PerAWaT - Final Summary Report

Abstract:

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 Final Summary Report is the final publishable report of the Performance Assessment of Wave and Tidal Array Systems Project (PerAWaT). It provides an overview of the background and structure of the project, and summarises its results, conclusions and the environmental impact.

Technical Conclusions

• Hydrodynamic interactions between WECs and TECs operating in arrays can be significant thereforemodelling of array effects is essential when estimating the energy yield of potential project.
• Wave tank testing of WEC arrays is extremely demanding and needs to be carefully planned and analysed. In particular the effects of reflections can be of the same order as effects of the interactions you are trying to measure. Despite the challenges, it is possible to measure significant interactions in the tank.
• Linear potential flow theory (used in WaveDyn) is sufficient to accurately model device interactions. Weakly non-linear wave kinematics (non-breaking) do not have a significant influence on device response and performance for operational conditions.
• The spectral approach in WaveFarmer is capable of accurately predicting energy yield for a large wave farm.
• Model-scale & full-scale validation of WaveDyn has been invaluable as has model scale validation of WaveFarmer. However, full-scale validation of WaveFarmer will be essential when data becomes available.
• The mean performance of a tidal device can be predicted usinga Reynolds Averaged Navier Stokes (RANS) model, however, more work is required in order to `correct’ this type of model so as to accurately capture wake recovery.
• Basin scale modelling using linear momentum actuator disc theory (LMADT) for one row of devices was successful. The limitations of the model are well understood, and the upper limit of energy extraction compares well to analytical methods. However, 3D models such as TidalFarmer are required for detailed assessment of annual energy production
• .Whilst progress has been made on the analysis of blockage effects of arrays and devices, further work is required to fully understand and model the flow reduction through the array.

• The launch of WaveFarmer & TidalFarmer is only the first step in increasing project developers’ confidence in their return on investment in WEC & TEC arrays.
• Effective commercial exploitation will be required to stimulate use of the tools.
• The resulting data generated by full scale deployments will enable further development of the tools and the reduction of uncertainty.
• The reduction of uncertainty could be accelerated by investment in trials to generate full scale data for validation

Publication Year:

2014

Publisher:

ETI

DOI:

https://doi.org/10.5286/ukerc.edc.000330

Author(s):

Knowling, P.