A Flexible Hybrid Generator for Efficient Dual Energy Conversion from Raindrops to Electricity

Electromagnetic generators are conventionally used to harvest energy from large water bodies, but they are ineffective for harvesting low hydro-energy, such as raindrops or fogs, due to their bulky, heavy and immovable. Unfortunately, developing new strategies that are lightweight, small, and have high conversion efficiency to convert such low hydro-energy into electricity remains a challenge. Herein, a flexible droplet-based hybrid electricity generator (DHEG) consisting of a droplet-based electricity generator (DEG) and an electromagnetic generator (EMG) is proposed to convert the dual energy of water droplets into electricity simultaneously. The DHEG is assembled by facilely merging DEG and EMG using conductive elastic multi-walled carbon nanotubes/polydimethylsiloxane (MWCNTs/PDMS) film. The MWCNTs/PDMS film can not only serve as a bottom electrode for switching on the DEG, but also as an elastic component for the EMG to vibrate the coil when impacted by water droplets. Activated by a single 58.2 µL droplet falling from a height of 50 cm, the peak voltage, current and power generated by the DHEG are ≈84.6 V, ≈19.85 mA, and ≈595.8 µW, respectively. The energy conversion efficiency of the DHEG is up to ≈13.8%. This flexible hybrid generator may provide a promising strategy for effectively harvesting energy from raindrops.