Performance prediction of contrarotating wells turbines for wave energy converter design

Wave energy can be captured and converted to a vertical pistonlike oscillatory motion by semiinsertion of a chamber with a submerged opening into the ocean. The roof of the chamber will open onto a ducted Wells air turbine, which will be driven by the oscillatory airflow developed by the forcing action of the surface of the Oscillating Water Column (OWC) inside the chamber. The design of such an OWC conversion plant is considered with particular reference to the air turbine stage and its synthesis into the system. Consequently, a semiempirical method for predicting the performance of the contrarotating Wells turbine configuration is presented, notably, detailing aerofoil performance into the stall region. The predicted turbine performance is subsequently utilized to facilitate the design of a 310 kW plant, including efficient accommodation of the pneumatic power levels for maximal aerodynamic conversion.