The cable-stayed rotor: what the Vestas patents cover and why it matters for large blades

Why do very large blades need a new rotor concept?

A longer blade sweeps more area, but its mass grows faster than its length, and the gravity bending moment at the root grows faster still, because both the mass and the lever arm increase. Every revolution the blade's own weight bends it edgewise, first one way and then the other, a fully reversing fatigue load that cannot be pitched away. On a very large rotor that load contributes to sizing the root laminate, the pitch bearing and the hub. The blade also has to reach the site, and a one-piece blade beyond 100 metres tests the limits of roads, ports and cranes.

The technology qualification paper Mohammed Fajar co-authored in Energy Reports starts from the same point: turbines beyond 15 MW, blades beyond 100 metres, and scale-induced failure modes that must be qualified before deployment. Very large rotor scaling is a structural, logistical and certification problem at once. A cable-stayed rotor answers the structural part by giving the blade a second support part-way along the span.

What is a cable-stayed rotor?

The root patent sets the concept out in plain terms. The turbine is pitch controlled and has at least three blades. At least three blade connecting members, described as cables such as braided or laid steel wire ropes, run between a connection point on one blade and a connection point on the neighbouring blade, both points spaced from root and tip. At least three pre-tension members connect those blade connecting members to a hub part, illustrated as a hub member extending forward along the rotor axis, and tension the arrangement; in the European grant the pre-tension is adjustable, with hydraulic linear actuators mentioned as one means. The stated purpose is that loads are shared among the blades rather than carried by each root alone.

In effect, three separate cantilevers become one triangulated structure. When a blade is horizontal and its weight tries to bend it edgewise, part of that load travels along the cables into the other two blades and the hub member, and the pre-tensioned rotor cables stay taut so the connection acts in both directions of the gravity cycle. Because every blade keeps its own pitch bearing and drive, the machine remains a pitch controlled cable stayed wind turbine. Keeping that pitch control while the blades are tied together is what two of the later filings address.

What do the Vestas cable-stayed rotor patents cover?

Everything below comes from the published documents on Google Patents, read on 20 September 2026. The assignee of every filing is Vestas Wind Systems A/S, which owns the inventions; Mohammed Fajar is a named inventor on each and no longer works there. Claim wording is paraphrased, and nothing beyond the public documents is described.

The root patent

Priority 17 December 2020, six named inventors including Mohammed Fajar, granted in the United States and Europe and published in Japan, Australia, China and Korea. It is the wind turbine rotor patent the rest of the family builds on: blades, blade connecting members between neighbours, pre-tension members to a hub part.

Attaching the cables at the leading edge

Two filings with priority 10 June 2022 deal with where the cable meets the blade. In US12577933B2 the connecting members attach near the leading edge and are independently movable in two orthogonal directions at their connection points, so the blade can pitch without twisting the cable. In EP4536957A1 each blade carries a leading edge extension; the connection point sits on it and the pitch axis lies aft of the leading edge, giving the cable clearance as the blade pitches.

A split blade wind turbine that carries the cable point

US20250297595A1, same priority date, makes the machine a split blade wind turbine: each blade has an inboard and an outboard portion joined by a connection joint with a connector, and the cable connection point sits on that connector, so one part carries both the split and the cable load.

Feeding cable load into the spar cap

WO2023237169A1 is the filing the Apex Wind expert page lists as a blade to cable composite connection. A concentrated cable load cannot simply be bolted to a composite shell. The patent describes a composite reinforcing member laid into the blade, running from the cable connection point back onto and overlapping the spar cap, and a moulding method for it.

A family of blades sharing root and tip

EP4544173, priority 22 June 2022 and granted 4 March 2026, is where rotor modularisation appears explicitly: blades of different lengths for cable-stayed rotors that share identical inboard and outboard portions and differ only in the intermediate portion, with the cable connection point placed there at a spanwise distance that increases with blade length. The description uses the term "cable-stayed pitchable rotor".

Testing a blade with its cables

WO2024223888A2, priority 28 April 2023, is a test method: a blade specimen with a cable connection point is loaded by an actuator, and part of that load is carried by tensioned cables attached at the point, reproducing on the test stand the relief the stay cables give in service. It cites the root patent directly.

Repowering an existing rotor with cables

US20260002512A1 and EP4630684A1, priority 9 December 2022, turn the concept towards installed turbines: enlarge the rotor of an existing machine with used blades, by tip or root extensions, longer blades or hub extenders, fit a connecting fixture to each blade and tie neighbours together with blade connecting members, optionally with tension members and actuators to the hub, so that the existing root, hub and bearings can stay. We are not aware of any public report of it being applied.

