Ocean Kinetics and Green Marine (UK) have formed a Joint Venture Partnership to decommission OpenHydro’s tidal turbine energy platform in the Orkney Islands.

The decommissioning work at EMEC’s Fall of Warness test site involves removing the steel superstructure installed in 2006. EMEC awarded the contract in April.

The OpenHydro test rig included two steel piles drilled and grouted into the seabed, with a steel superstructure attached to the piles. The tidal turbine was previously fixed to the piles using two steel collars and operated with two 15-tonne hydraulic winches.

The decommissioning involves removing the superstructure, cutting the piles with diamond wire, and disconnecting cables. Ocean Kinetics is providing divers, riggers, welders, and ROV services, while Green Marine is handling offshore management, using the Green Isle vessel and providing moorings and cable operations expertise. Both companies are sharing responsibilities for operational engineering, cutting, and heavy lifting.

The OpenHydro superstructure has been dismantled into smaller components for removal. Green Marine Operations Manager Terry Norquay stated that the topside infrastructure has been removed and work is progressing to pile removal and cable termination.

decommission OpenHydro
Structure removed, crane holding walkway against bow

Tidal turbine in harsh environment

“The OpenHydro project has demanded a strong understanding of operations within harsh marine environments combined with solid preparation and execution,” Norquay said. “While Green Marine and Ocean Kinetics offer a broad range of marine services, this particular job demonstrates the turnkey solution we offer specifically for subsea superstructure removal projects. By combining our respective expertise, we are able to deliver all manner of EPCI (Engineering, Procurement, Construction, and Installation) contracts. There are few operators in the UK who can match us for experience, reliability and cost efficiency.”

The work is being conducted during Neap tides, with water speeds approaching 6 knots. Engineering teams aim to capitalize on slack tide windows, when water speeds drop to 0.5 meters per second.

Ocean Kinetics Marine Projects Manager Roger Goudie said: “This project cements Ocean Kinetic’s status as a leader of offshore decommissioning works. Our experienced rope-access-trained decommissioning team have worked alongside the Green Marine crew to safely deconstruct the topside structures and prepare the piles for removal. We have also had our dive team working onsite which proves the skills offered by Ocean Kinetics given the tidal nature of the site.”

To complete the project, the Green Isle will be spread moored in a four-point configuration to remain stationary and allow safe diver operations. The seabed must be returned to its original condition, requiring cutting each pile foundation flush to the seabed with diamond wire cutting machines.

OpenHydro was the first developer to use the Fall of Warness tidal test site in 2006. The device was the first tidal turbine to be grid-connected in Scotland and the first to generate electricity to the national grid in the UK.