[samuel]

It's not that easy, and the 2025 blackout good evidence of that. Renewables need a grid that's engineered for them and that require significative investments. Without them, closing power plants (of any kind) is, IMO, nonsensical.

Ironically, Spain has plenty of Uranium, but there is an environmental law that doesn't allow its mining.

https://alpoma.medium.com/uranium-in-spain-8ef975763257

This country is crazy.

[yayachiken]

> It's not that easy, and the 2025 blackout good evidence of that. Renewables need a grid that's engineered for them and that require significative investments.

The outage in spain had multiple complex causes.

While the grid had a rather routine instability/oscillation on-going during time of the incident, the actual point-of-no-return was completely non-technical: Prices crossed into the negatives, which caused generation to drop by hundreds of megawatts and load to increase likewise within a minute (!) because the price acted as a non-technical synchronized drop-off signal for the grid.

In grids where the price action is not forwarded directly to the generators and consumers there would be no incentive to suddenly drop off decentralized generation. So for example in Germany a black-out would not happen like this.

You can download the full ENTSO-E report here: https://www.entsoe.eu/publications/blackout/28-april-2025-ib... (See page 10 for a broad incident timeline)

Unfortunately, to have an informed opinion, you pretty much have to read all these pages, because the situation is just so complex. Otherwise, you just fall for agenda pushing from all sides.

[phatfish]

Yup, its interesting that a community supposedly of "engineers" are happy to claim expert knowledge of domains in which they have no experience.

[yayachiken]

That being said, I was apparently also under the impression of outdated or just plain wrong information.

While the report I listed mentions the sudden loss of decentralized generation as starting point of the blackout, and also specifically mentions small-scale rooftop PV, it says that the cause for that sudden synchronized drop-off is actually unknown.

[robocat]

You can't get an "informed opinion" by reading crap like that report.

The Spanish systems have systematic design failures for stability and electricity market design. Working out the political failures that led to the design failures is much harder.

Consultancies like https://www.nera.com/capabilities/power--utilities--and-rene... specialize in advising about electricity networks and market design.

Only those working closely in that profession have any knowledge of the underlying causes.

Most everyone else (including this comment) is different levels of ignorance and cluelessness.

Edit E.g. Crap quote from the report "but no significant oscillations with amplitudes above 20 mHz". The rest of it is about that level from what I could tell.

[yayachiken]

> crap like that report

> Only those working closely in that profession have any knowledge of the underlying causes.

This report is literally from the ENTSO-E which is the main regulatory body for the grid in Europe.

> Crap quote from the report "but no significant oscillations with amplitudes above 20 mHz".

What is the "crap" about that? An amplitude can still be measured in Hz, if you are looking at oscillating frequency deviations, if that is what you mean.

[samuel]

Very timely, the final report has been released today.

I hadn't read the document you referenced, and I admit don't have the prior knowledge, nor the time, to fully understand all the implications of what it says. My opinion is then the result of reading and listening a variety of experts and news sources, and it will have some biases, for sure.

Still, I have skimmed the final report to see if there was something that I could understand from first hand (and to support my original point, not gonna lie), and I found this:

_The increasing penetration of variable renewable and distributed generation, further market integration, broader electrification, and evolving environmental and geopolitical risks place the European electricity system under increasingly challenging operational conditions, requiring higher levels of resilience._

Do you really think that my original point (as uniformed as it might be), namely, that the levels renewable energy currently present in the spanish grid require significative investments, was wrong?

[yayachiken]

Yes, I think it's wrong, or at least way over-exaggerated.

You can run a grid to supply approximately 80% renewables (long-term average) without significant technical changes.

Only if you want to get the last 20% to renewables, you get technical challenges, e.g. related to synchronization and load-matching. But that is also not unsolvable problems, e.g. instead of relying on the inertia of steam turbines you can "just" build specific-purpose fly-wheels to do the same thing. It's just less elegant.

Source: Volker Quaschning "Understanding Renewable Energy Systems", too lazy right now to look up the exact page.

