Two largish storage projects are under close study in my local habitat.
(and many more some what further away)
This first uses water head and heat "exchangers" to store energy as compressed cold air with the water head maintaining pressure. Essentially its a middle capacity load leveller , frequency and phase lag stabilser etc. (FACS)
Canadian / Australian (branch office) technology. Though CSIRO do something similar ... (maybe later)
Its probably the flexible nature and dedicated network focus that is most interesting. Hydrostor Announces Australia’s First Compressed Air Energy Storage Project, Secures Funding from ARENA and South Australia Renewable Technology Fund - Australian Energy Storage Alliance
ADELAIDE, February 8, 2019 – Hydrostor Inc., a leader in Advanced Compressed Air Energy Storage (A-CAES), is pleased to announce that its subsidiary, Hydrostor Australia Pty Ltd, has been awarded a combined total of $9 million of grant funding from the Australian Renewable Energy Agency (ARENA) (and others)
This second (local) project is _much_ larger. M U C H.
... the project will transform a former mining site into one of the lowest cost electricity storage projects in Australia, at a time when “synchronous generation and bulk storage is critically needed.”
-- Hillgrove Managing director Steve McLare
The "spokessuit" is possibly overselling the need but both capabilities are needed.
This project is *classic* pumped hydro.
"expected to have capacity of 250 MW and eight hours of storage"
There are _at least_ 3 more large storage schemes and a couple of large scale distributed schemes.
If nothing else its an after market for mining companies ;> AGL plans 250 MW pumped hydro project in South Australia
Australia's biggest power producer has secured the right to develop, own and operate a massive pumped hydro energy storage project at Hillgrove Resources' Kanmantoo copper mine in South Australia’s Adelaide Hills region.
 design and application. Rather than well understood possibly ancient goodness.