Offshore lifting: Strong winds, heavier lifts21 November 2022
The newest developments in offshore lifting nowadays are in the wind energy field. As turbines get heavier, blades get longer and towers get higher, demands on lifting technology increase. Julian Champkin reports.
Ten years ago any article about maritime and offshore lifting would have been about oil and gas. Even five years ago the same thing would have been primarily true, though offshore wind farms might have got a brief mention. Today this article is almost entirely about lifting for the offshore wind industry.
The reasons for the change are clear: the engineering challenges that faced offshore oil and gas exploration in its early days were huge. How, actually, in real life do you drill a hole into the seabed a hundred metres below the surface of the storm-swept North Sea, and insert a pipe into that hole, and get the gas or oil that comes out of that pipe safely ashore? Nothing remotely like it had ever been done before. If today we take the achievements of the offshore fossil fuel industry for granted it is only through over-familiarity: we ought still to marvel at the complexity, the power, the sheer size of a floating oil rig and at the cumulative human ingenuity that went into creating it and getting it into position 50 miles out to sea, and anchoring it there to float and function as we want it to.
Offshore wind is in the same position of novelty and of challenge today. The towers are huge: 60 metres meters tall in the early days, General Electric’s latest Halaide-X design has blades 107 metres long whose tips sweep 260 metres above the sea surface. How exactly do you lift the tower for such a thing from a dock onto a ship, then at sea lift it again, tilt it upright, lower it down to the seabed and secure it?
And having done that, how do you then attach three 100-plus-metre blades to its nacelle, from a vessel that is bobbing around in fair weather (we hope) all that distance below the attachment point? For windfarms on land it is a challenge, requiring new cranes and techniques; for offshore farms the towers are roughly twice as high and the challenges – shall we call them 20 times as great?
Which of course is why they are interesting. The technologies are new and big and ingenious. And offshore wind is also a boom industry as well as a challenging one.
The 2022 offshore wind market report from the US Office of Energy Efficiency and Renewable Energy, published in August, finds the U.S. offshore wind pipeline to be growing by 13.5% over last year, with 40,083 megawatts (MW) now in various stages of development. The Biden- Harris Administration has significantly expanded areas available for offshore wind development, opening up the almost-untapped US East Coast with lease areas auctioned in New York Bight and Carolina Long Bay, and plans for the West Coast, Gulf of Mexico, Oregon, and the Gulf of Maine. Globally, offshore installations in 2021 had a record year with 17,398 MW of new projects commissioned. Three floating offshore wind projects - the newest technology, and the one with greatest potential - came online in 2021, including the largest floating offshore wind project built to date, the 50 MW Kincardine Offshore Wind Farm in Scotland. All this of course is given even greater concentration of minds by the prospect of an energy-starved European winter without Russian gas.
And the industry continues its trend toward larger turbines. It is not only General Electric: all three major European manufacturers are working on developing 15-MW-class wind turbines with rotor diameters up to 236 metres, compared to 158-metre-average rotor diameters in 2021.
Costs per megawatt are coming down. As an example, in September this year (2022) Seaway Heavy Lifting and Sif completed the installation of all 140 monopile foundations at the 1.5 GW Hollandse Kust Zuid farm in the Dutch North Sea; and a little earlier, in August, the first electricity from the farm flowed into the Dutch national grid. The farm is notable as the world’s first subsidy-free offshore wind farm. The lesson from that is that development costs of offshore technology have been largely amortised, and installation methods and efficiencies are such that offshore wind farms can now generate profits as well as power.
For the lifting technologies of offshore wind let us start at the water’s edge where towers and blades are loaded onto their transport ships. In July this year Huisman unveiled a new Travelling Quayside Crane specifically for the load-out of offshore wind turbine components.
Current methods, say Huisman, involve crawler cranes, or a tandem-lifting by two cranes with a capacity around 200t to 300t. With its 700t machine the load-out process of offshore wind turbine components can take place significantly faster.
It is fully electric, with a direct connection to the quayside grid and feeding regenerated energy (from lowering the load) back into it, which reduces the net energy consumption of the crane.
It travels on tracks 16m apart, though this can be adapted for narrower quays. The boom is 57m; lifting 700t at a radius of 25m it is designed to bring turbine components to any place in the hold of the majority of the cargo vessels currently used for turbine transportation.
