Solar Evaporator Based On Photo-electro-thermal For Efficient Seawater Desalination

At present,global freshwater resources are not only scarce,but pollution problems are also very serious.Seawater desalination is undoubtedly one of the most promising solutions.Currently,the most widely developed are reverse osmosis technology,multi-effect distillation and multi-stage flash technology.However,these technologies require a large amount of energy consumption,which may aggravate the possibility of global warming and environmental pollution.Solar energy as a clean energy source for desalination can save resources while alleviating the water shortage crisis.The new solar energy interface evaporation realizes the limited-domain heating,which utilizes the light energy reasonably,heats a small amount of water to evaporate,reduces the energy loss,and thus has higher evaporation efficiency.At the same time,in remote areas without power grid coverage and areas where water supply facilities are not perfect,solar evaporation technology can eliminate the need for electric energy to provide clean drinking water.The realization of this concept also needs to consider the problem of water production when the weather conditions are not good.Therefore,the development of a high-absorbance,high-rate,continuous-type solar evaporator has an extremely important role in promoting the application of solar distillation.In this paper,the photo-electric-thermal combined effect is taken as the core to improve the evaporation efficiency of solar evaporator.The photo-electric-thermal combined evaporator with high water yield is prepared.It is applied to the desalination field of seawater and so on,and the potential of application is analyzed.Materials of evaporator made of cotton by dipped in graphene oxide solution and calcinated.Porous material by capillary action can be constantly supply moisture to the top that achieve efficient thermal and electric conversion,to limit water heating performance,reduce the heat to a large number of water body and surrounding,improve the efficiency of evaporation.The evaporator surface temperature can reach 82.6°C under one sun.The evaporator was tested in the laboratory under simulated sunlight.The evaporation rate of the evaporator was 1.85 kg m^-2 h^-1 under one sun by the action of photothermal heat.The evaporation rate of the evaporator under the combined action of photo-electricity was 4.7 kg m^-2 h^-1,the increase in electric heating effect further increases the evaporation effect.Under the multiple sunlight intensity,th e evaporation efficiency shows a linear growth trend,so the double lens concentrating system can be used to enhance the light intensity,thereby further improving the evaporation efficiency.The evaporation rate under the combined effect of photo-electricity is higher than that of only one energy input.It shows that compared with the solar thermal evaporator with only photothermal,the photo-electric combined evaporator designed in this experiment can effectively increase the amount of evaporated water,and the prospect of application is very considerable.In the desalination treatment of seawater,the concentration of positive ions in seawater includes Na⁺,Mg²⁺,Ca²⁺,K⁺.The removal rate before and after desalination is over 99.9%.The negative ions include SO₄^2-,Cl^-,F^-,NO₃^-.The removal rate is 99.8%.The conductivity of seawater is 56 900?S cm^-1,and after desalination,it is reduced to 6.42?S cm^-1,and the removal rate is 99.989%.It is proved that the photo-electric combined evaporator has high removal efficiency of salt in seawater,which is close to 100%.Due to the removal of various ions,the pH of the water sample is closer to 7.0.The TOC content in seawater was 125.8mg L^-1.After treatment,the TOC in the desalinated water was 23.45 mg L^-1,and the removal rate was 81.36%.At the same time,the turbidity of the water is reduced.