What has been shown in public: the demonstrator at Høvsøre

The public record on the Vestas cable stayed rotor hardware is short. In May 2023 Vestas posted on LinkedIn that it was testing an early-stage rotor technology demonstrator with cables between the blades that "distribute and reduce gravity loads". The following month Windpower Monthly ran an exclusive whose headline said the Vestas cable-stayed rotor achieves a "technology leap" (paywalled). Secondary listings such as wind-turbine-models.com report the demonstrator as a V136-4.2 MW turbine with a cable stayed wind turbine rotor, installed at the Høvsøre test centre in Denmark in May 2023 with a measuring campaign; we cite that as reported, not verified.

In January 2024 Vestas announced gold for Best Innovation at Windpower Monthly's Turbines of the Year Awards, shared with a pitch bearing unit from thyssenkrupp rothe erde, said the demonstrator was still under test at Høvsøre, and said the technology promises "substantial reductions in blade root loads" together with rotor modularisation and scalability. No measured or predicted load-reduction figures are public in any of these sources, and we state none.

Is the cable-stayed rotor a new idea?

Guyed and stayed rotors go back to the early days of the industry; the Gedser mill is the usual reference, and commenters on Vestas' 2023 post pointed to the Windmatic 14S of 1983. A 2012 application by an unrelated applicant, US20120051914A1, also uses the words cable-stayed rotor in its title. What distinguishes the Vestas family, whose root patent the European and United States offices have granted, is the combination: full pitch control on every blade, blade tied to neighbouring blade, pre-tension applied and adjusted from a hub part, and attachment details that let a stayed blade pitch.

What does a cable-stayed rotor mean for blade design, testing and certification?

For a blade engineer the concept changes the load path, and with it the list of things that must be right. The connection region becomes a primary structural detail, carrying a concentrated load into laminate that was previously shell and spar. Cable tension becomes a design variable with a control system and a maintenance regime behind it. Loss of a cable, or of its pre-tension, becomes a load case in its own right. The connecting members, pre-tension members and hub member couple the blades to each other, so the aeroelastic model must include them as structural members, and the rotor's coupled modes change with them. None of this argues against the concept; it is why blade root loads reduction cannot be taken on trust from a headline.

For testing, a full-scale test of a blade designed with cable relief has to represent that relief, or it tests a structure that does not exist. Anyone witnessing such a test should ask how the cable load was set, how it was measured, and how the test loads relate to the design loads with and without the cables.

For certification, a cable-stayed rotor is a textbook case for the risk-based route: identify the failure modes that scale or novelty introduce, rank them, and map each high-risk mode to the simulation, laboratory test, field trial or in-service monitoring that retires it. That is the route DNV-RP-A203 sets out for novel technology, and the structure the technology qualification paper applies to very large blades.

For an owner, insurer or lender offered such a turbine, the questions are those for any novel component: does the design load basis include cable loss; which parts of the qualification were done by test and which by analysis; what field evidence exists beyond the demonstrator; how are the cables and tension system inspected and maintained; and what does the warranty say.

Frequently asked questions

What is a cable-stayed rotor on a wind turbine?

A cable-stayed rotor is a wind turbine rotor in which each blade is connected to its neighbouring blades by cables attached part-way along the span, held in pre-tension from a part of the hub. The aim stated in the published patents is that loads are shared among the blades instead of being carried entirely by each blade root.

Does a cable-stayed rotor still allow the blades to pitch?

Yes. In this family the turbine remains pitch controlled and every blade keeps its own pitch bearing and drive. Two filings exist to make that work: cables attached near the leading edge with two-axis freedom, or on a leading edge extension with the pitch axis aft of it, so the blade rotates without twisting the cable.

Which patents is Mohammed Fajar named on?

Mohammed Fajar patents in this family include the root patent (WO2022128040A1, granted as US12066003B2 and EP4264039B1) and the later filings in the table above, from the leading-edge attachment to the repowering method. All are assigned to Vestas Wind Systems A/S; he is a named inventor, not the owner.

Has a cable-stayed rotor been built and tested?

Vestas has said publicly that a cable stayed rotor technology demonstrator was under test from May 2023, reported as a V136-4.2 MW turbine at the Høvsøre test centre in Denmark, and in January 2024 that it was still under test there. No test results or load-reduction figures appear in the public sources we cite, and this article draws on nothing beyond those public statements.

Is Apex Wind connected to Vestas?

No. Mohammed Fajar left Vestas in 2023 and founded Apex Wind ApS the same year. Apex Wind is independent of every turbine and blade manufacturer, has no partnership, licence or referral arrangement with Vestas or anyone else, and sells no hardware. This article is written from the published patents and public announcements only, and discloses nothing else.

How Apex Wind can help

Novel rotor concepts, whether cable-stayed, split, modular or simply very large, need someone independent to read the design basis, the qualification plan and the test evidence with a designer's eye. We carry out design assessment of new blade and rotor concepts, support technology qualification against a structured risk method, and witness full-scale blade tests so that the test demonstrates what the certificate will claim. For buyers, lenders and insurers facing a rotor concept they have not seen before, our technical due diligence puts the open questions into terms a transaction can use. If you have a rotor concept to assess, or one being offered to you, contact us.