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A 900 MW pumped storage hydropower plant located in a subterranean cavern 600 meters below ground.
The big picture
The plant offers flexible power generation, playing a key role in stabilizing the grid across Europe and in safeguarding Switzerland’s power supply.
Nant de Drance SA, a consortium of Alpiq, SFR, IWB, and FMV.
How it works
The Nant de Drance power plant works like a gigantic battery that allows excess electricity to be stored or to produce the necessary energy when demand exceeds production.
Placed into operation last month, the plant is located in a cavern between the Emosson and Vieux Emosson reservoirs in the Finhaut municipality of Valais in the Swiss Alps. The hydropower plant features six pump turbines with a capacity of 150 MW each. The highly flexible machines make it possible to switch from pumping at full power to turbining at full power in under five minutes, i.e., from -900 MW to +900 MW. The volume of water passing through the turbines corresponds to the flow of Geneva’s Rhône River during the summer.
The upper reservoir of Vieux Emosson holds 25 million cubic meters of water, which represents a storage capacity of 20 million kWh.
The Vieux Emosson dam was raised significantly in order to double the capacity of the reservoir, thus providing adequate storage capacity for the facility. The speed of the six pump turbines can vary in both pump and turbine modes, enabling the power plant to operate as close to its optimum efficiency as possible by adapting to the slightest fluctuations in the electricity market.
Why it matters
With an uptick in intermittent renewable energies like wind and solar, the plant’s flexibility will help compensate for power grid fluctuations and help maintain continuous balance between production and electricity consumption.
To minimize environmental impact, Nant de Drance worked closely with environmental organizations at the outset of the project. Fourteen projects have been or will soon be completed to offset the environmental impact of the construction of the power plant and the high-voltage line connecting it to the power grid. Most of the measures aim to recreate local habitats, including wetlands.
Nant de Drance SA and its stakeholders will officially open the power plant in September.
Stay tuned for the next installment of the Energy Edge Innovation Series!
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