Storing natural gas on-site is difficult, so fuel is supplied through a “just in time” distribution system. Failure of that distribution system drives generation plants off-line suddenly, as happened in Texas in 2021. While not as bad a wind/solar variability, grids must account for this JIT risk.
Large electric grids are complex systems. And any grid, regardless of its dependence on variable renewables, can fail. Remember the great northeast (US) blackout of 2003?
Inertia has been important for managing grids based on relatively slow-to-respond mechanical generators, not necessarily for those based on inverter-based resources. The NREL study you quoted noted: "Zero-inertia microgrids have been in operation for decades, which demonstrates that inertia is not needed to operate an AC power system."
The authors noted: "Using power electronics, inverter-based resources including wind, solar, and storage can quickly detect frequency deviations and respond to system imbalances. Tapping into electronic-based resources for this 'fast frequency response' can enable response rates many times faster than traditional mechanical response from conventional generators, thereby reducing the need for inertia."
And they concluded "Although growth in inverter-based resources will reduce the amount of grid inertia, there are multiple solutions for maintaining or improving system reliability—so declines in inertia do not pose significant technical or economic barriers to significant growth in wind, solar, and storage to well beyond today’s levels for most of the United States." So let's all be cautious before leaping to conclusions.
Before condemning the entire renewable-energy effort, let's consider that Spain's results have been quite good, up to this failure. They've achieved 50% annual generation from renewables, and 100% on many days. And they aren't ignorant of the inertia challenge, as they have installed sync condensors (sometimes repurposing thermal plants). And while doing this, they've kept electricity costs reasonable, or even lowered costs, depending on the analysis.
If it does turn out that lack of inertia was a contributing factor to the blackout, it's not an unsolvable problem, even in systems with fairly high levels of intermittent power sources. The Spanish engineers may have miscalculated the needs, or incorrectly modeled the scenarios. They'll need to re-calculate.
See, for example, the success of the Australian Hornsdale Power Reserve in providing frequency stabilization.
I agree that the lack of inertia of intermittent power sources is not unsolvable. The obvious solution is battery backup. And in the more northern countries the dunkelflaute has to be backed up with gas centrales. I miss a honest debate to compare the cost of all this with the cost of nuclear without dogmatic considerations.
Question about the subscription levels: You go from basic to pro and it is a big jump. I imagine that a $250 midpoint might pull some away from the pro level while adding more to the mid level, so you decide. Otherwise you might add a donate option, or let me know where to find that feature.
Thanks for this! I had an electrical engineer colleague try to explain renewable grid frailty to me a few years ago, but your explanation of inertia was far more digestible.
Great post. This is the fourth, but best, discussion of the Spanish grid collapse I've seen with attribution to insufficient inertia. The power generation chart was helpful in showing how quickly they reestablished the system, and I appreciated the link to the Oxford Institute paper from which you took the included chart of inertia by power source.
Given the publicity of this event and how Spain restored power relatively quickly (certainly compared to Texas in 2021) this whole story will appear to many people more like a win for alternative energy then of further proof of its limitations. Sixty percent daytime power plus another 20% wind/hydro is pretty impressive.
Of course I've yet to read about the economic consequences of the event, and had it happened in a cold winter climate where dependence on electric home heating is widespread the potential adverse affects would be much greater.
Seven people died as a result of the blackout. The government is trying to cover up the cause being low system inertia, denying their plan to move to 100% renewables has any flaws, therefore we are likely to face identical blackouts in the future. However, the National Audience has started a formal investigation, and it's likely to conclude there has been criminal negligence by allowing a risky generation and grid system to be built.
There's much more than an economic consequence. Hundreds were stuck in elevators and subway tunnels for hours, parents were hysterical trying to get to their children, there was a lot of panic buying, and the radio stations that worked didn't have any official information, which even today claims they don't know the cause but insists wind and solar can't be blaimed .
Thanks for this information on the consequences. I've been getting a little to used to local short term outages to scale the impact to almost 60 million. Size matters.
