Hydroelectricity: the energy produced in Haute Maurienne
Since the beginning of the 20th century, the Mont-Cenis plateau, whose waters flow naturally towards Italy, had been developed for hydroelectric production. After the Second World War, following the Peace Treaty of 1947, the border that passed through the Mont-Cenis pass was moved in favor of France, which thus recovered the entire plateau, an ideal position to build a large dam. The new dam, built by EDF between 1962 and 1969, created a reservoir with a capacity of 320 hm3, shared between the two countries at the rate of about 1/5 for Italy and 4/5 for France.
At 120 m high and 1.4 km long, the Mont-Cenis dam is the main component of the Haute Maurienne Vanoise hydraulic system. It is a so-called "gravity dam", meaning that its enormous mass of rock opposes the pressure of the water. To fill it, water is drawn from sources such as Bonneval sur Arc. The reservoir is even connected to the Plan d'Aval dam in Aussois, on the other side of the valley! A complex system of tunnels and penstocks transfers water from one reservoir to another, supplying the Villarodin, Avrieux and Aussois power stations as required.
The Mont-Cenis site has been the focus of a program of works designed to improve the landscape and preserve an international heritage, including the rehabilitation of the Grand-Croix mountain pasture, the undergrounding of power lines and the creation of a Franco-Italian network of hiking trails. Some of the water from this development is also used to produce artificial snow for several ski resorts on Haute Maurienne Vanoise.
The Mont Cenis dam is the last one in France to be guarded because of its location on the border between France and Italy. The barragists, one French and one Italian, spend several days on the site to survey the kilometers of galleries that crisscross the mountain, to take readings and to check the quality of the installations.
At the end of the 1930s, the Société Hydroélectrique de Savoie (SHES) wanted to create the Plan d'Amont and Plan d'Aval reservoirs, above Aussois, to improve the production of its electrometallurgical plants in the valley. The works, started in 1939, were interrupted by the Second World War, then resumed by EDF at the end of the conflict. For the anecdote, or for the movie lovers, the construction site was used as a set for the movie "La Meilleure Part" with Gérard Philippe.
Above the Plan d'Aval dam, the platform of the old cable car which was used for the works, has been fitted out as a belvedere. Panels give information on the dams, the power plants but also the landscape and the environment. Since 2016, it is also possible to cross the dam of Plan d'Aval, in particular to make a 2h walk around the reservoir (for the amateurs of bicycle, it is also possible to make a superb cross-country course). You will be able to discover an amazing black sand beach and even, if the season allows it, taste some wild raspberries that grow along the path.
Built at the time of the Mont Cenis development, the Villarodin power station, at the foot of La Norma, has the particularity of being fed by the waters of 2 structures: the Plan d'Aval reservoir on the Aussois side and the Mont Cenis dam on the Val Cenis side. In 1968, when it was commissioned, the Villarodin power station held the world record for power with its 180,000 kW produced by each of its 2 Pelton turbines. Designed to supply electricity during peak demand, the plant can start up in a few minutes and supply the French electricity grid very quickly.
Because of its architecture and history, the Villarodin power plant is part of the cultural discovery itinerary Les Chemins de l'hydroélectricité: accompanied by Facim Foundation guide-lecturers, it is possible to visit the power plant in the summer and discover its links with the development of the territory, from its construction to the present day.
The Aussois power plant, in Savoie, was commissioned in 1950. The power station is equipped with 3 Pelton type turbines. It turbines the water coming from the Plan d'Aval reservoir, thanks to a metallic penstock. This pipe feeds either the hydroelectric power station of Aussois, or the wind tunnel of the ONERA center of Modane-Avrieux, located just next door (wind tunnel of aerodynamic tests of the National Office of Studies and Aerospace Research). A good example of coexistence on the same site of
hydroelectricity and hydromechanics
The Avrieux power station is the oldest in the Haute Maurienne Vanoise hydroelectric group. Construction began in 1917, but was not completed until 1923. It is fed by the Bramans dam. With its distinctive architecture and impressive engine room, it is open to visitors in summer (registration required).
The Haute Maurienne Vanoise dams supply 10 hydroelectric power stations: Bissorte, Super-Bissorte, Orelle, Villarodin, Combe d'Avrieux, Aussois, Avrieux, Plan d'Amont, Le Carrelet, Bois d'Aussois.
These developments produce, on average, each year the equivalent of 2 times the residential consumption of the Savoie department.
At the entrance to Haute Maurienne Vanoise, the Bissorte and Super-Bissorte power plants, located in the communes of Le Freney and Orelle, turbinate water from two reservoirs: the Bissorte dam at high altitude, and the Pont des Chèvres dam along the road.
Commissioned in 1986, the Super-Bissorte power station is one of six French pumped-storage power stations (STEP), the principle of which consists of transferring the same water between two reservoirs separated by a steep slope. This system allows the water to be reused, as in a closed circuit. During periods of high demand for electricity (morning, day and evening), water from the high altitude dam (Bissorte dam), descends to the power plant through a penstock. Powered by the water, the turbines produce energy. But instead of being returned directly to the river, the water is stored again in the lower reservoir (Pont des Chèvres dam). At night, when the demand for electricity is low, the water is pumped back to the Bissorte dam. The next day, the circuit can start again...
Super-Bissorte is a generation facility of national interest, capable of injecting approximately 800 MW (Bissorte and Super-Bissorte combined) in a few minutes into the electrical grid to meet a peak in electricity consumption.
