Linear permanent magnet generator concepts for direct-drive wave energy converters: A comprehensive review

During past three decades, marine energy has become an attractive topic in renewable energy. Among various types of marine energy, present study focuses on wave energy because of its advantages such as high availability, high predictability, high stability, and high power density. Nowadays, most wave energy converters (WECs) installed have complex mechanical interfaces in their power-takeoff (PTO) system which results in complicated system structure and more maintenance requirements. These problems are solved in direct-drive wave energy converters (DD-WECs) by using linear generators, which simplify PTO system. The present review discusses different designs and technologies of linear generators employed in DD-WECs. After a brief explanation about WECs based on linear generators, all proposed topologies of linear permanent magnet generators are discussed and compared based on specifications such as flux path, core type, installation and magnetization of permanent magnets, etc. Finally, the best types of linear generators, in term of being economical and operational, are identified.