Improved design of linear electromagnetic transducers for large-scale vibration energy harvesting

Abstract

ABSTRACT This paper presents the design and optimization of tubular Linear Electromagnetic Transducers (LETs) with applications to large-scale vibration energy harvesting, such as from vehicle suspensions, tall buildings or long bridges. Four types of LETs are considered and compared, namely, single-layer co nfiguration using axial magnets, double-layer configuration using axial magnets, single-layer configuration using both axial and radial magnets, double-layer configuration using both axial and radial magnets. In order to optimize the LETs, the parameters investigated in this paper include the thickness of the magnets in axial direction and the thickness of the coils in the radial direction. Finite element method is used to analyze the axisymmetric two-dimensional magnetic fields. Both magnetic flux densities B r [T] in the radial direction and power density [W/m 3 ] are calculated. It is found that the parameter optimization can increase the power density of LETs to 2.7 times compared with the initial design [Zuo et al, Smart Materials and Structures , v19 n4, 2010], and the double-layer configuration with both radial and axial magnets can improve the power density to 4.7 times, approaching to the energy dissipation rate of traditional oil dampers. As a case study, we investigate its application to energy-harvesting shock absorbers. For a reasonable retrofit size, the LETs with double-layer configuration and both axial and radial NdFeB magnets can provide a damping coefficient of 1138 N·s/m while harvesting 35.5 W power on the external electric load at 0.25 m/s suspension velocity. If the LE T is shorten circuit, it can dissipate energy at the rate of 142.0 W, providing of a damping coefficient of 2276 N·s/m. Practical consideration of number of coil phases is also discussed. Keywords: linear electromagnetic harvester, vibration energy harvesting, radial magnet, power density, regenerative vehicle suspension, structural control