Regulation Of Latent Heat Of Evaporation Of Water In An Efficient Solar Interfacial Thermal Evaporation System

At present,there is a serious shortage of water resources in the world.For this reason,scholars at home and abroad have put forward a lot of seawater desalination technologies,but most of these technologies need to consume electricity and chemical energy.Compared with traditional desalination technology,solar desalination technology does not require the consumption of fossil fuels at the cost of clean,green and sustainable advantages,and is considered one of the most promising fresh water production methods.Interfacial solar steam generation system was especially studied for its high solar-thermal conversion efficiency.However,the phase transition process of water evaporation is energy intensive and salt cluster is easily accumulated at the surface of evaporator,which limits the water yield and stability of the distiller.Here,we demonstrate a multistage solar distillation unit that can regulate latent heat,recover latent heat and realize spatially located low concentration zone distillation to achieve stable and efficient solar water collection.The main research contents of this paper are as follows:（1）In this paper,with Balsa wood chips as the base material,polypyrrole（PPy）as the light absorption material,polyvinyl alcohol（PVA）as the hydrophilic material,efficient solar driven evaporator PPy/PVA-wood was successfully prepared.The results of interfacial evaporation experiment show that the evaporation rate of PPy/PVA-wood under 1 k W m^-2simulated solar illumination increases first and then decreases with the water supply height h,and reaches the maximum when h is 5 cm,namely 1.56 kg m^-2h^-1.We further studied the relationship between the state of water and the latent heat of water evaporation in the evaporation process,and concluded that the evaporation form of water can be changed by regulating the state of water in the evaporator,so as to reduce the latent heat of water evaporation and significantly improve the evaporation rate of water in the solar evaporator.（2）When the PPy/PVA-wood evaporator is used in the solar distiller,the water collection rate of the distillation system changes with the change of the water supply height h,showing a trend of first rising and then decreasing with the increase of h.When the water supply height h of the wick of the membrane distillation device is adjusted to 5 cm,the water yield reaches the maximum value of 1.08 kg m^-2h^-1.When the water supply height h of the wick of the two-level distiller is adjusted to 9 cm,the water yield reaches the maximum value of 1.62 kg m^-2h^-1,about 1.43 times that of the distiller without wood,and the solar-steam conversion efficiency can reach 110%.The amplified bilayer distillation unit can also be operated outdoors for a stable week.This work provides an effective strategy for efficient solar distillation and is expected to be applied in seawater desalination and domestic water supply.