Where the wind blows

27 Oct 2017
Deep sea floating windfarms could eventually become a significant sub-sector with its own vessel requirements

Deep sea floating windfarms could eventually become a significant sub-sector with its own vessel requirements

Technology and cost improvements are driving an offshore wind revolution. And ship owners serving the sector are having to adapt as quickly as the market itself, writes Gavin Lipsith.

Like the turbines that are the sector’s hallmark, offshore wind is a looming presence on the energy horizon. At the end of 2015, installed wind energy capacity (both onshore and offshore) stood at 435GW- or seven percent of global energy supply - according to the World Energy Council. Offshore wind accounted for just 12GW of that. Leap forward to 2050, and offshore wind alone is expected to cater for more than 12% of the world’s energy needs, according to DNV GL’s Energy Transition Outlook 2050.

That growth will be driven by the accelerating demand for emission-free energy sources. But until very recently there was a question mark over the economic feasibility of offshore wind. That changed in April when two consortia led by Energie Baden-Wuerttemberg and Dong Energy, competing for a 1,490MW German wind farm project, placed bids that – for the first time in the history of offshore wind – do not rely on state subsidies. The bids promise electricity at €4.40 a megawatt-hour; less than a tenth of the cost of Germany’s previous deal.

Whether zero-subsidy offshore wind is feasible yet beyond Germany – where state utilities pay for infrastructure connecting wind farms to the grid – is uncertain. But the breakthrough has already had a significant policy impact. It has encouraged Germany to reconsider its offshore wind targets for 2030, convinced the Dutch government to introduce a zero-subsidy round in its own bidding processes, and given the UK executive pause for thought before pursuing its nuclear energy strategy.

The reduction in costs is the result of advances in both turbine technology and the construction of offshore wind facilities. Offshore wind turbines have grown from around 60kW for the earliest commercial models, more than 25 years ago, to 9.5MW for units currently being planned (for use in projects from around 2020). If the weight of those early models was extrapolated in linear fashion, today’s turbines would weigh as much as a containership. In both power generating capacity and weight, huge advances have been made. And the ship technology used to transport and install turbines has had to keep pace.

BIGGER CRANES

“Bigger turbines mean heavier foundations, which require better cranes,” explains Dolf Elsevier van Griethuysen, business development manager, Van Oord Offshore Wind Projects. The ship owner operates across three sectors – offshore wind, dredging and oil and gas – and owns a fleet of five offshore wind vessels. One of those, the Aeolus, is currently being fitted with the biggest crane ever to be installed on a wind farm installation vessel.

A 1,600-tonne lifting capacity crane built by Huisman will be fitted on Aeolus as part of a major conversion underway at Damen Shiprepair Rotterdam. The 139.4m loa, 44.46m beam ship entered the yard in September is due for delivery in January, stopping briefly at Huisman’s adjacent quay for the new crane to be fitted.

As well as removing the old 900-tonne crane, Damen will replace the ‘spud cans’ or feet at the end of the jack-up vessel’s 81m legs with bigger units. Further work includes deck strengthening, extending sponsons and upgrading jack-up hydraulics.

Van Oord has been involved in around 50% of all offshore wind installations in Europe, including (in partnership with Shell) the Gemini project off the Dutch coast which began operating this year. In that field, 130m tall turbines generate 4MW each.

The pace of progress in design means that the next round of projects are already discussing turbines of 164m in height generating 9.5MW each – a power output that has already been revised upward since planning started. That rapid development explains the need to retrofit the Aeolus, explains van Griethuysen.

He says: “Future projects may require half the number of turbines but the increase in weight of the foundations means that we have to add crane capacity earlier than we had planned. Aeolus is a well-built vessel and can easily accommodate the new crane.”

ACCELERATING MARKET

The fact that Aeolus is already being retrofitted after just two years in the water reveals exactly how fast the sector is moving. And with the weight of wind turbine foundations set to exceed the capacity of the vessel’s new crane in the early 2020s, it is easy to see how ship owners might find it difficult to make money even as growth in the market for wind vessels accelerates.

“There needs to be more security about the pipeline of projects on a global level, otherwise it will be challenging for ship owners to invest in this sector,” explains Peter Robert, director of business development and market intelligence, Damen Shipyards Group.

