Water tank triboelectric nanogenerator for efficient harvesting of water wave energy over a broad frequency range

A water tank triboelectric nanogenerator based on polytetrafluoroethylene (PTFE) is fabricated for harvesting water wave energy. The impacts of contact frequency over a broad frequency range including the frequency range of ocean waves and output characteristics under resistive and capacitive loads for different liquid types are investigated in order to identify the optimal contact frequency and load conditions for maximizing the power density and energy conversion efficiency. In addition, surface modification of PTFE with different patterns for enhancing its hydrophobicity is implemented in order to reduce charge screening. Furthermore, the impact of contact frequency on the output characteristics for the surface modified PTFE is also studied. It is observed that the open-circuit voltage and short-circuit current exhibited opposite trends with increasing contact frequency. The highest power density of 9.62 W/m2 and energy conversion efficiency of 63.2% are achieved using saline water and rhombic pattern surface modified PTFE at contact frequency of 0.1 Hz, representing 8 fold improvement compared to the reported water tank based triboelectric nanogenerator based on fluorinated ethylene propylene. The results demonstrate that the nanogenerator has promising potential in scavenging water kinetic energy.