Assessment of a Diffuser-Augmented Hydrokinetic Turbine Designed for Harnessing the Flow Energy Downstream of Dams

Abstract

Harnessing the remaining energy downstream of dams has recently gained significant attention as the kinetic energy available in the water current is considerable. This work developed a novel study to quantify the energy gain downstream of dams using a horizontal-axis hydrokinetic turbine with a diffuser. The present assessment uses field data from the Tucuruí Dam, where a stream velocity of 2.35 m/s is the velocity at which the highest energy extraction can occur. In this case, a 3-bladed hydrokinetic turbine with a 10 m diameter, shrouded by a flanged conical diffuser, was simulated. Numerical modeling using computational fluid dynamics was carried out using the Reynolds averaged Navier–Stokes formulation with the κ – ω shear stress transport as the turbulence model. The results yield good agreement with experimental and theoretical data available in the literature. Moreover, the turbine power coefficient under the diffuser effect could increase by about 55% for a tip speed ratio of 5.4, and the power output increased by about 1.5 times when compared to the same turbine without a diffuser. Additionally, as there are no hydrokinetic turbines installed downstream of dams in the Amazon region, the present study is relevant as it explores the use of hydrokinetic turbines as an alternative for harnessing the turbined and verted flow from dams. This alternative may help avoid further environmental impacts caused by the need for structural extensions.