Cylindrical PVC pipe: 2D macro light trapper and macroscopic photoprotective tube for fabricating high-concentration brine desalinators?

To date, almost all efforts to develop photothermal materials in the field of photothermal interfacial evaporation have been devoted to exploiting, fabricating and modifying absorbers, which, to some extent, have complex photothermal mechanisms, leading to health risks in fresh water production. This work revealed that a PVC pipe not only can act as a light trapper (2D macro light trapping effect) to almost completely absorb incident solar light by just reabsorbing and multireflecting but can also serve as a macroscopic photoprotective tube to guide light (macroscopic photoprotective tube effect). In terms of the optical guidance effect, photoprotective effect, reflection focusing, geometric constraint and interference of light, a surface that receives an optical power density of 1 kW m⁻² will significantly increase in optical power density when a PVC pipe of a certain diameter and height on it, which is at the bottom of the PVC tube, is standing vertically. Driven by this light mechanism, the optical power density at the solar receiving interface can increase from 1000 to 1651 W m⁻² when the length of pipe 32 in diameter is increased to 7 cm. The fabricated evaporator was bundled with three PVC pipes, as expected, the evaporative interface fully deployed with the macroscopic photoprotective tube (three pipes) performed the best in terms of solar steam generation (2.65 kg m⁻² h⁻¹). On the basis of the trend of salt formation and development, the production of salt and regeneration of evaporators can be easily achieved simultaneously by scraping and wiping. Our proposed photoprotective tubes not only can be exploited in the field of photothermal evaporation but can also be exploited in the field of acupoint photothermal therapy and other fields.