Hacker News

points by Someone 19 hours ago | 0 comments

For comparison, US grid capacity is about 1250 GW, average usage 500 GW.

So, this adds over two minutes of average usage.

https://seia.org/research-resources/energy-storage-market-ou... says total storage now is about 200 GWh, or about 25 minutes of average demand.

[–] nomercy400 19 hours ago

So if ALL power generation of the US would stop right now, EVERYTHING would still have power for 25 minutes. (ignoring all safeties tripping, and perfect load balancing)

That sounds so impressive.

[–] clarionbell 19 hours ago

No. Because neither storage nor generation is evenly spread. In some places you would have nothing, in some you could have potentially hours.

In practical terms, you would most probably get nothing, because situation like this would lead to complete grid breakdown and interruption of service.

[–] viraptor 18 hours ago

Technical detail question: if all of those batteries were on connecting allowing feeding back to the grid, would they be able to synchronise the frequency/phase? What's the threshold/requirement for that to happen?

[–] crote 18 hours ago

It can be done, but it would requires additional equipment. Batteries are traditionally grid-following, so they'll just follow whatever frequency the grid is already running on. The frequency itself is then provided by the rotational inertia of "spinning metal" power plants.

But there's no reason that has to be your frequency source. Any single battery installation on its own is perfectly capable of making up some frequency, which is why home power banks with island-mode AC output are a thing - or even just a traditional UPS. Doing the same with thousands of individual battery installations across the grid? You'll need some way to get everyone to agree exactly on frequency and phase, which in practice is probably going to mean getting them to agree on time to within a few microseconds, which could be done (albeit not very sabotage-proof) using GPS.

[–] bluGill 18 hours ago

> The frequency itself is then provided by the rotational inertia of "spinning metal" power plants.

This might or might not be true. I used to live near a large plant that took HVDC from a power plant several states away and transformed it into AC. They used electronics to provide the grid frequency, not spinning metal. All the other local peak power generation was run in grid following mode.

[–] tialaramex 14 hours ago

Grid Forming Batteries are a thing - but since it's not free to implement of course such a provider would like to get paid, not give it away, whereas both a conventional thermal plant or a hydro plant unavoidably has spinning metal, their stability comes free with the electrical supply.

The risk vs reward isn't great. If you made your country's 10GW grid work with only batteries for 15 minutes to show it's possible, maybe you get one half page in a "Electricity Weekly" industry newspaper. But if anything goes wrong and ordinary people notice - now you're on TV News for a week.

[–] bluGill 14 hours ago

I'm under the impression that most grid scale batteries are owned by the utility which in turn cares about this. And the rest are only going to be bought if a utility \ grid gives them a contract where again those who care will give better terms of they need it.

My home battery might participate without the above but in to small to matter.

[–] viraptor 11 hours ago

> Batteries are traditionally grid-following, so they'll just follow whatever frequency the grid is already running on.

Is there in theory an amount of batteries with inverters where enough energy is created to "not notice" the spinning generators going away? I.e. everyone is trying to follow the frequency that's already flowing therefore everyone sees some frequency flowing? Or would it be like talking with echo/delay where they start slowing down by always being behind until everyone stops?

[–] bob1029 17 hours ago

> What's the threshold/requirement for that to happen?

The RoCoF (rate of change of frequency) must be low enough that the inverters can form the grid without letting out the magical smoke. Having inertia is what slows this rate down.

[–] oblio 17 hours ago

Considering the accelerating rate of installation and the ever decreasing costs of manufacturing, both problems should be alleviated in 10 years. Instead of 25 minutes, most likely 4-6 hours. Instead of extremely uneven distribution, likely all the major population centers will have at least some non zero coverage.

[–] DJBunnies 18 hours ago

It's not public.

[–] wtch98 18 hours ago

Only if that battery was connected to 500GW of inverter capacity (and the grid was a spherical chicken -- enough intertia-replacement devices to keep timing working, enough capacity to link supply with demand etc)

[–] rcxdude 18 hours ago

inertia-replacement is what batteries do best, so in this kind scenario that's probably the least of the problems.

[–] pletnes 19 hours ago

That means a huge ability to absorb production or consumption peaks!

[–] baxtr 18 hours ago

Compared to what is this a good measure?

"How much is needed during a no sun and no wind period" could be reasonable comparison.

[–] teamonkey 13 hours ago

Any amount is good if it reduces costs to the consumer and reduces the usage of fossil fuels.