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'Multimodal the watchword in offshore wind crew transfer'

OPINION | A mixed approach to offshore wind crew transfer has served the industry well, but challenges loom, writes Tim Börner

Transferring personnel safely and efficiently to their workplace – the turbine – has tested the ingenuity of the industry since Vindeby, the first offshore wind farm, was installed in Denmark more than 25 years ago.

The key word here is ‘multimodal’ – the combination of at least two different means of transportation that get you from A to B. We’re all familiar with the concept from our daily commute to work or from the international shipment of goods.

Various solutions have been tested and further developed to transfer offshore workers from shores to wind farms, and back. They include crew transfer vessels (CTVs) of different sizes and designs, man-baskets, helicopters as well as various types of passive or active motion-compensated gangway systems, mobilised on dynamic positioned (DP) vessels. Any combination of the above is an option, too.

Alongside important factors such as location, the time of the year and the work scope, costs play a key role in the decision-making process. Therefore, it is to be expected that in the future, different transfer methods will be used to get the best value for money ratio for specific projects.

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Over the past few years, there has been a steep technological development especially in the segments of CTVs, gangways and service operation vessels (SOVs). Various gangway providers, with Ampelmann as one of the first movers, have entered the market with versatile concepts, resulting in a more commoditised market with competitive prices. CTVs have grown to sizes of 30+ metres with large capacities for cargo, fuel and personnel aiming to fill the gap between smaller CTVs and Walk to Work (W2W) vessels. The latest example is the 40-metre design released recently by Manor Renewables.

Such developments will continue and they will contribute to the safe and economically efficient operations of offshore wind farms. However, with wind farms being built further away from the coast, the benefits of helicopters will become ever more attractive. Unfortunately, helicopters are an expensive means of transportation with limited cargo capacity.

Clearly, all of these methods have advantages and disadvantages but using the right combination can represent a reliable and effective setup to transfer personnel in different weather conditions and times of the year. To return to the commuting example, just like on your journey to work you might use a car or bicycle to get to the train, and switch to the subway after five stations to get to the office.

In offshore wind this could mean that a W2W vessel with accommodation for 50 technicians remains in the wind farm as a logistical hub and the main means of transfer in higher sea states. In addition, two or more CTVs that can be refuelled offshore, may be used simultaneously to increase the speed of transfer on the days with lower wave heights. For urgent troubleshooting, crew change or emergencies, helicopters round off the selection.

Such transfer concepts are not new to the industry and have proven themselves over the last few years. However, there are two main challenges to maintain and further increase the efficiency.

On the one hand, the interfaces between these different vessels and equipment need better alignment – contractually as well as in operation. On the other hand, the use of W2W vessels has become common practice, while shipowners have had little incentive to build such vessels specifically fitted and designed for the renewables market.

Should this not change soon, we will see a shortage in the supply of W2W capacities. At this moment the wind industry is still (too) dependent on tonnage from the comparably volatile oil & gas market.

Tim Börner is business development manager, offshore wind, for Ampelmann

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