Here's a relevant new Substack post from David Turver at Eigen Values: Offshore Wind: Follow the Money - UK billpayers subsidising overseas investors and getting expensive, unreliable energy in return by David Turver, March 9, 2024.
While U.K. centric, this article will help you to understand why the economic elites advocating for fickle offshore wind oppose safe, reliable, abundant, cost-effective and zero - emission nuclear power, such as that produced at Diablo Canyon Power Plant.
For some historical context, here's an article from a dozen years ago that is spot on today:
Broken down and rusting, is this the future of Britain's 'wind rush'?
By Tom Leonard, Published 21:00 EDT, 18 March 2012, The Daily Mail (U.K.)
Here's a post by Robert Bryce that is complementary to several themes I wrote about in this article. https://robertbryce.substack.com/p/these-10-charts-caused-an-ngo-hissy My next article will cover how hydroelectric pumped storage is being used for grid frequency stabilization instead of bulk energy storage.
Here''s some additional information regarding grid inertia. (However, I disagree with the author's claim that wind power is capable of providing significant amounts of synchronous grid inertia. This glossary provides definitions for the acronyms included below.)
Glossary of Electric and Gas Industry Terms and Concepts - Indiana Utility Regulatory Commission, Updated and Revised February, 2022
Inertia – as Voltage Support (see also Automatic Generation Control - AGC, Area Control Error (ACE), Frequency, and Kinetic Energy): Baseload coal and nuclear generators, like natural gas generators other rotating machines (motors and generators) including wind turbines provide needed inertia to support frequency throughout an entire electric interconnection. At the instant load changes, the system must change generation to match so power into the system must equal power out. Since it is not feasible to change the fuel output or steam input of the generators on a split second basis, the rotating kinetic energy of every machine in the entire interconnection serves to help balance the system. For example, when a light is turned on, the energy needed comes from kinetic energy and the machines slow down and frequency drops. For a single light switch the drop in frequency is imperceptible. However, a rolling mill at a steel plant may cause a perceptible change. The Automatic Generation Control (AGC) system, on most large generating units, almost instantaneously recognizes the Area Control Error (ACE), which is a combination of the frequency drop and the importation of power from the rest of the interconnection as energy is supplied by their machines, and adjusts the output setting of the generators to restore frequency and tie-line flow. Thus, every piece of rotating equipment supplies inertia, including wind turbines (but not solar panels). Of course, large steam-powered turbines have considerably more inertia than a wind turbine (unless there are a few hundred of them) and wind turbines generally do not have the automatic generation control aspect of being able to react to the area control error.
Inertial Response: This is the kinetic energy stored in the rotating mass of all of the synchronized turbine generators and motors on the interconnection. Produced by the slowing of the spinning inertial mass of rotating equipment on the interconnection that both releases the stored kinetic energy and arrests the decline of the interconnection frequency. This happens immediately following a disturbance.
There is a fundamental lack of understanding of the technical electrical power engineering theory and practice and how inductive and capacitative supply and loads on an electrical system.
The system is designed around synchronous generation which is inductive and renewables are capacitative on my understanding.
I'm not an electrical engineer, I was a Reactor Physicist and latterly an Operations Engineer for over 20 years, and a lot of people just think its power in and out.
They have no idea of the potential problems of large amounts of intermittent non synchronous generation might have on the reliability of a power grid system.
Thanks for attempting it! beyond my engineering skills!
Thank you. I agree the AC power grid has been designed around synchronous generation. Please note my comments posted on March 13, 2024 above which outline the "TGFI problem."
No problem and thank you. Sorry for the delay in replying but my campaign against expensive renewables driving the UK to the most expensive energy in the world continues!
Please maintain your advocacy. Solar, wind, and batteries fail to provide the important synchronous grid inertia (SGI) that the UK needs. Gas-fired peaker (turbine) generators do not supply significant amounts of SGI. The task is left to nuclear, combined-cycle gas, and coal-fired generators. Since large hydroelectric generators run a much lower RPMs than the above thermal generation, they don't provide as much SGI, since SGI is proportional to the angular frequency squared.
Perhaps those leading us into the wind and PV ‘black hole’ are ignorant of the differences between AC and DC systems .. to them is ‘just electricity’. That’s what you get when the decision makers have no physics or engineering knowledge/background ☹️ The man leading us into the Net Zero black hole in the UK has a degree in Politics, Philosophy and Economics which would explain a few things. Oddly he did study advanced math at high school.
The situation you describe is very dangerous. It is one of the reasons for my public outreach to help decision-makers to understand the folly of "Net Zero."
