a spinning mass moving at a mostly consistent speed, though at least hydro can black start itself relatively easily
fsh
I don't see why. Battery-backed renewables should be much easier to synchronize than spinning generators.
whyever
Do you mean solar energy sources? Wind turbines have plenty of "spinning mass"...
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lifty
Not sure why you are downvoted but this rings true to me.
rdtsc
Just like there is vibe coding, this is vibe downvoting: “they are probably right, but kinda feels like they are dissing renewables, and I like renewables, better downvote just in case”
moralestapia
For about 2-3 years the default for people here has been to downvote everything rather than driving discussion; much more reddit-esque than what it used to be. There are no other sites like this one to jump to, unfortunately.
On-topic: Wind power brings in about 20% of Spain's electricity, and that one fluctuates a lot indeed. I hope they put out a detailed post-mortem, I'd be an enjoyable read.
amelius
Sounds like these systems are extremely vulnerable to sabotage. But adding more complexity such as distributed digitally controlled loads will not necessarily make the situation much better.
pjc50
In theory maybe, but Ukraine are doing a great job of keeping their grid up in a hot war despite attacks on power infrastructure.
matkoniecz
But according to production data it has never dropped to zero? Why it would be a black start?
It dropped from about 32GW to about 8GW
source: https://transparency.entsoe.eu/generation/r2/actualGeneratio...
though admittedly https://en.wikipedia.org/wiki/Black_start mentions that partial shutdown may be also requiring a black start?
scrlk
Dropping from 32 to 8 GW usually means that an interconnected grid has fragmented into islands. If an island has a blackout, you need to black start it and resynchronise it with other islands.
joha4270
But what prevents you from connecting the stopped power plants to one of those islands and then running it from there? I'm not claiming that is easy, but its not a black start.
It looks to me like the author of this article has fundamentally misunderstood what a black start is. The fact that some power generation remained both on the peninsula, but also on imported power being available means that to my understanding this cannot be classified as a "black start". A lot of overtime, a lot of careful coordination yes, a black start, no
franga2000
A black start is a process, not a situation. The situation they're in might not fully necessitate a black start, but a black start procedure might still be the best course of action. Some plants have that capability and the rest (should) have a direct tie to one that does. For all practical purposes, that's a black start.
flysand7
Oh man, this reminds me of factorio. When you miscalculate your power needs and your generators eat up the fuel that isn't being produced enough. I've had to make a bootstrapping mechanisms and power switches for some of my powerplants to ensure I can get it back up in case it goes down and I can then re-enable my factory bit by bit.
pbmonster
Unfortunately, you can't simply hand-feed 100 coal into all the Spanish thermal plants and then plop down two more to be on the safe side until you've fixed supply...
pas
but sorta you can, that's not the hard part
it's that in Factorio there are no problems with phase synchronization, and the devices, consumers, producers, so the machines don't get damaged from a lot of abrupt starting/stopping.
still, it's strange that operators and grid controllers have to do the restart manually.
m4rtink
The machines might still end up being eaten by giant alien bugs due to the power outage shutting down automated defenses. :)
ffsm8
It's even worse in satisfactory imo, because the game is build around your fabs consuming wildly varying amounts of power throughout their production cycle... And after a power loss, they'll not only need the initial burst (can be handled via batteries) but will also now all be synchronized to have their power spikes at exactly the same moment.
Dyson sphere program is the by far most forgiving in that regard. You can overdraw to something like 200% before it becomes really problematic, and even that quickly resolves itself the moment you get more power online
seanalltogether
If you're interested in the process of a black start
https://www.youtube.com/watch?v=uOSnQM1Zu4w
from Practical Engineering
ahmedfromtunis
We had something similar happen in Tunisia in 2002. The reliance on diesel turbines meant a very long rebooting process.
As a result, the government invested heavily in installing gas turbines all over the country.
When we had another blackout event in 2018(?), it only took an hour or so to get things back again.
rightbyte
Why is that? Are turbines easier to speed regulate than diesel engines?
brohee
Yes, the huge rotating mass is inherently more stable than a diesel. They key to grid stability is mostly huge rotating mass, either producing or consuming.
null
actionfromafar
Or I guess, by inference, huge battery banks.
prox
I imagine a lot of sunshine in Tunisia (not too familiar with your country) , is there a big transition to solar?
ahmedfromtunis
Yes. Many laws have been enacted in the last 5 years to enable more solar project.
