Giant battery in the mountains
Deep beneath Australia's highest peaks, a massive renewable energy project called Snowy 2.0 is underway. It connects two existing reservoirs, Tantangara and Talbingo, through 27 kilometers of new tunnels. The core of the project is a new, underground power station built within a cavern roughly 800 meters below the surface. This system is a massive pumped-hydro battery.
When there is an excess of wind and solar power in the national grid, the station's six reversible turbines use that cheap electricity to pump water from the lower Talbingo Reservoir to the upper Tantangara Reservoir. This process effectively stores the renewable energy as gravitational potential energy in the water. When the grid needs power, the water is released back down through the turbines, generating up to 2,200 megawatts of electricity. The total storage capacity is approximately 350,000 megawatt-hours, enough to power about three million homes for a week. This "closed-loop" system recycles the water, ready for the next surplus of renewable power.
Tunnels through ancient geology
The construction requires excavating some of the longest and deepest tunnels for any pumped-hydro station in the world. A fleet of enormous tunnel boring machines (TBMs) carves through the region's complex geology, which consists of Ordovician and Silurian-era metamorphic rocks and granites. One of the main TBMs is 205 meters long with a diameter of about 11 meters. These machines are excavating the tunnels that connect the two reservoirs, which have a height difference of over 700 meters.
This significant elevation difference is a direct result of the region's geological history. The Snowy Mountains were uplifted during the Cenozoic era, and their highest peaks were later shaped by glaciers during the Pleistocene ice age. These glaciers carved out the landscape, creating the steep gradients that now make the pumped-hydro scheme so effective. The project's engineers must navigate this ancient rock, which includes hard granite, fractured rock, and softer zones that have presented challenges to the TBMs. The main power station cavern itself is one of the largest and deepest ever excavated.