The new Nant de Drance pumped storage power plant is characterised by its flexibility, output and storage capacity. Each of the six machine groups, with an individual output of 150 MW, can be independently switched from pumping to turbining mode within a matter of minutes. In addition, the rotational speed of each machine can be seamlessly adjusted. The available volume of the Vieux Emosson reservoir is 25 million cubic metres of water, which translates into 20 GWh of electricity. This opens up a wide range of options for the deployment of the six machines. Determining the optimal configuration is a major challenge, especially since each of the four shareholders of Nant de Drance SA (Alpiq, SBB, IWB, FMV) is free to develop its own generation schedule. Alpiq is responsible for the deployment planning, which is why everything converges in Lausanne. The objective is to make the best possible use of the wide range of capabilities and to put the flexibility of this exceptional power plant to profitable use for all partners, in particular on the spot and intraday markets.
Alpiq utilises the “Pump Storage Management Tool” (PSMT) for the operation of Nant de Drance. This tool factors in a number of components, such as energy accounting, generation schedules and dispatching, and utilises algorithms to determine the most efficient combination for the deployment of the six machine groups. When it comes to storage power plants, the optimisation team usually has a given volume of energy at its disposal. This is not the case at Nant de Drance, because the quantity of available energy constantly changes. In order to track this wide range of fluctuations and to incorporate the uncertainties associated with the energy market prices, Alpiq developed a new stochastic model based on optimisation algorithms.
The Nant de Drance pumped storage power plant was commissioned on 1 July 2022 following a 14-year construction period. Thanks to its high pumping and turbine capacity, the power plant is capable of handling consumption and production peaks. The power plant functions as a gigantic battery, which at short notice stores excess electricity from the grid or generates electricity when demand is high. In view of the growth in renewable energies, such as wind and photovoltaic power with their fluctuating outputs, this flexibility is of major value for the stability of the European extra-high-voltage grid.