This is also consistent with the section they quoted. Generally, the load matching in grids is done by the system itself. If you add more wind and solar, which depends on the weather and location, you have to more large-scale intervention, e.g. allow generation re-dispatch. But that doesn't immediately imply that this is a dangerous process.

[adrian_b]

I have not read the report yet, but in another thread someone gave a very plausible explanation of what happened.

The high levels of renewable energy happened to contribute to this incident, but not because of something inherent in renewable energy. All renewable energy sources are connected to the grid through inverters, and in Spain most of these inverters do not use an adequate control policy, i.e. they do not compensate the phase fluctuations of the grid, like the synchronous electromechanical generators do (i.e. they do not generate an appropriate amount of reactive power for compensation).

Technically it is easy to implement such control policies in all solid-state inverters, but it was not done in Spain because there were no incentives, i.e. there were no regulations specifying how the inverters connected to the grid should behave, otherwise than disconnecting when the frequency went outside a permissible range.

[yayachiken]

Yes, that is plausible indeed, but the problem is that there are many explanations which are plausible, but there doesn't seem to be a smoking gun.

Strange about that explanation for example is that the time correlation is backwards. First the solar generation started to drop out and only then central generator stations tripped. Also the on-going frequency oscillations had already stabilized. If it was related to frequency issues, the solar inverters would either have shut down 15 minutes earlier (while the frequency oscillations were at the peak) OR 1-2 minutes later (when power stations tripped and frequency would have dipped)

[tfourb]

But doesn't nuclear power present a complication when designing a power grid for renewable energy? It is basically very expensive caseload energy that needs permanent demand, when the entire proposition of a renewable-focused grid is that you manage a non-certain production with dynamic demand (via batteries and price-sensitive usage).

[modo_mario]

Nuclear production doesn't react in seconds but it doesn't need permanent demand as far as I know? What makes you think that?

[tfourb]

A nuclear reactor can load-follow (increase or decrease their output) by up to 5% of their rated capacity per minute in normal operation: https://snetp.eu/wp-content/uploads/2020/05/SNETP-Factsheet-...

For power plants, this is glacial. A power grid has to balanced perfectly on a sub-second level. Also, you can only do this down to about 50% of rated capacity. Below that you have to switch it off completely.

If you combine this with renewable generation, it all falls apart. A cloud passing over a large PV installation will drop generation much faster than nuclear plants will ever be able to follow (by increasing generation). So if you want to have a substantial share of renewable generation (which, remember, is the cheap stuff), you can't have more than a token nuclear capacity, because you need to invest the money you might want to spend on nuclear on battery and hydro storage.

The other aspect is the economics of nuclear itself. Nuclear power plants are the most capital intensive generation capacity you can build. Even when driving them at the maximum of their rated capacity, the have a levelized cost of electricity several times that of PV and Wind per kwh. Requiring routine load following for nuclear would basically guarantee that no one ever builds a nuclear reactor again.

There are reasons to build new nuclear, but it's not cheap/reliable power generation. You build it to have access to a nuclear industrial base, as well as the research and professional community to run a military nuclear program. Or you actually succeed in creating a Small Modular Reactor, which might be suitable for niche applications (i.e. power isolated communities in extreme remote locations). Or you are simply fascinated by the technology and want to invest a ton of money on the off chance that it will produce some unforeseen technological breakthrough (though arguably you'd do better with investing in nuclear fusion from my limited understanding of the research).

[modo_mario]

>For power plants, this is glacial

But as far as I know this is a non issue since we 've mostly been able to cover this where it props up. Especially since the grid's demand doesn't tend to go 0-100 or the other way around that fast. Even with a significant amount of nuclear there's multiple of those solar farms, wind farms, etc

For the small fluctuations the turbine's governor response can provide frequency stabilization and pressurised water reactors also provide moderate load following.

>The other aspect is the economics of nuclear itself. Nuclear power plants are the most capital intensive generation capacity you can build. Even when driving them at the maximum of their rated capacity, the have a levelized cost of electricity several times that of PV and Wind per kwh.

