[Manuel_D]

There's no double counting. The estimate of 350 GWh ignored the fact that the lower reservoir of Snowy 2 is smaller than the upper reservoir.

In case you're unfamiliar with how pumped hydro works: There's an upper reservoir and a lower reservoir. To charge the system, water from the lower reservoir is pumped into the upper reservoir, and to withdraw energy the water is passed to the lower reservoir driving a turbine.

In Snowy 2, the upper reservoir is large enough to accommodate 350 GWh of energy. But the lower reservoir is not, and actually attempting to actually use that much storage would cause the closed loop system to lose water and permanently reduce the storage capacity unless additional water is added. If I have a 100 liter bucket up top and a 10 liter bucket down below. If I fill up the 100 liter bucket to the brim I could drain 100 liters once, but then I'd lose 90 liters and only have enough water to fill it back up to 10 liters. So does it have a capacity of 100 liters? In a pedantic sense, yes, but in practice you only have 10 liters of usable capacity.

Pumped hydro storage requires very specific geography to function, so deceptive messaging is often required to convince people of its efficacy.

[Schroedingersat]

I'm quite aware of how it works, but I guess it was too much to expect a good faith response. That 200GWh that is 'lost' is dispatchable energy that recharges after a few months, after it is dispatched, about ~240GWh can be cycled and another 100GWh can be dispatched. The 40GWh is only a limit in precisely those cases where the dispatchable energy isn't being utilised

The 240 and 40 are also a lowball because parts of the losses were already accounted for at the beginning. That part is the double count.

[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.