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Inverters can easily replace physical inertia, it just requires technology developed within the past 30 years, and most grid folks haven't thought about new technology for far longer than that.

As more and more intermittent renewables get pushed onto grids, they become more reliable. Most outages are from single points of failure from large generators or transmission. Dealing with highly distributed renewables means that grid ops get used to acting fast, and there's greater redundancy instead of so many SPOF. Kind of how cloud services got reliable by expecting there to be failure and designing it into the system.

Storage is advancing super quickly, is super fast to deploy, and can replace a lot of more expensive things like transmission upgrades.

We have all the tech to replace fossil fuels on the grid with the above. The only question is the final cost. It's likely to be far far lower than using existing "hard" energy, because by the time we can deploy 50 TWhs of storage, it will have gotten so cheap. We don't know when costs will stabilize, but they have a loooong distance to fall.

And we have all sorts of other technologies that will make all this far cheaper: enhanced geothermal, enhanced geothermal with temporal storage based on injection pressure and release, iron air batteries, flow batteries, thermal storage for industrial process heat, etc. etc. etc.

For every area of the energy economy, there are two to three solutions that look promising. Fusion and fission look promising for none. That's not to say that they can't have some serious innovation and start dropping their costs, but nobody currently operating in the field has demonstrated a path. Yet.

What new technology changes things to not require spinning turbines?

Massive improvements to battery technology.

That’s a non answer - what improvement

It is an answer, in that batteries were used for frequency regulation far before they were used for energy arbitrage.

But the real innovation is communication networks and IC control of the inverter. It's completely possible to create a waveform that modulates and responds to variation in frequency in the same way a large spinning mass would. And if reactive power is for some reason not enough, synchronous condensers are very old technology to solve that.

Integrated circuits, basically. The term if "grid forming inverter" and the standards are somewhat new. I'm not an expert, but here is one standard, I don't know if it has been adopted or if others are preferred:

https://www.energy.gov/sites/default/files/2023-09/Specs%20f...

And they have been used where? Everything I can find suggests they are theoretical, not in use even on micro grids yet, and many have huge concerns about them being able to support a grid on their own.

Also the technology required has been around for decades it’s not new and no one’s done it yet.

So again what’s changed because it seems like for now there is no “I have a grid and need something now” solution it’s a “maybe one day”

> As more and more intermittent renewables get pushed onto grids, they become more reliable

This is called grid firming, and it’s massively expensive.

I don't think that's the same thing, but what expenses are you thinking of specifically? The German grid for example got much more reliable with additional solar.

Grids were designed to operate in tight tolerances. Cycling power levels up and down a lot, while handling the frequency variation lots of renewables inputs bring, wears down the grid without protective measures. Those measures are called firming [1].

Not sure what Germany did (or plans to do—you can run an unfirmed grid until stuff starts failing for several years).

[1] https://www.gevernova.com/gas-power/applications/grid-firmin...

If every (second) house would have a powerwall, wouldn't that make the grid stable?

A powerwall is $12k installed.

That's about 5 years worth of power bills for most people.

> every (second) house would have a powerwall, wouldn't that make the grid stable?

At 131mm American households [1] and $11.5k per PoweWall [2] that’s over $750bn at 50% loading.

[1] https://www.statista.com/statistics/183635/number-of-househo...

[2] https://www.thisoldhouse.com/solar-alternative-energy/review...

China is starting to mass produce NaCl batteries. They will be cheaper.

And also only Powerwalls produced in this quantity would have way lower prices. My point was batteries are getting cheaper every day.

It could be less stable, if each and every powerwall is slightly out of phase.

But this is something, one can avoid by only allowing well tuned batteries to the grid? Or is this a serious problem to get right?

"Capacity firming" will be carried out by legacy gas turbines as they run less and less, and eventually by batteries.

Batteries are also much better than gas at frequency regulation, and even at the prices a decade ago, completely took over the market for frequency regulation in the PJM market in the US. But frequency regulation is very very tiny in terms of power needs, it only takes a very small number of grid batteries to completely solve that problem.