There is a fundamental difference between Ed Milliband's understanding of energy and that of someone who works in the industry. He hasn't a clue about the intermittency of renewables, the cost of hydrogen or grid batteries or of reactive load management of system inertia. He's going to come a cropper very shortly.
He came very close to having that moment of awful realisation last month. I highly recommend watching the Unherd documentary on this which puts in the details AND the cover up.
Secretary of State for Energy and Climate Change of the United Kingdom
Ed Miliband needs to obtain some knowledge of how the electric grid actually works from knowledgeable scientists and engineers. This GreenNUKE article would be a good place for him to start. Could you please send it to him?
He wouldn't listen if you explained it in a children's book. What we are hoping for is that he goes ahead, bills go through the roof and we get blackouts and then that's finally the fantasy of net zero in the bin and he will have done the world a great service and got rid of net zero and this government in one move.
Sigh.... The challenge is that when the blackouts hit the U.K. while it is freezing outside, people will die. Since humans are warm-blooded animals, about 5 times as many people die during extreme cold events compared to extreme heat events.
A very informative 2018 technical article regarding the importance of synchronous grid inertia [SGI] from the Electric Reliability Council of Texas (ERCOT) is "Inertia: Basic Concepts and Impacts on the ERCOT Grid," April 4, 2018, Electric Reliability Council of Texas (ERCOT,) Austin, Texas, USA.
This article underscores that nuclear power plants (like DCPP) provide the largest amount of SGI. The article notes neither solar nor wind provide significant amounts of SGI. Since ERCOT has negligible interconnection to any other U.S. power grids, their grid functions effectively as the power grid on an island. ERCOT established a minimum SGI constraint they call "Critical Inertia;," described in section 6 of this report. Since ERCOT is a large system, the value of Critical Inertia is also large. To ERCOT's credit, their real-time system dashboard shows the amount of inertia available to ERCOT. CAISO needs to supply real-time inertia information on their website. "Inertia" appears 34 times using the CAISO website search tool.
Nukes as all base load plants require off site power or emergency generators to keep the plant auxiliary equipment running when in startup or offline. Auxiliary systems are for example Coolant pumps to name one, but hundreds of other systems require vital power, both AC and DC. When a plant trips and goes offline the party is over. But an off line plant is not the same as an “Islanded Plant” requiring Black Start Power. Few understand the mechanics of elecric power generation let alone the transmission system and “Grid”. Last of all are the political hacks who are responsible for the mess they have created with a “Green Grid”. It takes a lifetime in the Industry to understand the dynamics of the Electric Power System. And no one knows it all.
My first month working in a 1200 MW plant I asked my Mentor where is the master frequency source for plants to sync to should the entire grid collapse. He said thats a good question son, and its a complicated answer. That began my long career in the Power Generation Industry. And I retired knowing that answer. Its too complicated for details here, but somewhere there will be a 60hz voltage available to synchronize to, even if it comes from a single Black Start plant that is islanded and becomes the master frequency generator at 60.8 hz for the next plant to sync to. Its a delicate dance to add loads and maintain frequency and voltage in increments as more plants are paralleled together. Sometimes it takes many tries at getting it right. Its so rare an event that few ever get to put into play what they think they know. The inertia of multiple rotating generators together adds stability as more loads and generators are added. And thats why what the Author of the Blog is telling is so terribly important. To my knowledge there are no Inverter based Black Start plants and for good reason. No rotational inertia.
And I ask are the Grid Modeling tools in use today good enough ? I dont know. My life in the industry was in Plant O&M. We had to make work what the Master Wizard Inventor Tesla gave us. We are literally back to the differences and shortcommings of Edisons DC system vs the Polyphase creations of Tesla.
Thanks for this excellent write-up on this subject. A question occurred to me while reading - shouldn't it be possible to outfit inverters with a feedback circuit that tracks the instantaneous grid frequency and continously adjusts the output frequency to match it?
The challenge is the massive amount of energy storage that would be required at each inverter based resource to achieve this frequency control (as well as the robust electronics required to handle the large instantaneous power requirements.) This is akin to the theoretical grid forming inverters (TGFI) mentioned in the article. Given that TGFIs are not yet available, I believe the best approach is to use synchronous grid inertia, as has been the case since about 1895. https://edisontechcenter.org/AC-PowerHistory.html
Hi EntropyWave you raise a key question, and the answer is absolutely yes. Inverters can be (and are) made to electronically mimic the effect of physical inertia and other effects needed for grid stability.
