The marine energy industry is in its early stages but has a large potential for growth. One of the most significant challenges is the reduction of operation and maintenance costs. Magnetic gears (MGs) offer the potential for long periods between maintenance intervals due to their frictionless torque transmission which could reduce these costs. This study presents a summary of the state of the art in MG technology and then investigates its potential for marine energy applications. A brief overview is given of the state of the marine energy industry and the environment in which marine energy converters (MECs) operate. A short history of MG development over the past century is then presented followed by a discussion of the leading MG technologies and their relative advantages. In order to demonstrate the potential of MGs in marine applications, the current technologies, i.e. mechanically geared and direct drive machines, are examined in terms of sizing, reliability and economic value using previous studies on a similar technology, namely wind. MGs are applied to four types of MECs to demonstrate how the technology can be incorporated. The potential to deploy at scale and potential obstacles to this are then discussed.
A coupled electromechanical and hydrodynamic time-domain simulation of a direct-drive generator connected to a heaving buoy for wave energy conversion is presented. The system is based on a novel direct-drive power takeoff unit referred to as snapper. The simulation is based primarily in MATLAB using its built-in ordinary differential equation solvers. These solvers act on the data derived from electromagnetic finite element analysis and from the WAMIT wave interaction simulation software. Test results of a generator prototype for comparison with the electromechanical simulation are presented. Results from wave tank tests of a full system incorporating the power takeoff are also provided for comparison with the hydrodynamic model.
Tidal current conversion systems are moving towards commercialisation. Tidal energy developers are looking to optimise their systems by testing all the available options and taking advantage of the experience from the wind energy industry. The key focus of this paper is to compare an induction generator with a permanent magnet synchronous generator in a tidal current conversion system with onshore converters. The architecture of a tidal system with onshore converters is an option for tidal sites with small distances to shore as previous research has shown. In order to investigate the two generator technologies full resource-to-grid models in MATLAB/Simulink are developed. The analysis of these models compares generator efficiency, energy capture, losses at each stage, the cost and the maintenance for each system. Results show that the tidal system with PMSG is more efficient and generates fewer losses to transmit power onshore. In addition, since both systems tested are using a gearbox, the size, cost and maintenance of the PMSG are comparable to the reliable and cost-effective option of SCIG.
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