Since its commissioning on 1 July 2022, the Nant de Drance pumped storage power plant has proved extremely reliable and its availability has exceeded expectations. This excellent result is due in particular to the attention paid to commissioning these complex, high-performance machines.
The plant's reliability means it can react very quickly to changes in the electricity market. When there is a surplus of electricity on the network, Nant de Drance pumps water from the lower reservoir, Emosson, to the upper one, Vieux Emosson. Conversely, when demand for electricity is higher than production, Nant de Drance lets the water stored in the upper reservoir flow down through the turbines. This constant variation in electricity requirements determines the evolution of market prices.
"After just one year in operation, we can already see that the Nant de Drance machines are operating in line with market price trends. In this way, the power plant is fully playing its role in stabilising the electricity grid, thereby contributing to the security of electricity supply," confirms Amédée Murisier, Chairman of the Nant de Drance Board of Directors.
Since its commissioning, the plant has generated some 950 GWh of electricity and pumped 1,170 GWh. These figures confirm the predicted 80% yield of the pumped storage cycles. Alain Sauthier, Director of Nant de Drance SA, is very pleased with these results: "I'm delighted to see that the machines at Nant de Drance are being put to good use every day. Partners can take full advantage of the flexibility offered by the plant and optimise the power of the machines to suit their needs." It should be noted that Nant de Drance has only been able to access the full power of its six machines since the Chamoson-Chippis extra-high voltage line came into service on 30 September 2022.
Nant de Drance continues to implement the environmental compensation measures defined at the outset of the project in close collaboration with environmental organisations and the authorities. At the end of May, Nant de Drance invited Salvan primary school to join its teams in the fight against exotic and invasive plants. The children helped to uproot buddleias and narrow-leaved ragwort and also visited a compensation measure implemented in Vernayaz: the revitalisation of a black alder forest and the creation of environments favourable to the marsh frog and yellow-bellied toad.
In addition, three compensation measures carried out at the Col de la Gueulaz, the Vieux Emosson dam and around the Saxon canals will be the subject of an assessment report in 2023. The aim will be to check that the natural objectives defined when these measures were designed have been achieved, and to take corrective action if necessary.
For more information on Nant de Drance, go to www.nant-de-drance.ch.
Nant de Drance in brief
The Nant de Drance power plant is a 900 MW pumped storage power plant located in an underground cavern between the Emosson and Vieux Emosson reservoirs in the canton of Valais. It is operated by Nant de Drance SA, whose shareholders are Alpiq (39%), SBB (36%), IWB (15%) and FMV (10%).