Successful Installation & Retrieval Trials in Real Tidal Conditions
Recent testing of the Subhub operations model in high tidal flow conditions proved its ballast system capabilities and installation and retrieval methodology with great success. QED Naval were able to install the model on the seabed safely and in a controlled manner within minutes. The model was then secured on the seabed overnight before being recovered to the surface gracefully within an equally short time period and control.
Despite onerous wind, wave and current conditions experienced during testing, the Subhub coped admirably during the installation and retrieval trials. Scaling these extreme conditions to the prototype size, based on a 4.0m diameter turbine, would be equivalent to over 2m/s or 4 knots with a significant wave heights over 1.0m
Frontal profiles of turbine blades were added to the cross beam to simulate three turbines being installed on the Subhub; the blades acting against the current presented no issues.
QED Naval launched the Subhub Operational model last week at Forth Estuary Engineering’s (FEE) dock in Leith. The last few weeks has been a hive of activity finalising the setup of the ballast systems, instrumentation, and the dock access and testing arrangements.
FEE have provided outstanding support during the preparation and will to be on hand through the testing phase. The Subhub will now be put through its passes to test the stability during installation, ballast system control and installation/retrieval methods.
The Director of QED Naval was on site to witness the launch and initial testing and has stated, “A lot of hard work has gone into getting the Subhub project to this point which is a credit to the team and supporting companies. The Operations model represents a big step forward for the Subhub project de-risking the ballast system and installation/retrieval methods which is a key selling point used to reduce the cost of deployment and overall the cost of energy”.
Fabrication has been completed on the operational model of the Subhub at Pentland Precision Engineering allowing QED Naval to begin the pre-testing setup of the device. The Subhub looked magnificent in the Edinburgh Sun as weeks of work culminated in a device that will be tested to the limit by QED Naval. Over the next week the team at QED will be carrying out pre-testing preparations fitting extensive instrumentation and ballast systems to gain the most out of the coming testing phase.
Project team at Pentland Precision Engineering Gordon Hardman (left) Grant Middleton (centre) and Chris Scott (right).
It was great to be nominated for the Shell Springboard Regional finals out the cast of hundreds of noble projects aiming towards a sustainable, low carbon economy. Unfortunately, we didn’t win the top prize of £40,000 but made great contacts within the industry which I am sure will help us through the commercialisation stages over the next 18-24 months.
It may be small but the new model of the Subhub prototype really seems to bring the project to life. Built using the state of the art Selective Laser Sintering (SLS), 3D printing method, to tight tolerances required for the test tank models.
The tank testing will be used to validate design analysis carried out to date using our fluid modelling CFD software from ANSYS (Fluent). Verification of the drag forces on the Subhub and the velocities in way of the duct will provide confidence to go on to build the community scale prototype, capable of generating 600kW of energy into the national grid. The prototype is scheduled to go to sea in 2015, installed at the EMEC tidal test site in Shapinsay Sound, Orkney.
QED Naval have submitted an application to MARINET FP7 to complete scale testing of the Subhub foundation platform at IFREMER in France. The intent is to test a scale model in their circulation tank in the first quarter of 2014 to experience both wave and tidal conditions.
The objectives are to:
Validate the Subhub design and ballast calculations required to secure the turbines to the seabed;
To assess the accelerations in the flow field in way of the turbine rotor blades;
To assess the increased power outputs capable by using the Subhub foundation structure;
To assess upstream and downstream effects such as scour and wake recovery;
To determine the extreme loading effects on the turbines and Subhub caused by the interaction of waves and currents.
A start up meeting took place on the 28th September between ETP (Dr. Tom Davey), QED Naval and M.Eng Student, Steven MacKinnon who will be conducting experimental analysis on the stability and hydrodynamics of the Subhub during transportation, installation and operation within a wave and tidal environment.
Steven has just returned from a summer sabbatical with Xodus so we are confident that he is going to use this experience to the full and produce very useful results to take forward to a large scale prototype. The aim of the project is primarily to fulfil the requirements for achieving Steven’s M.Eng qualification but in doing so produce a scale model for laboratory testing using the facilities at Edinburgh University.
The geometry of the Subhub will be similar to the one produced from the initial sizing studies created by QinetiQ GRC but with some improvements integrating lessons learned from the original analysis. The model is scheduled to be completed by professional model builders by Christmas ready for tank testing early in 2013. It will be instrumented to provide validation of the numerical modelling that is due to be run in parallel to the tank testing as part of the Scottish Enterprise SMART feasibility study.
Dr. Tom Davey from Energy Technology Partnership (ETP) will be supervising a M.Eng student project to perform some model tank tests on the Subhub operating in waves, submerging during installation and in service on the seabed.
Marine renewable engineering and design consultants