South Australia's Big Battery half built. Already.

A few hours after Musk presented SpaceX's new rocket ship at the International Aeronautical Congress in Adelaide, he showed off the new Tesla Big Battery at the Hornsdale Wind Farm, 250 kms north of Adelaide.  The battery bank's grid connection agreement was only signed that afternoon, while Musk was speaking at the congress.  By the time Musk addressed the guests at Hornsdale, it had been connected to the grid, and the entire event was run using electricity from the batteries which had been charged up with electricity from the wind farm.

More to the point, the battery bank is half built.  The contract was only signed in July.   When last did an infrastructure project get built so fast?  (Answer: at Tesla's Aliso Canyon battery bank in California.)

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Progress at the Tesla big battery at Hornsdale (Source) 

Note that the South Australia battery bank isn't designed to "time-shift"  surplus generation from midday (solar) or night (wind)  It's not big enough for that.   It can produce 100 MW of electricity for about an hour and a third (100 MW of output/129 MWh of storage)  As I write this on a mild spring day, demand in South Australia is 1066 MW, but on a hot afternoon in January or February demand could reach 3000 MW.  So the battery bank could provide 3% of a high demand period for 80 minutes.

It's value lies in its ability to provide an instant response to  the "jerks" which can occur in a grid when big capacity goes off line or a power line goes down.  And it has enough capacity to allow gas peaking plants the ten minutes or so they need to ramp up.  Even a relatively small unsatisfied difference between demand and supply can cause voltage and frequency to dip, and this in turn can cause other perfectly working generators to go off line as they try to protect themselves.  That's what happened in the "system black" in South Australia in September last year.  Two HV lines were blown over by an unprecedented storm, so wind turbines disconnected, which caused a demand surge on the interconnector with Victoria which in turn tripped to protect itself, leading to a statewide blackout.

On the other hand, the new SA CSP plant will provide 150 MW of electricity 8 hours into the night, or 5 percent of potential peak demand between 4 p.m. and 10 p.m. on a very hot day, 10% on a more normal summer day.  This is  true "time shifting" storage.  Aurora will have 8 hours of storage and will deliver the whole tooty (base power plus storage) for A$75/MWh.  For a battery bank to provide 150 MW for 8 hours would cost US$110/MWh of storage times 8/24 = US$37 (A$49). Just for the storage, which gives a total cost of  A$104/MWh ($55 for the wind power + $49 for the storage), which is still more expensive than Aurora.  To put it another way, you'd have to build 9 similarly sized battery banks to provide the same storage as the Aurora plant will.

Why does this matter to the world?  If South Australia were a separate country, it would have the largest penetration (58% and rising fast) of wind and solar in the grid in the world (though not the largest penetration of renewables, because other countries, like Canada, Norway and Uruguay have hydro).  How it handles this essential and unavoidable shift to 100% renewables will be instructive for everyone.