Marine current generators use marine or tidal currents to generate electricity that is both renewable and predictable. In France, the main source of marine current energy is provided by tides.
How a tidal turbine works
The principle adopted for a tidal turbine is similar to that used for a run-of-water hydro plant, except in this case it is the marine current that drives the tidal turbines. They can therefore work on both the flood and ebb tides.
The potential capacity for tidal turbines is estimated at between 2,000 and 3,000 MW in France
The rotation of the turbines installed in the sea drives an alternator that generates a variable electric current (dependent on the sea currents), which is transformed in a converter before being transmitted onshore and fed into the power grid. The power, expressed in kilowatts (kW), of a tidal turbine also depends on the diameter of its turbine, or its blades, and the speed of the marine current.
Tidal turbines comprise a turbine anchored to a bearing structure that is sufficiently heavy to be simply lowered into the sea without any additional structural work, thereby minimising the impact on the sea bed. A tidal turbine’s operation has only minimal impact on the environment and the risks for marine fauna are very limited.
Paimpol-Bréhat tidal turbine: EDF innovates
In 2012, an EDF demonstrator project was initiated in Paimpol-Bréhat in Brittany, France. A major milestone was reached with the immersion of the first 2 MW prototype, designed by Open-Hydro (a subsidiary of DCNS). This tidal turbine has a diameter of 16 metres and weighs 850 tonnes.
“Normandy Hydro” project tidal turbines
Continuing with experiments in this field, EDF’s dedicated subsidiary EDF Energies Nouvelles, again in partnership with DCNS, is developing the “Normandy Hydro” project. It consists of seven tidal turbines installed in the Alderney Race between the Cotentin peninsula and the Channel Islands. On 2 December 2014, EDF Energies Nouvelles and DCNS won the call for expressions of interest (CEI) published by Ademe, the French Environment and Energy Management Agency, for this project.
The project aims to demonstrate the energy and economic performance of tidal turbines and marks a decisive step towards creating a new industrial sector in France. It should enable the two partners to establish an economic model for tidal farms before moving on to the industrial phase and the commissioning of the first commercial farms.
The next stages in the project include finalising its development, obtaining the necessary administrative permits and connecting the turbines to the grid in 2018.
With “Normandy Hydro”, EDF Energies Nouvelles has reached a decisive step in the creation of a new industrial sector in France.