James Allen

Abstract

Wave Energy Converters (WECs) have been shown to offer a promising option for power generation. The WaveCat is a moored WEC design which uses wave overtopping discharge into a variable v-shaped hull, to generate electricity through low head turbines. Physical model tests of the WaveCat WEC were carried out at the University of Plymouth COAST Laboratory to determine the device reflection, transmission and absorption coefficients. 60° and 30° wedge angles were tested, where wedge angle is the angle between the two hulls. Motion response of the WaveCat model was also quantified. The device heave and pitch motions were simulated using the CFD package STAR-CCM+. The results show the WaveCat absorption coefficient and expected power generation is highest during the largest Hs and smallest Tp conditions tested for both wedge angle cases. During the wave conditions that exhibit highest amount of power captured, the device has the lowest motion responses. When at a 60° wedge angle the device generated the highest power (0.4 W) during tests of Hs = 0.12 m and Tp = 1.09 s. When at a 30° wedge angle the device generated the highest power (1.8 W) during tests of Hs = 0.15 m and Tp = 1.46 s which would be normal operating conditions. The 60° and 30° configurations showed the highest surge Response Amplitude Operator (RAO) (0.68 and 0.79 respectively), pitch RAO (1.9 and 2.2 respectively) and heave RAO (0.97 and 0.92 respectively) values during tests where the wavelength is larger than the model length. Experimental responses were shown to be well predicted by the numerical model. The 60° configuration Capture Width Ratio (CWR) peaked at 1.5% during tests indicating greatest efficiency. This occurred at Hs of 0.08 m and Tp of 1.09 s. The 30° configuration CWR peaked at 5.4% during tests indicating greatest efficiency. This occurred at tests with Hs of 0.15 m and Tp of 1.46 s. At full scale the 60° configuration produced the equivalent of 64.6 kW in conditions of Hs = 3.5 m and Tp = 6 s. At full scale the 30° configuration produced the equivalent of 269.2 kW in conditions of Hs = 4.5 m and Tp = 8 s. These values show the device successfully captures and generates power and is suitable for further development. The findings presented in this thesis have increased understanding of behaviour of the WaveCat in a wide range of wave conditions and across two wedge angles.

Keywords

Wave energy, Overtopping, Wave field interaction, Wavecat

Document Type

Thesis

Publication Date

2022

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

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