Coordinateurs du projet
Context
Floating wind turbine projects are developing promisingly on a global scale. One of their key components is the dynamic power cable that connects the wind turbines to their electrical substation and to the underwater energy grid.
It is in this context that the BIODYTHERM project, winner of the WEAMEC Research call for projects in 2019, addresses the effect of BIOcolonization of DYnamic umbilicals on THERmal exchanges.
Scientific breakthroughs and innovation
Effect of BIOcolonization of Dynamic Umbilicals on THERMAL exchanges
One of the least known and most impactful effects is biocolonization. Biocolonization refers to the development of marine concretions (algae, mussels, oysters) that can reach several tens of centimeters in thickness. Through the effects of thermal shielding, additional mass, and changes in roughness, biocolonization will impact the behavior of the dynamic cable.
Among the major effects are:
hydrodynamic stresses that alter performance in stormy conditions or under fatigue.
Thermal effects around the cable. Given the variety of cable components (buoyancy modules, stiffeners) and
the variety of biological environments, modeling this phenomenon remains a challenge. It is therefore necessary to understand the role of biocolonization, in all its variability, in order to focus studies on specific components.
The BIODYTHERM project, in conjunction with the France Energies Marines (FEM) OMDYN2 project, will work on the thermal effect of mussels on the running part of an umbilical. These species are the main colonizers of structures on the French Atlantic coast.
The Biodytherm project therefore aims, in addition to the OMDYN2 project mentioned above, to:
- design tests on instrumented and artificially colonized tubes;
- immerse uncovered aluminum tubes and aluminum tubes covered with the outer polymer insulating layer of umbilicals at the UN SEA SMS Biocolmar station.
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Expected technical and economic impact
The project aims to qualify and quantify the impact of bio-colonization on the thermal properties of dynamic cables in order to better take these effects into account in cable design.
Results
Thermal characterization – Steady state
- The effective thermal conductivity of mussels depends on their age (juvenile, mixed, or adult), which has a different percentage of water porosity.
- The effective thermal conductivity of mussels is higher than the thermal conductivity of water due to internal convection in the porous water environment of mussels.
- Convective resistance is low compared to conductive resistance.
Monitoring the growth of biological fouling – Transient
- Two models are tested (capacitive and conductive). The quadripolar model is more robust.
- The overall heat transfer coefficient is sensitive to the effect of agitation and the age of the mussels.