Insights
Buoyancy-Assisted Installation
Upending and Lowering Monopiles with Reduced Crane Load
- Bas van Wuijckhuijse
- 15 May 2026
Introduction
Offshore wind energy is showing a trend of growing monopile foundations. As turbines grow and sites move into deeper waters, monopiles become larger, heavier, and harder to install. This puts pressure on available crane vessels with sufficient crane capacity, pushing the industry to explore new methods for handling these huge structures.
Key points:
- Traditional installation methods reaching limits
- Growing global offshore wind demand
- Increasing monopile size & weight
Market Trends
Achieving global climate targets requires installation rates to triple within a decade. Wind farms are increasingly built in challenging soils and deeper waters, meaning monopiles will soon exceed 120 meters and 3,000 tons. This surpasses common cranial capacities and reduces the number of suitable vessels.
- Installations moving into deeper, more difficult areas
- Monopiles are expanding significantly in size
- Shrinking fleet capable of lifting future monopiles
Buoyancy as Enabler
Buoyancy, based on Archimedes’ principle, provides an upward force by displacing water. By sealing and pressurizing a monopile, its large internal volume becomes a powerful source of lift, reducing crane requirements. However, stability, draft control, and sea conditions introduce challenges that must be addressed.
Creating Buoyancy
Different techniques can generate buoyancy in monopiles. Options include:
- Bottom caps: simple, but must be removed underwater
- Top caps: easy removal but require air pressurization
- Intermediate caps: improve control but add complexity
- Inflatable buoyancy bags: flexible and redundant, but require complex handling
Each method has trade‑offs in safety, complexity, and practicality depending on the project.
Three BAI Methods
The three following buoyancy concepts each show how a heavy monopile can be upended and subsequently lowered to the seafloor. The UpendHinge with buoyancy reduces crane load, allowing heavier monopiles than current hinge systems.Floating upending utilizes more buoyancy, enabling even larger monopile masses. Craneless upending relies entirely on buoyancy and ballasting, making it capable of handling the heaviest future monopiles without a crane.
Upend Hinge Installation
Upend Hinges (UEHs) assist in rotating monopiles from horizontal to vertical and can integrate buoyancy to reduce crane loads. UEHs can be used on jack‑up vessels, floating heavy lift vessels, or barges, each with its own benefits and limitations. Simulations show buoyancy helps, but dynamic sea motion remains a challenge that can be managed by smart UEH design and damping features.
Key points:
- Proven technology enhanced by buoyancy
- Similar workability to conventional methods
- Dynamic loads must still be managed carefully
Floating Installation
Floating installation is an alternative for handling larger monopiles. Using controlled buoyancy, the monopile is towed and hooked to the crane by a motion compensated lifting tool or an inline heave compensator. After the pile is brought to deck level, the crane finishes upending and lowering whilst assisted with buoyancy. This expands vessel options and reduces dependency on heavy‑lift assets.
Key points:
- Effective for larger monopiles
- Requires motion‑compensated lifting tools
- Workability of ~84% in North Sea conditions
- Higher engineering complexity but larger vesselflexibility
Craneless Upending
Key points:
A completely different approach to monopile installation is craneless installation. Craneless methods use ballasting, external moments, and pressurization to upend and lower the monopile without a crane. A semi‑submersible barge provides stability and positioning.
- Large potential cost savings and flexibility
- No heavy‑lift crane required, enabling radically new T&I methods
- Ideal for very large future monopiles
Conclusion
Buoyancy‑assisted methods offer a powerful response to the increasing scale of offshore wind foundations. As monopiles grow, traditional crane-based approaches face real limitations. Buoyancy can reduce lifting requirements and expand vessel availability. Each project needs a tailored approach, and further development is required, but BAI is a promising path toward meeting future installation targets.
In this video presentation, our R&D Manager, Bas van Wuijckhuijse, provides a more in-depth explanation of the topic. Watch it here:
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