|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.
The purpose of WG3WP4 is to develop, validate and document an engineering tool that allows a rapid assessment of the energy yield potential of a tidal turbine array on non-specialist hardware. The specific objective of WG3WP4 D10 is to document the method by which TidalFarmer interfaces with regional scale numerical models. This report includes some background on the requirements for communicating with regional scale numerical models, a description of the interface protocol for communicating with the regional scale numerical modelling software Telemac and a description and discussion around the parameterisations of an array within regional scale numerical models.
It is not possible to fully represent a tidal turbine within a regional scale model of a realistic tidal flow and hence the focus of the TidalFarmer software is to develop a suitable parameterisation of the hydrodynamic performance and operation of an array of devices for regional scale numerical modelling. TidalFarmer is an array-scale tool that can predict the energy yield given a flow field input. Decoupling the flow field solver and the intraarray wake solver enables a fast (and hence practical) computation of the energy yield for a chosen layout. However, a suitable interface with a regional scale model is required. To address this point TidalFarmer has been developed to allow a common interface with the majority of leading regional scale numerical modelling software packages and has specifically createda link with EDF Telemac software.
This report outlinesa number of strategies that could be used for the representation of tidal devices within a regional scale numerical model, all of which have been compared against experimental measurement data. At this stage it is unclear which parameterisation best represents both the upstream and downstream effects of an array of devices. Experiments performed in WG4 WP4 D3 suggest that the LMADT theory predict the correct upstream effects and is also able to account for some of the downstream wake mixing. It also avoids the necessity of having to use an upstream reference velocity. However, there are draw backs to using depth integrated models to capturethe intra-array wake mixing and hence GH propose to avoid this step by simply replacing the whole array with a parameterisation. In this case it would involve modelling the total momentum extraction via a head drop across the array