Published: August 18, 2026 | Updated: August 18, 2026
POLICY & REGULATION
On 5 August 2026, Japan’s Ministry of Land, Infrastructure, Transport and Tourism (MLIT) opened the first FY2026 session of its study group on ports for offshore wind deployment, and reset three premises for floating wind. The construction period moves from “two or three years” to a two-year target. The distance from the base port to the wind farm moves from 20 km to a three-day towing radius of roughly 400 km. And multi-port operation, splitting mooring pre-installation, floater assembly and turbine load-out across separate ports, is now built into the analysis. Until last year the question was how large a single port needs to be. This year’s premises replace it with a different question: which ports get combined, and how.
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A three-year build assumption produces smaller facility requirements, and a port built to that smaller specification risks going unused. That was the committee’s objection last year. MLIT has now fixed two years as the target period. At two years, running the full sequence through one port becomes difficult.
A three-day towing radius of about 400 km is close to the 300 to 400 km range MLIT already uses for fixed-bottom projects, based on a one-day transit for a self-elevating installation vessel. It can be read as evidence that floating wind works without a nearby port. It can equally be read as evidence that one port can serve a wide area.
Asked for indicative costs to judge economic rationality, MLIT answered that ground and wave design conditions differ port by port, and that it will proceed through overseas case studies. The year-end summary is expected to give facility scale without a number attached to it.
Why MLIT fixed the build period at two years
Last fiscal year the study ran both a two-year and a three-year construction period. This year’s material records two objections to that. The first is that a port sized around a three-year build ends up with smaller facility requirements and may therefore go unused. The second is that because chartered vessel costs dominate offshore construction spend, two years should be treated as the standard.
MLIT’s response is one line: the construction period will be set as a two-year target period. Three years has been moved out of the base premises and into the list of other conditions to be considered.
Compressing three years into two means pushing the same 1 GW through a shorter window. The process diagram MLIT presented splits the work across three ports: one for pre-installing mooring equipment, one for large-block assembly of the floaters, and one for pre-assembly and turbine load-out. The three run in parallel, and parallel operation across multiple ports is the stated means of completing mooring installation inside two years. The two-year target and multi-port operation arrived together, not separately.
The facility requirements themselves were quantified last year, including three quays and twelve production lines on the Sea of Japan side. We covered those figures separately.
What matters now is that the premise behind those figures has moved. Last year the regional contrast was read as two years on the Pacific side against three on the Sea of Japan side. This year both sides target two, and the difference is absorbed through how ports are combined and how large the facilities are.
From 20 km to a 400 km towing radius: base ports acquire a catchment area
The second change is distance. Last year the analysis assumed the wind farm sat 20 km from the base port. A committee member noted that actual sites are expected to be further than 20 km, and asked MLIT to set a catchment area for base ports, as it does for fixed-bottom projects, and to test longer distances.
MLIT’s response sets the base port to wind farm distance at a three-day towing radius, roughly 400 km. The derivation is stated in the material: an anchor handling tug supply (AHTS) vessel, the workboat that sets anchors and tows floaters, towing at three knots for three days covers about 400 km. Three days is the limit tied to how far ahead weather and sea state can be forecast with confidence.
This year’s cycle times are calculated separately for a one-day radius, up to about 130 km, and a three-day radius of roughly 260 to 400 km. For fixed-bottom projects MLIT has used 300 to 400 km, a one-day transit for a self-elevating platform (SEP) vessel, the jack-up type that lifts its hull clear of the water to work in calmer conditions. Floating wind now inherits the same catchment logic.
The material illustrates this with the Port of Nigg in Scotland: roughly 29 GW of projects fall inside a 400 km radius of that port, based on 4C Offshore data. It is a map of how much one port could serve.
The change reads two ways. Floating wind can proceed without a base port nearby. And if one port can serve a wide area, ports do not need to be built close to every designated zone. The material asserts neither. What has been decided is the premise for analysis, not a siting policy. For a prefecture weighing port investment, however, the difference between those two readings is the whole question.
At each of Japan’s seven base ports, the area formally positioned as the hub for installing and maintaining offshore renewable energy facilities is 8 ha (Kashima 5 ha, or 8 ha with back-up land). The floating facility-scale estimates run from 21 to 32 ha on the Sea of Japan side and 19 to 21 ha on the Pacific side. The two are not directly comparable, one being a regulatory designation and the other an estimate of required area, but both sit in the same meeting’s material and the orders of magnitude do not line up. In DeepWind’s reading, whether extensions to existing ports can close that gap is the substantive question for the rest of this fiscal year.
Storage deserves attention as well. Installing 30 floaters per year over two years on the Sea of Japan side was assessed as requiring wet storage water area for six units, against one unit under the same conditions on the Pacific side. Because offshore work stops in winter, units have to be built ahead and held afloat. Wet storage remains an area where Japan has no settled operating framework.
