A recent series of posts at Judith Curry’s Climate Etc. blog has examined the Australian renewable energy transition. Here is Part 3.
It’s well worth reading.
It’s a fact that a stable, reliable, modern electricity grid requires mechanical inertia which up until the point where we became obsessed with ‘Green’ energy, was provided by the large moving flywheels of gas turbines and coal fired power stations. Solar and wind power provide no inertia to the grid. So, if you’re expanding the use of renewables and closing down fossil fuel power stations, then you are reducing the total amount of inertia available, which is essential for grid stability, i.e. maintaining the frequency of current measured in Hertz within very narrow and strict limits, right across the grid. Large variations in frequency can cause generators to trip, resulting in widespread blackouts.
The authors of the article above explain the importance of inertia for stability:
Frequency Control & Inertia
The frequency is the timing between wave cycles in an AC system 60Hz (a Hertz is one cycle per second) and 50Hz in most of the rest of the world. The frequency has to be the same across the whole grid – it is one of the things that defines it. A stable grid frequency is critical for effective operation. Thermal plants usually provide this by using governor control, whereby the frequency drives the plant output through a negative feedback device. The grid system operators may also run real time or short period dispatch, whereby the plant operators increase or decrease load over short time periods on grid operator’s instructions.
The inertia, provided by the rotating machinery of the generator, serves to slows the rate of change of frequency (RoCoF) . The slower the frequency changes occur, the less stress for the plant on governors. And as there is linkage, a small RoCoF in “normal” grid fluctuations will also stabilise the voltage and reactive power requirements.
However in recent times, there have been significant and rapid swings in the Australian grid frequency between the control limits, shown in the graph below. The gray region is the deadband of allowable frequencies where no intervening measures need be taken by the grid operators. When outside the deadband region, generators are supposed to be offering primary frequency response support – for underfrequency (load is greater than generation), grid operators increase the generators’ output. This is either done automatically or by dispatching plant to increase load. From the rate of frequency decline, calculations indicate there could have been at least 600MW shortfall in generation over the five minute dispatch process. The cause of the variability observed hasn’t been positively identified, but is likely to be uncontrolled solar generation. If that is the case, then it indicates that faster acting and more expensive frequency control services are needed.
Where traditional power stations are being decommissioned and replaced with renewables, inertia can be provided by either batteries or so called ‘synchronous condensers’. However, it would appear that batteries are not really suitable, so it comes down to synchronous condensers:
Inertia on a renewables grid can be provided by synchronous condensers or by large battery banks with specialised electronics. Of course, the batteries have to have enough charge in them to function, so they are reserved for just that purpose and thus can’t be used for other purposes like general market dispatch. However, AEMO does not appear to believe that renewables and batteries are a substitute for the frequency response provided by synchronous units. To quote the latest available report:
“To comply with the requirements of IPFRR, Semi-Scheduled generators will typically need control of active power that allow for simultaneous MW curtailment, MW ramping, frequency response outside a relatively small frequency deadband, and ongoing variation in input energy. While such MW control capabilities do often exist in isolation, when they are tested simultaneously, and in an ongoing manner, software problems have often been found. This then requires further development, updates and testing to address, a process that has in some cases proven significantly more time consuming than initially expected.”
Synchronous condensers are all the rage nowadays; they’re the exciting ‘new’ technology which will enable renewables penetration into national grids, so the ‘just’ clean energy transition can go ahead:
But it’s not a new technology; it’s a 100 year old sticking plaster needing to be applied (at huge expense) to national grids everywhere in order to ensure that increasing wind and solar power do not destabilise those grids, which they are currently doing, and causing major blackouts. Modern national grid infrastructures were hugely stable, efficient, reliable wonders of engineering before the introduction of renewables; power generation from fossil fuel burning and nuclear plants was seamlessly incorporated into the national distribution infrastructure to reliably power homes and businesses throughout nations, even exporting any surplus to other nations. Now, we have clunky, unreliable ‘Green energy’ mal-adapted grids which are failing. Here’s the truth:
Synchronous condenser technology has been around almost as long as the electric grid itself to support transmission system reliability, says GE. As the grid became more mature and reliable over the decades, synchronous condensers eventually became regarded as obsolete, with many utilities discontinuing use of the technology. Today, however, as the grid has experienced increasing instability, the technology is undergoing a major comeback with all major synchronous condenser manufacturers reporting higher sales.
Synchronous condensers were obsolete. Despite this, GE claim to have ‘reinvented’ the technology for the new age of renewables:
GE’s air-cooled high inertia synchronous condenser systems can be rated to 2,000+ MW with added flywheels. Due to the nature of the rotating equipment, the enhanced inertia is system inherent, providing an instantaneous power feed in the event of a grid frequency drop. The synchronous condenser system can boost system inertia and provide voltage support with a unique overload capability and provides significant short-circuit strength to the grid network.
Can GE stabilize my grid with synchronous condensers?
YES. We have been leading the way with synchronous condenser technology for over a century, and as part of our renewable steam power portfolio, we have reinvented this technology to support grid owners with the challenges that accompany the use of more renewable energy. Globally, we have supplied more than 200 synchronous condensers in our efforts to support our customers with critical technology and services for a transforming grid and cleaner energy future. This is the Power of Yes.
What utterly absurd, boastful claims from GE: ‘New improved 100 year old technology (with added flywheels) because renewables screwed up perfectly stable and reliable national grids, so we have to try and make them more reliable again by applying sticking plasters all over the place’.
I live in Luddite country- looking forward to a version of Pol Pots year zero and the death of science. Our energy minister Bowen needs an IQ test and a psych assessment. Yesterday he was saying we can’t have nuclear energy because we don’t have a nuclear industry or expertise. We’ve had a nuclear reactor in Lucas Heights since 1956 for nuclear medicine. Then the Marxist leader of Victoria has commissioned an offshore wind farm using public money,and sold it to a Danish investment company. He has spent enormous amounts on green energy, won’t allow gas production and doesn’t have even one solar panel on his house. The hypocrisy of these green energy zealots knows no bounds.
"as part of our renewable steam power portfolio"
Steam? Renewable? Our up-to-the-minute tech invented by James Watt and George Westinghouse, with a timely assist by Nikola Tesla.
With GE now a Franco-American partnership, could this be brand positioning for green nuclear?
Added 1 day later....
Turns out that it is coal and nuclear:
Massive amounts of new renewable energy capacity and the need to reduce CO2 emissions are impacting the use of coal power and prompting a renewed interest in nuclear energy. At the same time, nearly half of all power globally today is still produced from coal and nuclear. Our customers are balancing the challenge of lowering CO2 and providing affordable, reliable power.
I approve. Australia already produces most of its electricity from coal, and is commited to invest in GB Roll-Royce nuclear steam turbines for its submarines. Stop messing about with inadequate, unreliable Chinese wind turbines and pv panels.