This is not a new problem. "Planning Engineer" has been writing about grid instability from renewable at Judith Curry's for a decade. Originally he was writing anonymously IIRC because he worked for a company supplying electricity. Now he contributes under his name, Russ Schussler
Super helpful primer! I fear our leaders in the US have not cared much, especially at FERC. Fortunately Messrs. Wright and Danly are at DOE and can get to the matter right quick!
Data driven, fact based analysis, is why I appreciate and enjoy reading THB. A significant portion of the solar and wind power infrastructure in the world is supplied by China who rely on coal based generation. The expansion of coal based generation to produce goods that are perceived to be green in other regions of the world is underappreciated, as is grid inertia.
Dr Pielke, the Spanish grid had too much generation at the time of the incident (the market price had gone negative, encouraging consumers to consume more and generators to reduce output). Around 1233 a solar power plant in Andalucia disconnected, and the grid went unstable because it had insufficient inertia. Then about one and a half seconds later a second plant shutoff. This started oscillating frequency so much that the French lines disconnected. The French disconnection led to a full system shutdown.
Right now the Socialist government is lying about the cause, insinuating it may have been a cyberattack or a private generator company fault. The grid company is a private (20% government owned) but heavily regulated monopoly whose president is a political appointee named by the Socialist prime minister, Sanchez. He has been on TV lying about the situation and even went as far as criticizing the nuclear plants (which he intends to close). Because seven individuals died as a result of the blackout the Supreme Court has ordered a criminal investigation, and this means there's a lot of finger pointing.
The cause is now being discussed by social media pundits, and it's easy to see which of them are on the government payroll. The real cause is of course excessive solar and wind generation without investing in equipment to create synthetic inertia, and additional investment to de bottleneck some of the high voltage lines. This investment was requested and denied by Sanchez, and this is why he's now lying and trying to cover up his crime.
You describe, in passing, another important flaw of solar and wind- its business model. When you overbuild solar and/or wind so that they generate more electricity than needed, the market price collapses. Thus, the clamor to build more and more wind and/or solar, beyond the maximum generation that can be used, not only increases grid instability, but decreases profitability. "Planning engineer" on Judith Curry's site is a good reference.
Indeed, the Spanish grid is now subjected to a grossly overbuilt solar kit. And more panels are being installed because the Socialist government plans to close down the nuclear power plants. Unfortunately the woman who runs the electric grid company was previously a real estate registrar, and has been a Socialist party apparatchik for 15 plus years. The government likes to place its people in very important positions and then gives them orders to follow their dogmatic programs, so things are bound to fail.
The irony of RE's president attacking nuclear is staggering and adds insult to injury. Thanks for this insight, I hope you've prepared for recurrence: battery-powered radios, cash, and the rest of the analog things so conspicuously being purged from our society. Stay safe and well!
Even as a science & engineering ‘numpty’, there is sufficient fundamental data to joining of dots and wires,sun and wind
I understand the nonsense of reliance only on these fluctuating energy generators and the ongoing ABSOLUTE NEED for nuclear generation in particular, as gas in any form is still considered by idiots to be ‘Dirty CO2 pollution !
"The whole energy transition if you step back and think about it is an enormous challenge. In Australia, we will be rebuilding the grid and the power supply multiple times. This is like an industrial revolution 2.0 in many respects in terms of the scale and the speed we need to do this."
And
"Chris Davies from AEMO says rebuilding Australia's electricity system is one of the most monumental tasks the country has ever undertaken. To that end, he says ensuring system strength services are maintained is just one part of the overall challenge."
All this, and renewables are the cheapest power and power bills will be reduced? And I'd be willing to bet that these costs and trade-offs weren't factored into the CSIRO's "famous" report on the cost of nuclear power.
Today I saw a readout on this from The Planning Engineer (who is referenced a few times above):
https://judithcurry.com/2025/05/05/casting-blame-for-the-blackout-in-spain-portugal-and-parts-of-france/
Storing natural gas on-site is difficult, so fuel is supplied through a “just in time” distribution system. Failure of that distribution system drives generation plants off-line suddenly, as happened in Texas in 2021. While not as bad a wind/solar variability, grids must account for this JIT risk.
Excellent, Roger.
Large electric grids are complex systems. And any grid, regardless of its dependence on variable renewables, can fail. Remember the great northeast (US) blackout of 2003?
