The first phase of a major project to investigate cost-effective methods of cable laying for tidal energy arrays has been hailed a success.
Funded by Scottish Enterprise, the £2.4m Tidal Array Cabling Solution project was launched in December 2013 to develop and demonstrate effective methods of locating, securing, protecting and retrieving cables for tidal energy arrays.
Stromness based energy and environmental consultancy Aquatera Ltd was one of a number of companies that took part in the initial concept development stage of the project in 2014, subsequently being awarded a contract to undertake two demonstration projects. The first of these, completed in partnership with subsea engineering and training firm, Jee Ltd, involved the construction and deployment of Jee’s unique ‘U-tube’ cabling protection structure in Orkney.
The Aquatera role involved lifting, moving, positioning and recovering the 50m long Jee cable protection system – thought to be the largest single dimensioned structure yet lifted, moved and placed for the wave and tidal sector. Tests of this innovative array cabling solution were carried out at the European Marine Energy Centre’s Shapinsay Sound tidal test site,
Several support companies from Orkney’s marine energy supply chain also played a key role in the project, which saw a unique and novel configuration of local vessels used to install the 50m long structure. The vessel spread used included a specialised heavy-lift barge – belonging to Stromness firm Green Marine – along with a tow vessel and MulticCat provided by Green Marine and a second MultiCat vessel operated by Scotmarine. These vessels were supported with a quayside duel crane lift by Heddle Construction. Management of the marine operation by Aquatera was backed up by Orcades Marine..
Aquatera’s Daniel Wise, who managed the operation, said the project partners were delighted with the outcome of the first phase of tests.
“Cable laying in other energy sectors and industries has traditionally been carried out by large and expensive offshore dynamic positioning (DP) vessels,” said Mr Wise. “However, the budgetary constraints within renewables require innovative thinking and more cost effective solutions, hence our decision to use Green Marine’s locally based heavy lift gantry barge and MultiCats.
“The installation, operation and recovery of the Jee Ltd cable protection structure was a unique, interesting and challenging marine operation, one which required meticulous planning and execution, but the barge and other vessels proved to be the ideal solution, with the operation running very smoothly.”
He added: “Once again, the experienced Orkney supply chain has proven that it is more than capable of rising to the challenges presented by complicated bespoke marine renewable operations. The input of local companies, who have a long track record in providing support to the renewables industry in some of the harshest waters in the world, was central to the success of the operation.”
Mr Wise said the second project to test a range of different cable laying configurations would be completed later this year.
Neil Ferguson, senior executive, Energy and Low Carbon Technologies, Scottish Enterprise, said: “We are delighted that the demonstration of Jee Ltd.’s tidal cabling solution went so well and offer our congratulations to both Jee and Aquatera for their highly professional approach to turning R&D into practical reality. This success is exactly what Scottish Enterprise had hoped would emerge from our Tidal Array Cabling Solution Project, developing effective solutions to key issues for the growing tidal energy industry and contributing to the drive to reduce costs.
“We look forward to the rest of the project being completed in the near future and bringing the results to the industry.”
Central to the project was Jee’s ‘U-tube’ cable protection system technology. This involved the successful deployment of a free-flooding submarine conduit, which was rigidly fixed between two subsea structures.
“At the terminating ends of the conduit are J-tubes, which rise up toward the turbine itself, creating a full turbine-to-turbine conduit through which the array cables can be pulled,” explained Jee’s project lead, Joe Gransden. “This system allows for simple installation and retrieval for maintenance, whilst fully locating, securing and protecting the cable.”
He added: “This project success has accelerated the technology for the tidal energy sector by presenting an opportunity to reduce the through life costs to developers and operators. Our system addresses the design challenge of locating, securing and protecting subsea inter-array cables within a tidal environment. However, it also presents a significant cost saving to the end user, by being suitably designed to utilise more standard, readily available and cheaper alternative vessels, compared with typical DP vessels used for cable laying operations.”
In the coming months Jee Ltd, alongside Aquatera, will be presenting the results of the trial demonstrations to Scottish Enterprise and their steering group members, along with other interested organisations from within the renewables sector.
Click below to view a video of the Tidal Energy Array Cabling Demonstration