WaveNET arrays are made up of interconnected SQUID units which react to the motion of the waves to generate electricity
Each SQUID unit comprises a hollow central riser tube connected to 3 buoyancy floats by linking arms. The connections between each of these components is made by 6 identical fully articulated pumping modules. The buoyancy floats also have hollow structures, allowing them to house the PTO (Power take-off unit) along with other components for communications and hydraulic operation.
The array in motion
When interconnected as an array, WaveNET’s movement is like a three-dimensional Mexican wave: the ocean’s energy pushes and pulls the array’s structure; each SQUID unit’s articulated joints flex, absorb some of the wave’s energy, with any unabsorbed energy passing to the next unit, all the way through the array. This unique design allows the array to respond to the full orbital motion of the waves, from any direction, and allows power capture from 5 of the 6 elements of wave energy: pitch, roll, heave, surge and sway.
Power conversion stages
Each SQUID unit’s 6 identical pumping modules convert the mechanical power of the waves first into hydraulic power, and then to electrical power via a on-board generator set.
The latter stages of this power conversion process take place within WaveNET’s unique ‘Plug and Play’ Power Take-Off (PTO) modules. Each PTO module is housed within a sealed casing which is fitted inside a buoyancy float. The PTO module comprises a hydraulic motor, electrical generator, control apparatus and communications. A WaveNET array will contain a number of PTO modules – the optimum quantity depends on the available energy at the site, the number of units in the array and the degree of redundancy required.
Handling, installation and operations
The design of the WaveNET system has been driven by an awareness of the need for a low cost operations strategy to achieve economically viable energy generation, where maintenance costs are a large element of lifetime project costs. Individual SQUID units are transported and lifted in their horizontal towing configuration, with each of the linking arms folded to minimise the unit’s footprint. Each SQUID can then be towed to it’s deployment position within the array using a small boat thanks to the low-draft profile of the folded-up unit.
The central riser of the SQUID is then ballasted with seawater, causing the node-end to sink and rotates the unit 90° into the vertical operating configuration.
The linking arms can now be released allowing the SQUID to be connected to the array and the Integrated Mooring Web.
Moorings and connections
Albatern’s innovative ‘Integrated Mooring Web’ (IMW) is a no-snatch mooring grid with connection points adapted to receive individual units, and a built in electrical collection grid providing passive fault handling and redundancy.
The IMW is deployed prior to the deployment of the individual units and defines the overall size of the array
The IMW provides dramatic cost savings over alternative approaches by sharing mooring infrastructure between devices, minimising the electrical cabling length and seabed infrastructure. The use of tried and tested mooring techniques and equipment also keeps costs low.