UC San Diego

As the world transitions towards carbon free energy sources there remains enormous untapped potential for hydropower generation. Hydrokinetic turbines have shown significant potential to harness this resource at a variety of scales. A unique open-centered turbine geared towards pico-scale power generation is introduced. A robust prototype with an annulus outer diameter of 0.40 m is assembled to serve as a test bed for continuing blade optimization studies. Benefits of the open-center type turbine include: improved blade structural efficiency as blades mounted on the annular rotor have reduced spans compared to a traditional rotor covering the same area, ability for aquatic life and debris to pass through, potential for hub to augment flow through the center.

The completed system is outfitted with additive manufactured (AM) polylactic acid (PLA) blades and an above-water generator. Current blade geometry was developed by Oceana Energy Company for a grid scale hydrokinetic turbine. Successful tow tests conducted over a range from 1 m/s to 3.2 m/s demonstrate moderate AM PLA blade performance. Approximately 600 W of power was produced at the top test speed of 3.2 m/s. Maximum hydrodynamic efficiency, after accounting for electromechanical losses in the powertrain, is found to be 25%. Experimental performance compares favorably with a blade element momentum theory (BEMT) code developed for application to open-centered turbines.