Inertia has been important for managing grids based on relatively slow-to-respond mechanical generators, not necessarily for those based on inverter-based resources. The NREL study you quoted noted: "Zero-inertia microgrids have been in operation for decades, which demonstrates that inertia is not needed to operate an AC power system."
The authors noted: "Using power electronics, inverter-based resources including wind, solar, and storage can quickly detect frequency deviations and respond to system imbalances. Tapping into electronic-based resources for this 'fast frequency response' can enable response rates many times faster than traditional mechanical response from conventional generators, thereby reducing the need for inertia."
And they concluded "Although growth in inverter-based resources will reduce the amount of grid inertia, there are multiple solutions for maintaining or improving system reliability—so declines in inertia do not pose significant technical or economic barriers to significant growth in wind, solar, and storage to well beyond today’s levels for most of the United States." So let's all be cautious before leaping to conclusions.
Before condemning the entire renewable-energy effort, let's consider that Spain's results have been quite good, up to this failure. They've achieved 50% annual generation from renewables, and 100% on many days. And they aren't ignorant of the inertia challenge, as they have installed sync condensors (sometimes repurposing thermal plants). And while doing this, they've kept electricity costs reasonable, or even lowered costs, depending on the analysis.
If it does turn out that lack of inertia was a contributing factor to the blackout, it's not an unsolvable problem, even in systems with fairly high levels of intermittent power sources. The Spanish engineers may have miscalculated the needs, or incorrectly modeled the scenarios. They'll need to re-calculate.
See, for example, the success of the Australian Hornsdale Power Reserve in providing frequency stabilization.
I agree that the lack of inertia of intermittent power sources is not unsolvable. The obvious solution is battery backup. And in the more northern countries the dunkelflaute has to be backed up with gas centrales. I miss a honest debate to compare the cost of all this with the cost of nuclear without dogmatic considerations.
So helpful as are the comments.
Question about the subscription levels: You go from basic to pro and it is a big jump. I imagine that a $250 midpoint might pull some away from the pro level while adding more to the mid level, so you decide. Otherwise you might add a donate option, or let me know where to find that feature.
Actually, The Pro+ plan can be accessed at any level above the normal subscription. Just enter your preferred amount. Thanks!
But...the $1000 is non-clickable, and I don't see any place to fill in an alternative amount.
Glad I asked.
Thanks for this! I had an electrical engineer colleague try to explain renewable grid frailty to me a few years ago, but your explanation of inertia was far more digestible.
Great post. This is the fourth, but best, discussion of the Spanish grid collapse I've seen with attribution to insufficient inertia. The power generation chart was helpful in showing how quickly they reestablished the system, and I appreciated the link to the Oxford Institute paper from which you took the included chart of inertia by power source.
Given the publicity of this event and how Spain restored power relatively quickly (certainly compared to Texas in 2021) this whole story will appear to many people more like a win for alternative energy then of further proof of its limitations. Sixty percent daytime power plus another 20% wind/hydro is pretty impressive.
Of course I've yet to read about the economic consequences of the event, and had it happened in a cold winter climate where dependence on electric home heating is widespread the potential adverse affects would be much greater.
Seven people died as a result of the blackout. The government is trying to cover up the cause being low system inertia, denying their plan to move to 100% renewables has any flaws, therefore we are likely to face identical blackouts in the future. However, the National Audience has started a formal investigation, and it's likely to conclude there has been criminal negligence by allowing a risky generation and grid system to be built.
There's much more than an economic consequence. Hundreds were stuck in elevators and subway tunnels for hours, parents were hysterical trying to get to their children, there was a lot of panic buying, and the radio stations that worked didn't have any official information, which even today claims they don't know the cause but insists wind and solar can't be blaimed .
Thanks for this information on the consequences. I've been getting a little to used to local short term outages to scale the impact to almost 60 million. Size matters.
This is not a new problem. "Planning Engineer" has been writing about grid instability from renewable at Judith Curry's for a decade. Originally he was writing anonymously IIRC because he worked for a company supplying electricity. Now he contributes under his name, Russ Schussler
https://judithcurry.com/2014/10/22/myths-and-realities-of-renewable-energy/
"Power has now been restored to the Iberian peninsula. But the scenes of gridlock and confusion will not be quickly forgotten. . ."