Despite this difficulty, there is opportunity. Damen believes there are too few heavy lift vessels working in the North Sea to meet wind project demands over the next few years. The zero-subsidy project in the German Bight, expected to begin operations in 2025, will feature 145m tall turbines pumping out 13-15MW each. At present only two ships could cope with that load – the converted Aeolus and Seajacks Scylla. Vessels for that project will need to be under construction by 2021, meaning that investment decisions must be taken over the coming year.

There will be a need for more and bigger wind installation vessels. Further, as wind project cargos become heavier, it will become harder for multipurpose vessels to compete. Traditionally out of work offshore oil and gas vessels have tried to find employment in the wind sector. But, as Sjaak Jan Jiskoot, tender manager, Damen Shiprepair & Conversion explains, this will become increasingly difficult.

“The crane on an oil or gas installation vessel is designed for heavier loads but at much lower frequency than wind installation cranes,” he explains. “Wind projects require perhaps fifty foundations to be lifted in one project, while oil and gas vessels must only lift four. A conventional installation vessel might struggle to bear the strain of that number of lifts even if it can easily handle the weight of the individual load.”

LIFTING FACTORIES

In keeping with the rapid development in foundation sizes, the latest wind installation vessel concepts feature suitably pumped-up cranes. One concept seen by The Motorship features a 2,500-tonne crane. The ‘on spec’ design is capable of carrying three complete 10MW Siemens wind turbines (including tower, nacelle and blades). It also achieves a 10% weight reduction compared to current vessels as a result of abandoning jack-up legs in favour of installing foundations while in dynamic positioning mode.

The switch from jack-up to floating installation (using advanced dynamic positioning) represents a potentially major shift in practice for the offshore wind industry. Dutch shipbuilding group Royal IHC’s in-house engineering consultancy, IHC Vuyk, has developed its own future wind installation concept in partnership with a major ship operator. It has opted for a 3,000-tonne capacity crane and has also chosen floating rather than jack-up installation.

It is not the first time that the wind turbine sector has considered the notion of floating installation, says Kuno van den Berg, commercial manager – consultant, IHC Vuyk. Dynamic positioning vessels were considered in 2008-2010, when it became clear that wind turbines would get bigger faster than expected.

“It was understood that floating installation vessels would be faster and more effective in capacity terms,” says van den Berg. “But they were too expensive, there were not enough such vessels available and people thought that wind turbines would not be adapted for this method of installation.”

Now that wind projects are reaching the capacity limits of the largest jack-up vessels, van den Berg believes it is time to consider DP installations once more. Their efficacy is backed up by growing experience in offshore oil and gas, with early heavy lift giants like Seaway Heavy Lifting’s Oleg Strashnov (boasting a 3,000-tonne crane) and Van Oord’s Svanen (with a lifting capacity of a staggering 8,000 tonnes) begetting more modern vessels: Boskalis will this year convert its Bokalift 1 semi-submersible heavy lift vessel into a self-propelled crane vessel with a lifting capacity of 3,000 tonnes. Rival DEME is meanwhile building Orion, an offshore installation vessel with a similar lifting capacity to Bokalift 1, at COSCO in China for delivery in 2019.

VESSEL GROWTH

Van den Berg notes: “Today large floating installation vessels are competitive in price with very large jack-ups and are much more readily available than in 2010. The bigger these ships become the less advantage jack-ups have because stability is not such a concern. You still have a smaller operational window with floating vessels, but that is offset by the shorter installation times.”

As with installation vessels, so too will the service and operation vessels which shuttle maintenance crews to windfarms grow in size and number – with the market growing by 11-14% each year for the foreseeable future, according to Damen’s Robert.

It’s not just the size of the vessels that will change. Ships are also becoming more specialised. Royal Dutch Shell is a participant in several offshore wind projects and works closely with ship owners on the construction of windfarms – notably with Van Oord for the Dutch Gemini project. Hessel de Jong, Shell’s commercial director offshore wind, believes that ships better suited to the job are a main reason for the rapid progress of offshore wind.