“We see a need in the offshore wind logistics market for increased efficiency in smaller ports in newly developed offshore wind areas,” says Cees van Veluw, product manager Cranes at Huisman. “The traditional use of crawler cranes or multiple smaller quayside cranes would require a very large backyard. It also requires the transport vessel to be moored along the quayside for an unnecessarily long time. With this crane, offshore wind ports can be ready for a quick load-out of turbine components in a sustainable manner.”
Maritime heavy lift and project cargo carriers SAL Heavy Lift, with its partner Jumbo Shipping recently (September 2022) signed building contracts for four new generation heavy lift ships, with options for two more. The first two ships will be exclusively used for transportation of offshore wind turbine components. The ships, called the Orca class, are to be built in China. “They set the new benchmark in global heavy lift shipping” says Dr Martin Harren, owner and CEO of SAL Heavy Lift and the Harren Group.
Ultra-efficient and with carbon-neutral potential, “they will be the most efficient vessels in their class with consumption and emission figures far superior to any existing heavy lift vessel today. The group has committed to the decarbonisation of shipping activities by 2050 and the order, is significant, concrete action towards that.”
The vessels measure 149.9 m x 27.2 m and provide a capacity of 14,600 dwt. Each vessel is fitted with two 800 t Liebherr cranes specifically designed for the ship type; in tandem they can handle cargo items weighting up to 1,600t.
“Despite extremely high crane pedestals of more than 11 m, the overall crane height and thereby the vessel’s air draft remains at just about 38m. This makes it possible for the vessel to pass through the Kiel Canal and enter strategically important ports worldwide,” says SAL’s Sebastian Westphal. “The fully electric cranes have a battery storage system that can be used with conventional gensets in hybrid mode, or in combination with the vessel’s shore power connection for fully electric port operations. That makes them perfect for the vessel’s intelligent energy management and recovery system.”
The Orca vessels will have an innovative propulsion system: the main engines have a diesel-electric booster function. At a service speed of 15 kn, the vessels will consume significantly less than the 20 tons a day of similar vessels. Alternatively, the vessels will be able to trade at a slow, ultra-efficient speed of 10 kn at 6 t/day while still being able to reach a maximum speed of 18.5 kn for urgent deliveries – if a windfarm installation vessel is waiting for an urgent component delivery, for example.
The vessels are equipped with dual-fuel engines, which means that they can use methanol as an alternative fuel. If green methanol becomes available in key ports - a development that is anticipated towards the end of the decade - the ship will carbon-neutral transport.
Still on the subject of lifting vessels, MacGregor has been chosen to supply cranes for Van Oord’s new generation wind turbine installation vessel being built in China by Yantai CIMC Raffles Offshore.
The 175-metre vessel has an advanced jacking system. Four giant legs, each measuring 126 meters in length, allow the vessel to be jacked up and work in waters up to 70 meters deep. It is considered to be one of the largest such vessels in the world. The main crane lifting capacity is more than 3,000 tons.
MacGregor will be supplying two auxiliary offshore telescopic cranes, which are used to support the cargo and load handling during the installation of wind turbines in the offshore environment.
They are customized according to the ship owner’s requirements, with high lifting performance and long outreach but a very compact and robust design and are equipped with an anti-collision system.
If you want an illustration of the physical size of offshore wind towers, here you have one: the next generation offshore installation vessel ‘Orion’ operated by DEME of Belgium has Liebherr’s HLC (Heavy Lift Crane) 295000 installed on board; and this is actually the largest crane that Liebherr has ever built. It has a maximum lifting capacity of 5,000 tons and it will be used to install wind farms, and to decommission oil platforms - both functions that help to reduce CO2 emissions.
As with Liebherr’s cranes on the Orca, the compact design of the HLC 295000 contributes to the crane ability to serve. The base column, at only 16.8 metres diameter, is unique in the market. It requires little space on deck and offers more storage space for transportation. Its maximum lifting height of 175 metres enables the HLC 295000 to operate at the required height for large towers without special measures.
In April the Orion underwent its naming ceremony and took a series of offshore testing, including several overload tests, which it successfully passed. It set sail for final departure to Arcadis Ost I, a windfarm under construction in the Baltic.
Luc Vandenbulcke, CEO, DEME Group, emphasised the size and height needs of offshore wind: “The new era in the offshore energy industry will be dominated by multi-megawatt turbines, jackets and components,” he said. “The combination of load capacity and superior lifting heights of ‘Orion’ will play an important role in helping the industry successfully navigate the energy transition. In decommissioning, its focus on dismantling parts as large as possible will reduce resources on transport, which means the Liebherr crane can function at ‘both ends’ of the contest for greener energy.”
