Separating photo-thermal conversion and steam generation process for evaporation enhancement using a solar absorber

Solar steam generation is an effective method combining solar energy utilization with water treatment. Photo-thermal conversion and steam generation are typically integrated to enhance the evaporation process, which have wide applications in seawater desalination, waste water treatment, sterilization and power plant fields. However, the photo-thermal enhancement for different evaporation areas remains unclear, and there are a number of important issues for membrane process (e.g., blockage of pore structures and contamination of nanoparticles). To overcome these issues, we herein propose a separating design involving a C-TiO2 absorber and a polyvinyl alcohol fiber material as the photo-thermal and steam generation units, respectively. A C-TiO2 absorber with good spectral and photo-thermal conversion characteristics was prepared. And the evaporation enhancement effect was investigated with different evaporation areas by experiments and simulations. The equivalent evaporation rate reached the maxima with the evaporation area and decreased thereafter for this separating design. The optimum behavior was achieved when the evaporation region area to photo-thermal area ratio of ca. 2.06, providing guidance for large-scale use. These results can be explained in terms of the changed thermal gradient generated between the center C-TiO2 film and the evaporation region. The design achieved equivalent evaporation rates and evaporation efficiencies of 1.24 kg·m−2·h−1 and 77.83%, respectively, paving the way for the further improvement of solar steam generation processes.