The downside is that the choice was made to focus on smaller 10-20 MW projects, with the occasional 100+ MW installation.
Hence, despite new projects entering service every couple months solar only accounts for less than 3% of electricity production nationwide.
ashoeafoot
How do energy intensive processes like aluminium smelters or window glass producers preven their machines from self destruction ?
exar0815
Can't answer for aluminium, but I can answer for window glass: One of our plants was threatened by massive flooding 2021, threatening the float glass oven (which doesn't float itself despite the name). It was closed off with insulation, turned off, and everyone hoped for the best and no steam explosion. In the end, only the cellars with the control equipment flooded and it could be gradually (as the control cabinets were checked and restarted) brought up again without loosing too much heat a day later.
In short: Heat Inertia of large molten bodies is massive with good insulation. If the time is too long tho, only dynamite will dismantle a solid chunk of material again.
echoangle
Is the heater keeping the material liquid not enough to re-melt it again?
exar0815
Its not an oven alone, its a kiln that smelts up the components for glass of the desired recipe, then purs the glass on a long (~half a km) basin of molten tin where it stretches and cools slowly, pushing the solidifying mass down the basin until the end. Re-Melting it is as far as i know not possible, as the melting is done before the pouring. You can melt the tin again, but not the glass.
xnx
I'm guessing that liquid glass gets into some spots/crevices that it cannot be remelted from using built-in heat sources.
m4rtink
It works also with cold/frozen stuff - you can even store snow over the summer if needed: https://www.slf.ch/en/snow/snow-sports/schnee-und-ressourcen...
LunaSea
Interesting! Does this mean that you could use intermittent energy sources, like solar power, to heat up the float glass oven during the day and it woul keep enough heat during the night so that it could keep running in the morning?
exar0815
Float glass is a continuous process, so it runs 24/7 and too much product is recycled into the smelter at the start again (Funnily, glass waste is actually a scarce resource). Getting the process dialed in to emit the desired quality is a long winded thing as far as i know (not involved in the process myself). Also, the heating is done with gas (LNG/CNG/H2) and electric in combination.
jerven
Yes, in theory, but your process control would be terrible, thus your product would also be terrible. Unless you invent something very clever.
Mistletoe
How did you find that much insulation quickly and what kind was it?
exar0815
The Insulation is in place all the time because the process is very energy intensive and the glass over the whole basin is supposed to cool evenly. Just the end is not closed off as the glass is ejected in a continuous endless stream[1].
https://www.blindex.com.br/-/media/blindex/site-content/xx-n...
bob1029
In some cases they don't have any practical ability to.
The Texas winter storm resulted in a lot of scrap at semiconductor lines due to power loss. There are industries that are completely dependent on grid power. You can't generate enough on site to back up 100% of your operation. Think about how much power one EUV source consumes.
The only reason Samsung is building additional factories in Texas is because the local utilities are effectively treating them as a critical load. The new plants are right by the ERCOT operation center and likely have access to the same cranking paths that the grid uses for black starts.
adrianN
I have no idea how much power an EUV source consumes, but I’m surprised to hear that it’s more than a handful of kW. What’s the right ballpark?
brohee
ASML says 1.3 MW for a single system. So off by three orders of magnitude.
https://www.asml.com/en/news/stories/2024/a-sustainability-m...
justlikereddit
>They require up to 10.2 gigawatt hours per tool annually
First hit off google.
Assuming they run them 24/7 that amounts to a power usage a bit over 1 megawatt, but they could be pulsed for all I know and use quite a bit more
_3u10
Power guarantees and insurance.
They are also frequently situated close to reliable power sources such as nuclear or hydro, usually fed by more than one generating station.
A friend of mine lived close to a brick plant his power NEVER went out.
consp
Anecdotal example: The, now closed, Aluminium plant here was build only because the government build a nuclear plant, which is still going. There was a coal plant next to it (closed now) as a backup for when nuclear was not available. Funny thing is most people thought the coal plant was the nuclear plant when driving by since it looks more like a plant, the nuclear dome structure is kind of hidden from the road and since natural water is used as cooling no big towers are close by.
ehnto
I had the same experience living near a hospital. The whole city has gone out a few times, and our grid was either still up, or is one of the first grids back up.
showsover
That was a fun 10 hours or so that we were without power in most of Barcelona. Some barrios had ~some~ power but most of us were without.
