Limerick Wave: using flywheel technology to convert the power of the waves to electricity: Technical Report

Limerick Wave Ltd. has developed an innovative wave energy converter (WEC) technology. They use a recently-patented flywheel technology to use the power from the movement of the waves (via the movement of a cylindrical floatation device) to generate electricity. The use of flywheel technology in this area is novel in that its rotation is unidirectional despite the bi-directional natural oscillation of the floatation device. In this report a mathematical description (model) of the WEC device’s operations is presented. Limerick Wave’s current experimental prototype is a 1:20 model; this model serves as a way to check the performance of a scaled-up rig. The model allows Limerick Wave to fine-tune their device’s design in order to maximise, say, the energy extracted from the ocean waves. By applying standard physical laws (conservation of angular momentum etc.) to the device’s operation, we show that such a device will demonstrate periodic behaviour regardless of its initial orientation. A crucial finding of the report concerns the power take-off mechanism. We identify two qualitatively different operational states: the first (second) state corresponds to extracting a small (large) amount of energy per cycle. Each operational state has its own benefits and shortcomings – these are examined in detail in the report. We perform a preliminary run of device-tuning; we take data from the observation buoys in Galway Bay to compute an optimum arm length for the device for harnessing power from the ocean. The data contains a strong seasonal variance and this is incorporated into the optimisation.