Irish Offshore Wind Ports: Role in development

By Maurice Kerr, Andrija Krivokapic, Casper Holmgaard Jensen, COWI

Marshalling and stagging operations for towers, blades and nacelles at the Port of Grenaa, Denmark
Marshalling and stagging operations for towers, blades and nacelles at the Port of Grenaa, Denmark (photo: The Port of Grenaa)

In November 2021, targets were set by the Irish Government in the Climate Action Plan 2021 for 80% of electricity to be generated from renewable sources by 2030, of which 5 GW is to be from installed offshore wind [1]. To achieve these targets, a significant number of offshore wind projects are planned around the Irish coast.

As many of the country’s existing ports are considered poorly suited to servicing the rapidly evolving needs of the offshore wind industry, a key aspect of delivering such a significant commitment to offshore wind will be the development and upgrade of port facilities to support construction, operation, and maintenance activities. In many cases, the provision of adequate facilities to support construction lie on the critical path for delivery of the development.

The first part of this article provides a high-level overview of Ireland’s offshore wind projects and industry, outlines the key roles of ports as well as key attributes and infrastructure requirements with respect to supporting offshore wind developments.

The article’s second part reviews the general suitability of Irish Ports and outlines potential next steps for ports with regards to supporting the offshore wind industries 2030 targets.

Industry Status Overview
With a maritime area over seven times the size of Ireland’s land mass, there is enormous potential for offshore wind (OW) development in Irish waters; however, to date progress has been slow. While there are over 40 offshore wind projects [2] in the concept or planning phase, currently there is only one relatively small scale operational offshore wind farm, the Arklow Bank Wind Park Phase 1. Commissioned in 2004, this offshore wind farm host’s seven turbines based on mono-pile foundations (bottom-fixed) with an installed capacity of 25 MW. By comparison, in the waters surrounding the United Kingdom, as of January 2022 there are approximately 2,300 installed turbines with a capacity of over 10,000 MW [3].

Indicative Offshore Wind Farm Arrangement (illustration: COWI)
Indicative Offshore Wind Farm Arrangement (illustration: COWI)

Limitations in the existing national grid electrical infrastructure and the lack of an effective maritime planning system have been flagged by the industry as key reasons for the lack of progress in Ireland, with a need for large-scale port infrastructure to support project deployment and smaller-scale port facilities to provide ongoing operation and maintenance (O&M) services also identified. However, with the launch of the “National Marine Planning Framework” (July 2021), publication of EirGrid & SONI’s “Shaping Our Electricity Future Report” (November 2021), publication of a “Policy Statement on the facilitation of Offshore Renewable Energy by Commercial Ports in Ireland” (December 2021) and passing of the Maritime Area Planning Bill 2021 through the Oireachtas (December 2021), a pathway for accelerated progress is emerging. In particular, the Maritime Areas Planning Bill 2021, which aims to develop a simpler permitting process for offshore wind projects, is likely to be a significant catalyst for development once enacted. Additionally, EirGrid & SONI’s Shaping Our Electricity Future Report suggests the technical feasibility of reinforcing and upgrading the key areas of Ireland’s electrical infrastructure to support the 2030 targets and sets out a roadmap for key developments needed to support the transition [4].

Map of Ireland detailing potential electrical network reinforcements (illustration: EirGrid Plc, SONI Ltd 2)
Map of Ireland detailing potential electrical network reinforcements (illustration: EirGrid Plc, SONI Ltd 2)

In general, it is planned that the 2030 target for offshore wind will primarily be achieved through development of sites off the East and Southeast coasts with bottom-fixed foundation turbines on account of relatively favourable conditions and existing relatively strong onshore transmission. A relatively small contribution to the 2030 target is anticipated from installations off the West coast. In the longer term, development of sites along the Southwest and West coasts, characterised by deeper waters and a less developed existing onshore transmission systems could include the widespread deployment of floating turbines [5].

Role of Ports in Offshore Wind Development
Ports are an integral part of the offshore wind farm supply chain by virtue of their function as an interface between land based and marine activities. They play a role in all OW project development stages although the importance of location, demands on the quayside infrastructure, importance of the industry-relevant supply chain presence and other factors which dictate the development greatly differ.

