A high-performance electromagnetic vibration energy harvester based on ring magnets with Halbach configuration

This paper proposes and studies a ring-shaped architecture with Halbach configuration for electromagnetic vibration energy harvesters. The proposed transducer consists of three ring magnets with a linear Halbach array that concentrates its magnetic field in the inner space of the mechanism where a single vertically-centered concentric coil has been located. This particular structure allows to increase the resonant mass within a fixed dimensions of the transducer and reduces the coil resistance for the same number of turns, enhancing its power generation capabilities. The ring-shaped architecture has been compared with several ring magnet arrangements, including single magnets, double-magnet arrays, and an alternative linear Halbach array, using numerical simulations to determine their influence on its performance. Consequently, this work is the first contribution to the applicability of Halbach configurations for electromagnetic vibration energy harvesters within ring-shaped architectures. Also, a geometrical optimization of the proposed transducer has been conducted, mainly as a function of the inner radius, the height, and the wire diameter of the coil, to increase its power generation. The maximum simulated output power for the optimized generator reaches 3.61 mW for an input harmonic vibration of 0.03 g at a frequency of 61.7 Hz, corresponding to a 29.08 mW/cm3g2 normalized power density performance, significantly higher than devices described in the literature for similar applications. Besides, a harvester prototype based on the proposed configuration has been fabricated to validate the modeling strategy used and to certify the reliability of the proposed design regarding power generation capabilities. Several experimental tests have been conducted under harmonic excitation with frequencies ranging between 10 Hz and 100 Hz and a vibration amplitude of 0.03 g. The experimentally measured induced voltage and electrical output power have been found in good agreement with their corresponding simulated values, with a difference of about 2.1% and 5%, respectively.