Simulating streaming current output of water evaporation driven carbon nanogenerator.*

Electricity generation from streaming current induced by water evaporation in nanostructured carbon material was first demonstrated in 2017[1]. Since then, the phenomenon has been demonstrated for a variety of different materials and the efficiency improved by modifying the nanoscale structure of the active material. We present a multiphysics simulation of power generation by water evaporation in a nanostructured porous film generator. A finite element model is used to compute the dynamics of the water flow in the device, simultaneously solving for both the liquid and vapor phase.

The FEM simulation accounts for the combined effects of capillary action in the porous carbon material and external factors, such as humidity and temperature. The FEM solution of the water dynamics is used to create an electrical model of the device and solve the output current-voltage characteristics of the generator. The simulation results are verified experimentally for both long steady-state operation and transient phenomena in the device. The presented simulation enables efficient optimization of the parameters of the device such as film geometry and material choice, in a wide range of ambient humidity, temperature and airflow conditions.

 [1] Xue, Guobin, et al. "Water-evaporation-induced electricity with nanostructured carbon materials." Nature nanotechnology 12.4 (2017): 317.