Study On High Efficient Solar Steam Based On Low Dimensional Carbon Materials

In recent years,the environmental problems caused by traditional energy are becoming more and more prominent,and people begin to pay attention to the development and utilization of clean energy.As an inexhaustible clean energy source,solar energy is being pursued.Solar steam as an important form of solar transformation shows a potential application in desalination,fractionation,sterilization,etc.However,the traditional solar steam conversion efficiency is relatively low(to 40%)due to the optical loss of absorber and thermal loss caused by heat exchange between absorber and environment that largely limits its wide application.Based on this background,this paper focuses on solving optical loss,thermal loss and energy sources of absorber,and exploring some new applications,such as waste water treatment,heavy metal recovery and power generation.(1)This part focuses on solving the optical loss of the absorber and the conduction heat loss of the absorber through the water.In this paper,graphene oxide film(absorption rate>94%)is used as an absorber to reduce the optical loss of the absorber.In order to reduce the conduction heat loss of the absorber,a two dimensional water path was proposed to make the indirect contact between absorber and bulk water that can achieve effective water supply and low conduction heat loss simultaneously.Moreover,layered structure of two dimensional material with low cross-plane thermal conductivity was also utilized.As a result,80%efficiency can be achieved under one sun without insulation.Moreover,the graphene oxide film can be folded,which can promote the development of desalination technology for portable,efficient and low cost.(2)This part focuses on solving the heat convection and radiation losses of the absorber,and applies the technology to waste water treatment.The artificial transpiration structure with three-dimensional hollow cone structure is proposed and achieved,breaking through the limitation of traditional two-dimensional planar devices,which can greatly alleviate the dependence of the device on the solar incident angle in the real environment.Meanwhile,it effectively increases the effective evaporation area of absorber and reduces the evaporation temperature of absorber that effectively depressed the heat convection and radiation losses of absorber.As a result,85%efficiency can be achieved under one sun without insulation.At the application level,the work firstly extend this technology to waste water treatment.The experimental results showed that this technology can not only get clean water,which can meet the drinking standard of World Health Organization,but also can effectively recover heavy metals(such as gold and copper).It provides a new idea for the efficient utilization and development of solar steam.(3)This part mainly solves the single energy source in the evaporation process(traditional solar steam only depends on solar energy),and further improves the evaporation by introducing the environmental energy.Through the design of a columnar evaporator,the evaporation temperature is lower than the ambient temperature.Under this condition,the environmental energy will drive into the absorber through the convection and radiation due to the temperature difference between absorber and environment that will further promote the evaporation.The experimental results showed that the evaporation rate of the absorber can reach 1.62 kg/m~2h under one sun,which is larger than 100%solar energy conversion efficiency(1.47 kg/m~2h under one sun).The concept of this work will provide a new idea for further improving the evaporation rate of solar steam.(4)This part focuses on utilizing the latent heat of condensation of steam for the simultaneous generation of clean water and electricity.The high temperature steam generated by the absorber is introduced into the chamber connected with the thermoelectric module for condensation,and the latent heat of condensation is stored in the chamber.And then the current is generated through the thermoelectric module,while the distilled water flows through the chamber to achieve the purpose of simultaneous generation of clean water and electricity.The experimental results showed that the device can obtain the electric energy of?27 W/m~2 and to 74.7%of the solar steam conversion efficiency under the condition of 30 kW/m~2.In addition,the power generation module is still working for a period of time when the light source is closed due to the design of heat storage.This method effectively combines the conversion,storage and utilization of solar energy,which provides an effective way for the simultaneous generation of clean water and electricity.