The best example of this on a large scale is the South Australian grid. South Australia is a large flat state with excellent wind and solar resources and very limited coal and limited interconnection with the rest of the Australian national grid. They installed the world's first large grid connected battery years ago. They now have multiple big batteries including several with what are called "grid forming inverters". These inverters provide everything you need to start and stabilise a grid and in fact they do it better than traditional fast response generation such as gas or hydro. They use these to successfully operate a grid that regularly reaches 100% wind and solar generation.
If Spain had installed batteries with grid forming inverters rather than relying on gas and hydro as backup they might have avoided their recent blackout. Blackouts caused by frequency control problems have been happening basically since large grids were first built. One good example was the massive 2003 blackout that covered a large part of US and Canada.
If you are interested finding out more reneweconomy.com.au is Australian website with a lot of information about these issues.
Regrettably, your post is filled with exaggerations regarding the current capabilities of inverter-based resources. The more than century-long history of alternating current generation shows the most cost-effective means to keep a grid stable is large rotating machines such as Diablo Canyon Power Plant with 500 tons of rotating mass per generator. This machine has currents of 25,000 Amperes flowing inside the generator while it provides about 5% of the dispatchable power to the large state of California. Perhaps in a century there will be advances in solid state electronics.... but there will also be advances regarding large rotating machines!
Hi Gene. My father had a slide rule; he showed it to me once when I was a kid. It certainly did a job but when he showed it to me, he had already moved on to using a calculator instead. The point I am trying to make is technology changes and new ways are found to do things.
I don't think I was exaggerating anything. The first grid forming inverter was installed in 2018. The grid regulator has been extremely cautious in relying on it. Over time the regulator has slowly decreased the amount of spinning generation mandated to the point as I said above the grid now regularly operates with !00% wind and solar. The grid is as reliable now as it ever was with 100% coal and gas.
I agree 500 tons of spinning mass is a huge amount of inertia and it provides a lot of stability to that grid. What I am saying though is technology changes and we find new and better ways of doing things.
You should look into the history of the SA grid. The interplay of politics, economics, engineering, new technology and basic physics is fascinating.
Hi, D.O. I'm old enough to own a really good Pickett Log-Log Decitrig metal slide rule. :-) The May, 2024 IEEE Spectrum has a good status report regarding grid forming inverters at https://spectrum.ieee.org/electric-inverter. (You will need to supply your name and get your email verified (which seems to take two passes.) to obtain no-cost access to this informative article.) The article focuses on the Kauai Island Utility Cooperative's (KIUC's) work with grid forming inverters, but also discusses Southern Australia's work. The KIUC experience includes a 26 MW oil-fired generator tripping off on a grid with an approximately 80 MW peak load. There will be significantly larger costs in scaling up this technology. Nuclear power plants are safer and much more cost effective while not producing air or water pollution.
The article shows the battery electric energy storage requirements for this small power grid are substantial, but is silent regarding their substantial cost.
California recently had a very expensive battery fire at Moss Landing. The likely total cost will be several hundred million dollars. The Socialist government of Spain has been taxing their nuclear power plants to subsidize solar power plants. https://www.wsj.com/opinion/how-the-lights-went-out-in-spain-solar-power-electric-grid-0096bbc7?st=eGskdG&reflink=desktopwebshare_permalink The Spanish and Portugese power grids suffered a major blackout on Monday, April 28, 2025. The IEEE Spectrum article underscores the importance of synchronous grid inertia. Spain's recent experience demonstrates the folly of legislation which ignores the laws of physics.
This is an important and well-written article regarding the important role of inadequate synchronous grid inertia as the root cause of the 28 April 2025 Iberian Peninsula blackout which killed at least nine people.
"Casting blame for the blackout in Spain, Portugal, and parts of France,"
by Russ Schussler (Planning Engineer) 05 May 5, 2025, Judith Curry Weblog.
As the amount of solar generation increases in Texas, there is a greater risk of insufficient synchronous grid inertia. The state could be on track to emulate Spain with the April 28, 2025 Iberian Peninsula blackout due to insufficient synchronous grid inertia.