A similarly green-fuelled Service Operation Vessel (SOV) is being built in Turkey for Danish shipowner Esvagt. It will be powered by batteries and dual-fuel engines and is being fitted with a new type of heavy-duty davit for lifting and lowering larger workboats into and out of the water to service wind turbines. Norwegian company Vestdavit is providing five davit systems for the vessel - two large FF-30000 dual-point workboat davits which have a unique solution for flexible hook distances, as well as a pair of L-3500 liferaft davits and one PLRH-5000 davit for fast rescue craft.
The FF-30000 system, which has a heavyweight lifting capacity of 25 tons, has been specially adapted to handle Esvagt’s newly in-house developed Safe Transfer Boat 15, (STB15), a workboat that is longer, wider and heavier than existing craft used in the offshore wind sector. It has a length of 15 metres, against the industry standard of 12 metres.
“The greater dimensions and weight pose handling challenges for existing davits to ensure that personnel and equipment can be deployed safely and reliably under variable sea conditions,” says Vestdavit’s sales and business development director, Bjørnar Dahle.
The solution was to adapt the so-called F-frame (FF) system. It is a large frame with no structure behind or underneath the boat to be lifted (the ‘daughter craft’); the main structure is all aft or forward of it. This allows it to lift daughter crafts of widely varying shapes and volumes.
The FF-30000 has two lifting points, to attach at the bow and the stern of the daughter, with a dual-winch system with each winch having its own autonomous tension function so they can operate independently of each other.
“This dual-point lifting functionality permits a wider weather window as the vessel can still launch and recover daughter craft even in rough sea conditions,” says Dahle. Computer augmentation assists the operator with a safe launch and recovery in the most difficult conditions
But Dahle says that probably the smartest and most impressive feature of the system is the flexible hook distance: the aft lifting wire, which can be adjusted forward to cater for smaller boats with a shorter distance between the bow and the stern lifting points.
The SOV is lined up to work at Hornsea 2 - the world’s largest offshore wind farm - off the UK’s east coast after scheduled delivery in late 2024. A fair wind would seem to be blowing for offshore lifting as long as it can rise to the challenges.
Most Windfarm towers rise from the seabed. They therefore have to be placed where the seas are shallow. The future of offshore wind, though, is floating turbines set in deeper waters further offshore: winds are stronger and more consistent there, and there will anyway soon be a shortage of suitable near-shore sites. Floating wind towers, like floating oil rigs, must be anchored to the seabed. One method of doing so is by 'dynamically installed' anchors, also known as 'torpedo piles.' They are essentially long spikes with a pointed tip that are lowered overside from an installation vessel to a set distance above the seabed, and then dropped: they free-fall through the water, under their own weight, gathering speed until they strike the sea floor point-first and embed themselves in it under their own momentum, like an arrow falling to ground. The floating structure is then joined to them with wire ropes using an ROV.
A torpedo pile is necessarily heavy. Until now the standard method of installing them has required two lifting and handling vessels working in tandem, sometimes even with a third vessel in support Jumbo Offshore has just used a new technique, and just a single vessel to install 24 torpedo piles in deep water for Petrobras; they are to hold a floating production, storage and offloading unit (FPSO) in 1900 meters of water 150km from the Rio de Janeiro coast. Each torpedo pile weighed 120 tons.
Instead of an onboard crane lifting the torpedo clear into the air before lowering it into the sea, the lifting vessel 'Jumbo Fairplayer' pioneered a 'tilt, lower and launch' method. It used one of its two 900-ton cranes to tilt each torpedo over the side of the vessel before winching it down to the 'launch' depth.
The technique has been in development since 2010. "Working with one vessel enabled a much more controlled process,” said Brian Boutkan, Jumbo's head of sales and business development Americas. “Further, compared to previous campaigns with anchor handling vessels, the operations at the port were also more efficient. The Fairplayer has its own cranes, which meant we could pick up the equipment ourselves. And she has a large deck so she carried more torpedoes and needed fewer trips to port."
"There are always waves and swell when working in the South Atlantic region offshore Brazil. During the installation we encountered all seasons, from summer to winter. This definitely gave us some challenges, but we improved our efficiency in working with the piles to a point that we could install them even in higher waves."