(111g) Risk Assessment Model for Defining Minimum Distance of Shipping Lanes from Offshore Wind Farm Location

With the rush of Energy Transition, Offshore Wind Farms are rapidly becoming a greater contributor to the energy grid, as presented by DNV in the 2023 Energy Transition Outlook (https://www.dnv.com/energy-transition-outlook/index.html). For its development, several wind farms are planned in waters with high shipping density. This may create a potential conflict of interest between navigation of ships and the wind farms due to different operational aspects. When a wind farm is installed, safety distances from wind farms will be defined and this implies in modification of shipping lanes, that will interfere on commercial shipping. It can also influence on fishing ships, for the farms located in shallow waters. Additionally to that, an increase on shipping traffic is expected based on requirements for installation, maintenance and supply for wind farm operations.

Although a collision is an undesired event for both segments, the understanding of impacts to business continuity and in terms of who is responsible for tanking the proper measures to reduce the risks sometimes is not entirely clear. These uncertainties can escalate turning in a scenario of implementation of restrictions by regulatory agencies. This scenario can delay the installation of new wind farms and therefore delaying the energy transition.

The best way to understand the possible impacts and also to promote important discussions about the subject is to gather the maximum information about the risks associated with using a formal safety assessment to ensure that all actions will be taken to reduce the probability of collision.

The safety assessment will help to understand the expected consequences from a ship collision against a wind turbine offshore, as:

• production loss due to impact on offshore transformer;
• total loss of ships and loss of life due to collision of smaller ships (fishing ships, pleasure boats);
• ship impact against manned installation, with structural loss and potential fatalities;
• potential serious damage to ships and multiple fatalities in case of impact of passage ships;
• potential oil pollution.

The objective of this paper is to present a model to estimate shipping collision frequency and shipping collision impact towards offshore wind farms, with focus on merchant passing vessels, considering different volumes of shipping traffic and shipping size versus distances from shipping lanes.

This paper explore methodology for ship frequency calculation, based on DNV Recommended Practice DNV-RP-F107 and the methodology presented in The Centre for Marine and Petroleum Technology (CMPT), A Guide to Quantitative Risk Assessment for Offshore Installations, 1999, that define how to calculate the likelihood of having a ship collision of a passing vessels against an offshore platform. This methodology has been adapted by authors to estimate frequency of collision against wind farm turbines installed offshore.

This paper will calculate two events of collision, powered collision where Merchant vessels can collide against wind farms with powered engines or they can drift-off and be trawled by the currents, waves and wind towards wind farms.

For this paper, model is adapted to use data extracted from AIS, regarding density (number of ships passing), ship velocity, and typical ship size.

Results are presented as expected number of incidents per year, and expected design accidental load to support decision on possible mitigations as:

• Location of Offshore Wind Farms;
• Definition of collision load for design of offshore structures;
• Additional mitigation for reducing likelihood of ship collision.

Additionally, different distances and volumes of traffic are assessed in order to defined tolerable distance from shipping lanes, for several volumes of traffic. This information is relevant to support decision of location of offshore wind farms, focus in minimizing impacts of shipping collision, especially for areas located near high traffic areas.