What Early U.S. Offshore Wind Projects Reveal About WTIV–Feeder Productivity

AEOLUS (Jan De Nul)

Early U.S. Offshore Wind projects relied on European wind turbine installation vessels (WTIVs) operating in coordination with U.S.-flagged feeder barges to comply with the Jones Act. We looked at the compared installation performance between the first to commercial scale U.S. Offshore Wind projects to better understand productivity and workability of the feeder barge solution.

Our study evaluated installation cycle performance from two early U.S. offshore wind projects:

South Fork Wind (Ørsted)

WTIV: AEOLUS (Jan De Nul)

Feeder Configuration: One feeder barge with ocean tugs (Crowley)

Vineyard Wind (CIP / Avangrid)

WTIV: SEA INSTALLER (DEME)

Feeder Configuration: Two feeder barges with ocean tugs (Foss)

We evaluated installation cycle characteristics, feeder interaction efficiency, weather exposure, and overall time-in-position for wind turbine generator (WTG) installations.

Methodology

South Fork Wind – AEOLUS

• 11 WTG installations reviewed

• Installations 4, 6, and 7 excluded due to AIS coverage gaps

• Analysis reflects early-project performance

Vineyard Wind – Sea Installer

• First 11 WTG installations reviewed to align learning curve stage with South Fork

• First installation excluded from summary due to extended initial waiting-in-position time

Each installation cycle was segmented into:

• WTIV Time in Position

• Pre-Feeder Barge Time

• Feeder Barge Alongside Time

• Post-Barge Time

• Waiting-on-Weather

• Total Cycle Time per WTG

• Barge Workability (Barge Alongside Time / Barge On-Scene Time)

Project 1: AEOLUS – South Fork Wind

Metric	Average	Min	Max	Total
WTIV in Position (hr)	149	16	409	1,342
Pre-Barge (hr)	67	0	299	606
Barge Alongside (hr)	42	18	119	374
Post-Barge (hr)	118	19	328	1,058
Waiting-on-Weather (hr)	39	0	218	355
Total Cycle Time (days)	11	5	25	99
Barge Workability	39%	7%	90%	—

 Observations

• Average total installation cycle: 11 days per WTG

• Feeder barge was alongside only 39% of the time the barge was available in the field

• Weather impact present but not dominant relative to total cycle time

• Installation productivity appears strongly influenced by feeder synchronization

Project 2: Sea Installer – Vineyard Wind

Metric	Average	Min	Max	Total
WTIV in Position (hr)	393	144	819	3,929
Pre-Barge (hr)	46	0	224	456
Barge Alongside (hr)	393	144	819	3,929
Post-Barge (hr)	141	10	259	1,409
Waiting-on-Weather (hr)	160	0	769	1,599
Total Cycle Time (days)	18	7	38	178
Barge Workability	37%	40%	37%	—

Observations

• Average total installation cycle: 18 days per WTG

• Feeder barge was alongside only 37% of the time the barge was available in the field

• Significantly longer WTIV time in position relative to South Fork

• Higher waiting-on-weather exposure

• Greater variability and weather sensitivity observed in early campaign phase

Comparative Insights

1. Total Cycle Time

• AEOLUS: 11 days per WTG

• SEA INSTALLER: 18 days per WTG, 60% greater than AEOLUS

  
  

2. WTIV Time in Position

SEA INSTALLER averaged more than 2.5x the time in position per turbine compared to AEOLUS.

This may reflect:

• Different site conditions

• Weather exposure

• Project execution strategy

• Vessel operating profile

• Early campaign inefficiencies

3. Feeder Barge Performance

Barge workability was similar across projects (~37–39%).

This suggests that:

• Adding a second feeder barge does not necessarily translate into materially higher alongside utilization

• WTIV productivity is not purely a function of feeder count

• Synchronization and sequencing may matter more than asset quantity

• Motion compensation technologies may not have been as effective as expected

4. Weather Sensitivity

Sea Installer experienced materially higher average waiting-on-weather time.

Weather exposure appears to amplify total cycle variability, particularly when installation campaigns extend over longer durations per turbine.

Strategic Implications

These early U.S. offshore wind campaigns suggest several structural observations:

• WTIV idle time is substantial relative to productive barge interaction time

• Feeder synchronization appears to be a primary driver of cycle efficiency

• Weather exposure compounds inefficiencies when cycle duration extends

• Simply increasing feeder count does not guarantee higher productivity

For developers, EPC contractors, and lenders, installation cycle duration directly impacts:

• Project schedule risk

• Contingency requirements

• Vessel day rate exposure

• Insurance and financing cost

• Weather window strategy

As the U.S. market wrestles with the Jones Act feeder model, understanding the real-world performance of feeder models is critical in evaluating future capital allocation and risk models. Early projects offer valuable empirical data on installation cycle mechanics under feeder-based logistics structures. Future analysis will reveal learning curve effects and mid-campaign performance improvements as more installation data becomes available.