Low cost anchoring system for floating tidal generators

The anchor deployment formed part of a novel tidal anchors project for floating technologies, which was carried out in partnership with McLaughlin & Harvey, SeaRoc and Scotmarine. The aim of the project was to develop an innovative low cost anchoring system for floating tidal energy converters which could be readily installed and decommissioned utilising low cost vessels and to demonstrate the anchors on the Scotrenewables SR2000 2MW turbine installation, the largest floating tidal turbine in the world.

The project was supported by the Scottish Government’s Marine Renewables Commercialisation Fund, which was established to support the development of enabling technology for marine energy arrays and by Invest NI.

Scotrenewables’ philosophy for both its floating tidal turbine and anchors technology has always been to engineer out expensive, highly specialised vessels in preference for lower cost workboat style vessels for all major aspects of installation, maintenance and decommissioning. In so doing it says it can ‘deliver game changing cost reduction in the levelised cost of energy from tidal energy generation’. The engineering challenge has been to maintain this design approach as the company’s technology and its anchoring requirements have increased in scale.

To achieve this, Scotrenewables, in collaboration with its partners McLaughlin & Harvey and Scotmarine developed a novel installation methodology where locally cast, modular interlocking anchor blocks, could be transported to the quayside and placed on the sea-bed where they would be picked up for deployment on site using bespoke, specially designed, remotely operated lifting equipment mounted on readily available work boats. The pre-cast fibre reinforced concrete anchor modules were manufactured by McLaughlin & Harvey at a casting yard specifically set up within the harbour complex, transported to the quayside at Hatston, Orkney and placed on the sea-bed adjacent to the quayside using local heavy lifting engineers Heddle Construction. From there; anchor modules, each in excess of 64 tonnes, were transported to the EMEC tidal test site, some 30km, away by Scotmarine’s MV Orcadia II workboat with the use of the bespoke deployment frame. The process was refined such that multiples of modules could be safely deployed in a single working day.

The system, approach, installation and decommissioning procedures were developed from initial concept through to full-scale demonstration and deployment over the course of the two-year project and have proven highly successful.

Andrew Scott, Scotrenewables CEO said, “The floating tidal anchors project has demonstrated how inexpensive gravity anchor materials can be utilised in conjunction with a highly innovative deployment approach towards a low cost anchoring solution for floating tidal installations.

The entire anchoring system was fabricated within Orkney and installed using a locally based workboat vessel, further illustrating how this approach can make full use of the local supply chain for tidal energy installations.”

Michael McSherry, McLaughlin & Harvey Marine Renewables Manager said,

“McLaughlin & Harvey are delighted at the successes of the project. We were extremely thrilled to be involved as a project partner from conception through to delivery of yet another innovative solution to provide foundations in the tidal energy sector. Through collaboration with Scotrenewables, Scotmarine and supported by the MRCF and Invest NI and drawing on our experience of over 10 years of working in the offshore renewables market McLaughlin & Harvey with our designers MMI and RPS and our suppliers have been able to deliver a cost effective foundation for the SR2000 tidal turbine, the largest tidal turbine currently being deployed anywhere in the world. We look forward to building upon our relationship with Scotrenewables to help progress the offshore renewables sector”.

Scotrenewables Tidal Power Limited is an engineering company based on the Orkney Islands specialising in the development of a tidal energy turbine technology with the potential to produce a step-change reduction in the cost of energy from tidal stream flows.

McLaughlin and Harvey have been actively involved in the Marine Renewable Energy Sector since 2006 and is market leader in the deployment of tidal energy devices, including foundation installation, cabling and operation and maintenance. McLaughlin and Harvey continues to work with various developers and is also developing a unique installation technique for tidal energy device foundations to suit a range of ground conditions and a variety of tidal and wave energy turbines.

By Jake Frith