Roles of ports in OW project lifecycle (illustration: COWI)
Roles of ports in OW project lifecycle (illustration: COWI)

When focusing on ports as enablers for OW turbine deployment (or roadblocks) it is particularly important to mention the installation phase. Ports used in the installation stage are known as staging or marshalling ports and are required to be in relative proximity to the OW site to reduce the duration of installation (steaming distance) and optimise the use of weather windows. This is in part driven by the high cost of leasing specialised Wind Turbine Installation Vessels which are used to shuttle and install the components.

Wind turbine installation vessel (with legs deployed, installing mono-pile transition pieces) (photo: GeoSea NV)
Wind turbine installation vessel (with legs deployed, installing mono-pile transition pieces) (photo: GeoSea NV)

A staging port serves as a marshalling yard for receipt and storage of the components. In a way, it is a final station of a distributed production line where secondary components are put together into sub-assemblies and various other finishing operations are done. To minimise offshore operations, pre-assembly and pre-commissioning of components (towers and nacelles) are undertaken here as well.

From review of the facilities used to support offshore wind farm construction at key international ports, planning and design of facilities aiming to support the offshore wind industry in future as well as through dialogue and collaboration with offshore wind developers, COWI has identified and developed a comprehensive benchmark for such facilities.

Schematic overview of the sourcing and installation process (illustration: COWI)
Schematic overview of the sourcing and installation process (illustration: COWI)

A brief overview of often critical attributes and requirements for bottom-fixed staging (marshalling) ports is listed below:

  • Based on a sample of 40 most recent projects, the median distance range between staging port and the site is 50-100 kilometres with the vast majority being less than 250 km from the staging port.
  • Sufficiently deep water in the entrance, manoeuvring area and along the berths. Generally, a minimum depth of 8 metres from Chart Datum is considered appropriate although 10-12 metres is recommended. Air draft should be unrestricted.
  • A sufficiently wide entrance to the port to facilitate vessels and cargo adequate clearance to the port and berths. Considering the significant size of some components such as the turbine support tower, transition piece, foundation section and pieces, typically an entrance width more than 200 m is appropriate, though wider is often recommended.
  • Adequate berth length, depth, and bed material to facilitate mooring, unloading, and loading of vessels. Bed material is particularly relevant as wind turbine installation vessels are to be used/deployed at berth for loading to facilitate installation of spud legs.
  • An appropriate load capacity for marine infrastructure and storage areas with regard to their proposed use within the port arrangement (e.g., storage of specific elements, loading activities etc.) and transport/handling arrangements (i.e., SPMT or crane loading etc.). Typically, bearing capacity requirements range from 5-25 tons/m2. This greatly depends on the type of berth structure and area across which the peak load can be distributed.
  • Substantial available yard area for storage and ancillary activities. In the order of 20 ha is typically required to support installation of 500 MW during one season.
Typical bottom-fixed and floating offshore wind platform types (illustration: COWI)
Typical bottom-fixed and floating offshore wind platform types (illustration: COWI)

In the case of floating offshore wind farms, many of the same roles and requirements as bottom-fixed offshore wind farms can also apply, however, further requirements are likely. This could for example be larger yard areas or facilities for launching of the floaters, if the port is to support their fabrication. If the port is intended for integration between the floater and turbine, it could require significant water depth at berths. Requirements can greatly differ depending on the type of floater that is chosen for the project.

Due to smaller vessel sizes, operations and maintenance (O&M) ports generally do not need heavy infrastructure and typically requirements are like those of commercial fishing ports. With regards to selecting an O&M base port, the distance between the port and development is a critical factor. Typically, Crew Transfer Vessels are used for distances up to 50 km though possibility extended to 100 km with accommodation facilities on substation platform or if assisted by helicopters. Use of Service Offshore Vessels allows for base port to be located anywhere from 100 to 200 km away and can be effectively located to service/maintain several offshore wind farms from one operation centre.

The focus of developers with respect to O&M ports are often primarily commercial and aimed at securing strategic long-term commitment from a port to prioritise and support O&M activities throughout the development’s service life. As such, further important factors which influence the selection of a base port are the existence of a suitable local supply chain for services and facilities associated with maintenance (typically like those associated with small vessel shipyards and the oil and gas industry) and the availability of qualified workforce. O&M can account for up to 30% of an OW development’s total cost. Spread over the service life and captured by a local supply chain, these activities often present opportunity for sustained social and economic gain in coastal communities.