👉 Japan’s Wet Storage Gap: From Specification to Delivery in Floating Wind Logistics
One base case: semi-submersible, steel, 15 MW, two years
Last year several cases ran in parallel: 15 MW and 20 MW turbines, semi-submersible, barge and spar platforms, steel and concrete, chain and hybrid mooring lines, two-year and three-year construction. This year MLIT narrowed these to a single base case.
| Parameter | FY2025 (multiple cases) | FY2026 (base case) |
|---|---|---|
| Construction period | Two or three years | Two years (target) |
| Distance from base port | Around 20 km offshore | One-day to three-day tow (about 400 km) |
| Turbine rating | 15 MW and 20 MW | 15 MW |
| Platform and material | Semi-sub / barge / spar, steel / concrete | Semi-submersible, steel |
| Mooring | Catenary, chain / hybrid | Catenary, six chain lines, drag anchor |
| Turbine load-out | Quayside | Quayside (offshore load-out studied separately) |
The stated basis is global deployment trends, and the material quantifies them. In the 4C Offshore database as of 1 June 2026, covering turbines of 1 MW and above, semi-submersibles account for 58% and steel for 48% of the 48 planned projects totalling 28,840 MW. Among the 23 projects under construction or operating, totalling 375 MW, semi-submersibles at 43% sit close to spars at 40%. The tilt toward semi-submersibles is in the planning pipeline rather than the installed base.
The excluded parameters have not been dropped. Water depths of 500 to 1,000 m, 20 MW turbines, TLP, barge and spar platforms, concrete floaters, suction anchors, taut and tension-leg mooring, hybrid mooring lines, three and nine mooring lines, a three-year build, and offshore turbine load-out from a floating work base are all listed as other conditions to be considered. The sequence is to size the facilities against the base case first, then map how these conditions change that sizing. Concrete floaters remain at the research stage, so MLIT will document points to note rather than size for them.
Fixing one premise is what allows port design work to start, and that is reasonable. The consequence is that projects falling outside the base case, a 20 MW machine or a deep-water site, sit outside the facility scale now being calculated. How those are handled is the open question for the second half of the year.
From operational fixes to institutional design
A second document covers more efficient use of base ports. Last year’s output was five operational improvements covering lease fees, restoration obligations and related terms, which we examined separately.
This year the discussion moved past that. Two medium to long-term issues are on the table: measures to secure port facilities as projects grow larger, and further efficiency in coordination between the national government and port managers, and among ports themselves. On that basis MLIT states it will pursue a review of the base port framework itself for floating wind. The subject has shifted from adjusting operations to designing the institution.
The volumes behind this are set out in the same material. Since the occupancy permit regime for general sea areas was created, project formation has run at about 1 GW per year, and is assumed to run at 2 to 3.5 GW per year from 2030. Japan’s Seventh Strategic Energy Plan targets 10 GW of project formation by 2030 and 30 to 45 GW by 2040, with floating wind at 15 GW or more by 2040. Seven designated base ports absorb that pipeline.
FLOWRA, Japan’s floating offshore wind technology research association, submitted material to the same meeting on multi-port coordination in Europe. In its assessment, a port operating entity needs the capability to assemble floaters and install turbines at a rate of roughly 30 to 50 units per year. It also frames a transition from developing single ports as individual infrastructure to operating multiple ports as public infrastructure under integrated management, and sketches a joint venture between several port managers and private operators with port operating capability. These are presented as the association’s own views.
Returns on port investment depend on utilisation across the recovery period. Last year’s operational improvements, cutting the first tenant’s contract guarantee to 50% of investment and allowing lease payments to be deferred until commercial operation, addressed how that burden is distributed. Levelling and deferral move where the cost sits; they do not raise utilisation. For a lender the question is not the lease rate but how firmly a continuous pipeline can be demonstrated. Whether 2 to 3.5 GW per year of project formation converts into actual construction starts is what underwrites the port investment case.
On cost, this fiscal year again produces no figures. Asked for indicative costs to assess economic rationality, MLIT replied that design conditions such as ground and wave climate differ between individual ports, and that it will work through overseas case studies. The schedule is to present a draft facility scale in autumn or winter and a draft summary at the end of the fiscal year. Scale will be published. A number will not.
👉 Japan Offshore Wind Policy Reforms: Speed and Risk Reduction
The base port debate has moved from how large a port must be to how ports are combined.
The three changes are not independent. Set a two-year target, and running the full sequence through one port becomes hard. Widen the distance premise to a 400 km radius, and combining distant ports becomes arithmetically viable. Build multi-port operation into the premises, and what the system needs is no longer floor area but a coordination mechanism between ports. Read in that order, MLIT naming coordination efficiency as a medium-term issue and opening a review of the framework itself looks like the logical consequence rather than a separate initiative.
The hard part starts here. Making a port bigger is an investment problem: expensive and slow, but well understood. Combining ports is a coordination problem, and different managers hold different objectives. Europe is exploring private operating capability as the answer, while Japan’s base ports are designated by the national government and run by port managers. Whether the year-end summary stops at indicative facility scale or reaches into the coordination mechanism is what DeepWind is watching. Even without a cost figure, once it is clear who coordinates, developers can begin fixing schedules.
Related DeepWind Articles
- MLIT Simulations Reveal Massive Infrastructure Needs for 1GW Floating Wind: “3 Quays and 12 Lines” Essential on the Sea of Japan
- A Turning Point for Base Port Rules: MLIT Proposes 5 Operational Improvements for Leases and Restoration
- The Shock of the “15MW Era”: Port Scaling and Integrated Operations in the Latest FLOWRA Report
- Japan’s Wet Storage Gap: From Specification to Delivery in Floating Wind Logistics
- Japan Offshore Wind Policy Reforms: Speed and Risk Reduction
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