Highly efficient evaporative cooling by all-day water evaporation using hierarchically porous biomass

We developed a 3D solar steam generator with the highest evaporation rate reported so far using a carbonized luffa sponge (CLS). The luffa sponge consisted of entangled fibers with a hierarchically porous structure; macropores between fibers, micro-sized pores in the fiber-thickness direction, and microchannels in the fiber-length direction. This structure remained after carbonization and played an important role in water transport. When the CLS was placed in the water, the microchannels in the fiber-length direction transported water to the top surface of the CLS by capillary action, and the micro-sized pores in the fiber-thickness direction delivered water to the entire fiber surface. The water evaporation rate under 1-sun illumination was 3.7 kg/m2/h, which increased to 14.5 kg/m2/h under 2 m/s wind that corresponded to the highest evaporation rate ever reported under the same condition. The high evaporation performance of the CLS was attributed to its hierarchically porous structure. In addition, it was found that the air temperature dropped by 3.6 °C when the wind passed through the CLS because of the absorption of the latent heat of vaporization. The heat absorbed by the CLS during water evaporation was calculated to be 9.7 kW/m2 under 1-sun illumination and 2 m/s wind, which was 10 times higher than the solar energy irradiated on the same area (1 kW/m2).

EFFECT OF CHEMICAL TREATMENT WITH OXIDANTS ON THE MECHANICAL PROPERTIES OF LUFFA SPONGE/UNSATURATED POLYESTER COMPOSITES

This study investigates a synergistic treatment comprising alkali, permanganate, dichromate, silane and bleaching pretreatment on Luffa sponge (LF) fibers intended to be used as reinforcement in an unsaturated polyester (UP) matrix to improve the mechanical properties of Luffa sponge fibers reinforced unsaturated polyester composites. Treatment effects by NaOH (5 wt%), K2Cr2O7 (0.2 wt%), KMnO4 (0.0125 wt%), NaClO (13°) and silane (0.5 wt%) on the performance of the prepared composites were evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), SEM and mechanical tests (flexural strength and modulus). The results of the analyses indicated that composites reinforced with treated fibers have higher flexural strength than composites reinforced with untreated fibers.