||The Performance Assessment of Wave and Tidal Array Systems (PerAWaT) project, launched in October 2009 with £8m of ETI investment. The project delivered validated, commercial software tools capable of significantly reducing the levels of uncertainty associated with predicting the energy yield of major wave and tidal stream energy arrays. It also produced information that will help reduce commercial risk of future large scale wave and tidal array developments.
This document outlines the issues associated with array scale modelling within an energy yield analysis and array layout optimisation. The aim of the array scale modelling in the context of an energy yield assessment is to both evaluate the energy yield for each individual device within the array, and to predict the changes in the inter-array flow field due to the energy extraction process.
A summary isprovided of the standard guidelines for performance assessment of tidal energy devices and tidal energy resource assessments that have been written in recent years.
This is followed by a review of existing methods for modelling an array of tidal turbines for the evaluation of energy yield. The GH array scale modelling approach is described and explained. The GH array scale modelling approach incorporates many different aspects: the use of a rationalised flow field model to represent the tidal flow as a series of flow maps and a long term flow occurrence distribution; the use of an assimilation method to correct the numerical spatial flow model using site data, yielding 3-d array flow speed and turbulence intensity fields for each flow state; and the use of a perturbation method to allow the array influenced flow modelling to be imposed upon the tidal spatial flow model. This allows an efficient wake modelling approach, coupling a rationalised eddy viscosity model with wake interaction models.
This report provides an overview of the approach adopted by TidalFarmer for energy yield assessment, and a discussion of how the arrayscale models are implemented within the software.