For a jacket construction, in the extreme case of a 100% coverage of its
underwater surface by stuck aquaculture material during a storm, the overturning
moment at the seabed could increase by 200–300 MNm (Janssen and van der
Putten 2013), and eventually lead to the collapse of the wind turbine. However, this
risk is merely theoretical, considering the type and construction of aquaculture
materials being far less massive than the foundation itself and the unrealistic
assumption of a 100% coverage. Nevertheless, appropriate methods to avoid this
small risk can be investigated in the design phase of such infrastructure, for instance
modular aquaculture structures that fall apart in case of drifting under severe
conditions.
In severe storms with extremely high waves, an intact aquaculture structure that
is physically directly connected to the turbine foundation could theoretically lead to
the collapse of the turbine if the overturning moment at the seabed becomes too
large. For this reason, the investigated scenarios only consider aquaculture installations that are not attached to any wind turbine foundations (Lagerveld et al. 2014).
Nonetheless, if a connected wind farm-aquaculture infrastructure is considered and
designed, methods to reduce and prevent high tensile forces on the turbine foundation should be taken into account. For example, use of suitable anchors to hold
the aquaculture structure in place or application of so-called safety wires that break
at predefined tensile forces. Although the aquaculture farm will be lost in the latter
case, the turbine foundation will stay intact.
Finally, a few recommendations for the future implementation of a multi-use
platform offshore, based on Noël (2015); van der Putten (2015) and Lagerveld et al.
(2014):
• Appropriate measures should be taken to protect aquaculture and offshore wind
constructions from corrosion attack either by selection of corrosion resistant
materials or by application of suitable protective techniques or coatings.
• Type and size of aquaculture activities determine the extent of effects on water
and sediment quality. In turn, water and sediment quality may affect corrosion
resistance of the materials used. This aspect should be dealt with in a dedicated
risk assessment for the specific location.
• Maintenance aspects of materials for both offshore wind and aquaculture constructions should be taken into account already in the design phase to ensure
optimal lifetime of infrastructure.
References
Bartoli, M., Nizzoli, D., Naldi, M., Vezzulli, L., Porrello, S., Lenzi, M., et al. (2005). Inorganic
nitrogen control in wastewater treatment ponds from a fish farm (Orbetello, Italy):
Denitrification versus ulva uptake. Marine Pollution Bulletin, 50, 1386–1397.
5 Technical Risks of Offshore Structures
125
underwater surface by stuck aquaculture material during a storm, the overturning
moment at the seabed could increase by 200–300 MNm (Janssen and van der
Putten 2013), and eventually lead to the collapse of the wind turbine. However, this
risk is merely theoretical, considering the type and construction of aquaculture
materials being far less massive than the foundation itself and the unrealistic
assumption of a 100% coverage. Nevertheless, appropriate methods to avoid this
small risk can be investigated in the design phase of such infrastructure, for instance
modular aquaculture structures that fall apart in case of drifting under severe
conditions.
In severe storms with extremely high waves, an intact aquaculture structure that
is physically directly connected to the turbine foundation could theoretically lead to
the collapse of the turbine if the overturning moment at the seabed becomes too
large. For this reason, the investigated scenarios only consider aquaculture installations that are not attached to any wind turbine foundations (Lagerveld et al. 2014).
Nonetheless, if a connected wind farm-aquaculture infrastructure is considered and
designed, methods to reduce and prevent high tensile forces on the turbine foundation should be taken into account. For example, use of suitable anchors to hold
the aquaculture structure in place or application of so-called safety wires that break
at predefined tensile forces. Although the aquaculture farm will be lost in the latter
case, the turbine foundation will stay intact.
Finally, a few recommendations for the future implementation of a multi-use
platform offshore, based on Noël (2015); van der Putten (2015) and Lagerveld et al.
(2014):
• Appropriate measures should be taken to protect aquaculture and offshore wind
constructions from corrosion attack either by selection of corrosion resistant
materials or by application of suitable protective techniques or coatings.
• Type and size of aquaculture activities determine the extent of effects on water
and sediment quality. In turn, water and sediment quality may affect corrosion
resistance of the materials used. This aspect should be dealt with in a dedicated
risk assessment for the specific location.
• Maintenance aspects of materials for both offshore wind and aquaculture constructions should be taken into account already in the design phase to ensure
optimal lifetime of infrastructure.
References
Bartoli, M., Nizzoli, D., Naldi, M., Vezzulli, L., Porrello, S., Lenzi, M., et al. (2005). Inorganic
nitrogen control in wastewater treatment ponds from a fish farm (Orbetello, Italy):
Denitrification versus ulva uptake. Marine Pollution Bulletin, 50, 1386–1397.
5 Technical Risks of Offshore Structures
125