ERCOT released on April 16, 2025 a very informative study examining their annual trends for inertia. The Spring, 2025 trends shown on the next to the last slide in the slide deck are concerning, as they show significant displacement of CC Natural gas-fired generation by solar during the mid-day https://www.ercot.com/files/docs/2025/04/16/ERCOT_Annual_Inertia_2014-2024_2025_PDCWG_Final.pptx
Kenneth Kaminski, who worked at DCPP for more than 30 years informed me that I had an incorrect value for the rotating mass for each DCPP generator. The total rotating mass of a DCPP generator and turbines is an unprecedented 500 tons, not the 50 tons that I used. That means each DCPP generator produces roughly 25 times the SGI as each Helms Pumped Storage generator. There are two generators at DCPP. DCPP's SGI is far more important for California than I initially calculated. Keep Diablo Canyon running!
As of February 2, 2025, GreenNUKE has grown to 608 subscribers. "Why is Grid Inertia Important?" remains the most popular article with 75 likes and 65 comments. I appreciate the relevant content being added in the comments. This illustrates the power of Substack.
Very good explanation of inertia. It might be worth noting that inertia in the network is actually defined as kinetic energy MW-s. What is your opinion of the potential of sync condensers to replace generator inertia?
Thanks. I actually work in this area professionally, although my training is Mech Eng. My team is studying FFR, SFR, ROCOF etc and NERC has issued some good white papers on the subject. Obviously LOTS of people are studying this subject and to me the main questions are A) Can a very high VRE penetration system with mostly IBR operate with required reliability at all? and B) At what cost? Most people are working with the assumption that it IS possible to operate even a fully IBR system with no inertia and fully relying on power injection via batteries (and maybe some inertia with sync condensers and synthetic inertia from wind) but it is not yet demonstrated. If you have any good references from CIGRE, IEEE, NERC or others I would love to read them. Thanks.
Empirical Science posted a couple comments for me with links sharing information on the Great Britain flywheel synchronous condenser installs. GB has very heavy offshore wind intrusion in their system. They run the flywheels in a vacuum to reduce windage.
Thanks for that. So are these actual sync condensers where the fields can be controlled, or more storage devices for power injection? Running in vacuum makes sense, but never heard of for sync condensers before.
Since the formula for SGI has an "omega squared" term, high RPMs in synchronous condensers would be advantageous. They are motor-generator units. Where can I find the rotation speed for typical synchronous condensers?
Very well said. And for some reason, very few people understand this issue. Even professionals. This is one of the few articles I've read that actually describes things correctly, using the correct units and values.
Without inertia, the grid simply cannot function.
To put it another way, wind and solar may cost less than nuclear to generate but often are worth much less in the market. Wind and solar are just not very desirable to a utility, since they lack inertia and dispatchability, and often create more headaches than they are worth.
I agree. My summary is that solar, wind, and batteries are "junk power." Solar, wind, and batteries are actually parasitic, serving only public relations purposes. A grid without solar and wind tends to have lower emissions and certainly lower costs. (Please consider liking my article.)
Looks like technology has caught up with the issue of IBRs providing ancillary services. Grid forming inverters (GFM) are now available and are providing grid inertia for grid frequency stabilization. These new inverters can also provide black start capability. They are successfully being used in a small grid in Kauai. A large grid like ERCOT is working towards adding more GFMs.
NERC issued a standard for them in 2023, “GFM specs for Battery Systems” BESS
Thank you for the new reference. Per https://www.kiuc.coop/generation-portfolio, their Tesla BESS system is rated at 13 MW for 4 hours. It is a tiny start, but a far cry from DCPP, which is rated at 2,256 MW and runs for about 13,500 hours between refueling outages. The link I provided shows that the KIUC generation fleet is mostly fossil-fired instead of solar. This makes sense as the solar generation runs only about 25% of the time. Solar plus batteries would not be a cost-effective power grid for Kauai.
Here's a relevant new Substack post from David Turver at Eigen Values: Offshore Wind: Follow the Money - UK billpayers subsidising overseas investors and getting expensive, unreliable energy in return by David Turver, March 9, 2024.
https://davidturver.substack.com/p/offshore-wind-follow-the-money
While U.K. centric, this article will help you to understand why the economic elites advocating for fickle offshore wind oppose safe, reliable, abundant, cost-effective and zero - emission nuclear power, such as that produced at Diablo Canyon Power Plant.
For some historical context, here's an article from a dozen years ago that is spot on today:
Broken down and rusting, is this the future of Britain's 'wind rush'?
By Tom Leonard, Published 21:00 EDT, 18 March 2012, The Daily Mail (U.K.)
https://www.dailymail.co.uk/news/article-2116877/Is-future-Britains-wind-rush.html
A similar look at solar would be very useful, I expect the pattern is similar
Here's a post by Robert Bryce that is complementary to several themes I wrote about in this article. https://robertbryce.substack.com/p/these-10-charts-caused-an-ngo-hissy My next article will cover how hydroelectric pumped storage is being used for grid frequency stabilization instead of bulk energy storage.
