Gathering energy from ultra-low-frequency human walking using a double-frequency up-conversion harvester in public squares

Abstract

Conventional human walking energy harvesters suffer from low-frequency problems. A double-frequency up-conversion magnetostrictive energy harvester was proposed, analyzed, fabricated, and tested. The harvester is mainly composed of a gear rack and a multi-leaf cam. The rack acts as the first frequency up-conversion mechanism for low-frequency walking. The multi-leaf cam carries out the second frequency up-conversion operation. After the two steps, the low walking frequency is increased. A theoretical analysis of the energy harvester was conducted to find factors that influence its performance. A standard concrete block was proposed, which made the application of the energy harvester easy and fast. The energy harvester was fabricated and experiments were carried out. The ratio of the frequency up-conversion mechanism was 8.13. The maximum output voltage and output power of the harvester were 10.06 V (peak-to-peak) and 31.3 mW, respectively. The harvested energy could light up 100 light-emitting diodes (LEDs) at the same time. It could also power an electronic clock normally for more than 90 min. The proposed energy harvester can be applied for gathering low-frequency human walking energy in public squares.