Design and fabrication of LTCC electro-magnetic energy harvester for low rotary speed

This study focuses on the design and fabrication of a planar rotary electromagnetic energy harvester with a low rotary speed for bicycle dynamos. The primary components of a dynamo system include planar multilayer and multipole coils, a soft magnet (iron) used to enhance magnetic efficiency, and a multipole Nd/Fe/B (neodymium, iron, and boron) permanent magnet. Finite element analysis and the Taguchi method were used to design this dynamo system. The optimal parameters of the magnet, coil, and soft magnet were determined by using the Taguchi method. Low temperature co-fired ceramics (LTCC) technology was applied to fabricate silver planar multilayer coils with 10 and 20 layers, respectively. Nd/Fe/B was sintered to obtain the desired characteristics of a permanent magnet. A 28-pole magnet Nd/Fe/B with an outer diameter of 50 mm and a thickness of 2 mm was also sintered and magnetized, creating a magnetic field of 1.4 T. Simulation results show that a harvester with 20-layer and 22 poles coils, a linewidth of 200 μm, an interspace of 100 μm, and a layer thickness of 40 μm can generate voltages of 1.796 V at a rotary speeds of 300 rpm. This harvester system was approximately 50 mm × 50 mm × 3 mm in volume (including 20-layer micro-coils + magnet + spacing between the coil and magnet surface). The experimentally induced voltages of 20-layer coils were 1.539 V. Measurements show a similar trend with finite element simulations. The power output was 0.788 mW with an external resistance load of 737 Ω. This harvester is capable of powering 200 LEDs (forward voltage (VF) < 2.2 V and 20 mA) using a rotary speed of 250 rpm, and could be used for bicycle dynamo lighting.

► The design and fabrication of a planar rotary electromagnetic energy harvester with a low rotary speed for use in bicycle dynamos are finish successfully.
► Finite element analysis and the Taguchi method were used to design this dynamo system.
► This harvester is capable of powering a minimum of 200 LEDs (forward voltage (VF) < 2.2 V and 20 mA) using a rotary speed of 250 rpm, and can be used for bicycle dynamo lighting.