Global corporate media, four days later: "What outage?"
Super helpful primer! I fear our leaders in the US have not cared much, especially at FERC. Fortunately Messrs. Wright and Danly are at DOE and can get to the matter right quick!
Bet you won’t read this in USA Today? Is California heading in the same direction? The post regarding Canada gave me the chills literally.
Data driven, fact based analysis, is why I appreciate and enjoy reading THB. A significant portion of the solar and wind power infrastructure in the world is supplied by China who rely on coal based generation. The expansion of coal based generation to produce goods that are perceived to be green in other regions of the world is underappreciated, as is grid inertia.
Dr Pielke, the Spanish grid had too much generation at the time of the incident (the market price had gone negative, encouraging consumers to consume more and generators to reduce output). Around 1233 a solar power plant in Andalucia disconnected, and the grid went unstable because it had insufficient inertia. Then about one and a half seconds later a second plant shutoff. This started oscillating frequency so much that the French lines disconnected. The French disconnection led to a full system shutdown.
Right now the Socialist government is lying about the cause, insinuating it may have been a cyberattack or a private generator company fault. The grid company is a private (20% government owned) but heavily regulated monopoly whose president is a political appointee named by the Socialist prime minister, Sanchez. He has been on TV lying about the situation and even went as far as criticizing the nuclear plants (which he intends to close). Because seven individuals died as a result of the blackout the Supreme Court has ordered a criminal investigation, and this means there's a lot of finger pointing.
The cause is now being discussed by social media pundits, and it's easy to see which of them are on the government payroll. The real cause is of course excessive solar and wind generation without investing in equipment to create synthetic inertia, and additional investment to de bottleneck some of the high voltage lines. This investment was requested and denied by Sanchez, and this is why he's now lying and trying to cover up his crime.
Fernando,
You describe, in passing, another important flaw of solar and wind- its business model. When you overbuild solar and/or wind so that they generate more electricity than needed, the market price collapses. Thus, the clamor to build more and more wind and/or solar, beyond the maximum generation that can be used, not only increases grid instability, but decreases profitability. "Planning engineer" on Judith Curry's site is a good reference.
Indeed, the Spanish grid is now subjected to a grossly overbuilt solar kit. And more panels are being installed because the Socialist government plans to close down the nuclear power plants. Unfortunately the woman who runs the electric grid company was previously a real estate registrar, and has been a Socialist party apparatchik for 15 plus years. The government likes to place its people in very important positions and then gives them orders to follow their dogmatic programs, so things are bound to fail.
The irony of RE's president attacking nuclear is staggering and adds insult to injury. Thanks for this insight, I hope you've prepared for recurrence: battery-powered radios, cash, and the rest of the analog things so conspicuously being purged from our society. Stay safe and well!
Even as a science & engineering ‘numpty’, there is sufficient fundamental data to joining of dots and wires,sun and wind
I understand the nonsense of reliance only on these fluctuating energy generators and the ongoing ABSOLUTE NEED for nuclear generation in particular, as gas in any form is still considered by idiots to be ‘Dirty CO2 pollution !
While I was refreshing my memory on Synchronous Condensers and Static VAR Compensators, I came across this ABC article from 2023 (https://www.abc.net.au/news/2023-07-15/search-for-new-glue-to-hold-australian-grid-together/102598974). While it's a little reassuring that action is recognised as required, it also contains the following:
"The whole energy transition if you step back and think about it is an enormous challenge. In Australia, we will be rebuilding the grid and the power supply multiple times. This is like an industrial revolution 2.0 in many respects in terms of the scale and the speed we need to do this."
And
"Chris Davies from AEMO says rebuilding Australia's electricity system is one of the most monumental tasks the country has ever undertaken. To that end, he says ensuring system strength services are maintained is just one part of the overall challenge."
All this, and renewables are the cheapest power and power bills will be reduced? And I'd be willing to bet that these costs and trade-offs weren't factored into the CSIRO's "famous" report on the cost of nuclear power.