The power plant will use two existing reservoirs to operate.
The lower reservoir, Lac d'Emosson, is formed by the 180 m (590 ft) tall, 555 m (1,821 ft) long Émosson Dam, an arch dam which was completed in 1974.
It withholds a reservoir with a storage capacity of 227,000,000 m³ (184,000 acre⋅ft) and surface area of 327 ha (810 acres).
The lower reservoir is 4 km (2.5 mi) long and when full, lies 1,930 m (6,330 ft) above sea level.
The upper reservoir for the plant, Lac du Vieux Emosson, is formed by a 45 m (148 ft) tall and 170 m (560 ft) long arch dam originally completed in 1955.
The dam is undergoing a raising and will be 65 m (213 ft) tall when done.
When raised, Lac du Vieux Emosson's storage capacity will be doubled and it will withhold 25,000,000 m³ (20,000 acre⋅ft) and have a surface area of 55 ha (140 acres).
When full, the upper reservoir will lie 2,225 m (7,300 ft) above sea level.

The power plant will lie in-between both reservoirs and use the pumped-storage hydroelectric method.
To accomplish this, when energy demand is high, water will be released from the upper reservoir, down a series of 425 m (1,394 ft) penstocks to the six 150 MW reversible Francis turbine-generators in the power plant.
The large underground power house measures 194 m (636 ft) long, 52 m (171 ft) high and 32 m (105 ft) wide.
After generating power, water from the power plant will be discharged to the lower reservoir.
When power demand is low, such as at night, the turbines will reverse and water can be pumped back up to the upper reservoir for use during high demand periods.
As such, it will serve a peaking power plant.

Under the guidance of AF-Consult Switzerland Ltd as general planner, the civil engineering works were carried out by GMI (a joint venture of Marti and Implenia) and the electro-mechanical works are being undertaken by GE Hydro.
The power plant will use two existing reservoirs to operate. The lower reservoir, Lac d'Emosson, is formed by the 180 m (590 ft) tall, 555 m (1,821 ft) long Émosson Dam, an arch dam which was completed in 1974. It withholds a reservoir with a storage capacity of 227,000,000 m³ (184,000 acre⋅ft) and surface area of 327 ha (810 acres). The lower reservoir is 4 km (2.5 mi) long and when full, lies 1,930 m (6,330 ft) above sea level. The upper reservoir for the plant, Lac du Vieux Emosson, is formed by a 45 m (148 ft) tall and 170 m (560 ft) long arch dam originally completed in 1955. The dam is undergoing a raising and will be 65 m (213 ft) tall when done. When raised, Lac du Vieux Emosson's storage capacity will be doubled and it will withhold 25,000,000 m³ (20,000 acre⋅ft) and have a surface area of 55 ha (140 acres). When full, the upper reservoir will lie 2,225 m (7,300 ft) above sea level.
The power plant will lie in-between both reservoirs and use the pumped-storage hydroelectric method. To accomplish this, when energy demand is high, water will be released from the upper reservoir, down a series of 425 m (1,394 ft) penstocks to the six 150 MW reversible Francis turbine-generators in the power plant. The large underground power house measures 194 m (636 ft) long, 52 m (171 ft) high and 32 m (105 ft) wide. After generating power, water from the power plant will be discharged to the lower reservoir. When power demand is low, such as at night, the turbines will reverse and water can be pumped back up to the upper reservoir for use during high demand periods. As such, it will serve a peaking power plant.
Under the guidance of AF-Consult Switzerland Ltd as general planner, the civil engineering works were carried out by GMI (a joint venture of Marti and Implenia) and the electro-mechanical works are being undertaken by GE Hydro.
Nant de Drance Hydropower Plant