2025 Iberia Blackout Report [pdf]

> Because the only reason that solar is still generating power at negative prices is because they are getting subsidies to do it.

This massively simplifies reality.

E.g. in Finland where I live we also have issues with negative power prices. A few years ago we had some really low prices. It turns out, a fair bit of wind power producers never opted to add to their windmills any remote shutdown possibility, nor did they have the ability to monitor prices and react to them automatically. I.e. they just kept generating no matter the price, and had offers in at the network level at the lowest permissable price.

Since then, when they lost a non-insignifcant amount of money by running at negative prices, they've started installing control electronics in windmills and building IT systems and prediction algorithms to be able to react to this.

In the EU it is not as simple as "turning off when the prices are negative" since producers offer a certain capacity to the grid in an auction system the day before. You have to predict the weather + overall demand and set your offer accordingly.

I’m a bit mystified as to how the grid controls voltage at all. The non-renewable plants follow the rules here:

https://www.boe.es/buscar/doc.php?id=BOE-A-2000-5204

7.1(b) seems to be saying that generators connected at 200kV adjust their reactive power generation/absorption in real time according to the voltage they observe, based on a lookup table provided by the grid operator.

This seems sort of sensible according to my limited understanding of the theory of AC grids. You can write some differential equations and pretend everything is continuous (as opposed to being a LUT with 11 steps or so), and you can determine that the grid is stable.

However, check out this shorter report from red eléctrica:

https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_Sp...

Apparently these 220kV plants are connected to the 400kV grid via transformers in substations that are not owned by the generator operators. And those transformers have “tap changers” that attempt to keep the 220kV secondary side at the correct voltage within some fairly large voltage range on the 400kV side. Won’t this defeat the voltage control that the 220kV generators are supposed to provide? If the grid voltage is high, then absorption of reactive power is needed [0], and the generators are supposed to determine that they need to absorb reactive power (which they can do), but if the tap changer changes its setting, then the generator will not react correctly to the voltage on the 400kV side.

In other words, one would like the generator to absorb reactive power according to P_reactive(primary voltage • 220/400), but the actual behavior is P_reactive(primary voltage • 220/400 • tap changer position), the tap changer position is presumably something like 400/primary voltage, and I don’t understand how the result is supposed to function in any useful way. Adding insult to injury, the red eléctrica repoet authors seem to be suggesting that a bunch of tap changers operators didn’t configure their tap changes well enough to even keep secondary voltages in range.

Does anyone with more familiarity with these systems know how they’re supposed to work?

[0] I can never remember the sign convention for reactive power.

> caused by the reaction of renewable generation to those conditions

No, that is not what the report says. It says, just like you say, that renewables reacted to market prices, causing a generation drop. It then says explicitly that synchronous generation caused oscillation, while PV plants showed a flat non-oscillating pattern.

From your comments I worry there are emotional factors clouding how you're reading the report - this was a systemic failure involving many separate technologies:

- Market signals - negative prices - caused a drop in PV generation (as frequently occurs)

- Synchronous plants caused oscillations as a side effect

- Plants procured to dampen exactly those oscillations did not deliver as requested

- TSO then took measures using interconnections to stabilize via other balance area

- This caused - presumed - overvoltages in distribution grids

- PV inverters then shut off, as mandatory by regulatory requirement in response to over voltage

You're absolutely right that PV played a large role here, but that point is diminished by making it out that PV is both the source of the initial generation drop and the source of the oscillations; it is neither.

The market design caused the generation drop, synchronous generators caused the oscillations, TSO action caused distribution overvoltages and regulatory requirements on PV firmware design in response to overvoltage caused the final blackout.

Creating an level playing field is part of the complexity. The fact is we must migrate to mostly CO2-free power generation within the next decades and also replace fossil energy for transport and heating.

Market-based economies are great to follow technology trajectories and are efficient at capital allocation but even for them we need additional incentive structures to speed up the process.

I also think that most countries have massively reduced subsidies for new projects but existing subsidies will still be served for a long time.

> but the fans of renewables just flagged it

As moderators we can only guess why people flag things, but there are other reasons why people may have flagged that comment, the foremost being that it broke the guidelines due to its inflammatory style.

On Hacker News we want to be able to discuss difficult topics involving arguments people may find counter to their assumptions, but you need to express things in a way that's persuasive rather than combative.

https://news.ycombinator.com/newsguidelines.html