A simple description of Snowy 2.0
Uses two existing reservoirs which were built as part of the existing Snowy Hydro scheme. That is Talbingo Dam as the lower storage (elevation 546m ASL) and Tantangara Dam as the upper storage (elevation 1222m ASL).
There's no need to fill the reservoirs - they're already there right now.
Electrical specifications are a generating capacity of 2000 MW with energy storage of 350 GWh. So that's enough to operate at constant full load for 175 hours (or half load for 350 hours etc).
In operation it's essentially a battery. Take electricity from the grid (generated from solar, wind, coal, gas or anything else) when there's a surplus available and use that to run the pumps transferring water from Talbingo to Tantangara. Then when there's a need to operate the power station run the water back down the other way by gravity.
There's no magic here and it's all absolutely proven technology with many comparable schemes in operation worldwide. In Australia we have Tumut 3 (1800 MW generating / 600 MW pumping, Snowy Hydro), Wivenhoe (500 MW, Qld government) and Shoalhaven (240 MW, Origin Energy).
We also have other proposals in Australia including a 300 MW scheme on the edge of suburban Adelaide with storage for about 4.5 hours (Tilt Renewables), the 250 MW Kidston project in Qld with storage for 8 hours (Genex Power), an additional 160 - 240 MW capacity at Shoalhaven (Origin Energy) and an assortment of projects totaling 5000 MW, of which the intention is to build approximately half, in Tasmania collectively known as "Battery of the Nation" (Hydro Tasmania). For the record with the exception of Snowy Hydro and Hydro Tas which are government owned, the rest are listed companies. AGL and Energy Australia have also publicly disclosed their interest in building similar schemes, likely to be on a smaller scale comparable to the other privately owned ones.
So do we have surplus power with which to pump the water?
The short answer is yes. In the short term that would be unused capacity from existing coal or gas plants but in the longer term it will be renewables.
If we look at Victoria during the past week for example then total demand, supplied or not supplied, has ranged from a bit under 4000 MW to a bit over 10,000 MW. Generation from solar, including small scale on houses, has ranged from literally 0 up to about 1200 MW and wind has had approximately the same range during the past week.
Or to be somewhat more blunt, there was a pretty decent surplus in Victoria just a few hours before the lights went out and there was once again a surplus that night after all the drama.
Now consider that SA already has periods when wind + solar exceeds total consumption. Consider also that Victoria is about to triple its wind generating capacity. NSW and Vic between them are about to add another 1500 MW of large scale solar farms. Qld is adding about 500 MW more wind and also increasing large scale solar. And that's just the firmly committed projects 100% certain to be built in the next two years. Plus there is small scale solar being installed nationally by homeowners and others.
So on the energy side we have an increasing supply from renewables and there's nothing to say we have to stop building 2 years from now so those figures can be pushed higher, the only obstacle there is government policy.
The harsh reality however is that with the peak demand late in the afternoon solar is of limited (most states) or close to zero (SA) effectiveness at supplying it directly unless by pure chance the peak happens to come earlier in the day (as it did on Friday in Victoria but that isn't usually the case). Likewise the wind also frequently dies late in the afternoon. Meanwhile we have periods, for example very commonly on weekends during daytime, when existing hydro and gas plant is shut down, coal is operating well below capacity and there's plenty of wind and sun. That's before we build all the new wind and solar farms....
That's not to say we could never be lacking in energy. If we stop building wind and solar and let the coal plants fall in a heap, or if we run out of coal or gas to run them with, then absolutely we could be seriously short on energy and it must be said that the gas supply situation is indeed problematic.
That's sort of a different issue though and applies regardless of whether or not we build Snowy 2.0 given that any realistic alternative also requires that we obtain energy from wind, solar, coal or gas. Nobody's seriously proposing nuclear or geothermal at this point, it's really just a question about the relative shares of coal, gas, wind and solar and the technology used in conjunction with them.
What about emissions?
Short term it's really no benefit. More efficient running of fossil fuel plant offset by pumping losses. Longer term though it avoids investing in new fossil fuel plant with a long lifespan and is very long lived infrastructure of use in a predominantly or totally renewable system. It could in that sense thus be considered an investment that pays dividends down the track but not from day one (unless of course we build enough wind and solar by 2024 which is possible).
Snowy 2.0 is not a silver bullet however. It provides 2000 MW of firm generating capacity assuming there's energy to pump the water with at other times. So it does rely on the assumption that we keep running existing coal and gas until we've built more wind and solar and that we actually do build more wind and solar.
It is also only 2000 MW. That's a lot but consider that NSW peak demand is about 14,500 MW and Victoria's is about 10,500 MW and it's clear that it's ultimately not enough. It's the first big step but it won't be the only one we need to take, not by any means.
In a practical operational sense it's all fairly even really in that the peak generating capacity of Snowy 2.0 is roughly equal to that being closed elsewhere (coal and gas). So it stops the problem getting worse more than fixing it as such. Got to start somewhere though.
What are the alternatives? Realistically considering time, politics and so on:
*Other pumped storage schemes of which Battery of the Nation (Hydro Tas) is the only large scale advanced proposal.
*Coal
*Gas but only if someone can work out a sufficient source of gas which is problematic.
*Diesel or other petroleum fuels if someone's keen to burn money.
Anything else either doesn't have major energy storage potential at an economic price (batteries are economic for a few hours but not a week although there's certainly a role for them), would in practice take far too long to be up and running (nuclear) or will give us a very hit and miss power supply (more wind and solar without storage).
For the record I have no association with Snowy Hydro unless you count being a taxpayer.