[ssl-3]

Yep.

It's a measure that makes perfect sense for conventional electricity production: 10,000MW of aggregated coal generation can hypothetically produce 10,000MW more-or-less indefinitely, as long as it keeps being fed things like fuel, water, and maintanence.

But it doesn't make any sense at all, by itself, for energy storage: A net 10,000MW battery might be able to produce 10,000MW, but for how long can that output be sustained? Unlike a group of coal plants, it absolutely cannot do this indefinitely; at some point, that battery will become completely discharged.

It takes at least two figures to describe a working bucket of energy (whether that bucket is Lithium cells or pumped storage or whatever): The capacity (megawatt-hours is a fine figure here, and units like Joules also work), and the maximum input/output (and plain megawatts works fine for this part). Using only one figure doesn't really describe anything at all.

I don't know when or why we stopped doing this, but it's misinformative in a way that leads to a bad generalized understanding of the these concepts with the populace that is actually paying for all of this stuff.

[icehawk]

Its fine as long as the amount of time it can provide rated output is longer than it time it takes to bring replacement generation capacity on line.

I don't care how long my UPS will actually last as long the holdover time is long enough to cover the time it takes to deal with all of the foreseeable problems in starting up the backup generator.

[ssl-3]

I don't think that grid-scale batteries are working with consumers on the grid in the same way that your home UPS is with you in your house.

Perhaps most-obviously: Consumers who are suddenly running on grid-scale batteries have no idea that this is a thing that is happening. There's no signal for them to shut their stuff off -- automated, or not.

It's a whole different paradigm than your UPS under your desk is: With your UPS, your system(s) receive a signal that things are running on local battery, and you've elected to configure things to use that signal to order an automated shutdown.

But, again: That doesn't happen with the grid-scale batteries under discussion -- at all. You're comparing apples to dildos here.

(Which is not to say that grid-scale batteries offer new opportunities for power cuts, because the opposite of that is true. It is instead just to say that unknowingly using grid-scale batteries is nothing like monitoring a local UPS is.)

[icehawk]

> It's a whole different paradigm than your UPS under your desk is: With your UPS, your system(s) receive a signal that things are running on local battery, and you've elected to configure things to use that signal to order an automated shutdown.

The setup you described there wasn't the situation I was describing at all.

I was describing a situation where there is utility power, a UPS, and a standby generator. When the utility power goes out, the generator has to start, stabilize, and only then can the load be transferred off the battery.

The requirement is that the UPS meet this current power demand for longer than the generator start up and transfer time (the "holdover time" I was speaking about in the previous post.)

For things like frequency response the holdover time is a fixed requirement. ERCOT requires all energy storage resources be able to maintain output for 15 minutes.

[pixl97]

I mean during the great texas power outage natural gas plants ran out of fuel because of supply issues that were not typically supply issues it would be more honest if every power plant also listed it's on hand 'fuel battery'. Now I'm sure they may do this with ERCOT, but it's not something typically reported.

[ssl-3]

Why, sure. It would be good to know how long a conventional generator can keep running when everything around it has gone wrong. For coal, for instance, that might be represented by the mass of the piles of coal that are normally on-hand -- or by the electricity (in MW-h, say) those piles of coal should be able to produce. Having this information close by would seem to be a good thing for an organization like ERCOT, so as to be factored into their emergency playbook.

But that's still a different case than a battery, wherein: Even if everything is going right, using energy from a battery must eventually cause it to become depleted.

It's never like a coal plant that (ideally) consumes fuel at one end, and spits out electricity at the other end as a continuous process. A battery, in this context, can be in a charging or a discharging state, but it can never be in both of those states at the same time -- using a battery is not at all a continuous process.