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Commissioned in 2004, part of RWE’s 60MW Scroby Sands Offshore Wind Farm has become stranded by the rising sandbank on which it was built, effectively isolating four turbines from being accessed by service vessels.
The unique crew transfer vessel was created to tackle that problem. It was developed, designed and built by a collaboration between RWE and Commercial Rib Charter (CRC). Naval architects Chartwell Marine carried out design specifications, and the vessel was constructed by Diverse Marine in its Isle of Wight boat yard.
The vessel has two wheels at the front and one at the back. The wheels can be deployed, similar to those on an aircraft, when transferring from deeper water into shallow water and sand. The design means the craft can also drive on land, providing access to the stranded turbines.
CRC Walrus took its maiden voyage in early January with “positive” results, energy company RWE said. The 12m-long vessel has a top speed of 24 knots on water, and 6km/h on land. It can carry 1,000kg cargo, 10 technicians and two crew to any of the turbines in the Scroby Sands array off the Norfolk coast, including on the raised sandbank.
“We are thrilled to have had the opportunity to build this vessel for RWE,” said Stuart Hedges of Commercial Rib Charter. “Specialising in shallow water operations has always been our niche, so building a conventional CTV with amphibious capabilities has been very exciting. We are very pleased with trials that have been 100% successful.”
Scroby Sands was one of the first offshore wind projects to be built in the UK. Natural changes in the marine environment, coupled with coastal erosion, have caused the sandbank to rise over time.
General manager Phillip Croston-Clegg said: “This new vessel is a successful innovation and testament to the fantastic collaboration between Commercial Rib Charter and the RWE team. Working with experienced vessel operators to design a unique solution to a problem that was impacting our maintenance has been invaluable. In addition, this could pave the way for broader applications in similar areas.”
The vessel has now been working on site for the last four weeks, providing a safe method of access to turbines that had been out of reach for a “considerable time”, RWE said. It will be operated by CRC over a six-year contract.
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