High speed electrical power takeoff for oscillating water columns
This thesis describes research into electrical power takeoff mechanisms for Oscillating Water Column (OWC) wave energy devices. The OWC application is studied and possible alternatives to the existing Induction Generator (IG) are identified. The Permanent Magnet Generator (PMG) is found to be the most promising. Results showed that the IG could almost match the output of the PMG if it could be operated significantly above its rated capacity. This improvement would require only limited changes to the overall OWC system. The ability to operate overloaded is determined by the losses and cooling of the IG. The losses in a suitable IG were measured in tests at Nottingham University. Steady state measurements were made of the cooling ability of the OWC airflow at the LIMPET wave power plant operated by Wavegen (the sponsor company) on Islay. Thermal modelling combining the loss and cooling measurements allowed the maximum capacity of the induction generator in an OWC to be found. A simplified model that accurately represents this system is proposed for use in system design and generator control.