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Measurements of WEC motions and mooring loads

Date: November 05, 2013 at 15:08 GMT

This paper describes a campaign of sea trials of a wave energy converter (WEC) in Strangford Lough, Northern Ireland and presents a selection of the results obtained. Physical models of wave energy converters were first tested in the wave basin of the marine renewables group of Heriot-Watt University, and the results of their behaviour were then compared to the simulations performed using mathematical modelling[1]. A 1:20 model has subsequently been successfully deployed using a three point mooring installed at sea in 10 m depth and tested in the open water conditions. An OrcaFlex model was used to assess the dynamics of the mooring lines, and the results of open water tests are being compared with the model’s performance. The output from OrcaFlex is imported to Matlab for easy plotting and data presentation, as well as further statistical analysis. 

The results show that, in general, the model agrees reasonably well with the observations. The WEC’s motions and the measured loads on the leading mooring line appear to relate to the concurrent environmental conditions. The data obtained can therefore be used for the model’s calibration and further improvements, which is valuable for improving the WEC’s design and operational characteristics. This may be important not only in relation to the issues of reliability and power take off, but also in terms of minimising the adverse effects of mooring lines on bottom sediments, as well as indirect effects of the eroded particles on a wide range of aquatic processes [2,3]. 

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