Here''s some additional information regarding grid inertia. (However, I disagree with the author's claim that wind power is capable of providing significant amounts of synchronous grid inertia. This glossary provides definitions for the acronyms included below.)
Glossary of Electric and Gas Industry Terms and Concepts - Indiana Utility Regulatory Commission, Updated and Revised February, 2022
https://pubs.naruc.org/pub/DD7DB67E-1866-DAAC-99FB-36526B06C7C6
Inertia – as Voltage Support (see also Automatic Generation Control - AGC, Area Control Error (ACE), Frequency, and Kinetic Energy): Baseload coal and nuclear generators, like natural gas generators other rotating machines (motors and generators) including wind turbines provide needed inertia to support frequency throughout an entire electric interconnection. At the instant load changes, the system must change generation to match so power into the system must equal power out. Since it is not feasible to change the fuel output or steam input of the generators on a split second basis, the rotating kinetic energy of every machine in the entire interconnection serves to help balance the system. For example, when a light is turned on, the energy needed comes from kinetic energy and the machines slow down and frequency drops. For a single light switch the drop in frequency is imperceptible. However, a rolling mill at a steel plant may cause a perceptible change. The Automatic Generation Control (AGC) system, on most large generating units, almost instantaneously recognizes the Area Control Error (ACE), which is a combination of the frequency drop and the importation of power from the rest of the interconnection as energy is supplied by their machines, and adjusts the output setting of the generators to restore frequency and tie-line flow. Thus, every piece of rotating equipment supplies inertia, including wind turbines (but not solar panels). Of course, large steam-powered turbines have considerably more inertia than a wind turbine (unless there are a few hundred of them) and wind turbines generally do not have the automatic generation control aspect of being able to react to the area control error.
Inertial Response: This is the kinetic energy stored in the rotating mass of all of the synchronized turbine generators and motors on the interconnection. Produced by the slowing of the spinning inertial mass of rotating equipment on the interconnection that both releases the stored kinetic energy and arrests the decline of the interconnection frequency. This happens immediately following a disturbance.
Good one Gene,
There is a fundamental lack of understanding of the technical electrical power engineering theory and practice and how inductive and capacitative supply and loads on an electrical system.
The system is designed around synchronous generation which is inductive and renewables are capacitative on my understanding.
I'm not an electrical engineer, I was a Reactor Physicist and latterly an Operations Engineer for over 20 years, and a lot of people just think its power in and out.
They have no idea of the potential problems of large amounts of intermittent non synchronous generation might have on the reliability of a power grid system.
Thanks for attempting it! beyond my engineering skills!
Thank you. I agree the AC power grid has been designed around synchronous generation. Please note my comments posted on March 13, 2024 above which outline the "TGFI problem."
No problem and thank you. Sorry for the delay in replying but my campaign against expensive renewables driving the UK to the most expensive energy in the world continues!
Please maintain your advocacy. Solar, wind, and batteries fail to provide the important synchronous grid inertia (SGI) that the UK needs. Gas-fired peaker (turbine) generators do not supply significant amounts of SGI. The task is left to nuclear, combined-cycle gas, and coal-fired generators. Since large hydroelectric generators run a much lower RPMs than the above thermal generation, they don't provide as much SGI, since SGI is proportional to the angular frequency squared.
Perhaps those leading us into the wind and PV ‘black hole’ are ignorant of the differences between AC and DC systems .. to them is ‘just electricity’. That’s what you get when the decision makers have no physics or engineering knowledge/background ☹️ The man leading us into the Net Zero black hole in the UK has a degree in Politics, Philosophy and Economics which would explain a few things. Oddly he did study advanced math at high school.
The situation you describe is very dangerous. It is one of the reasons for my public outreach to help decision-makers to understand the folly of "Net Zero."
There is a fundamental difference between Ed Milliband's understanding of energy and that of someone who works in the industry. He hasn't a clue about the intermittency of renewables, the cost of hydrogen or grid batteries or of reactive load management of system inertia. He's going to come a cropper very shortly.
He came very close to having that moment of awful realisation last month. I highly recommend watching the Unherd documentary on this which puts in the details AND the cover up.
https://youtu.be/Kjl_HjEL3Sc
Secretary of State for Energy and Climate Change of the United Kingdom
Ed Miliband needs to obtain some knowledge of how the electric grid actually works from knowledgeable scientists and engineers. This GreenNUKE article would be a good place for him to start. Could you please send it to him?
