The choice between traditional monopile-transition piece (MP-TP) foundations and TP-less solutions in offshore wind projects is becoming a hot topic. Developers are constantly weighing cost-efficiency, supply chain constraints, and technical feasibility. But is one approach truly better? As with many aspects of offshore wind, the answer is nuanced.
When the Decision Isn’t Yours
Sometimes, the choice is dictated by external factors. For example, high loads on the lower TP flange can render MP-TP solutions unfeasible, pushing developers toward TP-less designs. Similarly, local content requirements—such as those in the U.S., where TP manufacturing is almost nonexistent—often steer developers to TP-less solutions that allow for local secondary steel sourcing.
Deepwater projects and those with large turbines may lean toward MP-TP designs due to supply chain bottlenecks, particularly in monopile production and installation capabilities. Crane capacity and lifting height further complicate these decisions, highlighting the critical role of procurement and installation planning.
When You Do Have a Choice: Cost vs. Complexity
In more standard projects (projects of average complexity featuring a SIP (Suspended or Supported Internal Platform) structure with the external platform, boat landing, and anode cage), TP-less solutions come out ahead on cost. This is largely due to savings from the reduced number of flanges, the omission of TP-skirt steel, fewer bolts, and other minor elements, as well as some reductions in operational and maintenance (O&M) costs.
Yet, the picture isn’t always straightforward. Transport and installation (T&I) costs for heavier, longer monopiles—essential in TP-less designs—can erode these savings, especially when vessel availability is limited.
Moreover, the TP-less approach requires more offshore lifts, introducing additional complexity. Integrated installation tools can mitigate some of these challenges but come with their own costs. Vessel selection adds another layer of complexity: while smaller jack-up vessels reduce costs, floating vessels—often used in TP-less installations—face operational delays due to weather sensitivity.
A Risky Proposition?
TP-less solutions also carry unique risks. Hard geotechnical conditions can damage monopile top flanges, necessitating expensive offshore repairs. The direct interface with the tower in TP-less designs introduces more stringent requirements, adding complexity during procurement.
For well-planned projects, TP-less designs can indeed deliver cost advantages. But when unexpected challenges arise, cost overruns in T&I or repair work can offset initial savings, making the MP-TP setup the more economical choice.
Supply Chain Constraints: A Bottleneck for Both Options
Europe’s transition piece supply chain remains constrained, with less than a handful of manufacturers. While investments in monopile production have surged, TP manufacturing lags behind. To meet growing demand, Europe must expand its TP production facilities while maintaining access to international suppliers to foster competition and keep costs in check.
Secondary steel production is evolving more rapidly. Suppliers with experience in TP components are transitioning to produce elements like SIPs, boat landings, and anode cages, lowering barriers for new entrants and driving industrialisation. This shift could help reduce the Levelized Cost of Energy (LCOE) over time.
The Bottom Line
Choosing between TP-less and MP-TP foundations is not just a technical decision; it’s a complex balancing act of cost, supply chain constraints, and risk management. With the offshore wind industry evolving rapidly, the right choice today may not hold the same value tomorrow. Thorough supply chain analysis, risk evaluation, and procurement planning are essential to navigating this critical decision.
Morten Thorhauge Boolsen is a Senior Director for JUMBO Consulting Group Denmark, a highly specialised advisory offering strategic services and project delivery consultancy for offshore wind, offshore transmission systems and energy island projects, covering the entire project lifecycle from early development, procurement, construction to O&M. Headquartered in Denmark, JUMBO Consulting Group’s services are founded on deep sector knowledge and delivery of contractual and commercial solutions within its core disciplines, development services, supply chain development, category-, procurement- and contract management and advisory.
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