ABSTRACT

Wave energy shows potential to provide electricity in a renewable manner. The TALOS WEC (Wave Energy Converter) is a unique design with six PTO (Power Take-Off) elements to provide six Degrees of Freedom (DOFs), which is potentially able to harvest energy more efficiently than traditional single-DOF devices. As a step towards its optimisation and control, a power prediction model is developed, using the wave elevation and motions of the WEC to predict the power output of each PTO. The results show that using LSTM (Long-Short Term Memory) has a higher prediction accuracy than the other approaches considered.

INTRODUCTION

Much research has been done on energy harvesting technologies over the past few decades, in part due to the incoming energy crisis. As a type of renewable energy, ocean waves provide significant energy via a sustainable and reliable approach. As a result, many different types of WECs have been designed and tested to produce clean and renewable energy (Li et al., 2012). Examples include Lancaster University's PS Frog (Taylor et al., 2002; McCabe et al., 2006), AquaBuOy (AquaBuOy, 2016), and Powerbuoy (Powerbuoy, 2016).

In general, WECs can be categorised as point absorbers, oscillating water columns, terminators, oscillating wave surge converters, attenuators, and submersed pressure differential devices (Aggidis and Taylor, 2017; Darwish and Aggidis, 2022). The majority of WECs are single-DOF devices, which means they could only extract energy from one direction of motion. Based on the single-DOF method, prototypes have been designed such as the Carnegie Wave Energy Limited prototypes (Wave Hub, 2016), the Archimedes Wave Swing (AWS Ocean, 2016), Oregon Limited's multi-resonant chamber (Orecon, 2009), and Salter's Duck (Salter, 1974). However, the kinetic power contained in the waves is in multiple directions. In hydrodynamic analysis, the waves have yaw, roll, and pitch motions in heave, surge, and sway axes, respectively. In total, there are six degrees of freedom in WECs that would be affected by the waves. Theoretically, if the device can extract energy from multiple DOFs, more energy can be thus generated.

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