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NARRATOR: Sun and wind in abundance. Australia is perfect for renewable energy. Assisted by government incentives, the nation's electricity grid is being transformed. But the green energy boom is creating a challenge.
How do you prevent blackouts when the sun doesn't shine and the wind doesn't blow? Australia's solution is pumped hydroelectric storage, an old technology that is enjoyed in Renaissance.
GUY BROADMAN: The beauty of hydros is that it's a renewable energy supply that's available on demand. So when the market needs the electricity, we simply use the water that we have now in our storage to drive the turbines in this power station, providing electricity to the market.
NARRATOR: A conventional hydroelectric plant generates power by running waters through pipes past a turbine. A pump storage plant generates power in exactly the same way. What's different is that when electricity demand is low at night, or when the wind is blowing, it can turn the pumps on and move the water back to the storage reservoir, storing potential energy for when it's needed. This makes it, essentially, a huge battery.
Last month's Snowy Hydro began a $5 billion expansion to more than doubled pump storage capacity by 2025. The government says it's critical to ensure the power grid can cope when solar and wind start replacing coal and gas power.
KIERAN CUSACK: Reliability of generation is critical to maintaining what we expect in our society. So around the clock electricity. And hydro plays a big role in its ability to fill in the gaps.
NARRATOR: Critics claim the mega project, which requires 27 kilometres of tunnels, runs the risk of delays and cost overruns. And they say that smaller pumped hydro plants, or even batteries could be cheaper. But the pressure is building as Australia falls behind on the targets set under the Paris climate change agreement. And there is little time to waste.
