The wind industry pioneer offered me as an example the installation of offshore turbines – a problem that quickly led to innovative solutions like Danish company A2SEA and UK installation vessel Mayflower Resolution.
Milestone year
He reflected on 2002, a milestone year for offshore wind, which saw the completion of the 160MW Horns Rev (phase 1) project, the world’s first large-scale wind farm, located in the harsh North Sea environment.
Garrad’s statement is equally relevant today: alarm bells have been ringing since last year suggesting that only a handful of turbine installation vessels worldwide are capable of handling turbines bigger than 10MW.
The bleakest projections indicate that demand for ‘capable’ installation vessels might outpace supply starting next year, continuing until the end of this decade; just as the volume of installations is expected to balloon.
In parallel, the new 14–15MW superclass entering markets outside China from next year looks likely to be succeeded – perhaps sooner than expected – by next-generation 18-20MW+ turbines. Each major new turbine scaling step requires bigger rotors and hub heights too, and thus matching installation vessels with enhanced cranes for installing next-size foundations, towers, nacelles and blades.
Not everybody seems equally worried about a looming shortage of self-propelled jack-up vessels, however, like one offshore expert asking a pointed question: “Why are these costly jack-ups still deployed to travel from European wind farm construction sites to distant supply ports for picking up new cargo?” He noted that these vessels are “expensive fuel guzzlers” too, as their hull shapes are not primarily designed for optimal fuel efficiency.
Early innovators
Just as the early pioneers did nearly two decades ago, we are faced with the challenge of finding innovative solutions – but this time on the back of substantial know-how and a significant track record to draw from.
Our predecessors, by contrast, faced the virtual absence of any know-how on turbine and offshore installation vessel systems, a virtually non-existent offshore wind market, and many uncertainties including whether or when an actual market would take off at all.
At least three different innovative wind turbine installation concepts were introduced early this century, plus the HLV Svanen for monopile installation initially developed for bridge building.
Jumping Jack with cable winch system in use at Q7 wind farm
In June 2002, I attended the inauguration ceremony of the Jumping Jack, a large ‘new-generation’ four-legged towed jack-up, near the port of Rotterdam. The 91-metre long and 33-metre wide towed barge could operate in maximum 32-metre water depths and raise the hull out of the waves in maximum 2-metre significant wave heights with maximum 4,000-tonne cargo.
The high-capacity 1200-tonne ringer-type crane, positioned centrally at the deck, was envisaged to enable – in the future – the lifting of 4–5MW turbine-tower full assemblies and install these in one go atop matching support structures.
A major system innovation were cable winches for pulling down the 42-metre legs, unlike common rack-and-pinion systems used with smaller jack-ups. Cable-winch solutions were said to work much faster, with jacking speed crucial to shortening the critical transitional phase between floating and standing firm on the seabed. When waves hit the hull during transition, huge bending loads are created where the legs and hull attach.
Operational window
Jumping Jack in use at Q7 wind farm
It was further claimed that the less rigid cable interface contributed to a reduction in additional loads, boosting Jumping Jack’s operational window. Construction was completed in a record six months, and the vessel moved to Danish waters in July 2002 to install V80-2.0 MW turbine monopiles at Horns Rev 1.
Jumping Jack operated initially under the joint umbrella of Dutch consortium partners Van Oord (Offshore) and heavy-lift specialist Mammoet.
Denmark’s A2SEA Group’s introduced a different offshore wind turbine installation vessel concept involving two existing commercial freighters, each with four legs incorporated in box structures welded to the hulls. The converted sister vessels were both fitted with a 450-tonne crane. They were first deployed at Horns Rev 1 to install all of the 80 Vestas turbines and towers.
A stable working platform is again created by pulling the legs down until the vessel stands firm on the seabed – but unlike jack-ups, the hull remains partly submerged.
An A2SEA spokesperson said this solution was “far superior to any existing alternative, especially with regard to cost efficiency and speed of work”. The company said its first aim was to install wind turbines at sea under the same working conditions as found on land. And its second aim was that the vessel should be easy to move from one location to another. Third and last was the capacity to transport turbines.
Self-propelled
Built between 2002 and 2003, the Mayflower Resolution is again a jack-up but a self-propelled installation vessel. Its large 130.5-metre long and 38-metre wide hull is equipped with six legs; the vessel can operate in maximum 35-metre water depths. It was first deployed from February 2004 to install 60 Vestas V80 turbines at the North Hoyle (UK) project.
The huge vessel could transport 12 complete Vestas V80-2.0 MW turbines – tower, nacelle and rotor – or 12 units of 2.75 MW NEG Micon NM 92/2750 from supply port to offshore destination.