The one thing that surprised me is how quickly rumors started about power being out in Portugal (true), France (true to an extent), Belgium (false), and the UK (false). Walking back home from work you heard the names of Trump being mentioned as well.
It's a bit scary to personally experience how quickly people can start panicking. On the other hand the bars that had some power had a great afternoon with tons of beer being served before it got too warm :-)
Zealotux
I am in Barcelona too. The combination of no power and patchy internet was the perfect recipe for rumors to spread, which was fun to observe. I went for a walk since I couldn't work and saw tons of people socializing, drinking beers (more than usual), and young people playing without their phones. It'll be a special day to remember, I think.
prox
Maybe make it a yearly event, turn off all power (like Earth Day) just for the socializing aspect.
api
Shutting off (anti-) social media would be enough.
Zealotux
I honestly thought we should make it a public holiday and shut down the electricity once a year, not so realistic unfortunately.
showsover
I was actually considering going for a ride on the motorcycle today if the outage lasted another day. Beautiful weather, a tank full of gasoline, and no stress about work? Sign me up!
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TheOtherHobbes
Spain and Portugal had to deny a fake social viral that said power was out across most of Europe and the Russians were cutting undersea cables.
On the upside, more people at all levels are going to be more prepared if it happens again.
diggan
Most people I spoke to around Maresme area yesterday believed someone incompetent made a mistake somewhere, and that was the reason. Some people jokingly suggested cyber attack/Russian probes, but afaik no one took those seriously.
Bad_CRC
I'm close to a refinery and seeing black smoke coming out 5 minutes later of the blackout was a bit of a scare tbh.
debugnik
A security guard at my workplace actually told me they had "received a call" about power being out in Romania as well. I'm not sure how that one rumour spread.
MaoSYJ
Most information was spread by car radios. Rest were people asking and talking to each other.
consp
As long as the beer is cool, you only need CO2! Great off grid mechanism. Or N2 in case of Guinness.
xenospn
I never have any cash on me. That would’ve sucked.
elric
In my experience, shops you frequent will be sympathetic to that problem and will just let you come back to pay later. And I imagine that any shops that sell stuff that needs to be kept cool were especially amenable to that ...
showsover
I spent my last 5 euros on a sandwich and a croissant to eat on the walk home. All in all a pretty decent experience.
solarwindy
Your comment immediately brings to mind this classic of croissant eating in ‘interesting’ circumstances: https://youtube.com/watch?v=wp84sRpM1Js
fifteen1506
Add the store on Foursquare, "good blackout sandwich, 5 stars"
AStonesThrow
How warm is "too warm"? I find cold beer, and cold soft drinks as well, quite repulsive. I usually try to order without ice entirely, and if I receive any bottles or cans, I permit them to come to room temp before consumption.
Refrigeration is sort of a scourge to those who enjoy food. We are so used to simply freezing our esophagus and not tasting anything! Food is kept cold because it lasts longer, not because it tastes better.
Sure, refrigeration makes restaurants and grocery stores possible. But it also presents challenges to cooking and it's very resource-intensive -- think about it -- basically everyone everywhere is always running their refrigeration -- that's a huge load on any system.
showsover
I was referring to the fact that generally people prefer cold beer, not room temp beer.
consp
Pedantic, but most beers should be drank (according to the manufacturers and experts) at 7-13c depending on type of beer. Exceptions always exist to confirm the rule. Which is above fridge and around "cellar" temperatures.
Unless you drink Schultenbrau, which tastes worse cold than at room temperature (/s, kind of).
AStonesThrow
> generally people prefer cold beer
Do they? But why? Why would they? Are they simply accustomed to tasting it that way? I should say "not tasting it" because chilling a beverage basically kills its flavours, and they never make it to your tongue correctly.
I would say that many people would be surprised and amazed if they tasted such things as Pepsi without ice, and without coming right out of the fridge.
Unfortunately, any lack of refrigeration really messes up supply chains and will eat into anyone's bottom line, so it's not a realistic goal.
