COMPUTATIONAL AND EXPERIMENTAL ANALYSIS OF TOWED-WATER POWER GENERATORS

Abstract

Towed-water power generators are used in long-distance sailing to generate power for charging battery banks. A basic configuration consists of a spinning turbine towed behind the boat and attached to an alternator or generator via a torque line. In the present work, a series of two- through six-blade, seven-inch-diameter, six-inch-pitch turbines were tested both in a water tunnel and using computational fluid dynamics techniques. Turbine rotation rates achieved in the water tunnel for both an alternator and generator were measured at a nominal speed of 3 m/s. Turbine torque vs. rotation rate results were obtained by solving the Reynolds-averaged Navier-Stokes (RANS) equations for turbines within the water tunnel, and unconfined turbines. RANS results were plotted against generator and alternator torque curves to predict operating rotation rates and associated power generation. Predicted rotation rate results for the water tunnel geometry were in good agreement with experimental results, particularly in the case of the generator, which operated at higher rotation rates. Peak efficiencies were found to depend strongly on rotation rate, but only weakly on the blade count. Additional RANS results were obtained for the turbines in an unconfined domain. Trends and conclusions were consistent with those for turbines within the water tunnel.