Our recent progress on development of a vertical-axis unidirectional rotary wave energy converter (WEC) is discussed in this work. The WEC features a vertical-axis rotor that preforms unidirectional rotation in waves. The vertical axis arrangement makes the WEC respond well to waves from any direction with no realignment needs. And, the unidirectional behavior of the rotor promises no wave frequency discrimination, which is in comparison to reciprocating WECs that employ the resonant principle and are very frequency-specific. In our earlier proof-of-concept studies, we have successfully demonstrated two types of rotor designs: a lift type employing hydrofoil blades and a drag type using cup blades. In the present work, the two rotor types were further explored experimentally by employing more rotor configurations and blade shapes. The focus was on revealing the rotor responsiveness in simulated waves under a freewheeling condition. The experimental results were compared between a lift-type and drag-type rotor. The comparison provided in-depth understanding on common features of the two rotor types and major differences between them. The yielded research findings will directly guide the development of a prototype vertical-axis unidirectional WEC