“If you look at the cost reductions since 2010, they have been a result of new designs – bigger wind turbines but also specially designed vessels,” says de Jong.
Going further, de Jong believes that longer term relationships with ship owners – even beyond the per-project partnerships it operates with ship owners like Van Oord today – could yield even more benefits in terms of ship capabilities.

“If you view offshore wind as a resource to be managed rather than a series of projects, you can start looking at producing so many gigawatts over ten years. We’ve already spoken to ship owners in these terms, asking theoretically if this was the case, could they build us a ship specifically for this port, this sea and this activity? The answer was yes.”

PEAK POWER

It seems likely that ships serving the offshore wind sector will grow bigger, more numerous and more specialised. But a caveat is required: The growth of windfarm vessels applies only to a point. According to Kim Mørk, executive vice president of renewables certification at DNV GL, offshore turbines in their present form are likely to grow only to around 15MW before some disruptive change is needed – in design, layout or materials.

“Our economic model does not go up to 20MW – but I would be careful about saying that given the pace of development so far,” he says.

There may therefore be a limit on the size of turbines vessels need to carry. But there could be an even more fundamental change in the kind of vessels serving the sector if the currently niche market in floating wind farms becomes significant.

There is a reason that the North Sea hosts the most well developed offshore wind market in the world. Apart from being subject to strong winds, it is also rather shallow and so easy to build in. But once waters reach a depth of more than 60m, bottom-fixed turbines become challenging. And as luck would have it, that is where the good wind is found; according to Wind Europe around 80% of the continent’s wind energy resource is in such waters – suggesting a floating wind energy potential of 4,000GW. Compare that to the world installed wind capacity of under 15GW.

How to reap that lucrative harvest remains a hotly discussed subject, with several demonstrator projects trialling different versions of floating turbines, including semi-submersibles, tension leg platforms, multi-turbine barges and spar concepts.

One company seeking to leverage its heritage in the offshore oil & gas market – particularly in floating production, storage and offloading (FPSO) facilities – is SBM Offshore. The company has developed its own floating wind turbine concept and has recently won a tender for a floating windfarm off Marseille in France, working with energy company EDF and Siemens. At the Provence Grand Large project, the partners will install three 8MW turbines in water of up to 100m depth.

SBM’s tension leg platform concept – and the turbine itself - can be built and assembled quayside before being towed to its mooring position. Beyond towing time, installation can take place in less than a day, with no need for the heavy lift vessels of the scale required for bottom-fixed facilities. SBM has two installation vessels of its own, although it will not necessarily use these if it can find a better price on the market.

FLOATING COSTS

It might be unfair to call the installation less sophisticated than that required by bottom-fixed windfarms – an installation vessel will need to fix the moorings to the seabed and a longer cable lay will be needed to feed electricity back to shore. But the installation can likely be carried out by less specialised and smaller vessels. Ultimately this may help to reduce costs – although for the time being the cost of floating offshore wind, in its experimental stage, remains high.

Joost Heemskerk, renewable energy product line director at SBM, believes that there is an opportunity for floating wind facilities as turbines reach a critical size. He explains: “Turbines are scaling up so quickly that they will soon hit the limits of the biggest jack-up vessels. The question then is whether it is cheaper to jump to floating wind, or to continue with monopile foundations. We hear from companies in the fixed wind sector that this point is rapidly approaching and that they are already preparing for life beyond monopiles.”

Further development of installation tools could make it even easier for smaller, less capable vessels to participate in floating wind projects. Rotterdam-based anchoring and mooring specialist Vryhof, for example, has developed a tensioner – a sophisticated ratchet for adjusting the tension in an anchor chain – which means that floating wind installations can be performed by small anchor handling tug supply vessels or local barges, instead of larger vessels.

It appears then that the offshore wind sector is reaching a critical juncture with regards to the vessels that serve the market. As turbines rapidly outgrow the biggest available jack-up installation vessels, ship designers are preparing to fulfil the market’s needs with even bigger ships that can perform installations using dynamic positioning. If the industry can move beyond the project-by-project approach, ships could be built even more specialised to their individual projects. But floating windfarms could be a wild card, and one of their major attractions is the lower capability vessels required for installation.

Having said that, it would be a bold forecaster who tried to predict where this rapidly evolving market is heading beyond the next round of projects. Likewise, the direction of the shipping sector that serves it.