Portal:MERMAID/North Sea - Wadden Sea

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Introduction study site

North Sea Site Factsheet
Geographical location North Sea, north of the Netherlands (Gemini project)
Offshore distance 55 km
Depth 29.5 - 33.4 m
Substrate Mainly sand (some thin clay layers)
Water temperature 2 - 20°C
Salinity 32.5 - 35.0 psu
Current magnitude 0 - 0.6 m/s
Mean tidal range Approximately 2 m
Significant wave height Generally lower than 2.1 m
Extreme wave height 10 m (1/50 yrs.)
Average wind speed 10 m/s

Combination User Functions & Design

In addition to wind energy, the combination with the following potential secondary functions will be studied and assessed:

  • Seaweed farming: Seaweed will increasingly gain importance as a raw material and is currently already imported by Dutch companies from Asia and France. The most relevant benefit of local cultivation is the possibility to offer wet seaweed on the market.
  • Shellfish aquaculture: The shellfish industry is looking for additional fishing grounds for mussel seed collectors and cultivation of mussels on longlines. An additional market for 50,000 tonnes of blue mussels is expected.
  • Wave energy extraction: Wave energy may be an option; however, the first studies reveal limited energy production potential.

A modular approach will be used for the structures for seaweed and shellfish cultivation, enabling an easy extension of the activities. These structures will be located inside and outside the offshore wind farm and will not be connected to the turbines. An alternation of seaweed and shellfish structures is envisaged. Fish farming is not feasible in this study site due to the high temperature (> 18°C in summer) and the relatively shallow water (30 m).

An artist's impression of the multi-use platform which was conceptualized in the framework of the MERMAID project for the study site in the North Sea - Wadden Sea.

Outlook & Challenges

In the future the multi-use platform may be extended to other user functions such as facilities for energy storage, tourism (recreational fisheries and diving trips) and fisheries (passive fishing gear).

Some of the key challenges that deserve further study are: the design of the seaweed/mussel farming system within the offshore wind farm (integration of the two types of aquaculture, design of harvesting equipment, etc.), the ecological challenges linked to aquaculture activities (e.g. risk assessment of environmental impact and the mitigation of diseases) and evaluation of the environmental and socio-economic benefits of this multi-use platform.

The operational challenges of this study site include the relatively high distance to the nearest main port (85 km) and the extreme wave heights which may occur during storms.