The federal government wants to use taxpayer funds to support new pumped hydro electricity generation across Australia.
Only three pumped hydro schemes exist in Australia at the moment.
The Clean Energy Finance Corporation has given $54 million to a Queensland project that will convert an old mine into a solar farm and pumped hydro generator, and it's expected more projects will follow.
But there are thousands more sites where pumped hydro could be viable, ANU renewable energy Professor Andrew Blakers tells AAP.
WHAT IS PUMPED HYDRO?
A pumped hydro scheme has two water reservoirs at different heights connected by a pipe. When power prices rise or there is low supply from other sources like solar and wind, water is released from the upper reservoir and runs through a turbine into the lower one, generating electricity as it goes. When power is cheaper, the water is pumped back up from the bottom to the top. This has the added advantage of using excess power generation, University of Melbourne's Dr Roger Dargaville says.
WHERE IS THIS USED NOW?
The three existing river-based schemes are at Wivenhoe Dam in Queensland, Shoalhaven in NSW and the Snowy River in NSW.
WHERE ELSE COULD IT OPERATE?
Any hilly farmland where you could build two 10-hectare reservoirs. Blakers says there are thousands of potential sites, including the western slopes of the Great Dividing Range and even "sunny, arid South Australia" including in the mountains from Adelaide up to Flinders Ranges National Park and along the eastern side of the Great Australian Bight.
Dargaville says schemes using sea water could also be an option in SA, meaning only an upper reservoir would need to be built with water pumped from the ocean.
HOW DOES IT COMPARE TO OTHER POWER GENERATION?
Pumped hydro offers all the benefits of other baseload power sources, such as coal and gas, but much quicker, more flexibly and without the emissions. For example, a coal-fired power station can take up to 24 hours to reach full capacity, where pumped hydro can do it in one minute.
Plus, the technology already exists and it's a fraction of the cost of battery storage. "If you want pumped hydro you just ring up a company and they'll build you one, nothing to invent," Blakers says.
WHAT ABOUT THE SCARCITY OF WATER?
Blakers describes the reservoirs as "over-sized farm dams" and says there's little chance of a pumped hydro scheme sitting empty once built, even if Australia goes back into drought. They use much less water than coal plants and recycle the same water over and over, with none lost in clouds of steam like thermal generators.
WHY AREN'T WE USING IT ALREADY?
Essentially, because we still rely heavily on coal-fired power the price of electricity is relatively stable - pumped hydro makes the most sense where there are large spikes and drops in price. Once there is more intermittent power like photo-voltaic solar and wind power in the grid, pumped hydro becomes more viable.
"It's off-the-shelf, waiting for when PV and wind reaches the point that it destabilises the grid then you just go and build it," Blakers says. He expects to see it soonest in SA, where he says the government needs to invest in another interconnector to import electricity from NSW, pumped hydro, or both.
Dargaville says: "By adding large-scale storage into the grid, it will allow more of the world-class renewable wind and solar generation resources in South Australia to be deployed, further reducing Australia's carbon footprint, without the current negative impacts on energy security."
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