Multi-objective response surface optimization of a centrifugal turbine for application in oscillating water column devices equipped with a twin turbine configuration

Oscillating Water Column (OWC) devices are one of the most widespread to harness wave energy. Their efficiency primarily depends on the performance of their Power Take Off (PTO) elements, which are normally air turbines. Self-rectifying turbines have been traditionally used to deal with bidirectional flows without the need for additional valves. However, Twin Turbine Configuration (TTC) systems emerged as an alternative solution based on the use of a pair of unidirectional turbines capable of achieving higher efficiencies. Although TTC systems typically employ axial turbines, the use of radial turbines is also a promising option due to the superior volumetric efficiencies. In this work, an innovative optimization process, specifically developed for its application in TTC systems, is presented. A CFD-based optimization of a centrifugal turbine has been carried out assessing its performance across both classical OWC operating stages. New rotor blades have been created by Bezier curves. Five geometric parameters, corresponding to the Control Points coordinates of those parametric curves, have been optimized. Results revealed that the optimized geometry notably improved the peak efficiency by 4 % when the centrifugal turbine works under steady flow conditions, and significant non-steady efficiency improvements exceeding 30 % have been achieved for the TTC system. • CFD optimization of OWC turbines. • Novel optimization methodology specifically developed for twin turbines topologies. • Response Surfaces generated by Genetic Aggregation to optimize Input Parameters. • MOGA algorithm for improving turbine efficiency and blocking capacity. • Notable improvements of up to 30% of the non-steady TTC system efficiency.