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NASH Maritime, part of APEM Group, explores offshore renewables Search and Rescue best practice to identify what Coast Guards are looking for in offshore wind farm layouts.
IntroductionÂ
Designing an offshore wind farm (OWF) layout necessitates considering multiple, often competing interests and constraints. Factors include engineering aspects such as wind yield and energy cost, in addition to external aspects, such as its appearance within the seascape and landscape, bathymetry and geotechnical properties of the seabed.
Another key constraint, sometimes overlooked by developers, is ensuring the safety and effectiveness of search-and-rescue (SAR) missions within the OWF. Coast Guards have a duty to provide SAR to persons in distress within their responsible regions, including within proposed OWFs, in line with many national and international conventions, such as Convention of the Law of the Sea (UNCLOS), Convention on Safety of Life at Sea (SOLAS) and Convention on Maritime Search and Rescue.
OWF layouts are expected to support SAR operations by adhering to relevant national guidance and key design principles. In the UK, this is primarily outlined in the Maritime and Coastguard Agency (MCA)’s Marine Guidance Note (MGN) 654. Ireland recently formalised its own guidance in June 2025, with the Department of Transport (DoT) and Irish Coast Guard (IRCG) publishing their Guidance on Safety of Navigation & Emergency Response and Guidance and Operational Considerations for SAR and Emergency Response, respectively. Similar guidance is published in the US Coast Guard’s NVIC 02-23 and Australian Maritime Safety Authority’s policy.
The overriding objective is to ensure that turbine layouts are designed to allow safe transit through OWFs by SAR helicopters operating at low altitude in bad weather, and surface vessels, conducting search and or rescue activities. Through our extensive experience advising developers with SAR considerations in OWFs, we have identified three primary SAR layout principles that coastguards look for, which developers need to consider from the outset when designing and proposing OWF layouts:
- Lines of Orientation
- SAR Access Lanes
- Linearity of Structures
Principle 1 – Lines of Orientation
Definition and Objective: A series of imaginary parallel lines drawn across the OWF on a consistent bearing aligned with all infrastructure. To ensure predictability of structures and provide multiple options for passage planning through the OWF.
Layout Principle
- Developers should strive to have multiple lines of orientation within the windfarm to create alternative corridors for both SAR aircraft and surface vessels to plan safe and efficient passage through the site under varying conditions and requirements.
- The layout should represent a grid pattern and be as regular as possible.
- Where possible, these should be designed to align with the prevailing wind direction to facilitate SAR helicopters.
- Proposals for a single line of orientation must be supported by an appropriate safety justification and may require additional mitigation.
Schematic showing lines of orientation for an ideal grid layout.
Principle 2 – SAR Access Lanes
Definition and Objective: Routes from one side of a windfarm to the other (or helicopter refuge area) on a consistent heading, with sufficent width and unobstructed by hazards. Primarily to be used by SAR helicopters at low altitude, in bad weather or poor visibility when relying on instruments.
Layout Principle
- Developers should ensure that SAR access lanes are at least 500Â m wide exist (when measured between adjacent turbine blade tips transverse to the lanes) exist between the lines of orientation, forming straight, parallel SAR access lanes between the structures (including any platforms or substations within the windfarm).
- SAR helicopters typically enter these lanes at a point 0.5 nautical miles (nm) perimeter of the OWF, aligned with the lane’s centreline, then travel along the designated bearing before exiting into safe airspace – either outside the windfarm on the other side, or into a designated refuge area.
- Once the layout has been approved and finalised, the location, spacing, length, and orientation of the lanes must be documented in the windfarm’s Emergency Response Cooperation Plan (ERCoP).
Schematic showing perspective down a SAR Access Lane centreline.
Principle 3 – Linearity of Structures
Definition and Objective: A measure of deviation of infrastructure from the lines of orientation. Turbines should be as far as practicable aligned with the lines of orientation; non-linear layouts may not necessarily provide an effective and safe search environment.
Layout Principle
- All search patterns used by SAR are essentially linear and therefore the layout of the OWF should be as linear as possible to facilitate this and ensure that the search area is consistently covered with a high probability of detection.
- Developers should ensure that all windfarm structures (turbines, substations, platforms, and any other structure within the windfarm site) are linear and well aligned with the lines of orientation.
- Linearity of structures reduces the possibility of unswept areas in the wind farm by a helicopter carrying out search and rescue operations and ensures that SAR units can navigate the site predictably and safely, especially when operating at low altitudes or in poor visibility.
- Micrositing should be carried out to ensure the least impact on the linearity of the layout within distances agreed with the Coast Guard.
- Perimeter turbines may have smaller spacing than internal turbines and form dense borders, provided SAR access lanes are not obstructed.
Schematic showing an ideal linear layout vs a non linear layout with turbines deviating from the lines of orientation.
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Conclusion
As the size and scale of OWFs continues to increase, the importance of ensuring SAR access within the OWF layout is essential. Layout sits within a wider suite of mitigation measures developers must implement to manage safety including monitoring, lighting and marking, developing emergency plans and training of personnel.
Decades of experience have resulted in clear guidance and best practice around layout principles that will support safe and effective SAR operations, particularly noting lines of orientation, access lanes, and structural linearity. Whilst these principles have proven effective, it’s recognised that each site is unique and may necessitate deviations, therefore a case-by-case approach, supported by early engagement, is essential.
NASH Maritime, part of APEM Group, has a highly experienced team with a long track record of supporting developers with site selection, navigation risk assessments, emergency response planning and post-consent plan discharge.
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