Page 16: of Maritime Reporter Magazine (December 2024)

OFFSHORE ENERGY

Through this decade, we anticipate that South Korea will be • A station keeping system is required for the ? oating tur- the largest ? oating market, but the ? rst half of the next decade bines. There are many different solutions available depend- is likely to be dominated by activity in Europe, with the UK, ing on the speci? c site conditions and ? oater design, but suc-

France, Italy, Portugal forecast to be the most active (but not tion anchors, drag embedment anchors and driven piles are only) ? oating wind markets. The U.S. enters the ? oating wind likely to feature in most projects in the short- to mid-term. stage during the forecast period with both pilot and commer- Again, depending on a number of variables, anchors can be cial scale developments on the West Coast and pilot arrays on shared by mooring lines or each mooring line can feature an the East Coast. anchor. The base case is for each ? oater to generally require three mooring lines, either in a 3x1 (3 lines per ? oater) con-

HOW DO YOU BUILD A FLOATING WIND FARM? ? guration, a 3x2 layout or even 3x3. The uncertainty over

At a high level, building a ? oating wind farm can seem to be the technical solutions drives us to develop our three base a simple exercise, as shown in the graphic. scenarios (mutualized suction anchors, drag embedment an-

However, the uncertainty over what we will be installed, chors and taut mooring with suction anchors) to present an volumes of components to be handled and their sheer physi- order of magnitude of the volumes of components, the de- cal size present many challenges to ? oating wind developers. mand for vessels and to highlight the impacts and major dif-

Let’s look at the differences that sets the building of a ? oating ferences in the various technical choices. It is likely, at least wind project apart from the established bottom-? xed segment in the short-to-mid-term, that mooring systems will feature to understand these challenges of technical uncertainty, vol- sections of large chain (~130-1800mm) and sections of large umes and sizes of components. ? ber rope (±300mm). • It starts with the ? oater, for which there are more than • Complete assemblies will be towed offshore by a spread 100 concepts being developed globally that are broadly of tugs including lead, support, and security tugs and then grouped in semi-submersibles, barges, spars and TLPs. hooked up to the pre-laid moorings. Tensioning of the

These concepts can be built from steel (rolled stiffened mooring system will generally be required, more often plate, ? at panel construction and heavy-walled tubular, etc.) than not from the vessel rather than the ? oater. It should or concrete (slip formed, pre-cast, with reinforcement, with be noted that the impact of larger turbines referenced ear- post tensioning tendons, etc.). Some concepts feature steel lier will likely be larger ? oaters and more robust (larger in plate construction familiar to shipbuilders while others rely number and/or size) moorings, which of course can increase on large diameter steel pipes produced at offshore wind the technical requirements for towing and hook-up vessels.

monopile and tower manufacturing plants. Steel concepts • Array cables can be pre-laid and wet-stored with the can be manufactured in sub-assemblies and shipped to as- moorings or installed when the ? oaters are hooked-up. A sembly yards or can be shipped as complete units from con- key difference in ? oating wind array cable systems to those struction yards on heavy lift vessels. Concrete concepts are found on bottom-? xed projects is that the subsea cables are generally more suited to local manufacture and assembly. ? exible or dynamic and are suited to deployment by vertical

Depending on the concept selected, each ? oater for current lay systems.

generation turbines could weigh from below 5,000 tonnes • Substations can be bottom-? xed, ? oating or even sub- to 20,0000 tonnes. A commercial scale project will require sea, depending on the speci? c project site characteristics. ~30-35 of these ? oaters per year to meet installation re- Export cable laying is for the most part the same as seen in quirements of one full installation spread. bottom ? xed wind farms.

• Turbine installation is generally expected to take place at the assembly port. Next generation turbines with larger TURNING THE FORECAST INTO VESSEL DEMAND diameters drive the hub height where a crane needs to lift We have prepared a bottom-up forecast for activity through weights of 750-1,050 tonnes to over 180 meters assum- 2035 and have developed demand models for three scenarios: ing the currently available large turbines. A key variable to • Mutualized catenary mooring lines (very large diameter monitor is the development by Chinese developers of tur- chain and ? ber rope) connected to suction anchors.

bines as large as 25 MW with rotor diameters of ~300-310 • Drag embedment anchors, two per ? oater mooring con- meters. Suitable crane supply is limited today and with po- nection, connected to individual catenary mooring lines tential increases in rotor diameters will become even more (large diameter steel chain, smaller than that of the mutual- limited. Once assembled, several turbines will likely be wet ized and taut mooring case, and a ? ber rope mid-section).

stored before being towed offshore for hook-up. Due to in- • A taut mooring system with a smaller footprint, with stallation season weather windows, this period could last predominantly ? ber rope mooring lines and connected to 4-6 months. The implication is that a suf? cient supply of induvial suction anchors.

suitable large, sheltered harbor facilities is required. The mooring scenarios deliver signi? cantly different results 16 Maritime Reporter & Engineering News • December 2024

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