Multi-port strategy where floaters are fabricated in one facility (semi-sub, in this case), transported to another port for integration with turbine and towed to the site (illustration: COWI)
Multi-port strategy where floaters are fabricated in one facility (semi-sub, in this case), transported to another port for integration with turbine and towed to the site (illustration: COWI)

An example of an Offshore Wind (OW) port prepared and used as a stagging port for both bottom-fixed and floating developments is the Port of Grenaa, Denmark. To service the offshore industry, a new section of the port was constructed to accommodate marshalling, preassembly of towers, blades and nacelles and stagging activities of the pre-commissioned components to the OW site. The new facilities include additional berth length to an appropriate water depth to accommodate load-out of pre-assembled turbine components onto installations vessels, sufficient hinterland for marshalling of components as well as a quay side area with increased bearing capacity to meet the requirements for loading by heavy turbine components and crane operations for load-out.

Grenaa is also used as an Operation & Maintenance Centre for Anholt offshore wind farm. At designated areas the seabed in front of the quay was reinforced to facilitate installation of spud legs from installation vessels during load-out. COWI# is the Port’s consultant and is currently planning and designing a new quay section for the offshore industry.

Another example of an OW port is the facility at Bladt Industries located in the Port of Aalborg, Denmark. The increasing demand for higher quay loading capacity for preassembly and stagging of bottom-fixed foundations was met by an upgrade of the port’s existing facilities (planned and designed by COWI#). Structural upgrade of the existing quay front area was performed to accommodate heavy loading with transition pieces, monopiles and top sided elements load-out activities. Designated areas of the quay front were further upgraded to accommodate heavy loading during crane load-out operations and for load-out by roll-on with SPMT’s (Self-Propelled Modular Transporter). Hinterland areas were also reinforced to accommodate operations for up-ending, preassembly and storage of transition pieces.

A further example of a port which has developed to support the OW industry is Belfast Harbour. Belfast’s D1 facilities include a maintained channel depth of 9.3 m, berths for vessels of up to 9.5 m draught, no air restrictions and a purpose-built 50-acre offshore wind terminal which includes a 480-m heavy-duty quay (capacity up to 50 ton/m2) with jacking-up capability for installation vessels. To date, Belfast Harbour has been instrumental as a staging port to support construction of the West of Duddon Sands, Walney Extension West and Burbo Bank Extension offshore windfarms.

[1] Department of the Environment, Climate and Communications (2021), Climate Action Plan 2021, published on the 4 November 2021, accessible at

[2] 4C Offshore (2021), viewed at on 28 December 2021.

[3] RenewableUK (2021), Wind Energy Statistics, viewed at on 28 December, 2021.

[4] EirGrid & SONI (2021), Shaping our electricity future A roadmap to achieve our renewable ambition, published on November 2021, accessible at

[5] Department of Transport (2021), Policy Statement on the facilitation of Offshore Renewable Energy by Commercial Ports in Ireland, published on 20 December 2021, accessible at

The authors:
Maurice Kerr, B.Eng. (hon) MSc C.Eng MIEI MICE, Associate (Maritime) with COWI’s Energy Practice (

Andrija Krivokapic, MSc, Head of Section of COWI’s Terminals Team (

Casper Holmgaard Jensen, MSc, at COWI within the port construction field (

COWI is an international consulting group, specialising in engineering, environmental science, and economics. Having assisted private and public clients with the review and assessment of port facilities to support offshore wind developments in countries including Denmark, Norway, United States, Japan, Korea, Turkey and Greece as well as working closely with offshore wind farm developers, COWI has amassed a wealth of experience in the offshore wind ports area. As an international leader in the renewable energy and transportation engineering sectors, COWI is also assisting clients with the achievement of development, efficiency, sustainability, and environmental goals in the Port of Oslo, Copenhagen Malmo Port, Port of Frederikshavn, Port of Skagen, and Port of Esbjerg to name a few. COWI has also been appointed as owner’s engineer to develop the world’s first energy island in the Danish North Sea.