Tension Technology International Ltd
Griffon Hoverwork Ltd, Kelvin Hydrodynamics Laboratory - University of Strathclyde, International Centre for Island Technology (Heriot Watt University - ICIT, Orkney Campus), PSG Marine & Logistics Ltd
NetBuoy integrates two enabling technologies for cost competitive wave energy – impermeable membranes to manufacture buoyant modules and fibre rope nets to encapsulate the buoyant modules. The net applies distributed restraint loads and agglomerates them back to structural ‘hard’ point(s). This is essential in enabling the use of membrane buoyant modules as they cannot be restrained otherwise.
This combination significantly reduces prime mover mass when compared to a steel; the density of the materials are around one-seventh that of steel and are much more compliant with strain at break of around 15% for the membrane. This compliance means it can locally deform under extreme waves whereas the steel structure must carry excess mass (and therefore cost) to provide the required rigidity to avoid plastic deformation.
Stage 3 has progressed the NetBuoy system to a high Technology Readiness Level and demonstrated its suitability for integration into commercial scale wave energy collector (WEC) technology. A qualification plan, addressing the residual technical risks identified at the end of Stage 2, was executed and included an extended sea trial of a NetBuoy system (to assess the effect of long-term exposure to seawater, environmental loading, biofouling and UV and ozone), laboratory material and fatigue tests, and further scale-model tests to demonstrate the applicability of the NetBuoy system to a broad range of WEC architectures. Further design engineering activities resulted in further improvement in the cost of energy.
The inflatable module affords significant advantages in all phases of the lifecycle. The buoyant pods can be manufactured globally in an existing supply chains. The deflated buoyant pod can be cheaply transported in standard shipping containers. CAPEX and LCOE calculations show very encouraging potential for step-change cost reductions.
The long-term vision is the deployment of large WEC arrays utilising the NetBuoy for their prime mover water plane, swept volume and buoyancy requirements.
More information on the NetBuoy system can be found on a dedicated website www.netbuoy.co.uk which includes a design tool for WEC developers to assess the suitability of and cost estimate for a NetBuoy based prime mover when integrated into their technology of interest.