Hidden away above the tiny Swiss Alpine town of Linthal, deep inside a snow-capped granite massif, sits Europe's newest engineering marvel. It is a hydropower plant like no other, able to generate as much electricity as a nuclear power plant and act as a giant battery at the flip of a switch. "It's the only grid-scale method of storing energy," says Maryse François, the hydro technology leader at G.E. Renewable Energy, the company that developed the technology powering the site.
The Linthal facility is a so-called pumped-storage power plant. It generates or stores electricity by moving water between two teal-coloured mountain lakes separated by a 630-meter cliff (2,000 feet) twice the height of the Eiffel Tower. When the operator, the Swiss utility Axpo, wants to generate electricity, it opens massive steel valves that can withstand titanic pressures and lets the water run down from Lake Mutt, located at 2,490 meters (8,100 feet) above sea level, to Lake Limmern, filling up a deep, dammed valley below with nearly 23 billion gallons of water (92 million cubic meters). The water runs through four G.E. pump turbines that turn G.E. variable-speed motor generators, converting the potential energy in all that falling water into electricity.
But if demand for power drops, the plant reverses the flow, pumping water back up to Lake Mutt. "It's as if the system was recharging the upper reservoir," François says. The system "becomes a giant natural battery, ready to be used again when needed."
To be sure, pumped storage is not a new idea. But the Linthal plant, the first place where G.E. installed the variable-speed technology, is different. The technology allows Axpo to fine-tune the plant, precisely monitor the amount of excess electricity in the grid and move just the right amount in the right direction. The technology's overall cycle efficiency — the ratio between the electricity supplied by "turbining" the water as it runs downhill and the energy used to pump it uphill — is as high as 80 per cent. "This is as much a power-generation play as it is an economic play," François says.