Design of a Horizontal Axis Tidal Turbine for Less Energetic Current Velocity Profiles

Abstract

Existing installations of tidal-stream turbines are undertaken in energetic sites with flow speeds greater than 2 m/s. Sites with lower velocities will produce far less power and may not be as economically viable when using "conventional" tidal turbine designs. However, designing turbines for these less energetic conditions may improve the global viability of tidal technology. Lower hydrodynamic loads are expected, allowing for cost reduction through downsizing and using cheaper materials. This work presents a design methodology for low-solidity high tip-speed ratio turbines aimed to operate at less energetic flows with velocities less than 1.5 m/s. Turbines operating under representative real-site conditions in Mexico and the Philippines are evaluated using a quasi-unsteady blade element momentum method. Blade geometry alterations are undertaken using a scaling factor applied to chord and twist distributions. A parametric filtering and multi-objective decision model is used to select the optimum design among the generated blade variations. It was found that the low-solidity high tip-speed ratio blades lead to a slight power drop of less than 8.5% when compared to the "conventional" blade geometries. Nonetheless, an increase in rotational speed, reaching a tip-speed ratio (TSR) of 7.75, combined with huge reduction in the torque requirement of as much as 30% paves the way for reduced costs from generator downsizing and simplified power take-off mechanisms.

3D Simulation with Flow-Induced Rotation for Non-Deformable Tidal Turbines

“…Both technologies use a rotor that needs a certain amount of energy density to start. For that reason, new foil designs are proposed to allow turbines to start with lower speed flows [4]. Some other options include telescopic blades in order to control the momentum and the load as presented in Jamieson's patent US6972498B2: "Variable diameter wind turbine rotor blades".…”

Assessing Hydrokinetic Energy in the Mexican Caribbean: A Case Study in the Cozumel Channel

“…Hernández-Fontes et al [6] performed a theoretical identification of resources in southern Mexico, finding that ocean energy harvesting could be profitable at some sites off Cozumel island, in Quintana Roo, where there is both high availability and persistence of the ocean current. Alcérreca-Huerta et al [17] evaluated potential sites off Cozumel, and [36] discussed the technical possibilities of using low-speed turbines there. In the Mexican Caribbean there is a persistent current that can generate a power density of over 176 W/m 2 (1.54 MWh/m 2 -year) to 512 W/m 2 (4.48 MWh/m 2 -year), which is available more than 50% of the time [6].…”

Numerical Study of A Generic Tidal Turbine Using BEM Optimization Methods

“…'modern' and 'veteran' design methods. Typical 'modern' optimisation methods include multi-objective surrogate models (Zhu et al 2020), genetic (Zhang et al 2019), decision model (Encarnacion et al 2019), and AI algorithms, while 'veteran' optimisation methods refer to approaches derived from the blade element momentum theory, such as Burton's model (Erich 2000), and Rosen's model (Rosen 1987). Zhu et al (2020) optimized the chord length distribution using the response surface and weighted average surrogate models, then the power coefficient of the optimal model improved 2%.…”