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Comment by ajross | Hacker News Reader

That... doesn't sound correct. Inverters are the cheap part, you can literally wire as many as you want in parallel. Batteries have immense power availability, with most chemistries you can trivially deliver the entire capacity in half an hour or so (more like 5 minutes with lithium cells).

Basically I'm dubious. I'm sure there are grids somewhere that have misprovisioned their inverter capacity, but I don't buy that battery facilities are inherently unable to buffer spikes. Is there a cite I can read?

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Agreed. The relatively small battery substation linked above can output 2GW of equivalent inertia generation (a measure to align batteries to inertial power systems) when needed. That's an entire power station they can match for short periods of time. Link: https://www.energymagazine.com.au/sa-approves-world-first-ba...

Australia's largest power plant has 2.9GW of inertial generation assuming all generators are running at 100%. As in the small battery substation alone comes close to the countries largest power station. I'm not sure where the idea that lithium ion can't dump power quickly comes from. They are absolutely phenomenal at it. Australia's building dozens of these substations too since they are so cheap and reduce overall power costs. It's a win from all points of view.

The article does not describe an inertia constant. Without the time component, any comparison to traditional systems is meaningless. Inertia is a measure of energy, not power.

Large spinning masses can provide several seconds of inertia. For 2GW of traditional turbine, you would have between 10-20 gigawatt-seconds of energy that is instantly available at any moment to resist RoCoF.

The switching rate of a good power MOSFET has a bandwidth in megahertz. It's... all solid state electronics. Again, this is just wrong, absent someone showing a cite. It's very weird seeing this kind of seeming ignorance of basic electrical engineering on a hacker site of all places.

> assuming all generators are running at 100%.

which they won't ever be given the habits of coal plants to suffer outages whenever it's convenient to pump the price up.

> Inverters are the cheap part

The whole point with actual inertia is that you get a large multiple of your maximum capacity without any redundant parts or added system complexity.

Keeping around 10x+ more semiconductors than you need to cover a tiny fraction of operational scenarios is difficult economics.

A semiconductor device cannot be overloaded like a spinning generator or transmission infrastructure can. You cannot trade temperature and maintenance schedule for capacity in the same way. Semiconductors have far more brittle operating parameters.

> Keeping around 10x+ more semiconductors than you need to cover a tiny fraction of operational scenarios is difficult economics.

Not according to the prices I see. Digikey tells me I can switch a MW of power for about the price of a MBP. I ask again, is there a citation for this nonsense?

it is technically correct, but so are you.

More inverters in parallel will achieve the same end goal - fast frequency response.

Are you actually certain there are insufficient inverters though? Again, that doesn't pass the smell test and I'd want to see a cite for "batteries don't work for high frequency spike buffering because of inverter shortfalls" or something.

i'm certain there are more than enough inverters.

what's correct is that each individual inverter can only increase its power output momentarily to 20% or so above its maximum. Add more inverters and that problem is solved.

You can google "system inertia" as a starting point.

When it comes to the grid, there's a lot of outdated information left over from the 20th century, so any web search for "system interia" needs to also include some searches on "grid forming inverter"' to make sure that the info is complete.

(And "reactive power" could be good too but not absolutely necessary to understand at first...

I understand the concept. I was asking for a cite about the seemingly-incorrect point about batteries. FWIW, that very search term doesn't produce the string "battery" anywhere on the first page.

This is what batteries can provide very well.

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