关键词: 织物, 太阳能蒸发器, 海水淡化, 光热

Abstract: With the increasing shortage of freshwater resources, using seawater desalination to produce freshwater is a broaden incremental technology for achieving water resource utilization. The current main methods of seawater desalination include reverse osmosis membrane method and distillation method. Compared with traditional seawater desalination technology, solar-driven water evaporation is less costly and more environmentally friendly. In recent years, low-cost solar thermal desalination has been favored by many researchers.
According to the different placement methods of solar absorbers, they can be divided into two types: suspended solar absorbers and surface solar absorbers. The photothermal materials and principles of the two evaporators are not significantly different. They both absorb specific wavelengths of light and cause electromagnetic field changes through plasma resonance or electron transitions. The interaction between electromagnetic waves and substances at the water interface heats up nanoparticles. The suspended solar absorber heats the bulk water, while the surface solar absorber heats the water soaked in the evaporator. Compared with suspended solar absorbers, surface solar absorbers have more advantages.
The loose porous structure of fabrics can provide efficient water transportation, and the flexibility and elasticity of the fabric structure can provide better compatibility with surface solar absorbers. It can also modify the fabric's properties to better combine with photothermal materials. In current research on solar-driven water evaporation, cotton, linen, nylon, aramid, acrylic, and nonwovens are mainly used as substrate materials, and metal nanoparticles, metal oxides, and carbon-based materials as photothermal materials.
Improving the salt resistance of the evaporator can effectively maintain its evaporation rate and extend its service life. There are two ways to improve the salt resistance: increasing the hydrophilicity or hydrophobicity of the evaporator. In improving evaporation performance, it is necessary to balance heat loss, water supply, and salt crystallization. Excessive water can lead to more heat loss, and rapid water evaporation can cause salt to crystallize on the surface of the evaporator, thereby affecting photothermal performance. In order to achieve a balance between heat loss and water supply, there have been two main types of surface solar absorbers in recent years: hydrophilic bilayer structure and structure with dedicated water transport channels. The hydrophilic bilayer structure loses more heat due to wetting during use, and the water absorption rate of the water transport channels structure is higher than the evaporation rate, which does not limit evaporation and can effectively reduce heat loss.
At present, the solar-driven water evaporation with the highest evaporation rate is the surface solar absorber with a bridge structure composed of Janus hydrogel and cotton fabric. The evaporation efficiency of solar-driven water evaporation is relatively low, making it impractical to provide water for households. However, a solar evaporator with a solar thermal area of 1 square meter can meet the drinking water needs of households. With the continuous improvement of solar desalination technology, it will definitely be more widely used in remote and underdeveloped areas in the future.

Key words: fabric, solar evaporator, desalination of seawater, photothermal