TTI’s NetBuoy™ scales-up with DOE funded transatlantic collaboration

The long-term vision of utilising NetBuoy™ as a lightweight, low-cost, and robust prime mover for wave energy converters (WECs) takes a major step forward with TTI Marine Renewables Ltd (a Scottish based subsidiary of Tension Technology International Ltd) confirmed as a subcontractor to California-based wave energy technology developer, Centipod.

Centipod, through its parent company Dehlsen Associates, has been awarded $1.8 million by the US Department of Energy’s (DOE) Water Power Technologies Office (WPTO) to complete the design of its C1P6 WEC where TTI’s unique NetBuoy™ concept will be used as the prime mover sub-system. The C1P6 design will be put through technology qualification, beginning the certification process that will allow for a seamless continuation into the fabrication, deployment, and prototype testing stages beyond the end of the award period in Q1 2024.

NetBuoy™ focusses on two strands on the path towards cost-competitive wave energy. Firstly, impermeable fabrics to provide compliant and load shedding, peak-load resistant, buoyant modules. Secondly, fibre rope ‘load nets’ that encapsulate the buoyant modules, applying distributed restraint loads and agglomerating the distributed load back to structural points to connect to the other parts of the WEC system, such as the power take-off (PTO).

Integration of the NetBuoy™ technology can reduce substantially the cost of construction and installation of wave energy converters.

Figure 1: NetBuoy™ deployed for sea trials in the Cromarty Firth, Scotland
during stage 3 of the WES programme. Credit: TTI

The C1P6 WEC system will integrate TTI’s lightweight NetBuoy™ prime mover with Centipod’s high-performance power take-off (a linear direct drive system known as Luma) to achieve highly efficient wave power conversion. The C1P6 WEC is targeting small utility-scale wave farms, micro-grids, and off-grid blue economy applications.

TTI’s NetBuoy™ concept was developed through Wave Energy Scotland’s (WES) precommercial procurement (PCP) programme “Structural Materials and Manufacturing Processes”, the aim of which was to develop, demonstrate and qualify new materials and manufacturing processes that would reduce the levelized cost of energy for wave energy systems.

Figure 2: NetBuoy™ concept development activities through WES's 3-stage PCP programme. Credit: TTI

Successful completion of stage three of the programme saw NetBuoy™ accomplish six months of sea trials in the Cromarty Firth, proving the technology’s resilience to prolonged exposure to sea conditions, environmental loading, biofouling and UV and ozone.

Alan McCall, Managing Director of Centipod said:

“NetBuoy™ has numerous advantages as a prime mover within our WEC system, the primary benefits being low mass, increased durability, and corrosion reduction.

“Low mass is particularly beneficial to Cost of Energy across a broad range of categories. There are obvious impacts such as lowering initial capital expense, but NetBuoy™ also benefits performance since the low mass means less impact on system dynamics from the prime mover’s inertia, allowing for greater overall control authority.”

Ben Yeats, Director of TTI Marine Renewables added:

“The WES funded programme has propelled the NetBuoy™ concept along the technical and commercial readiness path and has been instrumental in advancing the technology in readiness for this exciting transatlantic collaboration.”

Ruairi Maciver, Project Manager for Wave Energy Scotland said:

“It is exciting to see TTI continue to exploit the NetBuoy™ technology developed through Wave Energy Scotland’s programme. Integration into a fully functional wave energy converter system was the logical next step and the collaboration with Centipod provides the opportunity to prove the ability of NetBuoy™ to reduce the cost of wave energy."