In eight years, Australia wants to be four-fifths powered by renewables. Solar and wind investment is pouring in. But to firm the renewables and overcome the intermittency, we need overnight energy storage. That’s why there’s so much interest in pumped hydro.

At its simplest, pumped hydro involves two dams, one high on a hill and one down in a valley, with pipes and turbines connecting them. You store electricity by pumping water uphill to the upper reservoir on sunny and windy days – and turn it back into power at night or during calm or cloudy days by letting the water flow back downhill through a turbine. Think of this system as a giant “gravity battery”, where electricity is turned into gravitational potential energy and back again.

The question now is: where are the best locations? Last year, we released a global atlas of more than 600,000 greenfield locations for pumped hydro. These are sites where there is no existing reservoir. About 4,000 of those are in Australia, including the site for Queensland’s newly announced 5 gigawatt Pioneer-Burdekin pumped hydro scheme.

Now we’ve identified 1,500 new Australian sites in our new bluefield atlas. Bluefield refers to locations with one reservoir already in place, meaning only one new reservoir needs to be built. Existing reservoirs already have a social licence and are usually publicly owned. None of our sites require damming major rivers.