Bottom-fixed offshore wind farm
France Energies MarinesBottom-fixed offshore wind

Bottom-fixed offshore wind

A wind of maturity reinforced by R&D is blowing on bottom-fixed offshore wind sector

Mature technology, but challenges for increased performance

Bottom-fixed offshore wind technologyis emerging in Northern Europe as one of the main sources of renewable energy. At sea, as winds are more stable and often of higher average speed, offshore wind farms have a load factor of 45%, i.e. twice as high as a French onshore wind farm (22%) and 3 to 4 times higher than photovoltaic installations in France (15% maximum in the Southern Region). Since 2010, global offshore wind capacity has been growing at around 30% per year. The technology is now mature and the average cost of the energy produced has become very competitive. Challenges remain, however, to further improve the performance of bottom-fixed offshore wind sector and to integrate it into the energy mix of a number of countries, particularly France, which has the second largest coastline in Europe.

Bottom-fixed offshore wind sector faces technological, logistical and socio-economic challenges

The main challenges for a deployment of bottom-fixed offshore wind sector posed in France and in countries with geographical or political similarities are :

  • The integration of commercial wind farms into the maritime activities already in place on the French coasts, with first and foremost transport and fishing already fully integrated into zoning decisions;
  • The setting up of an industrial sector and dedicated port areas to manage the construction of a farm. As an illustration, the rotor disc of a 15 MW wind turbine is more than 200 m long and a farm has 35 to 50 machines;
  • The construction of an installation and maintenance chain with adapted means: boats for transporting large-diameter blades, masting systems at sea, intervention on nacelle, storage place for repairs in the port…;
  • The new generations of turbines whose increasing unit power implies the use of rigid piles for which standard design methods are not adapted;
  • The poorly known carbonated soils present on the seafront of Northern France;
  • The economic attractiveness that requires achieving an average cost of energy produced that is competitive with other sources of decarbonated energy. This concerns the optimum between the full costs of a wind farm and production, but also access to financing;
  • Socio-economic policies that set the framework for the medium- and long-term deployment of energy production technologies;
  • Applicable regulations and the acceptability of projects can lead to significant delays that then limit the deployment of technologies.

In France, the first calls for tenders for commercial bottom-fixed offshore wind farms were launched in 2011. However, it was not until 2019 that the first one was fully authorised and orders were placed for work to start in the wake. In 2019, the proposed tariff for the new wind farm awarded by the French government also reached very competitive levels.

Characterising winds and seabed, studying environmental pressures and induced effects

All the activities of France Energies Marines contribute to providing solutions to the bottom-fixed offshore wind sector. This is mainly achieved through collaborative R&D projects which allow in particular to :

  • Reduce uncertainties on the characterisation of wind resources and thus contribute to the optimization of production (CARAVELE and DRACCAR-NEMO projects);
  • Better characterise the physical environment such as wave fields, but also soils, and thus integrate more precise data for the design of systems (DIME, GEOSISMEM and OROWSHI projects);
  • Better characterise sediment transport, particularly that linked to the movement of underwater dunes, while integrating the study of the ecosystem (DUNES and MODULLES projects);
  • Better evaluate the interactions with soils representative of French sea facades (including carbonated soils) taking into account the new rigid behaviour of monopiles in order to design the foundations for a 30-year life span (SOLCYP+ project);
  • Optimise environmental, societal and economic impact studies by proposing original models integrating the ecosystem in the broadest sense to support project acceptability (TROPHIK, APPEAL and WINDSERV projects);
  • Evaluate the environmental impacts of certain components or systems used in ORE farms, such as galvanic anodes (ANODE project) or power export cables (SPECIES project), and thus help change the regulatory framework;
  • Propose environmental monitoring solutions such as passive acoustic monitoring of benthos (BENTHOSCOPE and BENTHOSCOPE2 projects) and characterisation of biofouling on submerged components (ABIOP, ABIOP+ and BIODHYL projects);
  • Identify ways to improve the environmental and societal sustainability of offshore wind farms by analysing their life cycle (LIF-OWI project);
  • Develop a research platform at sea (FOWRCE SEA project);
  • Carry out preliminary studies about hydrogen offshore production (OPHARM and OPHARM2 projects),
  • Propose multi-criteria optimisation for the supply of isolated grid (OPTILE 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.

