Growth in the offshore wind energy sector is generating a number of new design concepts and technology to serve the unique requirements of the industry
As highlighted previously in OSJ, demand is growing for service operation vessels (SOVs) for the maintenance of turbines on offshore windfarms. They are mostly chartered by turbine manufacturers such as Siemens, Dong, Vestas and others.
Speaking in conjunction with Voith Marine Turbo at a recent conference, Roman Grebe, chief executive of broker F3 Offshore outlined some of the specific challenges posed by the demands on SOVs. In particular, SOVs need to provide substantial, high quality accommodation for technicians who work off the SOVs on wind turbines but are not seafarers. “SOVs require a high level of passenger facilities and comfort for workers. The current benchmark is to have about 40 technicians on board plus about 20 crew members, but some operators are looking at bigger SOVs. SOVs must meet high operational requirements to work reliably in harsh weather. Other necessary features include DP2 dynamic positioning, walk-to-work, workshops and storage for spare parts. Mr Grebe said he expects a requirement for 25–35 SOVs by 2022, with a steady flow of tenders over the next few years. “SOVs need a dedicated design approach, customised for particular applications and windfarms,” he said
Voith is working with several designers and shipbuilders to develop an SOV featuring an innovative Voith propulsion system, which the company believes will enhance performance, comfort and fuel efficiency. Voith Turbo Marine head of research and development Dr Dirk Jürgens said that using a Voith Schneider Propeller (VSP) coupled with the Voith Inline Thruster (VIT) allows 25 per cent more wind turbines to be serviced in the same timeframe compared to azimuth drives. The VSP mechanism enhances DP performance while reducing fuel consumption by about 10 per cent, he said. A VSP-equipped vessel allows for operation in greater wave heights and with higher productivity than conventional propulsion systems. “The normal operating limit currently is about 2.5m wave height, but crew transfers have been carried out in greater wave heights, and the upper limit could be increased to 3.5m,” he said. This can result in up to 15 more operating days per year where transfers can still be carried out.
Dr Jürgens added that VSP drives also support improved comfort, which is especially important for the non-seafarer technicians working from SOVs. The danger of seasickness is reduced by the Voith Roll Stabilization system, and the ultra-low noise VIT ensures maximum comfort in terms of noise and vibration. “There will be big advances in the technology and design of SOVs for offshore windfarm maintenance operations,” Dr Jürgens commented. “As windfarms move further offshore, especially with floating windfarms, the demands will become greater.”
Voith Turbo Marine’s managing director Dr Dominic Dorfner said Voith is working with a number of independent institutions to develop its new concept for the offshore wind sector. He added, “We have launched the new linear jet motor for crew transfer vessels, and we will make a further push into the offshore wind industry where we see opportunities for us.”
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