Improving the Wave Energy Production Using Multi-Size WEC Arrays With Passive Control

Abstract One of the key aspects to consider before large scale deployments of wave energy converters (WEC), is to optimize the devices’ characteristics to improve wave power absorption. Typically, devices with passive control are designed to have the highest efficiency in wave power absorption/production in the range of the most frequent wave conditions. In general, there is an intrinsic “trade-off” between the range of wave conditions where a WEC can operate and the operation efficiency which, in the end, is linked to the energy production yield. Outside the most frequent wave conditions, there is still a non-negligible percentage of occurrences of more energetic sea states carrying high energy flux values. Given the specific design characteristics of a WEC device, lower operation efficiency is expected during these stronger sea states, which is translated as a lower production compared to the available (usable) resource. In the present study, a multi-size point absorber WEC array, using passive internal control, is proposed to optimize wave power production at the array level. The main aim of this work is to verify the combined use of devices designed to work in the most frequent wave conditions, with WECs which mass and dimensions are defined to improve their response during stronger sea states. A comparison of the mean produced power is performed between a proposed multi-array and a single size one. This is done using 30 years of spectral wave data obtained from an implementation of the WAVEWATCH III model, while response of the wave energy converters array is simulated with the boundary element model HAMS-MREL. Preliminary results, using 10-devices arrays, show a promising increase in production from 60 to 140% when larger WECs are included.