He wouldn't listen if you explained it in a children's book. What we are hoping for is that he goes ahead, bills go through the roof and we get blackouts and then that's finally the fantasy of net zero in the bin and he will have done the world a great service and got rid of net zero and this government in one move.
Sigh.... The challenge is that when the blackouts hit the U.K. while it is freezing outside, people will die. Since humans are warm-blooded animals, about 5 times as many people die during extreme cold events compared to extreme heat events.
A very informative 2018 technical article regarding the importance of synchronous grid inertia [SGI] from the Electric Reliability Council of Texas (ERCOT) is "Inertia: Basic Concepts and Impacts on the ERCOT Grid," April 4, 2018, Electric Reliability Council of Texas (ERCOT,) Austin, Texas, USA.
https://www.ercot.com/files/docs/2018/04/04/Inertia_Basic_Concepts_Impacts_On_ERCOT_v0.pdf
This article underscores that nuclear power plants (like DCPP) provide the largest amount of SGI. The article notes neither solar nor wind provide significant amounts of SGI. Since ERCOT has negligible interconnection to any other U.S. power grids, their grid functions effectively as the power grid on an island. ERCOT established a minimum SGI constraint they call "Critical Inertia;," described in section 6 of this report. Since ERCOT is a large system, the value of Critical Inertia is also large. To ERCOT's credit, their real-time system dashboard shows the amount of inertia available to ERCOT. CAISO needs to supply real-time inertia information on their website. "Inertia" appears 34 times using the CAISO website search tool.
Nukes as all base load plants require off site power or emergency generators to keep the plant auxiliary equipment running when in startup or offline. Auxiliary systems are for example Coolant pumps to name one, but hundreds of other systems require vital power, both AC and DC. When a plant trips and goes offline the party is over. But an off line plant is not the same as an “Islanded Plant” requiring Black Start Power. Few understand the mechanics of elecric power generation let alone the transmission system and “Grid”. Last of all are the political hacks who are responsible for the mess they have created with a “Green Grid”. It takes a lifetime in the Industry to understand the dynamics of the Electric Power System. And no one knows it all.
My first month working in a 1200 MW plant I asked my Mentor where is the master frequency source for plants to sync to should the entire grid collapse. He said thats a good question son, and its a complicated answer. That began my long career in the Power Generation Industry. And I retired knowing that answer. Its too complicated for details here, but somewhere there will be a 60hz voltage available to synchronize to, even if it comes from a single Black Start plant that is islanded and becomes the master frequency generator at 60.8 hz for the next plant to sync to. Its a delicate dance to add loads and maintain frequency and voltage in increments as more plants are paralleled together. Sometimes it takes many tries at getting it right. Its so rare an event that few ever get to put into play what they think they know. The inertia of multiple rotating generators together adds stability as more loads and generators are added. And thats why what the Author of the Blog is telling is so terribly important. To my knowledge there are no Inverter based Black Start plants and for good reason. No rotational inertia.
And I ask are the Grid Modeling tools in use today good enough ? I dont know. My life in the industry was in Plant O&M. We had to make work what the Master Wizard Inventor Tesla gave us. We are literally back to the differences and shortcommings of Edisons DC system vs the Polyphase creations of Tesla.
Thank you for your confirmation of the importance of synchronous grid inertia.
"It takes a lifetime in the industry to understand the dynamics of the Electric Power System. And no one knows it all."
The grid is literally the most complex thing ever created by mankind. It has taken a century to build.
But no worries, politicians and activists know everything they need to know to "fix" it. ;)
Thanks for this excellent write-up on this subject. A question occurred to me while reading - shouldn't it be possible to outfit inverters with a feedback circuit that tracks the instantaneous grid frequency and continously adjusts the output frequency to match it?
The challenge is the massive amount of energy storage that would be required at each inverter based resource to achieve this frequency control (as well as the robust electronics required to handle the large instantaneous power requirements.) This is akin to the theoretical grid forming inverters (TGFI) mentioned in the article. Given that TGFIs are not yet available, I believe the best approach is to use synchronous grid inertia, as has been the case since about 1895. https://edisontechcenter.org/AC-PowerHistory.html
Ah, gotcha. Thanks for pointing that out to me.
Hi EntropyWave you raise a key question, and the answer is absolutely yes. Inverters can be (and are) made to electronically mimic the effect of physical inertia and other effects needed for grid stability.
