Breaking wave in open sea

Waves

Wave-proof integrity of ORE systems

Wave observation and modelling for ORE development

The most accurate knowledge of sea states is crucial in terms of input data for the definition and optimal design of ORE projects. These properties are used throughout the life cycle of a farm:

  • evaluation of the wave energy resource at a given site;
  • estimation of loadings on wave energy systems, bottom-fixed and floating wind turbines and tidal turbines. This includes maximum loadings for survivability in extreme conditions and average loadings for fatigue design;
  • operations at sea, whether installation, maintenance or dismantling,
  • optimisation of farms electricity production.

Ideally, wave conditions are calculated from observations at the site of interest obtained from in-situ measurements and satellite observations. However, regional and local effects are important, particularly for coastal areas where waves are influenced by bathymetry and tidal currents. Since observations generally do not allow coverage of the whole area with sufficient spatial and temporal resolution over a sufficiently long period, they are supplemented by numerical simulations. France Energies Marines has been conducting R&D projects for several years with its members and partners. The Institute also studied the feasibility of developing an offshore research platform dedicated to offshore wind energy (FOWRCE SEA project).

The recent launch of DRACCAR, the first French research platform at sea dedicated to offshore wind power, coupled with an innovative R&D programme, will improve the understanding of the interactions between offshore wind power and the environment, the optimisation of the design of wind turbines and allow co-construction of a permanent observation network of the seafronts.

Wave breaking and ORE design

A collaborative R&D project set up and piloted by France Energies Marines has been completed on the characterisation of storm sea states and wave breaking with its application to the design of ORE systems (DIME project). Indeed, breaking waves induce slamming forces that are dangerous for the integrity of wind turbines or wave energy systems. The breaking is also the most important energy source for waves. It must therefore be precisely parameterised in the numerical models used to simulate and predict waves. The project has led to several innovations in the field of storm wave observation, including the capture of the breaking point and measurement campaigns carried out on a lighthouse at sea. The latter allowed 3D observations of giant breaking waves and correlation to the response of the structure in a wave-to-wave formalism.

The efforts induced by the breaking waves on floating wind turbines are studied within the framework of another project set up and led by France Energies Marines (DIMPACT project). These efforts will be explored through an experiment on a full-scale floating wind turbine, coupled tank tests and numerical simulations. The information collected will be used to develop new formulations of the slamming efforts and then integrated into the certification documents. Optimising the design of offshore wind turbines installed on sites exposed to hurricane risks is another problem encountered by technology developers. The Institute has just launched a project to better characterise the extreme winds and waves during tropical cyclones (OROWSHI project).

Resource characterisation and prediction of rogue waves

The improvement of wind characterisation in order to reduce uncertainties in resource assessment and wind turbine design was at the heart of a project set up and coordinated by France Energies Marines (CARAVELE project). The effect of waves, and in particular breaking waves, on the intensity and vertical structure of wind at sea was studied theoretically and numerically. Work was also being carried out on the impact of breaking waves on the radar signal emitted by satellites. The aim is to improve wind inversion from satellite images, in extreme conditions, thanks to an experiment conducted in the University of Miami test tank. The project also focused on the short-term prediction of the occurrence of so-called rogue waves, which could be applied to the safety of technical personnel deployed during operations at sea.

Towards a better understanding of the sea-atmosphere interface

The Gulf of Lion in Mediterranean will soon host three pilot farms and several commercial floating wind farms. In this context, a collaborative project has been launched at the initiative of France Energies Marines in order to set up a dedicated digital chain capable of accurately simulating wind, wave and current conditions in this area (CASSIOWPE project). This project focused on coupling an atmosphere model with an ocean model and a wave model. Through the development of specific parameterisations, this coupling will make it possible to accurately simulate the predominant interactions between winds, waves and the sea. The coupled numerical system will thus allow to better simulate the difficult and specific conditions of the Gulf of Lion. In particular, the effect of sea spray and marine aerosols projected into the atmosphere by the breaking waves on the heat and momentum flows at the air-sea interface are studied.

The integration of climate change impacts

Over the lifespan of offshore wind farms which is more than 25 years, the wind resource, or in other words the wind distribution, might evolve leading to a modification of the associated energy production, impacting the business plan established during the creation of these farms. Climate change could also affect the length of the seasons or their intensity and therefore impact the balance between supply and demand in the energy sector. The intensity of extreme wind events as well as their frequency can also change and impact the design of the wind turbines as well as the foundations, moorings, substations, and export cables. Extreme wave and water level events are also to be considered because they are dimensioning for these systems. An first project (2C NOW Project) has just been launched by the Institute on this subject.

List of publications related to waves (PDF)

Photo credit: Hans / Pixabay

Projects

In progress

2C NOW

Climate change impact on offshore wind

Closed

CASSIOWPE

Characterising the atmosphere and sea surface interactions for the deployment of offshore wind in the Gulf of Lion

In progress

DIMPACT

Design of floating wind turbines and impacts of energetic steep and breaking waves

Closed

ARCWIND

Adaptation and implementation of floating wind energy conversion technology for the Atlantic Region

Closed

CARAVELE

Wind characterisation for offshore renewable energies applications

In progress

DIME

Design and metocean: modelling and observations of extreme sea states for offshore renewable energies

Closed

COASTWAVE

High-resolution local analysis of wave and breaking variability from satellite imagery

In progress

DRACCAR

First French offshore research platform dedicated to offshore wind energy coupled with an innovative R&D programme

Closed

FOWRCE SEA

Future offshore wind research center at sea

Closed

MEDSEA CHECKPOINT

Assessment of the Mediterranean observational data system for targeted applications

In progress

OROWSHI

Offshore wind turbine design including joint wind-wave information in standard for hurricane-exposed sites

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Interlocutors

Florent Guinot

Florent Guinot

Site Characterisation R&D Manager

Fabien Leckler

Fabien Leckler

Modelling and Observation of Nearshore Sea States Researcher

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