| As the booming demand for energy and environmental pollution all over the world,the promotion and application of efficient and green renewable energy has become an inevitable trend in the future development of the world.As the“universal source”,solar energy plays an essential role in carbon peaking and carbon neutrality goals.Traditional solar photovoltaic and photothermal application based on sunlight absorption coating is rigid and their conversion efficiency is ranging from 30%-60%.Therefore,a new solar heat utilization method based on liquid evaporation sprout.Solar steam generation use solar absorber with multi-dimensional complex micro and nano structure to convert solar energy into thermal energy,and then heat the surrounding micro and nano scale liquid until evaporation,which is just like micro and nano scale kettle with localized heat.The photothermal application avoids heat loss caused by liquid convection in traditional heat utilization,thus significantly improving the efficiency of solar energy utilization to more than 90%.Based on new mechanism solar photothermal evaporation of thermal localization,this paper aims at how to efficiently utilize solar energy to improve seawater desalination,sewage treatment performance and suppress the photothermal effect parasitic on photoelectric conversion devices.Energy matching mechanism is promoted to design and prepare efficient photothermal evaporator to be used for desalination,sewage water treatment and evaporation cooling.Theoretical simulation is calculated via Comsol software,and gel evaporators with different characteristics and functions are prepared.Evaporator devices applied in various application scenarios are designed.Excellent photothermal water evaporation rate,hydroelectricity co-production performance and temperature control effect by evaporative cooling were obtained.Besides,the related evaporation mechanism and heat flow distribution were deeply analyzed and studied.The main results are as follow:（1）Using carbon nanotube chitosan aerogel as the main solar photothermal evaporator,the vertical pores of natural wood chips were coupled with the disordered pore structure of aerogel by in situ freeze-drying technique,and the microstructure,optical absorption and surface wetting properties of the evaporators were studied.Taking the evaporator as the research object,the energy matching enhanced photothermal water evaporation mechanism is proposed,which adjusts the water transport behavior of the evaporator to limit the amount of water to be evaporated on the surface.The experiment results show that the carbon nanotube chitosan aerogel not only possesses full spectrum absorptance of 93.3%but also has excellent hydrophilic properties.Under 1 k W m-2 sunlight illumination,its evaporation rate is 1.62 kg m-2 h-1.Furthermore,the evaporation rate has been improved by about 37%,reaching to 2.22 kg m-2 h-1 by improving the matching degree between the input energy of the energy required for evaporation.Besides,the evaporator has shown outstanding treatment effects in seawater desalination,sewage treatment and oil-water separation and so on.It provides a new strategy and optimization idea for improving the evaporation performance of solar water evaporation.（2）Using polyacrylamide hydrogel as the basic three-dimensional skeleton and modified with soluble starch,the robustness and stability of polyacrylamide hydrogel were enhanced.Taking starch-polyacrylamide hydrogel as solar photothermal evaporator,the micromorphology and the change of internal water state content were studied,and the photothermal evaporation performance was optimized.Then the optimized evaporator was coupled with thermal module to design a solar thermoelectricity-freshwater cogenerator,improving the solar energy utilization of the system and solving the compatibility of water and electricity.Based on the recovery and utilization of scavenging energy,the heat load at the cold side was optimized by Comsol simulation,increasing the waste heat utilization at the cold side and the evaporation performance of the cogeneration model.The spraying water supply not only completely eliminates the conduction heat loss between the solar absorber and the bulk water,but also promotes the electric property of the thermoelectricity-freshwater cogeneration.Moreover,a practical outdoor setup with an internal angle regulator was built to adapt to different solar incidence angles and maximize the solar input.The experimental results show that under the solar illumination intensity of 1 k W m-2,the cogenerator model obtained an evaporation rate of 1.79 kg m-2 h-1 and the maximum output power density of 11.39 W m-2.After continuous 8 hours natural sunlight irradiation,the maximum output voltage of home-made device reached about 4 V,which can directly light the LED light.（3）Using functional polyacrylamide hydrogel as gel cooler,the photothermal effect parasitized by photoelectric conversion devices is suppressed and the photoelectric conversion efficiency is improved.The evaporation behavior of the hydrogel was optimized under 1 k W m-2 illumination,and the influence of crosslinking degree on mechanical properties was studied.The introduction of functional ions on the change of the water state in the hydrogel and the relationship between different water states and the average enthalpy of evaporation were discussed.The evaporation barrier of water in the hydrogel was reduced and the heat dissipation rate of the hydrogel cooler was accelerated.The color of the hydrogel can change because of the different hydrated water molecules with cobalt ions.The cooling potential and working state of the hydrogel cooling can be directly reflected by color change to avoid inefficient cooling.The experimental results show that with the cooling of Co@Li-PAM hydrogel,the operating temperature of the solar cell is reduced by about 20 oC,and the photoelectric conversion efficiency is increased by 1.26%.Meanwhile,taking Co@Li-PAM hydrogel cooling for central processing unit of smart phone,an excellent temperature reduction of 12.9 oC was obtained.The work has a certain promoting effect on the solar photoelectric and the semiconductor heat dissipation field. |
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