Apollo’s feasibility study at the Port of Nigg explores how adapting existing oil tanker jetties can provide safe and cost-effective solutions for the mooring of floating offshore wind turbines. The full report is included at the end of this case study.
The problem
When planning for Floating Offshore Wind Farm developments, there is a need to consider holding points for the assembled turbines before their tow to field.
Early planning is required to ensure that fabrication, assembly and marshalling of Floating Offshore Wind Turbines (FOWTs) can be safely performed at the required scale.
There is also a need for temporary berths for FOWTs that have been towed to port for repair or maintenance.
Studies by Apollo and others for the ORE Catapult have found that there are very few berths in the UK with sufficient water depth to accommodate a FOWT at maximum draught with the Wind Turbine Generator (WTG) fully assembled.
With the UK’s floating offshore wind sector gearing up for large-scale deployment, cost-effective, near-term solutions are needed ahead of the first project rollouts.
The background
The Port of Nigg is one of Scotland’s most important offshore energy facilities, with a long track record in supporting the construction and deployment of fixed wind turbines.
In recent years, the port has significantly enhanced its infrastructure to support the floating offshore wind sector. As part of its upgrade programme, an opportunity was identified to repurpose the existing under-utilised oil-tanker jetty as a deep-water mooring berth to increase construction throughput.
Building on this opportunity, Apollo was commissioned by GEG – under Scottish Enterprise funding through the Scotland CAN DO Offshore Wind Innovation Feasibility Challenge Call – to carry out a feasibility study on adapting oil-tanker jetties for FOWT mooring.
Using the Port of Nigg as a base case, the study set out to demonstrate how modest berthing system upgrades could address key constraints and bottlenecks in the floating wind supply chain. The study highlighted how using existing Oil & Gas infrastructure can reinforce Scotland’s leadership in renewable energy deployment towards the 2030s and beyond.
The process
The study included:
- Design and operational criteria definition: the mooring, marine operations, and pre-commissioning activities requirements were defined for the jetty to function as a FOWT pre-commissioning berth.
- Jetty design: a mooring system design compatable with the Port of Nigg jetty was developed, specifying equipment modifications and additions to support mooring, berthing, and pre-commissioning activities.
- Marine execution: Using the Port of Nigg’s construction workflow, a full sequence of marine operations was defined covering operations from WTG integration completion to tow-out to field, including contingency procedures.
- Feasibility analyses: Multiple assessments were conducted to evaluate the viability of the proposed concept, including mooring analysis to confirm operability and structural capacity of the jetty, structural checks, and feasibility of the proposed marine operations.
- Cost and operational benefit: CAPEX was estimated, identifying operational gains, while highlighting additional opportunities.
- Universal applicability and stakeholder engagement: A review of alternative floating platform designs and jetties was performed to assess the broader applicability of the study’s findings. Additionally, a consultation programme was undertaken to gather insights on operational, technical, and commercial considerations, ensuring that practical feasibility and stakeholder needs were reflected.
The solution
- A safe and robust mooring approach was developed for berthing a 15 MW semi-submersible FOWT at the Port of Nigg jetty during from April toSeptember.
- An end-to-end outline of marine operations was produced, covering procedures from WTG integration completion through to tow-out to field.
- Recommendations were provided to floater developers to enable safe, efficient, and repeatable quayside berthing.
- Indicative CAPEX and operational benefits of repurposing jetties for FOWT mooring were provided.
📷 Figure 2 15MW UMaine VolturnUS FOWT at the Port of Nigg jetty – Orcaflex model
The outcome
The study shows that the proposed concept is viable and well-suited to the anticipated FOWT campaign, as well as being largely applicable to other jetties. It also provides key design recommendations, offering critical guidance in areas where industry standards are still emerging. Overall, the study demonstrates that repurposing existing jetties presents a strategic opportunity to alleviate major constraints and bottlenecks in the Scottish floating wind supply chain.
