OpenHydro structure removed, crane holding walkway against bow

Two Scottish companies to decommission OpenHydro’s tidal energy platform 

Two Scottish companies, Ocean Kinetics and Green Marine (UK), have made a joint venture (JV) partnership to decommission OpenHydro’s tidal energy platform in the Orkney Islands, Scotland.

Source: Green Marine UK

According to Green Marine UK, rapid progress is being made to remove the steel superstructure installed in 2006 at the European Marine Energy Centre (EMEC’s) Fall of Warness test site, used by OpenHydro for tidal turbine technology development. EMEC awarded the decommissioning contract in early April 2024. The search for the contractor for the removal started in August 2021.

The OpenHydro test rig has two steel piles drilled and grouted into the seabed, with a steel superstructure attached to the piles for a working area. The turbine was previously fixed to the piles with two steel collars, allowing it to be raised and lowered into the tide using two 15-tonne hydraulic winches.

The decommissioning work involves completely removing the steel superstructure, cutting the piles with diamond wire, and disconnecting and terminating the cables.

Ocean Kinetics is providing divers, riggers, welders, and ROV services, while Green Marine is offering offshore management, the Green Isle vessel, moorings, and operational cable expertise forming a package of marine services.

Both companies are jointly responsible for operational engineering, cutting, and heavy lift operations, drawing from the experience managing diverse marine projects such as subsea servers, port gates, aquaculture equipment, and sunken barges weighing up to 1,000 tonnes, as well as the decommissioning of the Buchan Alpha platform, said Green Energy UK.

So far, the OpenHydro superstructure has been dismantled into smaller components for removal from its static base through a series of lifts conducted by the Green Isle.

Source: Green Marine UK

“The OpenHydro project has demanded a strong understanding of operations within harsh marine environments combined with solid preparation and execution. 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,” said Green Marine Operations Manager, Terry Norquay.

“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.”

Currently, work is being carried out during Neap tides, with water speeds reaching up to 6 knots (3 meters per second). Engineering teams are focusing on utilizing slack tide windows, when the water slows to about 0.5 meters per second, enabling operations in calmer conditions.

“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,” said Ocean Kinetics Marine Projects Manager Roger Goudie.

To finalize the decommissioning project, the Green Isle will be spread-moored in a four-point mooring configuration, which demands extensive planning to maintain stability in the tide, enabling safe entry for divers.

According to the Marine Licence permitting OpenHydro’s operations, the seabed must be restored to its initial state, requiring cutting each pile foundation flush with the seabed. Diamond wire-cutting machines will be inverted to ensure an optimal finish.

Established in 2005, Dublin-based OpenHydro was the first to use EMEC’s tidal test site at the Fall of Warness. In 2006, they installed the test rig and a 250 kW open-centered turbine. 

The OpenHydro was the first tidal turbine to be grid-connected in Scotland and subsequently the first to successfully generate electricity to the national grid in the UK. The test platform at Fall of Warness test site was used to streamline its tidal turbine technology until its liquidation in 2018.