The amount of batteries waiting in the interconnection queue completely dwarfs gas. There will be no "firming" coming from new gas turbines, unless old-school corrupt utilities are able to sneak it by PUCs by creating some sort of crisis and tricking them.

> "Capacity firming" will be carried out by legacy gas turbines as they run less and less, and eventually by batteries

At least among the American TSOs, there are zero I know of that plan to do this. Do you have a source for one that does?

Trillions have already been spent on gas. That infrastructure will need to earn its return through the 2040s at the very least, and that precludes running them exclusively for firming. To the extent retrofits are being discussed, it’s as an add-on amidst full peaked functionality.

> Batteries are also much better than gas at frequency regulation

Limiting solar and wind by utility-scale battery capacity means scaling back EV adoption or solar and wind deployment. The math simply doesn’t work. (Again, in America. Without significantly raising rates. Not sure elsewhere.)

> it only takes a very small number of grid batteries to completely solve that problem

Frequency regulation is one component of firming. Batteries are good at some components, marginal at others. (As a system. Technologically, they're fine.)

Apart from de-industrialised grids, a batteries-only approach has been practically abandoned through the 2030s. It's why we're building so many turbines and abandoning nukes.

> grid... grid-scale power storage... stability of the grid ... grid-following inverter ... grid stabilized by ...

The problem isnt solar, or wind, or storage ... the problem is the grid. Were running on a system that was never designed to do what were asking of it, and yes its going to be a number of problems to solve. All of those are jobs, economic action and improvements to reliability and quality across the board.

> I don't think they're controllable enough to be mechanically synced to the grid frequency.

Google, there are a number of ways this gets addressed.

> There has been some work on grid-forming inverters

Yes, we know how, and the race to build them is on... this isnt a hard problem it's just a problem.

> grid-scale power storage (has never been done so ?

Already deployed in a few places with battery systems (hati, Australia both have them. Possibly Hawaii too). We're doing quite a bit of this. Again a quick google will give you a sea of sources.

Battery backed renewable energy with grid upgrades is cheaper today and getting cheaper.

https://www.csiro.au/en/research/technology-space/energy/Gen...

> Most current solar power sources rely on grid-following inverters

There are now inverters that simulate the rotational inertia. They simlpy shift the phase of the generated waveform just a bit if the frequency starts dropping.

And it doesn't require any expensive additional hardware.

I think the solution will come from storage but also from a massive grid-wide ability to shed non-critical loads on-demand. The current grid is built on early 20th century principles, before we had real-time digital communications.

As a though experiment - imagine a 19th century world suddenly getting all of our current digital tech and wind farms and solar power - there would be no point in trying to create a "static" grid where producers and consumers weren't communicating with each other. Every consumer would negotiate power availabity based on momentary price.

Batteries can mimic inertia better than physical spinning objects.

An operator in Australia has seen massive success and profits over the past few years using batteries to out-compete other grid stabilization. IIRC, they have already made enough to pay off the upfront costs. Even better, Australian government was super against the change, but now most places are positive on them because of the obvious success.

Regarding stability, this physical inertia is also present in rotating wind turbines. But I guess exploiting this at a meaningful scale would recquire a level of interconnectivity which boils down to the same issue of cost.

I am however optimistic about grid-scale storage. There is a long term trend of rapidly dropping battery prices, and with recent developments in sodium ion batteries there is no fundamental reason this won´t continue. Another enabler could be advancements in lifespan. This could allow storage being installed inside or near wind and PV, cutting down on space and installation costs. Even then however, grid improvements would be needed.

Some problems still need to be solved indeed, but in my (mostly uneducated) opinion, they seem easier than achieving economically viable fusion. But they do still require large investments in R&D and manufacturing capability.

Wind turbines do not provide grid inertia.

They do not spin at 50/60hz, they are deployed with frequency converters to match optimum generation to the grid and spin at whatever speed they can achieve.

They're essentially another type of solar plant.

Wind turbines don't get the same feedback like traditional generator turbines do.

