[Manuel_D]

When you say you have 350 GWh of storage, people expect to be able to draw 350 GWh and then store 350 GWh without waiting several months for the reservoir to fill back up. There is nothing bad-faith about pointing out how deceptive it is to say a facility has 350 GWh of storage when in reality the practical storage capacity is much smaller than that.

Also, you insist that there's an error in this analysis - "double counting" - yet you neglect to actually explain what was wrong with it. This [1] is the report that arrived at the 40 GWh figure.

> Whilst Talbingo’s level could be reduced to provide ‘space’ for Snowy 2.0 Tantangara water, this would reduce the energy storage and efficiency of Tumut 3. As Tumut 3 has 60 GWh of storage when Talbingo is full, any reduction in Talbingo water levels would reduce that capacity, which can be delivered at 1,800 MW for up to 33 hours. A reduction would also (marginally) reduce the efficiency of Tumut 3. Another reason to keep Talbingo close to full is that a call on Snowy 2.0 to generate for 7 days would normally be most unlikely. Also, Tumut 3 can very quickly generate and create space in Talbingo for Snowy 2.0 water, though this still means discharging water to Blowering, beyond whatever spare capacity there was in Jounama at the time. So, if the current operational arrangement remains largely intact, the available capacity for Snowy 2.0 before water is lost to Blowering would be approximately 28 GL. This volume equates to a recyclable energy storage capacity for Snowy 2.0 of about 40 GWh (28/239x350) – i.e. 20 hours at 2,000 MW.

If more than 40 GWh of storage were used, Snowy 2 would reduce the capacity of other hydro electric plants. It's the estimate of 350 GWh that relied on double counting, not the 40 GWh figure. If this analysis is wrong, then actually explain what's wrong with it instead of just insisting that it's double counting.

1. https://majorprojects.planningportal.nsw.gov.au/prweb/PRRest...

[Schroedingersat]

Gitchya. Going with the bad faith version. Could have said so more succinctly.

[Manuel_D]

Are you actually going to explain what's wrong with the analysis that points out how cyclic capacity is much lower than 350 GWh? Or are you just going to accuse people of bad faith when asked to defend your claims?

[Schroedingersat]

You can cycle 40GWh when it's full. Then you can get 350GWh out of it. Then put 240GWh back into it and cycle it a few times, then get another 350GWh out of it again in a month or two. The last 110 fills itself.

Trying to paint this as 40GWh is the very definition of bad faith.

[Manuel_D]

> You can cycle 40GWh when it's full. Then you can get 350GWh out of it. Then put 240GWh back into it and cycle it a few times, then get another 350GWh out of it again in a month or two. The last 110 fills itself.

But doing so would reduce the usable storage of other facilities using the same body of water. This is explained here:

> At the extreme, the water stored in Talbingo/Jounama could be reduced to 28 GL. This would allow 160 GL of Tantangara water to be accommodated in Talbingo. This equates to a recyclable energy storage capacity for Snowy 2.0 of about 235 GWh (160/239x350). In this case the energy capacity of Tumut 3 is reduced from 60 GWh to 10 GWh, so the net energy storage is 185 GWh (235-50).

How much can Snowy 2 store without adversely impacting other storage facilities? 40 GWh.

Cycling 240 GWh of energy would almost entirely eliminate Tumut 3's storage capacity, and yield a net increase in storage capacity increase of only 185 GWh. 240 GWh is only correct if we ignore the capacity reduction of Tumut 3. And of course, I doubt Tumut 3's operators would agree to this scenario without being bought out because it'd destroy their ability to turn a profit and have a chilling effect on future hydro projects.

[Schroedingersat]

Why would Tumut 3 be trying to be full in a scenario where the energy is needed? They'd run their turbines and sell energy. The downstream dams dispatch their dispatchable energy and you leave enough water in the middle two that the maximum can be pumped back upstream. The extra dispatchable energy is an upside. It's like having a battery that can't be charged past 70% but fills itself the rest of the way.

So yeah, bad faith. And now you've had it pointed out twice it's just lying.

[Manuel_D]

> Why would Tumut 3 be trying to be full in a scenario where the energy is needed? They'd run their turbines and sell energy.

The issue is that the maximum cyclical storage capacity is determined by the minimum of both the upper and lower reservoirs. Snowy 2's lower reservoir is Tumut 3's upper reservoir. And Tumut 3's lower reservoir is barely 1/10th the size of Snowy 3's upper reservoir. That's the bottleneck.

If your point is that we should just accept the fact that Tumut 3 can't be run at full capacity if Snow 2 is deployed, then yes that's correct.

> The downstream dams dispatch their dispatchable energy and you leave enough water in the middle two that the maximum can be pumped back upstream

Right: in order for Snowy 2 to avoid losing any water, then Tumut 3's upper reservoir (which, remember is Snowy 2's lower reservoir) has to start empty in order to accommodate the water from Snowy 2. And then Tumut 3 can't drain this water when prices are high because Snowy 2 needs it re-charge its upper reservoir when electricity prices are low. In order to run Snow 2 at maximum cyclic capacity, Tumut 3 has to essentially become totally subservient to it.

Imagine I have 3 cups: 30 Liter cup flows to/from a 15 liter cup, to a 5 liter cup. I only have 20 liters of actual cyclic storage capacity, not 50. The 15 and 5 liter cups have to start empty in order to catch the water flowing down from the 30 liter cup. If the 15 and 5 liter cup started full, they'd overflow and lose water.

So if Snowy 2 is running at max cyclic capacity, Tumut 3 can only store and release the water that can fit in its lower reservoir (the 5 liter cup). That's why running snowy 2 at max cyclic capacity would completely shaft Tumut 3.

> The extra dispatchable energy is an upside. It's like having a battery that can't be charged past 70% but fills itself the rest of the way.

But that metaphorical battery fills itself very slowly. It's not cyclic capacity and thus isn't nearly as useful.

Imagine you have company A that sells a battery that stores 1 GWh and you can charge and discharge it at a rate of 200 MW and charge it at a rate of 200 MW. Company B sells a battery that stores 10 GWh for the same price that can also discharge at a rate of 200 MW, but it's super sensitive to charging and can only be charged at a rate of 1 MW - it'll take a month and a half to get back to 10 GWh.

Which of these batteries is more useful? The first one, by a massive margin.