The office for Mines and Petroleum, Energy, Hydrogen Industry and Industrial Relations Minister Bill Johnston, who last year said the government was "very attracted" to pumped hydro in the South West, confirmed on Wednesday it was no longer being considered for WA.
A spokesperson for the minister said pumped hydro "wasn't viable" for Western Australia.
Pumped hydro stockpiles energy by pumping water uphill when electricity is cheap and in plentiful supply, to be stored and pumped back downhill through a turbine in high-usage periods when power costs are higher.
Last year, Mr Johnston touted pumped hydro as part of the state government's announcement it would shutter the two state-owned Collie power plants as part of a $3.5 billion shift to renewable energy by 2030.
"There's a number of proponents at the moment who have put forward ideas for how we can do pumped hydro around Collie and we're confident that that will work," he told ABC Radio Perth presenter Nadia Mitsopoulos in June 2022.
At the time he said the announcement was scheduled to make time for pumped hydro projects to be approved by 2030.
"That's why we're making the announcement now," he said.
"Because that gives you the pumped hydro being available before the last coal-fired power station's retired."
WA Premier Mark McGowan and Energy Minister Bill Johnston announce their green energy plan outside Muja Power Station near Collie last year.(ABC News: Sam Bold)
Minister's former hydro hopes
There were signs the WA government was backing away from the technology in May when Mr Johnston said in Parliament that Synergy was investigating but "every single option has lots of problems."
The likelihood of pumped hydro being adopted by Synergy in the South West by 2030 appeared to fade on Wednesday when Synergy boss David Fyfe cited a long list of problems with the technology.
"The approval process for them would be a long process because of the environmental impacts … you're building dams, you're cutting down state forests," Mr Fyfe said at an ABC Spotlight forum on WA's energy future.
"It displaces local populations potentially as well.
"So it's a difficult project. It's not a no, but we're still evaluating."
Synergy reports findings
The minister's office confirmed later in the day that Synergy's study into pumped hydro in the South West had found it was not feasible and "would face multiple challenges."
The WA government said it had only recently received Synergy's report, which examined five locations in the South West, and it was now under consideration.
A spokesperson said the finding would not affect Western Power's "mini-scale" pumped hydro pilot project near Walpole.
They said the report could not be provided because it was "commercial in confidence."
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Synergy said in a statement it was "continually exploring emerging technologies and assessing future opportunities to expand its fleet of electricity generation assets."
The state-owned energy provider said it had conducted a number of studies into pumped hydro since 2018.
The closure of the Collie plants is expected to affect around 1,200 staff in the Collie area.
Private proponents last year expressed interest in pumped hydro projects in the area, including the Collie Hydro Project from former WA premier Brian Burke and former CFMEU union boss Kevin Reynolds.
Former Collie-Preston MLA Mick Murray, who supported the rollout of pumped hydro in the South West, said the concerns cited by Synergy were "a very big surprise."
He said the government should allow private operators to use existing infrastructure in the area, such as a mining pit that fills with water, to start new projects.
"It's not up to the government at this stage to put their hand in their pocket," Mr Murray said.
"We're not asking for money. We're asking for a lease and then a private enterprise will then go forward.
But Shadow Energy Minister Steve Thomas said the Synergy findings only confirmed his belief that pumped hydro would never work in WA.
"Now perhaps the government can concentrate on energy storage that might actually work, which will be limited to batteries I suspect," Dr Thomas said.
As part of its plan to achieve net zero emissions by 2050, the state government said a battery energy storage system to be built in Collie would provide around 500 megawatts for up to four hours.
Wind power, solar energy, and battery storage were also part of the government's energy transition plan.
