Abstract
Wave Energy Converters (WEC) offer a technical solution to produce electricity without greenhouse gas emission. In this master thesis, the WEC design patented by Bj\o{}rn Sjetnan is studied. It consists of using the principle of the oscillating water column with the structure of decommissioned GBS platform. Such platforms possess a massive concrete cylinder fixed to the ground, by creating holes in this structure below the water surface, the water level inside the column is forced to oscillate as waves pass by the structure. This vertical movement of the water surface triggers a flux of air going in and out of the column which can generate electricity with the use of a bidirectional turbine at its opening. This study aims to evaluate the amount of energy that could be harvested using this device. To do so, several platforms that present specific structural conditions are selected. Then an evaluation of the wave energy available at these platform locations is conducted using the NORA-10 hindcast. The efficiency of the energy conversion is then estimated using several methods; the first method is based on a 2D linear potential flow model of one type of Oscillating Water Column developed by \citet{evans&porter95} and adapted for this situation using specific eigenfunctions from \citet{Porter_thesis} to define the spatial velocity potential. The influence of the turbine's characteristics were also considered using this model. The second method used is to evaluate the flow behaviour in 2D using CFD simulations. Several simulations are run with different wave periods to obtain the efficiency of the WEC for most of the conditions relevant to convert energy. The effect of the pressure forcing due to the turbine was not considered in the CFD simulations.