When I looked at actually honest comparisons this simply isn't true across the board. I mean it doesn't help that the west has built so few recently and managed some exceptional fuckups whilst also making a lightbulb in an unimportant sidebuildings toilet cost a couple dozen grand in a way that might as well be purposefull sabotage of nuclear but much of the world (read mostly china) does relatively fine with their costs and time frame. These comparisons also have a tendency to use absolutely unrealistic storage costs all the same or foresee continued storage costs of methods that are exhausted. (hydro over here) Additionally it's the cheapest solar that often pulls this down but the vast majority in let's say here in Belgium is residential which is a lot lot more costly and less efficient. The solar farms are all way more south so a lot of these american reports don't make much sense in most of europe either.

[robocat]

> If you combine this with renewable generation, it all falls apart

Rubbish. Only true if the renewable generation is poorly integrated. Solar plus batteries can provide synthetic inertia if the incentives/regulations are correctly designed.

Australia has been adding oodles of solar, and they have been doing it surprisingly well.

Nuclear can load follow, within limitations: https://news.ycombinator.com/item?id=36254716

[tfourb]

> Solar plus batteries can provide synthetic inertia if the incentives/regulations are correctly designed.

Yes, but why build nuclear at all, if you are already building PV + batteries? Nuclear is much more expensive than that combination. And if you add nuclear capacity on a level that actually matters (i.e. 30%+ of peak load), you run into real integration problems.

As I've written elsewhere, a toke nuclear program can make sense if you want to keep the industrial base, institutional knowledge and expertise around, i.e. to guarantee independent access to nuclear weapons. But it is ludicrous to make nuclear a cornerstone of your energy policy. Not even China is expanding its share of nuclear in total energy generation. They keep it around as a strategic asset, but a subsidized one.

For countries like Denmark and Spain I'd be pulling my hair out if my government would start throwing money into the money pit that is nuclear power (and it is inevitably is government money, because no nuclear power plant has ever been built without government subsidies and/or price guarantees).

> Nuclear can load follow, within limitations

Yes, but it makes zero economic sense to do so. Nuclear is multiple times more expensive per kwh than PV + batteries, even if you run it at max capacity continuously. If you require nuclear to load follow on a regular basis, not a single reactor will ever be built again.

[robocat]

> Yes, but why build nuclear at all

I wasn't suggesting that. Why did you assume that and then argue against something I didn't say?

[Krssst]

For reference: nuclear power plants can do load following: https://en.wikipedia.org/wiki/Load-following_power_plant#Nuc...

It's more cost efficient to keep them running all the time since most of the cost of nuclear is building the power plant, but power output can be adjusted if needed.

[ViewTrick1002]

Please tell me how renewables cause a lack of reactive power. Which was the source of the Iberian blackout.

All reasonable grids already force renewables to handle reactive power if they want to connect, like they do for all electricity generation.

It is a trivial expense, but still an expense so no one does it unless forced.

[adrian_b]

In another thread that comments the report it was said that most inverters used in Spain for the renewable energy sources do not implement a control policy to generate an adequate reactive power to compensate the phase fluctuations of the grid, like a synchronous electromechanical generator would do. The inverters only disconnected from the grid when the frequency went outside the permitted range.

Ensuring that the inverters produce compensating reactive power would have been easy to do, but it was not done simply because there were no regulations that requested this. Obviously, as a consequence of the report, this is likely to change.

[ViewTrick1002]

Yeah, been trivial forever. In the US it became a requirement for new all utility scale non-synchronous generators a decade ago. And then a bunch of statewide rules for rooftop solar as well.

https://www.ferc.gov/news-events/news/ferc-moves-implement-f...

[kuerbel]

No it's not. Nuclear plants are not compatible with climate change. Spain and it's rivers will be too warm to cool them down: https://www.euronews.com/2025/07/02/france-and-switzerland-s...

[surfaceofthesun]

That may require retrofitting the plants to use open loop cooling instead of closed loop. That would increase water consumption.

[Ekaros]

Well only to certain point. When the rivers will naturally be too hot. You can start making them even hotter and it does not matter anymore.