France - Underwater turbines to supply energy from the ocean

Ocean currents as a source of energy: the French start-up "Normandie Hydroliennes" (NH) wants to generate energy using the power of the tides. The company is planning to build a field of "underwater wind turbines" on the seabed to convert the power of the ocean's movements into green electricity.

Tidal power station

Wind, cooling processes on the water surface and the gravitational forces of the moon and sun are permanent drivers of water movement in the oceans - just as the wind is constantly moving above sea level. However, unlike wind, the energy of ocean currents has hardly been utilised for electricity production to date.

Realisation

As part of the first project 'NH1', Normandie Hydroliennes wants to install four underwater turbines with a total output of 12 megawatts in the Strait of Alderney, around 3 kilometres off the coast of Normandy, and connect them to the grid by 2028. According to the manufacturer, the tidal power plant works in a similar way to wind turbines, but with smaller rotor blades. This should not only reduce costs compared to other tidal power plants, but also make it easier to expand the plant.

Deployment area in the Strait of Alderney/Normandy. Source: Google/Map data 2025

Normandy

The location of a tidal power plant is crucial for its efficiency. In order to optimise electricity production, the plant needs a current that is as steady as possible with a sufficiently high speed - and this is exactly what the Strait of Alderney offers. Here, the current regularly reaches speeds of up to 12 knots (around 22 km/h). This should enable the power plant to generate around 34 gigawatt hours of electricity in up to 3,000 hours per year. Enough to supply around 15,000 people with energy.

Looking ahead

If the tidal power plant proves to be profitable, the plant is to be expanded to 250 megawatts. According to the operators, the total potential for tidal power plants off the French coast is around 6 gigawatts - equivalent to the output of two conventional nuclear power plants. However, in order to realise this potential, around 2,000 underwater turbines are needed, as well as funding: the European Union is supporting the project with 31 million euros from the Innovation Fund. And once again, it is a French company that is leading the way here.

Marineforum has already reported on this topic several times. You can find more background information in the article from 21 February 2024. Offshore energy: underwater turbines

kdk, Computerbild