Concept Design of a Novel Superconducting PTO Actuator for Wave Energy Extraction

The role of the Power Take-Off (PTO) as part of modern Wave Energy Converters is becoming more and more relevant and many efforts have been done or are ongoing to improve its performance especially in terms of force density and efficiency. Electric Linear PTOs are inherently the most efficient category, since they are really direct drives with no intermediate stages of energy conversion. Nevertheless, conventional electric machines are usually limited in force while their efficiency is better than other type of drives but still does not allow an intense energy capture in a broad band of wave periods. In this regard, superconductivity may become a very helpful alternative that allows improving both: efficiency and force density in spite of the technological difficulties that are introduced in the Wave Energy Converter. This paper, after justifying the need for better PTO performances, presents a new concept of superconducting PTO in which both, the stator and the translator work at cold temperature, performing a reciprocating displacement inside a flexible cryostat. The concept is later applied to a Cylindrical Switched Reluctance machine whose global design is also presented in the paper. This activity has been performed as one of the work packages of the EU H2020 Sea Titan Project in which also a resistive PTO with a novel configuration has been developed.