Hydropower: energy that can be tapped to meet peak consumption
Hydropower can be started up within a few minutes, at any time. It represents a low-cost way to meet sharp fluctuations in electricity demand, thanks to the water stored in EDF’s reservoirs. Due to its operational flexibility, hydropower is the primary source that EDF uses to cope with sudden variations in consumption.
A varied source of energy
Hydropower is generated by a wide variety of facilities that regulate the grid.
“Run-of-river” hydropower is generated by low-head power plants located on rivers with strong flow, such as the Rhine. Run-of-river plants generate electricity continuously. The largest such plants on the Rhine are at Fessenheim, Ottmarsheim and Marckolsheim.
Hydroelectric plants operating with dams generate what is called “modular hydropower”. They fall into two categories, depending on their location in the mountains:
high head power plants, with low flow rate
medium head power plants, with higher flow rate
Reservoirs constitute stored potential energy. When the water is released, the energy generated is proportional to the head and the flow rate.
The most powerful French hydroelectric plant, Grand’Maison in south-eastern France, can supply 1,800 MW within two minutes – the equivalent of two nuclear reactors.
EDF is also developing marine power capacity, through power plants that use tidal and ocean current energy to generate electricity. The world’s biggest tidal power plant is at La Rance in Brittany. It began operating in 1966 and for a long time was the only plant of its kind in the world until the Sihwa plant in South Korea came into service.
With 240 MW installed capacity, the La Rance plant generates 540 GWh a year. That is 40% of the electricity produced in Brittany or the equivalent of the power consumed by a city the size of Rennes, the regional capital.
EDF operates 622 dams in France. They have storage capacity of 7.5 billion cubic metres, accounting for 75% of French artificial water reserves.
This ability to maintain balanced and secure supply is also important for Europe. On 4 November 2006, an incident on the German grid caused a sudden 10,000 MW shortfall of supply to the interconnected grid in Western Europe. In less than 30 minutes, nine dams in the Alps and the Massif Central, with total installed capacity of 5,000 MW, began generating electricity to avoid serial load shedding. Hydroelectric power saved Europe from what would otherwise have been a historic blackout.