NREL - National Renewable Energy Laboratory

POSSIBLE EFFECTS OF THE OFFSHORE WIND FARM AT VINDEBY ON THE OUTCOME OF FISHING, The possible effects of electromagnetic fields and noise

Publication TypeReport
Year of Publication2002
Document Number1920-03-001, rev. 2
Pagination23 pp.
Date Published01/2002
InstitutionBio/consult as
CityÅbyhøj, DK

1. Introduction
Vindeby Offshore Wind Farm, the worlds first commercial offshore wind farm, was commissioned in 1991. It is situated in the Great Belt, Denmark, a couple of kilometres NW of the island of Lolland. The offshore wind farm, build by SEAS, has a capacity of 4.95 MW and consists of 11 Bonus 450 kW stall controlled wind turbines in two parallel rows from NW to SE. According to SEAS, the cables (or power lines) interconnecting the 11 turbines and connecting the offshore wind farm to the shore are all 10 kV tripolar, 50 Hz alternating current cables. The turbines are founded in conical “Gravitation Foundations” built in concrete and filled with sand and gravel. The distance between the turbines is approx. 500 meters. The water depth in the turbine area varies from 2-6 meters. For a map of the wind turbine area, wind turbines and cables, Figure 2, page 15.

2. Background
A professional fisherman, Bjarne Kolath from Onsevig, who fishes around the northern part of Lolland, states that although there seems to be an increase in the number of fish near Vindeby Offshore Wind Farm since the establishment of the offshore wind farm, the flatfish, especially turbot (Psetta maxima), do not migrate between the turbines when it is windy.

Bjarne Kolath has explained, that if series of gill nets designed for turbot are placed between the turbines perpendicular to the two rows of turbines (so that there are nets both between the turbines and outside the wind farm, on both sides) he will catch fish in both ends of the series but not in the middle of the series.

Bjarne Kolath claims that it is the alteration of the magnetic fields between the turbines when it is windy and associated electrical currents running through the cables, which are responsible for the lower catch inside the wind farm in windy weather since he does not observe a similar pattern in calm weather.

3. Objective
The objective of the investigation was to examine the observations of Bjarne Kolath regarding his catches of turbot in varying weather conditions and, on the basis of his observations and literature studies, set up an investigation to determine whether or not electromagnetic fields and/or noise from Vindeby Offshore Wind Farm affects fish and fishery within the turbine area.

An agreement was made between SEAS, Bjarne Kolath and Bio/consult, that Bio/consult should contact Bjarne Kolath and join him on a fishing trip, after which Bjarne Kolath should register all catches from the area.

The purpose of the investigation was as follows:

1. Is the observation of Bjarne Kolath correct, that there are no fish in the wind farm area when it is windy?

2. If so, more specifically, under what circumstances are catches reduced? For example magnetic fields, noise, altered hydrographical conditions, increased turbidity, shadow effects of the rotor blades etc. Wind turbines, like other tall structures, will cast a shadow on the neighbouring area when the sun is visible. When the turbine is operating the rotor blades chop the sunlight, causing a flickering (blinking) effect while the rotor is in motion.

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TagsDenmark; Offshore Wind; Turbots; 2002; Report