THE GND IS TOO CAUTIOUS:

Five pumped hydro projects promising a combined energy storage capacity of up to 60 hours have been given a financial leg-up by the New South Wales government, as the state races to replace its ageing coal fleet and shift to renewables. [...]

The funding, just under $50 million in total, aims to help pumped hydro developers to cover upfront costs and encourage investment from the private sector to back the state's target of at least 2GW of new long duration storage by 2030.

A new study by researchers at the Australian National University have identified 530,000 sites around the world suitable for pumped hydro storage that can store up to 22 million gigawatt hours of electricity--coincidentally about what other studies show would be needed to support a reliable electric grid powered entirely by renewable energy. 

The storage would be needed to take full advantage of renewable wind and solar power even when consumers are not demanding peak power, and then supply that power back to the grid at times when they do.

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