Lightweight energy harvesting backpack achieved with a slingshot-inspired flexible accelerator

The energy harvesting backpack (EHB) has been recognized as a sustainable power source for wearable electronics, but its daily applications have been hindered by the rigid and heavy frame and accelerator structure. Therefore, a flexible and lightweight design strategy for EHBs is proposed based on a slingshot-inspired flexible accelerator (FA). The proposed FA accomplishes the speed acceleration for harvester actuation by rapidly releasing accumulated elastic potential energy. Then, a 1.9 kg electromagnetic EHB with the FA (FA-EEHB) is modeled, tested, and applied to wearable electronics. Actuated by 3.0 Hz ultralow-frequency vibrations, the FA-EEHB with a 2.0 kg payload can generate 215.1 mW output power, which is over eight times the 26.6 mW output of an EHB without FA. With a small payload of 1.0 kg, the FA-EEHB can work well over a large traveling speed range from 4 km/h to 9 km/h. The application experiment of the FA-EEHB was conducted at 5 km/h traveling speed with a 2.0 kg payload to demonstrate the ability to continuously power a lamp, charge a smartphone, and sustain a tracking and positioning system. This study provides a distinctive strategy for the flexible and lightweight design of EHBs with small payloads.