The Grand'Maison Dam is an

embankment dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface and ...

on L'Eau d'Olle, a tributary of the

Romanche River The Romanche () is a long mountain river in southeastern France. It is a right tributary of the Drac, which is itself a tributary of the Isère. Its drainage basin is .Vaujany Vaujany () is a commune in the canton of Oisans-Romanche, in the Isère department in southeastern France. The village is picturesque, with excellent views of the Grand Galbert mountain at the head of the valley. Population Economy The hydroe ...

Isère Isère ( , ; frp, Isera; oc, Isèra, ) is a landlocked department in the southeastern French region of Auvergne-Rhône-Alpes. Named after the river Isère, it had a population of 1,271,166 in 2019.French Alps The French Alps are the portions of the Alps mountain range that stand within France, located in the Auvergne-Rhône-Alpes and Provence-Alpes-Côte d'Azur regions. While some of the ranges of the French Alps are entirely in France, others, such as ...

. The primary purpose of the dam is to serve as the upper reservoir for a

pumped-storage hydroelectric Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential ...

scheme where

Lac du Verney Lac du Verney is an artificial reservoir in the department of Isère, in the Rhône-Alpes of France. It serves as the lower reservoir for the Grand'Maison Dam pumped-storage scheme. Neighbouring lakeside communities include Oz and Allemond A ...

located lower in the valley is the lower reservoir. The dam was constructed between 1978 and 1985 with its power station being commissioned in 1987. With an installed capacity of 1,800 MW, it is the largest hydroelectric power station in France.

Design and operation

The Grand'Maison is an embankment dam with a height of from the riverbed and from foundation. It is long and has a fill volume of . The reservoir withheld by the dam, Lac de Grand Maison, has a storage capacity of . The power generation process begins with water stored in its reservoir at an altitude of . By means of a long head-race tunnel which splits into three long

penstock A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydro turbines and sewerage systems. The term is inherited from the earlier technology of mill ponds and watermills. H ...

s, water is sent down to the power station. It is located on the rear bank of Lac du Verney at which lies at an elevation of . The power station has above-ground and below-ground levels. On the above-ground level, there are four 150 MW

Pelton turbine The Pelton wheel or Pelton Turbine is an impulse-type water turbine invented by American inventor Lester Allan Pelton in the 1870s. The Pelton wheel extracts energy from the impulse of moving water, as opposed to water's dead weight like the trad ...

-generators which are used for normal conventional hydroelectric power generation. The below-ground level contains eight 150 MW

Francis pump turbine The Francis turbine is a type of water turbine. It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency. The proces ...

s which can be used for both power generation and pumping. After electricity is generated, the water is discharged into Lac du Verney, the lower reservoir. When storage in Grand'Maison needs to be replenished, the turbines reverse into pumps and move water from Lac du Verney back to the Grand'Maison Reservoir. The change in elevation between the reservoirs afford the above-ground station a maximum

hydraulic head Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum., 410 pages. See pp. 43–44., 650 pages. See p. 22. It is usually measured as a liquid surface elevation, expressed in units of length, ...

of and the below-ground station . The power station repeats the pumped-storage process as needed and acts as a

peaking power plant Peaking power plants, also known as peaker plants, and occasionally just "peakers", are power plants that generally run only when there is a high demand, known as peak demand, for electricity. Because they supply power only occasionally, the power ...

. Power generation or pumping can be initiated within minutes. On an annual basis, the power station generates 1,420 GWh of electricity and consumes 1,720 GWh in pumping mode. Because pumping occurs during periods of low demand when electricity is cheaper than power generation during those of high demand, the power station is profitable.

References

{{Authority control Dams in France Embankment dams Pumped-storage hydroelectric power stations in France Buildings and structures in Isère Dams completed in 1985 1987 establishments in France Energy infrastructure completed in 1987

Design and operation

See also

References