Analysis of the effect of friction on the efficiency calculations of an electric machine for a wave energy converter

Asker, FJ; Baker, NJ; Versey, MJ; Retzler, C

doi:10.1049/icp.2024.2182

Analysis of the effect of friction on the efficiency calculations of an electric machine for a wave energy converter

Lookup NU author(s): Farrel Asker, Professor Nick Baker ORCiD

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Abstract

© The Institution of Engineering & Technology 2024.Wave energy is a source of renewable energy that is reaching commercial reality. The low-speed, high torque oscillating motion and a desire for direct drive power take off favours the development of large radius magnetically geared generators. Lifetime cost of energy is a key performance indicator of the technology and is directly proportional to efficiency of power conversion. Friction loss is proportional to the electromagnetic airgap closing force within the electrical machine, meaning optimisation of the generator design and losses experienced in the drive train is a coupled problem. For favourable economics, losses in the electrical machine and lubrication system most both be reduced. This paper describes the development of a direct drive electrical generator and lubrication system for an attenuator wave energy converter. For the first time, the finite element analysis model of a flux reversal machine is coupled to a simplified tribology model to investigate the relationship between electrical machine design and bearing loss. An objective function is used to optimise the mechanical drive train for maximum annual energy yield for a specific wave energy converter in a known wave resource. It is shown that integrating the bearing losses into the objective function of an optimisation routine influences the final electrical machine design by putting a focus on mass reduction. Furthermore, the bearing loss is shown to decrease system efficiency by 1.1%.