Ocean Kinetics, Green Marine UK complete decommissioning of OpenHydro tidal turbine at EMEC

OpenHydro removal
An OpenHydro system

Two Scottish marine engineering firms, Ocean Kinetics and Green Marine, announced they have successfully completed the decommissioning of OpenHydro’s pioneering tidal energy platform at the European Marine Energy Centre (EMEC) in Orkney.

The decommissioning project, contracted by EMEC, involved a range of marine services. A joint venture partnership was formed in April 2024 to deliver the contract, combining Ocean Kinetics’ divers, riggers, welders, and ROV services, and Green Marine’s offshore management, vessel, moorings, and cable experience, with shared responsibility for operational engineering, cutting and heavy-lift operations.

Key work included dismantling the platform’s steel superstructure – including two 18-tonne steel piles, drilled and grouted into the seabed – as well as cable disconnection and termination. Pile foundations were cut to the seabed using reversed diamond wire cutters, returning the seabed as close as “reasonably practicable” to its original condition. Under the Marine Licence which allowed OpenHydro to operate, the seabed must be returned to its original condition, which means cutting each pile foundation flush to the seabed.

As Hydro Review previously reported, OpenHydro’s technology, called the Open-Centre Turbine, comprises four key components: a horizontal-axis rotor, a direct-drive permanent magnet generator, a hydrodynamic duct, and a subsea gravity base foundation. The commercial-scale turbine is 16 m in diameter and is rated at 2 MW. It weighs about 300 tons and is predominantly a steel assembly.

The OpenHydro test rig consisted of two steel piles drilled and grouted into the seabed, with a steel superstructure attached to provide a working area. The turbine component was fixed to the piles using two steel collars, which allowed the unit to be raised and lowered into the tide using two 15-ton hydraulic winches.

“We are very pleased to have successfully completed this complex and wide-ranging project,” Green Marine’s operations manager Terry Norquay said. “Significant planning was required to complete the recent phase involving the removal of the two 18-ton steel piles, with our vessel, the Green Isle, positioned in a four-point mooring configuration to remain stationary and allow divers to safely enter the water. This project has expanded Green Marine’s broad portfolio of work and demonstrates the turnkey offshore decommissioning solutions we can deliver in partnership with our trusted colleagues.”

“The OpenHydro platform stood at our Fall of Warness test site for 18 years, one of the longest tidal energy installations in the world to date,” Neil Kermode, EMEC managing director, said. “It’s great to see local Orkney and Shetland companies fulfill the decommissioning requirements, a testament to the world-leading supply chain capabilities that have built up here due to marine energy testing and demonstration activities. Now that decommissioning has been completed, we can complete a full lifecycle analysis with valuable insights around marine operations, structural integrity of long-term deployments as well as the impact of biofouling and corrosion. These lessons can help guide the tidal energy industry’s continued evolution as we ready our test sites for future clients and building out to tidal energy arrays.”

OpenHydro was the first developer to use the tidal test site at the Fall of Warness off the island of Eday when its test rig and 250 kW turbine were installed 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, according to a release.

Established in 2003, EMEC is a center dedicated to demonstrating wave and tidal energy converters in the sea. As a plug-and-play facility EMEC is meant to help reduce the time, cost, and risk of testing ocean energy and associated low carbon technologies. More marine energy devices have been tested at EMEC than at any other site in the world. EMEC was set up to kick start a marine energy sector in the UK and boost economic development in the Highlands and Islands.

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