Restoring power to the tidal stream energy sector with R&D support

Tidal stream energy, a high-potential sector still in the making

Systems that recover the kinetic energy of tidal currents have three major advantages: discretion, compactness and predictable production. There are many types of converters, but the most common are turbines, either horizontal or vertical axis, similar to wind turbines. The systems are either bottom-fixed or floating. With three pilot farms and numerous proven full-scale demonstrators, Europe is the world leader in tidal turbines. The most advanced developers now have thousands of operating hours under their belts and have injected large volumes of electricity into the grid. The tidal stream energy sector, mostly made up of small innovative companies, receives significant financial support from the European Union and the Member States concerned. It is currently in the process of developing, and is focusing its efforts on economic performance to ensure industrial development.

Profitability in the heart of challenges of tidal stream energy

In order to develop fully in Europe and internationally, the tidal stream energy sector must meet several challenges:

Profitably exploiting highly localised resources by orienting the sector more towards a market for which direct competition from mass power generation is less decisive, such as that of islands or offshore coactivity;
Reducing the investment cost, which is still much higher than that of offshore wind energy;
Improving the sustainability of systems that are subject to strong and sometimes turbulent sea currents, but also to the development of biofouling on key components;
Gaining in reliability to minimise maintenance operations and the extremely high associated costs;
Having tools and methods for the deployment of farms and their optimisation from a technical and economic point of view;
Achieving successful environmental integration by minimising impacts on marine life, both benthic and pelagic communities;
Being an integral part of the use of maritime space, notably by ensuring compliance with regulations and working for the acceptability of projects.

France Energies Marines became interested in the challenges of tidal stream energy at a very early stage and continues to meet the needs of the sector thanks to R&D activities dedicated to this sector or dealing with cross-cutting aspects of the various ocean energies.

Quantification of the resource, removal of technological locks and environmental integration

Several R&D projects set up and piloted by France Energies Marines have focused on the Alderney Race area with high tidal stream potential off the Cotentin peninsula. The interaction between winds, waves and currents was thus examined in order to assess its influence on the resource at seafloor level (HYD2M project). The turbulence of currents induced by their interactions with the seabed or the coast was also studied for applications related to the design of tidal turbines (THYMOTE project). A particular focus was carried out on the dynamics of sediments, and in particular pebbles, in the presence of strong tidal currents in order to anticipate the possible impacts on the turbines that would be installed in the area (PHYSIC project).

The R&D carried out by the Institute, its members and partners, also carries out innovative studies to lift specific technological locks: long-term stability of underwater glue joints (INDUSCOL project), behaviour of dynamic export cables of floating systems (OMDYN and OMDYN2 projects), polyamide mooring solutions (POLYAMOOR, MONAMOOR and BAMOS projects), monitoring of mooring lines (MHM-EMR project) and optimisation of control systems (ELEMENT project).

The environmental effects of tidal turbines are considered together with the passive acoustic monitoring of benthic species (BENTHOSCOPE and BENTHOSCOPE2 projects), the characterisation and quantification of biofouling on underwater structures (ABIOP, ABIOP+, ELEMENT and BIODHYL projects), the study of the potential impact of electromagnetic emissions on marine species (SPECIES project) and the quantitative assessment of metals released into the marine environment from galvanic anodes (ANODE project).

Collaborative R&D work is also carried out at the farm scale, mainly to develop numerical design and optimisation tools (VALARRAY and DTOCEANPLUS projects), but also to estimate the stability of power export cables in the high-stream environments (STHYF project) or to propose a multi-criteria optimisation for the supply of isolated grid (OPTILE project).

Representation and participation in tidal energy R&D networks

France Energies Marines is strongly involved in several international initiatives dedicated to supporting ocean energies in terms of R&D:

Support for the implementation of the European strategic plan for tidal and wave technologies (OCEANSET project),
Technology Collaboration Program to provide an accurate view of the entire sector (TCP/OES),
Monitoring the environmental effects of the development of these energies (OES-Environmental).

List of publications related to tidal stream energy (PDF)

Photo credit: Sabella