Subhub Appendages Arrive Ready for Commissioning and Testing

The recent arrival of the Subhub’s appendages brings the build phase of this fully integrated tidal platform to a conclusion. QED will soon validate claims that Subhub provides a “tidal array in a day” along with easy and quick recovery for maintenance at the surface or in sheltered water.

The Subhub is a universal foundation platform and deployment / recovery method suitable for any type of turbine. It can be modified to capture the benefits of both Horizontal Axis Turbines (HATs) and/or Vertical Axis Turbines (VATs). The platform’s ballasting methods can work equally well with wave turbines as well.

The principle benefit of the Subhub is its ability to install a fully integrated, gravity based structure to the seabed including turbines, PTO equipment, ballast. It does this in a single and quick offshore operation using small support vessels which are commonly available making it a very cost effective solution.

However, Subhub also provides large performance advantages by steering the turbulent flows into the turbines enabling them to perform as expected in rated flow conditions significantly increasing site capacity factors and energy yield.

Subhub with all her appendages including Cross Beam to support the tidal turbines and the Subsea Manifold in the background to control the Subhub remotely from small support vessel or barge.

Measurements being taken on the Cross Beam for the fairing structure to be added with the tidal turbines and rotor blades lined up for assembly onto the Cross Beam post launch.
Subsea manifold with the port and starboard umbilicals offered up ready to connect all the pneumatic, hydraulic, data and power cables.

Full Stream Ahead To Tidal Turbine Assessments

QED are delighted to announce the appointment of Dr. Corey Badger. Her role maintains the sophisticated CFD numerical capabilities employed as part of the Subhub tidal platform design process. This uses High Performance Computing (HPC) capabilities which clusters all the high end workstations together to provide 32 core processor power with shared memory of 256GB enabling massive numerical models to run quickly providing tangible results on turbine performance within weeks rather than months. These capabilities are part of the companies ANSYS Fluent CFD package which offer state of the art modelling methods.

QED offers these capabilities and services to other companies working in the sector including turbine and project developers. This includes the performance characterisation of tidal turbines both with and without the Subhub tidal platform to assess the impact of the structure on their performance.

More recently the company has been working with Queens University Belfast (QUB) to assess the impact of Subhub on turbulence within the TTT3 project. This involves taking ‘as measured’ ADCP measurements and determine the turbulence content in it and applying turbulence factors to a numerical model of a rotating turbine in steady state condition that provides accurate general loading and performance data (Ct, Cq, Cp). The next stage is to run these models in a transient solution providing unsteady loading results of the turbine and Subhub.

CFD numerical model of the TTT3 turbines including ‘as measured’ turbulence and flow conditions used to predict the steady state performance characteristics and unsteady loading conditions.

There have been some interesting results to date and this work will be a large part of Corey’s role to validate the claims that Subhub has major performance and unsteady loading benefits on tidal turbines. Further claims of reducing the effect of tidal shear on seabed mounted devices and lessening the issue of turbulence and cross flows on the turbine blades by steering the flow into the turbines like stators of a pump jet.

Corey has also taken on the development of the company’s Tidal and Wave Energy Evaluation Tools (TWEET).  The main module of TWEET takes as measured or theoretical tidal harmonic models along with CFD/BEM performance data of the turbines and projects the energy generated from the inlet condition over a period of a year or the life of the project. Monte Carlo simulations can then be run from within TWEET to determine the economic viability of the project.

Monte Carlo simulations for the cost of the mass including fabricated mass and ballast mass.

The company has also started building its own GIS mapping tool to store and maintain site data including bathymetry, flow rates, positions of moorings, pictures and videos of seabed conditions and mammal, bird and fauna sightings for EIA studies.

Output from QEDs GIS mapping tool showing the position of the selected Subhub test sites at the QUB test centre along with flow data and bathymetry.

Corey brings new capabilities to the company having completed her Ph.D in multiphase flows using OpenFOAM, the open source CFD package. She has used the Edinburgh Parallel Processing Centre (EPCC) super computer to complete her Ph.D and now QED Naval have implemented Linux on a dedicated compute server to run OpenFOAM  capable of completing very large numerical calculations in excess of 10 million cells. Transferring these models over to the EPCC will provide fully validated results within days rather than weeks.