Wind turbines are designed to run on unstable wind speed -- this meant it have to somehow decouple from the main grid

> grid-scale power storage (has never been done so ? on cost to build and upkeep)

This is out of date. Grid scale battery storage has recently become economic in lots of cases and is ramping up quickly.

> Grid scale battery storage has recently become economic in lots of cases and is ramping up quickly

Being economic and being cheapest are worlds apart.

Solar or wind + utility-scale storage come in at 46 to 102 and 42 to 114 $/MWh, respectively, in terms of LCOE [1]. That does not include grid firming costs [2], which could raise the upper end of those figures to $120 or more, and is based on current storage prices; if everyone tries to build at once, it rises. (On the other hand, there are further economies of scale to be realised.)

Fission clocks in around 141 to 221 $/MWh, which is why we aren’t building it, but $31 at the margin, which is why closing working plants is stupid. SMR focus on lowering capital costs through economies of scale. Fusion by reducing compliance costs. In all likelihood, the solution is fusion SMRs baseloading solar, wind and geothermal energy with peaker industrial processes running during the day. (Hydro can come too.)

[1] https://www.lazard.com/media/2ozoovyg/lazards-lcoeplus-april... slide 2

[2] https://www.gevernova.com/gas-power/applications/grid-firmin...

SMRs are based on the wishful thinking that, for the first time in history, making an industrial facility smaller increases economic efficiency. It's just not going to happen.

I'm pretty skeptical of the SMR thesis, but I think there are plenty of examples of modularization and miniaturization being economically advantageous.

For instance, I just the other day came across an article about how in the first wave of electrifying the textile industry, they replaced big centralized steam engines with big centralized motors. But then they realized that motors made it possible to mass produce small machines and put one at each station, and they turned out to be an advantage.

I think there are a number of specific reasons to be skeptical of SMRs, but I don't think the entire concept is per se flawed.

This is "the solution" on what time scale?

This all definitely sounds like a great way to meet all our energy needs without carbon emissions ... in like 30 years? maybe 20?

We haven't invented "fusion SMRs" yet, let alone commercialized and scaled them. We're still in the extremely early stages of commercializing geothermal at scale. I'm curious what "peaker industrial processes" you're thinking of that can be profitable while running only during high power supply periods?

I think if we build a bunch of batteries, and then they turn out to no longer be useful after all this other stuff scales up, that's totally fine, far worse things have happened!

We also haven't had a big disaster with battery storage yet, which is probably inevitable as the facilites are built out.

A 10MWh battery storage facility, if it were to release its energy all at once would be something on the order of the Chernobyl explosion (sans radioactivity) so certainly capable of destroying a building and killing people nearby. I'm not sure what is "normal" for a utility scale storage facility but 100 times[0] that doesn't seem out of the question

(From Wikipedia[1], the explosion "was estimated ... to be at 40 billion joules" and from unitconverters.net, 40 billion Joules is about 11 MWh[2].)

[0] https://www.energystoragejournal.com/worlds-largest-utility-...

[1] https://en.wikipedia.org/wiki/Chernobyl_disaster

[2] https://www.unitconverters.net/energy/joule-to-megawatt-hour...

That's not a useful comparison. The power of the explosion at Chernobyl, while deadly to the one person immediately next to it, was not the problem that made Chernobyl the catastrophe that it was. That was the radionuclide contamination that it spread and the remaining latent power in the fuel that, if released uncontrollably, would have spread it even further.

A grid scale lithium ion battery, even completely burned up and vaporized into the atmosphere, is not dangerous in a comparable way.

not to mention that battery fires don't release all of their stored energy at once, unlike explosives. Granted, they might burn uncontrollably for a long time, and difficult to extinguish.

Solar and wind are not "unreliable" any more so than any other power source we've used in the past. Just like transformers have been replaced by power electronics in many applications, the reliance on flywheels for frequency stability will be replaced by grid-forming power electronics. There isn't anything magical about this technology.

Another thing that's easy to miss is that, unfortunately, renewables tend to be correlated. An event that reduces insolation over a large area, for example, will affect solar and wind over a large area. So simply over-building is a lot more expensive than it seems when you need to be able to handle tail risks.