Fig. 1: Monitoring environmental parameters in mine with wind-driven triboelectric nanogenerators.

a A graphical overview illustrating the application of the TESS in an underground mine. The inset in the top-right corner presents a simplified outline of the TESS structure, showing its various modules and functions. b Comparison of starting wind speed between various turbine-based TENG wind-speed sensors reported in the literature (Ref. ^{27,28,29,30,31,32,33,34,35}) and that incorporated in the TESS. c Comparison of power density between single-end fixed TENGs from the literature (refs. ^{36,37,38,39,40,41,42,43}) and the Mixed-Mode TENGs employed to power the TESS. d Durability performance comparison, expressed in days of constant operations, between TENGs from the literature (refs. ^{37,38,41,42,44}) and that employed to power the TESS.