[danans]

> For some reason grid storage reporting always seems to use a power metric instead of storage metric

Grid scale batteries are used primarily for real time demand management, and therefore their most relevant property is how much immediate power they can output and for how long. If they were only described in terms of energy (i.e MWh) without separating the power and time components, then it wouldn't be clear how much immediate value they could provide to the grid.

It's analogous to how in an EV the max horsepower is determined in large part by the power output rating of the battery, but the range is related to the the energy capacity.

[ssl-3]

>their most relevant property is how much immediate power they can output and for how long.

You listed two properties there.

Only one of these two properties is present in a figure that is solitarily presented as "10,000 megawatts."

We can tell this because only one property is presented.

And because it is a very-clearly ambiguous and singularly-useless instance of a unit that sees frequently-erroneous use, we do not know if this singular figure relates to "how much" or if it relates to "how long."

It probably relates to one of them, I'd suppose.

However... we do know that it cannot relate to both things, as-presented. The singular property presented can't even be extrapolated to relate to both things.

[danans]

> The singular property presented can't even be extrapolated to relate to both things.

Both things aren't equally important.

The energy capacity of the battery isn't provided for the same reason that coal plants don't specify the size of their coal piles or hydro plants don't specify the potential energy storage capacity of their reservoirs.

Power is the most relevant property to the real time operation of the grid, and the specification of power (and not energy). The grid operators need to know how much power a battery (or other generation source) can provide, and for how long. That tuple <power, duration> what any dispatchable energy source ultimately bids onto the real-time electricity markets.

The energy storage capacity of a battery is a function of what energy market it is designed to fit into.

For example, a battery that primarily functions in the frequency regulation market (modulation of supply and demand every few seconds) doesn't need a lot of storage capacity, but needs high power output. In contrast, a battery that shifts supply over the course of a single day might need more capacity (4 hours).

From the grid operator's perspective, the storage capacity is an implementation detail of the particular power source, or at least a secondary consideration.

[icehawk]

> For example, a battery that primarily functions in the frequency regulation market (modulation of supply and demand every few seconds) doesn't need a lot of storage capacity, but needs high power output.

For ERCOT this is fixed as a hard requirement so there's no point in specifying the time-- it's all going to be the same. For example:

> Fast Frequency Response (FFR) – subset of RRS

> – Must be capable of sustaining its required response for at least 15 minutes (if necessary)

[ssl-3]

> The grid operators need to know how much power a battery (or other generation source) can provide, and for how long.

Sure do! They definitely need all both of those things! One thing, by itself, is definitely not enough information! Agreed. Absolutely!

But only one of those figures was presented here, and this here [waves arms around] is the context of the discussion.

And one figure is fewer than two figures, would you not agree?

[danans]

> Sure do! They definitely need all both of those things!

When a generation provider bids supply onto the grid, it doesn't tell the operator what the maximum storage capacity of its equipment is, it tells the ISO how much power it can output for a given time frame (or alternatively how much energy it can deliver during a timeframe).

That is different that the total energy storage capacity of the battery itself, which is what I think you asked for.

The grid operator usually pays more attention to the former when it comes to day to day grid stabilization, and especially so for batteries, because batteries today don't do long term energy storage.