OPERA wave energy project has released a document outlining the tests performed at the Instituto Superior Técnico (IST) with the bi-radial turbine generator set and its built-in high-speed safety valve.
The OPERA novel bi-radial turbine was designed to maximize the amount of energy absorbed from the waves, while taking into account its own rotation-speed-dependent aerodynamic efficiency and the efficiency of the electrical equipment under the widely varying sea states that characterize the local wave climate.
The aim of the turbine, produced by Kymaner, is to increase oscillating water column (OWC) annual mean efficiency by 50% and improve the reliability of the PTO in comparison with the most frequently used options.
Results from the turbine’s dry tests showed that the experimental values for the efficiency are fairly close to those predicted by the computational fluid dynamics (CFD) calculations, thus validating the turbine design method, it is stated in the tests summary document.
Electrical generator efficiency tests showed that very high efficiency is achieved in a wide range of rotation speeds and power, but a sharp drop of efficiency is observed for low power and low rotation speed.
Also, OPERA informed that HSSV valve safety control algorithm was implemented in order to shave power peaks under extreme wave conditions. Results showed that an aggressive valve control strategy successfully reduced any power peaks, which allowed the continuous operation of the turbine, even under excessively energetic wave climates.
Following the trials at the Mutriku wave power plant, Kymaner’s bi-radial turbine will be moved to Bimep for additional testing on Oceantec’s floating wave energy converter.
Project OPERA (Open Sea Wave Operating Experience to Reduce Energy Cost), coordinated by Tecnalia and Ente Vasco de la Energía (EVE), involves the consortium of 12 members working together to halve the cost of wave energy.