Design and Experiment Analysis of a Direct-Drive Wave Energy Converter with a Linear Generator

Abstract

Abstract:Coastal waves are an abundant nonpolluting and renewable energy source. A wave energy converter (WEC) must be designed for efficient and steady operation in highly energetic ocean environments. A direct-drive wave energy conversion (D-DWEC) system with a tubular permanent magnet linear generator (TPMLG) on a wind and solar photovoltaic complementary energy generation platform is proposed to improve the conversion efficiency and reduce the complexity and device volume of WECs. The operating principle of D-DWECs is introduced, and detailed analyses of the proposed D-DWEC's floater system, wave force characteristics, and conversion efficiency conducted using computational fluid dynamics are presented. A TPMLG with an asymmetric slot structure is designed to increase the output electric power, and detailed analyses of the magnetic field distribution, detent force characteristics, and no-load and load performances conducted using finite element analysis are discussed. The TPMLG with an asymmetric slot, which produces the same power as the TPMLG with a symmetric slot, has one fifth detent force of the latter. An experiment system with a prototype of the TPMLG with a symmetric slot is used to test the simulation results. The experiment and analysis results agree well. Therefore, the proposed D-DWEC fulfills the requirements of WEC systems.

Design and Analysis of Tubular Slotted Linear Generators for Direct Drive Wave Energy Conversion Systems

“…The design yields an output voltage of 3.5 V at the rated output power of 3 W [19]. Likewise, a PMLM design by Zhang et al [11] also employed a tubular structure for application at 0.4 m/s speed. The novelty of this design is the asymmetric slot structure which is reported to be able to reduce detent force and enhance the airgap flux density in the design [11].…”

“…Likewise, a PMLM design by Zhang et al [11] also employed a tubular structure for application at 0.4 m/s speed. The novelty of this design is the asymmetric slot structure which is reported to be able to reduce detent force and enhance the airgap flux density in the design [11]. A tubular switched reluctance linear machine (SRLM) has been proposed and analysed by Mendes et al [20] using FEA, mathematical modelling and experiments.…”

“…From the figure, the direct drive linear generator conversion method requires a primary interface and also an electrical generator. Typically, floating buoy or point absorber technology is used as the primary interface to capture the motion of sea wave as depicted by Zhang et al [11], Hodgins et al [12] and Franzitta et al [13]. As for linear generators, various specifications and topologies based on operating speed and applications have been proposed in the previous literature.…”

Maximum Power Point Tracking for a Point Absorber Device with a Tubular Linear Switched Reluctance Generator

“…The point absorber devices with direct drive extraction mechanism are the more efficient systems for ocean wave energy conversion at low velocity oscillations [1]. For this type of conversion devices, linear generators with permanent magnets are generally used [2][3][4][5][6]. However, linear electric machines with permanent magnets need a complicated winding system and are characterized by their elevated construction and assembly costs.…”

Optimal Design of Permanent Magnet Linear Generator and Its Application in a Wave Energy Conversion System

“…To achieve relatively high quality and efficiency for converting ocean wave energy into electrical energy, various ocean wave energy converters and corresponding electrical machines have been investigated. It was found that linear generators can be used in the direct drive wave energy conversion system, in which it can reduce the complexity of mechanical transmission and improve the reliability and efficiency of the system [6][7][8][9][10][11]. Several electrical generator topologies have been analyzed in the past years [12,13].…”