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Tidal Power in France

France is home to the world’s first commercial-scale tidal power plant, which is still the second largest in the world. The power station at the Rance River in Brittany France was opened in 1966 and has been operating continuously since then. It was surpassed in scale after forty-five years of operation by the Sihwa Lake Tidal Power Station in Korea. France is currently building a tidal farm for demonstration purposes that be the world’s largest tidal array when finished.

The Rance River Tidal Power Station

The Rance Power Station was opened in November of 1966 and has a 240 megawatt peak rating. It is a system consisting of a 750 meter long barrage and 24 turbines, each rated at 10 MW. The site at the mouth of the Rance River in Brittany, France was chosen for its large tidal ranges that can exceed13 meters.

The cost of installing the Rance Station was substantial, but its continuous operation since 1966 has resulted in recovery of those costs. Electricity generation by the plant is now lower than that of nuclear power. In 1997, the plant was upgraded with turbines that can spin during both ebb and flow, allowing the plant to supply roughly 300,000 homes with electricity.

Ecological impacts of the Rance Station have been extensively studied. Populations of sand-eels and plaice (a group of flatfish) and silting of the Rance ecosystem has occurred to a limited, but manageable extent. Sea bass and cuttlefish, which initially left when the barrage was built, have returned. Careful management of tide flow has allowed Rance Station operators to minimize the impact of the barrage, demonstrating that careful monitoring and control can allow barrage systems to function with minimal ecological impact.

The Paimpol-Brehat Tidal Farm

The long-term success of the Rance Station has prompted France to invest in another type of tidal power. This time, the scheme is a tidal stream farm that is currently only of demonstration scale at 8 MW. However, even at that size the tidal farm is the largest in the world.

The array is being built by OpenHydro, a company that produces seabed mounted Open-Center turbines. The open Center turbine is a modification of the Kaplan turbine that has been specifically designed to be slow-moving to minimize risk to marine life. It is also a lubricant-free system, which, when combined with the slow movement of the blades, results in a very low-maintenance system.

Each turbine is sixteen meters in diameter and is submerged in 35 meters of water. They are bidirectional, so they operate regardless of the direction of the current. Each turbine is 2 MW and four total will have been installed by the end of 2012. The total project will cost 40 million euros (56 million USD). As of its completion in 2012, the Paimpol-Brehat Tidal Farm represented the largest tidal stream generator scheme in the world.