The Mayflower Resolution originally came with two separate cranes, a surprisingly small-capacity 300-tonne main crane plus a 50T auxiliary crane. The main crane was mounted in between the vessel stern (rear) legs, while a monopile handling frame had to compensate for insufficient monopile crane hoisting capacity from the start.
Striding forward
Enormous strides forward have been made since this important ‘trial-and-error’ offshore-wind pioneering era: self-propelled jack-ups especially have become a big success story.
Four instead of six legs is now the standard design, including for the largest-scale turbine and foundation installation vessels.
The main crane position has evolved to mostly encircle one of the legs, a major innovation offering maximum utilisation of the ship’s deck for stowing cargo – as well as optimised flexibility and manoeuvrability.
Double-action rack-and-pinion solutions dominate - rather than ‘more trouble prone’ cable winches - which enable much faster jacking operations compared with single-action rack-and-pinion models.
The persistent fitting of small-capacity cranes at some new-build jack-ups remains hard to understand as turbine scaling has been a continuous trend and something I therefore view as an especially wasteful overall practice.
Option feeder solutions
Expanding on successful proven concepts sounds logical and makes sense. But if the installation vessel shortage is real; what is needed is a sense of urgency, fast decisive action and fresh thinking.
One possible option that comes to mind immediately is to consider using feeder solutions, such as those pioneered for the US market, in European offshore wind as well.
The benefits could be huge, through a much higher utilisation rate of available ‘capable’ turbine installation vessels, while allowing potential entrants to draw from feeder concepts already developed.
Advanced motion compensation technology, which is essential for the safe sea transfer of main components, is already a mature and proven practice in other applications, for instance.
Tetrahedron crane for US feeder system
A second option for the longer term is to refit modest-size jack-ups commissioned between 2008 and 2009 for installing 3.6MW class turbines with innovative Tetrahedron cranes.
These now 14–to–15-year old installation vessels have been continuously upgraded and optimised up to 8–10MW+ turbines, but this is likely the end stage.
A comprehensive retrofit with Tetrahedron cranes would give them a new lease of life and enable them to install 12–20MW turbines. The company currently builds a 130-metre tall prototype crane.
Artist's impression of Tetrahedron prototype on a jack-up-vessel next to the iconic Euromast for scale
This approach would face substantial hurdles, however, because some wind farm tender procedures promote the use of new-build vessels with engines burning methanol or ammonia. This offers a reduced carbon footprint when environmental performance is measured at the level of an individual project’s operations.
Older installation vessels burning marine gasoline oil (MGO) or worse heavy fuel oil (HFO) are at a disadvantage in that context, but a far more realistic carbon-footprint comparison on a lifecycle basis could align or reverse the outcomes.
Climbing cranes in tandem
Liftra/DEME offshore installation concept
A third option is an offshore installation concept announced at WindEurope 2023 and developed in a partnership between Belgian offshore contractor DEME Offshore and Danish crane specialist Liftra.
The concept offers a unique capability to install fixed-bottom or floating turbines from a floating vessel, thereby eliminating limitations regarding water depth.
The concept involves an existing DEME floating or jack-up vessel with, for instance, a 5,000-tonne main crane and two Liftra climbing cranes working in tandem, each with a hoisting capacity of 700–800T.
Once the main crane has installed a foundation and tower, the two climbing cranes can together install next-generation nacelles with a mass of 1,000 tonnes or more. A single crane at the upper level can perform single-blade installation and exchange.
Huisman wind turbine shuttle
Promising turbine installation concepts from the past like the wind turbine installation shuttle, an out-of-the-box concept introduced in 2009 by Dutch marine engineering solutions provider Huisman, are worth re-evaluating and reconsidering.
This catamaran-type self-propelled vessel can pick up and transport two complete assembled wind turbines including towers and place them with an integrated tower clamping and hoisting system atop a substructure.
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The Windlifter concept from Ulstein-IDEA
Out of several other innovators is Norwegian ship designer Ulstein-IDEA, which in 2011 presented an installation vessel concept called Windlifter. It can accommodate four completely assembled turbines on a type of rail system, with a combined lifting and placement device integrated into the vessel's stern.
None of these concept solutions introduced over a decade ago made it to a commercial product – mostly because of the inherent conservatism and risk-aversion that are typical of the offshore wind industry, according to insiders.
Dusting off
Dusting off those innovative concepts in today’s mature wind industry could create fresh opportunities through merging these ‘old’ ideas with fresh insights like on floating turbine assembly – and perhaps produce some of tomorrow’s winning solutions.
