[Kaliboy]

The main reason I could think of is when you consider the reality of our electric grid and how it remains stable.

Grid inertia is literally maintained by hundreds of thousands of pounds of metal spinning at 50 or 60 hz.

So as the grid moves towards solar and wind, it loses inertia. Solar has no inertia and wind is lightweight compared to baseload plants.

This makes the grid more sensitive to another that can cause the frequency to fall or rise, which will trigger automatic protections.

It takes longer to become an issue in large interconnected grids, but on islands it's like the leading cause of blackouts.

One badly timed cloud means problem, unless you can instantly replace the energy lost through other means.

With thermal power plants the inertia of the generator spinning gave utilities enough time to start up other generators. With solar and wind that's gone, hence the rise of grid batteries.

So then solar/wind costs should include ALL related costs, including grid batteries and such, and often it doesn't. And thus you get people who are against it for honestly a very good reason.

That said I love solar and run fully off grid, but I ain't deluded to think my island can go 100% green. Diesel will stay for now.

I do wonder if using solar to run huge heavy flywheels connected to generators can help with the interia issue.

[two_handfuls]

Inertia was an issue, now it's solved with grid-forming batteries that can provide the same inertia a rotating flywheel did.

Most projects today are solar+battery or just battery alone, so inertia is no longer a blocker, it's just part of designing the project right.

Here is a "Practical Engineering" video on the topic, mentioning that your concern is real: https://youtu.be/7G4ipM2qjfw?si=qfVymRpKFpuexQF_

And here is a more recent video about how Australia runs on a ton of solar with no issues thanks to grid-forming inverters: https://youtu.be/qavFbOpt4jA?si=dlkEEN4sZLCv2os5

[kalleboo]

The inertia issue is not some fundamental law of physics, it's just how the DC->AC inverters are commonly programmed, to follow the grid, since that is the easiest way to regulate the grid when non-AC generation is a minority.

The inverters can instead be programmed to form the grid frequency - Australia installed its big battery literally as a much faster way to stabilize grid instability events than spinning up gas peaker plants.

Grids with large amounts of renewables like California are moving toward VPPs (Virtual Power Plants) which are distributed collections of renewables and batteries which are programmed to work in unison to help form the grid, as an easier way to regulate the grid frequency than coordinating each tiny plant separately.

[qmmmur]

Western Australia also has a VPP program that is pretty successful.