Hydrokinetic turbine array analysis and optimization integrating blockage effects and turbine-wake interactions

Abstract

In order to maximize the energy extraction of a hydrokinetic turbine array deployment, turbines must be positioned judiciously within the array. In fact, it is possible to optimize the array configuration in order to benefit from blockage effects and to avoid negative turbine-wake interactions. The Effective Performance Turbine Model (EPTM) that has recently been proposed is a suitable tool for this purpose, allowing to test and analyze a large number of different configurations at a practical computational cost. In this work, assuming a turbulent flow environment, many vertical-axis turbine array configurations (VAT arrays) are tested to study the effect of local blockage, lateral and longitudinal spacing, array staggering and direction of rotation on turbine performance. It is found that the wake deflection associated to the specific turbine tested and the lateral force it induces has a great impact on the array optimization. Following this, results show that there is no advantage to stagger VATs and that aligned configurations should be preferred. In this context, turbines should rotate inward (looking downstream) with respect to the central plane of the array. Some guidelines are also provided in terms of lateral and longitudinal spacings, with the support of a novel parameter indicating the marginal power provided by the addition of a row of turbines.