K0balt
I can only imagine the difficulties facing technicians and engineers black starting a nation-scale grid.
I operate a microgrid facility in Hispaniola and have wonderfully cooperative users backed by a separately powered communications and control system. Even for us, a facility serving a small neighborhood and farm, a black start must be performed as a careful choreography of systems and loads…and we can just pick up a radio and tell people to turn the main breaker of their house on or off, and to leave their AC units off until we finish bringing everything up. In 12 years we’ve only had to do it twice, but even for us it’s a tedious process.
zeristor
I am no expert, however with solar power and more grid batteries (I don’t think Spain has many grid batteries) wouldn’t it be possible to charge the batteries and use that to drive a ‘black start’.
Sounds simple, and I appreciate from experience a huge amount of prep and validation needs to be done in the background.
myself248
At an extremely abstract level, it is conceptually simple, but most inverters are designed with safeguards to prevent exactly this. They only produce power when the grid is up, and in phase with it.
Because if not sequenced and interlocked, islanding behavior can result in back-powering parts of the grid that are supposed to be disconnected and down for maintenance, or creation of desynchronized islands that then cause more damage when reconnected.
This is absolutely a problem that operators need to solve. Radio synchronization is possible, neighborhood islanding could be beneficial, etc. There are entire village-wide micro-grids in remote places where everyone's inverters do perform these functions, it just hasn't been embraced in monopoly environments yet.
For instance, relays that close isolated parts back onto the main network would need to be phase-aware, to only reconnect if it's safe to do so. You could mandate that all island-mode inverters center themselves around 50.1 or 60.1Hz in the absence of outside influence so there's certain to be phasing opportunities. Distribution networks would need more switches to provide positive isolation during maintenance. And all of these things would need huge amounts of interoperability testing. It's possible, but it has a cost.
zeristor
Thanks for the excellent insight.
I’m guessing this could be more of a thing in the future to make the grid more robust.
Didn’t Australia have a similar issue a few years back, which Tesla built a large grid battery to resolve, not just for storage but for stability.
Symbiote
This article was published when over half of power was already restored.
boxed
99% up now. It's pretty impressive how fast they can get the system up and running again considering how seldom they need to do these types of things.
TheOtherHobbes
Initial estimates went from "No idea" to "Could take days".
In the end it took about 12 hours to restore most of the power in two countries. There are some knock-on effects from trains being in the wrong places, but a solid result overall.
vvillena
This is not correct. The REE press conference held about two hours after the start of the blackout gave an estimate of 6 to 10 hours, which was about right. Any other estimations were misinformation.
anonzzzies
Some outlets said days to weeks, but who knows where they got that info.
everyone
What caused it? Nowadays when anything like this happens in the EU, I immediately wonder if it was Russian saboteurs. They have certainly been destroying infrastructure here, eg. undersea internet and power cables.
null
tenthirtyam
I was wondering if a solar flare could cause something like this. But if it had been that on this occasion, the astronomers would've been warning about it for at least 8 minutes. :-)
ZeroTalent
It was American saboteurs. First thing that comes to my mind /s
Spain is mostly back up.
Plant startup is only the first step.[1] It's load pickup.
Here is a PJM training module on load pickup during system restoration.[2] It gives a sense of how touchy the process is. Power network control has good control over generation and transmission, but limited control over load.
When load is turned on, there are transient loads with different time constants. There's a huge load for the first second as inductors, capacitors, and incandescent filaments start up. That tails off in under a second. There's a second load as motors wind up to speed. Ten seconds or so. Then there's "cold load", where everything in HVAC starts trying to get temperatures back to normal. Maybe half an hour.
There's no mention of computer control. Listening to this, you visualize people running around reading meters and throwing big switches. It's probably people looking at display boards and sending commands to remote big switches, but the concept is the same.
Botching this means voltage or frequency goes out of tolerance, protective devices shut things down, and the system operators have to start over.
More PJM training modules on related subjects.[3]
Unclear what caused this yet. Something caused enough system instability to trip protective devices, but there's no good info yet. Once everybody has a chance to compare all the logging data from different points, it will make more sense.
[1] https://pjm.adobeconnect.com/_a16103949/p622tuwooba/
[2] https://pjm.adobeconnect.com/p6e5csm81ter/
[23 https://www.pjm.com/training/training-resources