These various studies provide the sector with validated models, adapted measurement methods, representative data and recommendation reports based on recognised expertise. The COME3T approach contributes, for example, to the acceptability of projects by offering summary reports for a very wide audience. These cover a wide range of topics related to the environmental integration of ORE, for which the scientific experts in the field provide neutral and independent insight.

List of publications related to bottom-fixed offshore wind (PDF)

Photo credit: Fokke / AdobeStock

Projects

In progress

DRACCAR – NEMO

New methods for turbulence measurements and models in offshore wind

Closed

DUNES

Dynamics of hydraulic dunes and impact on ORE projects

Closed

WINDSERV

Towards a multi-model approach of indicators of ecosystem services

Closed

ABIOP+

Consideration of biofouling using quantification protocols useful for engineering

Closed

ANODE

Quantitative evaluation of metals released into the marine environment from the galvanic anodes of ORE structures.

Closed

BENTHOSCOPE 2

Understanding and monitoring of ORE impacts on the benthic compartment via a measurement platform dedicated to passive acoustic

Closed

BHFM

Hydrodynamic benchmark for the study of non-linear wave/structure interactions for massive foundations of offshore wind turbines

In progress

BIODHYL

Biofouling characterization and description of hydrodynamic loadings

Closed

CARAVELE

Wind characterisation for offshore renewable energies applications

In progress

CEAF

Common Environmental Assessment Framework

Closed

COASTWAVE

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

In progress

COME3T

Committee of experts for offshore renewable energies environmental and socio-economic issues

Closed

DIME

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

In progress

DIMPACT+

Design of offshore wind turbines and impact of extreme and breaking waves

Closed

ECUME

French working group on cumulative effects of ORE projects

In progress

FISH INTEL

Monitoring the movements and favoured habitats of several important marine species through a cross-Channel acoustic telemetry network

In progress

FISHOWF

Effective monitoring strategies to identify and evaluate effects of offshore wind farms and their export cables on fish communities

Closed

FOWRCE SEA

Future offshore wind research center at sea

Closed

GEOBIRD

Development of an innovative geolocation tag for seabirds

Closed

GEOSISMEM

Geophysical surveys for the seabed characterisation of offshore renewable energy sites

Closed

LIF-OWI

Environmental, socio-economic and technological challenges for life cycle assessments of offshore wind farms

Closed

MEDSEA CHECKPOINT

Assessment of the Mediterranean observational data system for targeted applications

Closed

MODULLES

Modelling of marine dunes: local and large-scale evolutions in an OWF context

Closed

OPHARM

Hydrogen and offshore wind: decision-support tools

In progress

OPHARM2

Advanced analysis for offshore production of hydrogen from offshore wind

In progress

OPTILE

Multi-criteria optimisation for offgrid marine renewable electrical production

In progress

OROWSHI

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

In progress

OWFSOMM

Offshore wind farm surveys of marine megafauna: standardisation of tools and methods for monitoring at farm scales

Closed

SEMMACAPE

Monitoring and study of marine megafauna in wind farms by automatic characterisation

Closed

SOLCYP+

Cyclic loadings of offshore wind turbine monopiles

Closed

SPECIES

Subsea power cables interactions with environment and associated surveys

Closed

TROPHIK

Modelling the role of offshore wind farms in modifying the functioning of coastal food webs and cumulative impact

In progress

WREN

Collaborative initiative dedicated to the effects of wind energy on the environment

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Jean-Francois Filipot

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