The best example of this on a large scale is the South Australian grid. South Australia is a large flat state with excellent wind and solar resources and very limited coal and limited interconnection with the rest of the Australian national grid. They installed the world's first large grid connected battery years ago. They now have multiple big batteries including several with what are called "grid forming inverters". These inverters provide everything you need to start and stabilise a grid and in fact they do it better than traditional fast response generation such as gas or hydro. They use these to successfully operate a grid that regularly reaches 100% wind and solar generation.
If Spain had installed batteries with grid forming inverters rather than relying on gas and hydro as backup they might have avoided their recent blackout. Blackouts caused by frequency control problems have been happening basically since large grids were first built. One good example was the massive 2003 blackout that covered a large part of US and Canada.
If you are interested finding out more reneweconomy.com.au is Australian website with a lot of information about these issues.
Regrettably, your post is filled with exaggerations regarding the current capabilities of inverter-based resources. The more than century-long history of alternating current generation shows the most cost-effective means to keep a grid stable is large rotating machines such as Diablo Canyon Power Plant with 500 tons of rotating mass per generator. This machine has currents of 25,000 Amperes flowing inside the generator while it provides about 5% of the dispatchable power to the large state of California. Perhaps in a century there will be advances in solid state electronics.... but there will also be advances regarding large rotating machines!
Hi Gene. My father had a slide rule; he showed it to me once when I was a kid. It certainly did a job but when he showed it to me, he had already moved on to using a calculator instead. The point I am trying to make is technology changes and new ways are found to do things.
I don't think I was exaggerating anything. The first grid forming inverter was installed in 2018. The grid regulator has been extremely cautious in relying on it. Over time the regulator has slowly decreased the amount of spinning generation mandated to the point as I said above the grid now regularly operates with !00% wind and solar. The grid is as reliable now as it ever was with 100% coal and gas.
I agree 500 tons of spinning mass is a huge amount of inertia and it provides a lot of stability to that grid. What I am saying though is technology changes and we find new and better ways of doing things.
You should look into the history of the SA grid. The interplay of politics, economics, engineering, new technology and basic physics is fascinating.
Hi, D.O. I'm old enough to own a really good Pickett Log-Log Decitrig metal slide rule. :-) The May, 2024 IEEE Spectrum has a good status report regarding grid forming inverters at https://spectrum.ieee.org/electric-inverter. (You will need to supply your name and get your email verified (which seems to take two passes.) to obtain no-cost access to this informative article.) The article focuses on the Kauai Island Utility Cooperative's (KIUC's) work with grid forming inverters, but also discusses Southern Australia's work. The KIUC experience includes a 26 MW oil-fired generator tripping off on a grid with an approximately 80 MW peak load. There will be significantly larger costs in scaling up this technology. Nuclear power plants are safer and much more cost effective while not producing air or water pollution.
The article shows the battery electric energy storage requirements for this small power grid are substantial, but is silent regarding their substantial cost.
California recently had a very expensive battery fire at Moss Landing. The likely total cost will be several hundred million dollars. The Socialist government of Spain has been taxing their nuclear power plants to subsidize solar power plants. https://www.wsj.com/opinion/how-the-lights-went-out-in-spain-solar-power-electric-grid-0096bbc7?st=eGskdG&reflink=desktopwebshare_permalink The Spanish and Portugese power grids suffered a major blackout on Monday, April 28, 2025. The IEEE Spectrum article underscores the importance of synchronous grid inertia. Spain's recent experience demonstrates the folly of legislation which ignores the laws of physics.
Hi Gene thanks for the reference I'll look it up.
Very informative read! Thank you for going over this critical topic.
This is an important and well-written article regarding the important role of inadequate synchronous grid inertia as the root cause of the 28 April 2025 Iberian Peninsula blackout which killed at least nine people.
"Casting blame for the blackout in Spain, Portugal, and parts of France,"
by Russ Schussler (Planning Engineer) 05 May 5, 2025, Judith Curry Weblog.
https://judithcurry.com/2025/05/05/casting-blame-for-the-blackout-in-spain-portugal-and-parts-of-france/
As the amount of solar generation increases in Texas, there is a greater risk of insufficient synchronous grid inertia. The state could be on track to emulate Spain with the April 28, 2025 Iberian Peninsula blackout due to insufficient synchronous grid inertia.
