North Hoyle Windfarm Report
1 Introduction 1.1 Background Offshore wind farm installations are new to the United Kingdom and comparatively so to other countries’ waters. The installations are large in area, and in the number and size of their structures. However, at the few sites where wind farms have been constructed, little detailed practical research on their effects on navigation and communications systems has been undertaken. Some relevant known research is listed in the reference section at the end of this report [5][6][7]. Experience with other types of offshore structure and the results of desktop studies indicated that offshore wind farm structures might have the potential to interfere with shipborne, shorebased and airborne radar, VHF communications and also - although with a lower probability - position fixing, guidance and Automatic Identification Systems (AIS). Offshore wind farms, consented under Round 1 and proposed under Round 2, cover large areas of open water and hence present potential hazards to navigation. A number of them are considered to be close to or encroach into waters where there is a high density of shipping movements or be close to waters used by fishing vessels and recreational craft. Their positions are necessarily those which are exposed to weather conditions which could affect the navigation of vessels, particularly small craft. Their locations are, for technical reasons, in relatively shallow waters near shoals, and therefore in close proximity to restricted waters used by small craft and also shipping inshore gaining access to ports or to those waters providing a more sheltered passage required in inclement weather and sea conditions. Tidal streams of varying sets and rates pass through all wind farm sites. Some sites are within port limits and some lie within Vessel Traffic Services (VTS) operational limits. Of necessity, when a vessel is within or close to a wind farm, mariners should be able to place similar reliance on marine navigation systems as in open sea areas, or they should be fully appraised of any induced errors or limitations which might be encountered. From the aspect of collision avoidance, vessels need to be able to detect other craft with which they might be in an encounter and to take appropriate avoiding action. Port authorities and VTS operators require effective detection, identification and tracking of vessels navigating in their areas so as to be able to organise traffic or provide traffic information and navigational assistance services to vessels operating within port approaches or prescribed routing schemes to meet their statutory responsibilities in respect of the safety of navigation. The importance of effective detection and identification is further emphasised by the implementation of the International Ship and Port Facility Security (ISPS) Code from 1 July 2004. Emergency services such as Royal National Lifeboat Institution (RNLI) vessels, HM Coastguard and RAF helicopters require the ability to rapidly detect and react to maritime casualties. All of the foregoing require consistent and effective radio communications systems. Failure of any radar, navigation or communication system could give rise to increased risks to safety or lead to marine casualties and insurance claims or reduce the effectiveness of emergency service operations. Incidents involving passenger vessels and those carrying dangerous and polluting cargoes could have serious consequences for the public and the environment, both at sea and ashore. The proposed research was intended to obtain scientific and practical operational data on various navigation and communications systems’ performance within and in the vicinity of offshore wind farms. In particular, any degradation of the performance of systems was to be determined, quantified and, where considered necessary, cost effective solutions recommended. The offshore wind farm used in the investigation was the 30 turbine wind farm at North Hoyle, off the North Wales coast at Prestatyn. A map containing the wind farm is presented in Figure 1-1. These data will be used to inform mariners, the shipping and ports industries, the General Lighthouse Authorities, the National Federation of Fishermen’s Organisations, the emergency services, the Royal Yachting Association, wind farm developers and all other interested parties, of the extent of any system limitations, any consequent increased risks and, where necessary, recommendations as to how these should be mitigated. This outcome may also be used to inform the consents process of offshore wind farm applications. In addition to these aims, experiments were carried out to test the theoretical results from an earlier study [1]. This earlier study predicted the impact on marine radio systems by the North Hoyle wind farm. In the theoretical study [1] it was found that wind turbines have very large radar cross-sections (RCS), which means that they will scatter a large proportion of any incident electromagnetic energy. In addition to this shadows will be cast behind the turbines looking from the direction of the transmitter. The theoretical study suggested that small vessels within the North Hoyle wind farm would be detectable with marine radar (3GHz and 9GHz) if they were not in the shadow from a turbine. However, detection of the vessel could be compromised if it is very close and directly behind a turbine. The effect of the shadow at 3GHz was found to be much less severe than at 9GHz. The impact on GPS was found to be minimal and any interference would very rarely cause any corruption to the GPS data. It was determined that unless a GPS receiver is within 70m (based on a signal-to-noise ratio of 15dB) of a wind turbine then any interference would be insignificant. The theoretical study [1] also considered VHF communications. It concluded that due to the wavelength of the VHF systems any interference caused by wind turbines would be negligible. Four different trials were designed to test the validity of the results from the theoretical study outlined above. The full technical details of these trials are presented in the trial plan[2]. This report is separated into several sections that deal with the GPS, VHF communications and radar trials undertaken by QinetiQ and the MCA. In each section the experimental process is described and the results are presented in full. The structure to the report is as follows:
Figure 1-1: The wind farm at North Hoyle
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