Subhub Ready for Ballast Trials

QED Naval returned to Subhub following the completion of the tow on a cold but bright winter’s morning to tidy things up and secure Subhub for the initial ballast system and flow augmentation trials.

The moorings were re-set so that Subhub now aligns to flow on the flood and ebb tides where flow speeds of up to 1m/s are experienced which is ideal for conducting the initial ballast system trials.

Some of the marker buoys were reset and the umbilical and operations tether unraveled and stretched out. The umbilical allows the remote control of the Subhub platform from the support vessel which is a barge in this case.

The  video below you can see the umbilicals are tough outer pipe used to protect all the service lines to operate the Subhub remotely.  The service lines are further protected by bundling them into a tough PE coating . The service lines include:

  • Hydraulic lines to control the seawater inlet and tank vent valves;
  • Low pressure air to pressurise the tanks to deballast all the seawater which provide the required on-bottom weight to overcome all the wave and tidal forces;
  • Data/coms cable for monitoring the Subhub and control the operational condition of the Subhub;
  • Main export power cable.

The umbilicals are connected into the Subsea Manifold which is an subsea junction box so when the Subhub is installed all the services can be disconnect from the support vessel housing the air compressors, HPU, generators and control panels. It can then be lowered to the seabed so the support vessel can demobilised and site cleared of any visual impact. Equally, the Subsea Manifold can be easily retrieved and the systems connected up to take control of the Subhub again.

The video below also shows the final action of the day which was to make some modifications to tidal turbines. Supported by Cuan Marine’s small multicat, Cuan Cat, it made for easy access to the tidal turbines.

Subhub on its  mooring at Game of Thrones, Winterfell Castle.
Operations Manager on the top deck of Subhub with easy access to all systems.
Subhub sloping top deck used to access the Subhub and mooring lugs which double as lifting lugs used for the launch.
Full systems trials onshore with all the service lines connected to simulate installation and recovery of the Subhub.

 

Subhub Deployment to Strangford Lough

In mid January Subhub successfully completed the 50 nautical mile offshore passage from Belfast Harbour to Strangford Lough. The final stage of the departure was the approval from the Belfast Harbour Pilots.

The Pilot brought together all the contractors who included: Ian Coleman from Inyanga who were contracted as towing agents. Also included were the skippers of MTS Taktow, as the main tow vessel,  Ferran & Sons Farset as the rear tow vessel and the licensed operatots to handle the mooring lines on the D1 quayside. Final clarifications and adjustments were made with the departure plan and then the Pilot took control from that point forward.

Jeremy Smith, QED Naval’s Managing Director said:

“We are delighted with the performance of the Subhub during the deployment, which was not without its challenges, namely, the weather. The conditions experienced offshore reached 30 knot, near gale, wind gusts and over 2.0m significant wave height so they were far from ideal but underlines the capabilities of Subhub tidal platform and the commercial benefits and operational availability of this installation and recovery method for the through life support of tidal turbines”.

“The collaboration with Inyanga Tech as towing agents, Ferran and Sons and Cuan Marine worked very well and I wouldn’t hesitate to use them again”. 

Richard Parkinson, Inyanga’s Managing Director said:

“The towing operation from Belfast to Strangford went well with the Subhub handling well under tow as expected from the analysis- this demonstrates that the device can be installed using low cost support vessels. We are very pleased to be providing support to this exciting technology”.

MTS Taktow proved itself to be the ideal towing vessel with a bollard pull of 18t and at reasonable cost despite being mobilised from Brixham.

Belfast Harbour Pilots requested that another vessel of equivalent bollard pull was used in combination with Taktow within the confines of Belfast Harbour. QED Naval selected Ferran’s Farset with a 14t bollard pull. Ferran’s had been helping QED Naval with the towing setup and specification over the last few months so this was an easy decision.

The 50 nautical mile passage was carried out at an average towing speed of 3 to 4 knots and took just over 11 hours. The successful completion of the passage validates the claims made by QED Naval about Subhub in terms of high operational availability and hence high deployment rates and reliable maintenance schedules for tidal projects underlining the commercial benefits and reduced cost of ownership.

Arrival in Strangford Lough

Subhub arrived in Strangford Lough around 0930 on the Wednesday 16th January. The pilot from Cuan Marine joined the Taktow to guide them in over the treacherous Strangford Bar and through the Narrows on the flood tide at 1400.

The tow moved quickly through the Narrows at 4.5knots passing the iconic MCT tidal turbine now partially decommissioned. It was reputed to have cost £5m+ to install and something similar to remove. This encapsulates the driving principal of Subhub tidal platform given that it cost just over £100,000 to deploy including load out, launch, planning consents (MCA, MWS, BHC), launch, towing, moorings  and insurance. By anyone’s standard this is a transformational per unit cost reduction.

Passing the iconic MCT turbine in Strangford Narrows.
Subhub’s arrival at the holding mooring in Castle Ward Bay.
The beuatiful backdrop of Audley’s Castle better known as Winterfell Castle from Game of Thrones.

It is a pleasure to present the short video below of the deployment. If you have any questions or queries please contact QED naval directly.