ERCOT released on April 16, 2025 a very informative study examining their annual trends for inertia. The Spring, 2025 trends shown on the next to the last slide in the slide deck are concerning, as they show significant displacement of CC Natural gas-fired generation by solar during the mid-day https://www.ercot.com/files/docs/2025/04/16/ERCOT_Annual_Inertia_2014-2024_2025_PDCWG_Final.pptx
Here's an important update to this article:
Comparison of DCPP's SGI to Helms Pumped Storage
DCPP is the greatest contributor to California in-state Synchronous Grid Inertia (SGI)
GENE NELSON, Ph.D.
MAR 24, 2025
https://greennuke.substack.com/p/comparison-of-dcpps-sgi-to-helms
Kenneth Kaminski, who worked at DCPP for more than 30 years informed me that I had an incorrect value for the rotating mass for each DCPP generator. The total rotating mass of a DCPP generator and turbines is an unprecedented 500 tons, not the 50 tons that I used. That means each DCPP generator produces roughly 25 times the SGI as each Helms Pumped Storage generator. There are two generators at DCPP. DCPP's SGI is far more important for California than I initially calculated. Keep Diablo Canyon running!
As of February 2, 2025, GreenNUKE has grown to 608 subscribers. "Why is Grid Inertia Important?" remains the most popular article with 75 likes and 65 comments. I appreciate the relevant content being added in the comments. This illustrates the power of Substack.
Here's additional information dated October 30, 2024 regarding the topic of synchronous grid inertia at Kilovar 1959's Substack. "Power Systems - Inertia- Big Iron Rolling" https://kilovar1959.substack.com/p/power-systems-inertia-big-iron-rolling Please read this article.
Very good explanation of inertia. It might be worth noting that inertia in the network is actually defined as kinetic energy MW-s. What is your opinion of the potential of sync condensers to replace generator inertia?
Thanks. It would require such a large quantity of synchronous condensers to replace DCPP for example. It iis not a cost-effective approach.
Thanks. I actually work in this area professionally, although my training is Mech Eng. My team is studying FFR, SFR, ROCOF etc and NERC has issued some good white papers on the subject. Obviously LOTS of people are studying this subject and to me the main questions are A) Can a very high VRE penetration system with mostly IBR operate with required reliability at all? and B) At what cost? Most people are working with the assumption that it IS possible to operate even a fully IBR system with no inertia and fully relying on power injection via batteries (and maybe some inertia with sync condensers and synthetic inertia from wind) but it is not yet demonstrated. If you have any good references from CIGRE, IEEE, NERC or others I would love to read them. Thanks.
Empirical Science posted a couple comments for me with links sharing information on the Great Britain flywheel synchronous condenser installs. GB has very heavy offshore wind intrusion in their system. They run the flywheels in a vacuum to reduce windage.
Thanks for that. So are these actual sync condensers where the fields can be controlled, or more storage devices for power injection? Running in vacuum makes sense, but never heard of for sync condensers before.
Actual rotating sychronous condenser with field windings and stator, not Statcoms or static var compensators.
I invited Empirical Science to join the thread.
Since the formula for SGI has an "omega squared" term, high RPMs in synchronous condensers would be advantageous. They are motor-generator units. Where can I find the rotation speed for typical synchronous condensers?
Very well said. And for some reason, very few people understand this issue. Even professionals. This is one of the few articles I've read that actually describes things correctly, using the correct units and values.
Without inertia, the grid simply cannot function.
To put it another way, wind and solar may cost less than nuclear to generate but often are worth much less in the market. Wind and solar are just not very desirable to a utility, since they lack inertia and dispatchability, and often create more headaches than they are worth.
I agree. My summary is that solar, wind, and batteries are "junk power." Solar, wind, and batteries are actually parasitic, serving only public relations purposes. A grid without solar and wind tends to have lower emissions and certainly lower costs. (Please consider liking my article.)
Looks like technology has caught up with the issue of IBRs providing ancillary services. Grid forming inverters (GFM) are now available and are providing grid inertia for grid frequency stabilization. These new inverters can also provide black start capability. They are successfully being used in a small grid in Kauai. A large grid like ERCOT is working towards adding more GFMs.
NERC issued a standard for them in 2023, “GFM specs for Battery Systems” BESS
https://www.nrel.gov/docs/fy24osti/90256.pdf
Thank you for the new reference. Per https://www.kiuc.coop/generation-portfolio, their Tesla BESS system is rated at 13 MW for 4 hours. It is a tiny start, but a far cry from DCPP, which is rated at 2,256 MW and runs for about 13,500 hours between refueling outages. The link I provided shows that the KIUC generation fleet is mostly fossil-fired instead of solar. This makes sense as the solar generation runs only about 25% of the time. Solar plus batteries would not be a cost-effective power grid for Kauai.