Enhanced direct steam generation via a bio-inspired solar heating method using carbon nanotube films

In this paper, a novel direct solar steam generation method is proposed that realizes highly efficient vapour generation. The strategy was inspired by the evaporation of sweat from the human skin and the transpiration of plants in biological systems. A micro-porous structured broadband absorption paper-based carbon nanotube (CNT) film was prepared by a facile vacuum filtration process, and was utilized as both the solar harvesting surface and steam generation skin. The excellent optical absorptivity and water conductivity of CNTs make great contributions to the solar steam generation. The heat and mass transfer properties on the direct solar steam generation performance of CNT films was investigated. The evaporation rate and temperature distribution of the steam generation system were experimentally studied to evaluate the evaporation performance. The results demonstrate that the bio-inspired solar heating of CNT films has significant advantages for enhancing direct solar steam generation compared to those of direct volumetric solar heating. Through this research, it was found that the localized photo-heating of floating CNT films at the water-air interface and the fast capillary flow through the porous structures of the films enhanced the solar steam generation process. This bio-inspired direct solar steam generation method using carbon nanotube films has great potential in a variety of industrial applications, including electrical power generation, freshwater distillation, and solar hygiene systems. (C) 2017 Elsevier B.V. All rights reserved.