Severn Subsea Technologies (SST) began working with Marine Power Systems, a wave power technology development company, in 2014. The Swansea based start-up had heard about the work that the SST team had delivered with other wave energy companies and were looking for help with the design and build of a ¼ scale version of their device to carry out preliminary testing.

The WaveSub device is a wave energy converter, which consists of a barge and floating sphere tethered together by cables.  It is designed to generate power hydraulically from the relative motion of the sphere that reacts to the orbital subsurface flow of the waves. 

The WaveSub will be towed out to sea, it will then sink below the surface using the ballast tanks, this is when the sphere technology starts to work.  The device is able to react to the changing sea conditions by altering its depth and cable lengths. This means that in a storm with high sea conditions it can drop right down where the wave motion has less power. The barge based design also has obvious benefits for maintenance and overhaul.

SST designed the electro-hydraulic control system for the device and assembled and tested the Machine Room, which is in effect the heart of the system, at its premises in Redruth. The PLC control system includes solenoid and pump control to enable flooding and draining of the ballast tanks, as well as telemetry for monitoring performance.

The Machine Room assembly was delivered to Pembroke Docks WC 25th September for initial water testing. The official unveiling of the ¼ scale device took place on Friday the 13th October at Pembroke docks, where many of the stakeholders were present.  The next stage is for the device to be taken down to FaBTest in Falmouth where the device will be fully tested at sea.

For more information on the WaveSub and to watch the new WaveSub video visit For more information on Severn Subsea Technologies projects and products visit