Test rig for submerged transmissions in wave energy converters as a development tool for dynamic sealing systems

A submerged transmission, fitted with a dynamic sealing system, in a wave energy converter (WEC) serves the purpose of transmitting the force, absorbed by a wave activated body, to an encapsulated power take-off (PTO) system, while preventing seawater from entering the capsule. Dry generator operation is generally a prerequisite for attaining long technical service life. Little attention seems to be devoted in publications to the study of dynamic sealing systems in WECs, and to test rigs for experimental verification and/or evaluation of the ability/performance of existing dynamic sealing systems in a controlled laboratory environment. This paper begins by presenting some of our earlier research within the focus area of dynamic sealing systems, incl. design considerations and typical operating conditions. This part also presents the 1st laboratory test rig, used for verifying the sealing ability of the piston rod mechanical lead-through design in the 1st and 2nd full-scale experimental WEC prototype from Uppsala University. In 2021 project DynSSWE (Dynamic Sealing Systems for Wave Energy) was initiated. Drawing from experience, the project includes development of a new test rig, representing a tool for further development of dynamic sealing systems. This paper introduces steps in the design and development process of that new test rig, enabling accelerated long-term test runs with a setup of multiple piston rod specimens. The test specimens’ will be surface treated differently with the aim of improving the prospects of a long maintenance free service life. Since the new test rig is in the design stage, seal testing results are not yet reported. The presented work is funded by the Swedish energy agency with the aim of improving subsystem performance in wave energy devices.