Embedding of a Blade-Element Analytical Model into the SHYFEM Marine Circulation Code to Predict the Performance of Cross-Flow Turbines

Micol Pucci,Benedetto Rocchio,Stefania Zanforlin,Georg Umgiesser,Debora Bellafiore

doi:10.3390/jmse8121010

Abstract

Our aim was to embed a 2D analytical model of a cross-flow tidal turbine inside the open-source SHYFEM marine circulation code. Other studies on the environmental impact of Tidal Energy Converters use marine circulation codes with simplified approaches: performance coefficients are fixed a priori regardless of the operating conditions and turbine geometrical parameters, and usually, the computational grid is so coarse that the device occupies one or few cells. In this work, a hybrid analytical computational fluid dynamic model based on Blade Element Momentum theory is implemented: since the turbine blades are not present in the grid, the flow is slowed down by means of bottom frictions applied to the seabed corresponding to forces equal and opposite to those that the blades would experience during their rotation. This simplified approach allowed reproducing the turbine behavior for both mechanical power generation and the turbine effect on the surrounding flow field. Moreover, the model was able to predict the interaction between the turbines belonging to a small cluster with hugely shorter calculation time compared to pure Computational Fluid Dynamics.

Highlights

The Earth is called “the blue planet”; water occupies a large part of the Earth’s surface, and the oceans constitute immense reserves of energy, which can be exploited only in particular conditions
Tidal Energy Converters (TEC) can be classified into seven macro categories, as indicated by the EMEC (European Marine Energy Center) [5]: Horizontal Axis Turbines (HATs); Cross-Flow Turbines (CFTs), named vertical axis turbines; oscillating hydrofoil, in which a hydrofoil is connected to an oscillating arm; confined turbines in a conduit that concentrates the flow on the device; Archimedes screws that are helical-shaped devices rotated by the water flow; and even tidal kites attached to a turbine that, experimenting lift, allow it to float in the current
Devices are classified according to the Technology Readiness Level (TRL) [6]; currently, the devices that have reached the greatest maturity are HATs; these are the most developed devices, as proven by the fact that in 2018, all the seven tidal energy projects founded by the EU for technology at TRL7–9 were conceived for HATs [7]

Summary

Introduction

The Earth is called “the blue planet”; water occupies a large part of the Earth’s surface, and the oceans constitute immense reserves of energy, which can be exploited only in particular conditions. Devices are classified according to the Technology Readiness Level (TRL) [6]; currently, the devices that have reached the greatest maturity are HATs; these are the most developed devices, as proven by the fact that in 2018, all the seven tidal energy projects founded by the EU for technology at TRL7–9 were conceived for HATs [7]

Objectives

Methods

Conclusion