Scottish firms Ocean Kinetics and Green Marine (UK) have formed a joint venture partnership to decommission OpenHydro’s tidal energy platform in the Orkney Islands.
Work is rapidly advancing to remove the steel superstructure installed in 2006 at the European Marine Energy Centre’s (EMEC’s) Fall of Warness test site which OpenHydro used to streamline its tidal turbine technology development.
EMEC awarded the decommissioning contract in early April.
The OpenHydro test rig consisted of two steel piles drilled and grouted into the seabed, with a steel superstructure attached to the piles to provide a working area. The turbine component was previously fixed to the piles using two steel collars, which allowed the unit to be raised and lowered into the tide using two 15 tonne hydraulic winches.
The decommissioning work scope involves the entire removal of the steel superstructure, Diamond Wire Cutting of the piles, along with cable disconnection and termination.
A broad package of marine services is combined with Ocean Kinetics providing divers, riggers, welders and ROV services, while Green Marine is providing offshore management, the Green Isle vessel, moorings and operational cable experience.
Both firms are sharing responsibilities for operational engineering, cutting and heavy lift operations, where they benefit from significant experience managing a wide range of marine works – including subsea servers, port gates, aquaculture equipment and sunken barges (reaching 1000 tonnes in weight) and decommissioning of the Buchan Alpha platform.
To date, the OpenHydro superstructure has been broken down into a series of smaller components for removal from its static base following a series of lifts performed by the Green Isle.
Green Marine Operations Manager Terry Norquay said the entire topside infrastructure has now been successfully removed with work imminently progressing to the pile removal and cable termination.
In order to complete the final elements of the decommissioning project, the Green Isle will be spread moored, in a four-point mooring configuration to remain stationary in the tide and allow divers to safely enter the water.
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. To achieve this result diamond wire cutting machines will be turned upside-down to create an optimal finish.
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 250kW open centred turbine were installed in 2006. The device 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.
In 2028, the French energy developer Naval Energies, the parent company of Irish-based OpenHydro, decided to stop further investments into development of its tidal energy business, which forced OpenHydro into liquidation.