Construction Of Solar Energy Conversion Materials And Application Demo Systems

Solar energy has become one of the most promising renewable energy due to its huge reserves,wide distribution,pollution-free nature,and various forms of conversion and utilization.Therefore,research on solar energy conversion materials and utilization systems is of great significance.According to the role of sunlight and materials,the basic utilization of solar energy by humans can be divided into photo-electric conversion that mainly uses the short-wave part of sunlight(ultraviolet and part of visible light)and photo-thermal conversion that mainly uses the long-wave part of sunlight(visible and NIR bands).And the further conversion and utilization methods derived therefrom,such as photovoltaic power generation,photo-electric-chemical conversion,photothermal evaporation of water,photo-thermal-electric power generation,etc.The photo-electric-chemical conversion represented by photocatalysis utilizes the photo-generated charge generated in the materials to drive various types of chemical reactions,such as photocatalytic degradation of pollutants,water splitting for hydrogen production,synthesis of various organic and inorganic chemicals,etc.In recent years,photocatalysis has become a research hotspot,especially photocatalytic decomposition of pollutants in water and air is the most promising photocatalytic application process.Commercial photocatalysts and miniaturized equipment have been used for purification harmful substances in indoor air and water.The application of photo-thermal conversion has a history of thousands of years in human history,but it has not been valued because of its low efficiency and simple use.In recent years,people have made new breakthroughs in the conversion efficiency of light and heat through the design of new materials and device structures,and photo-thermal conversion has once again become a research hotspot.It is worth mentioning that the solar steam generation system based on heating localization emerged in recent years has solved the problem of low efficiency of direct heating of block water by sunlight,making solar water evaporation a technology with great application potential.In addition,by coupling photothermal materials with thermoelectric devices,solar energy can be further converted into electrical energy,which can drive electrolyzed water devices into clean hydrogen energy,storing solar energy in the form of chemical energy.At present,people have done a lot of research work on solar energy applications,but there is a lack of demonstration systems with practical value.Therefore,this authors construct prototype devices for solar energy conversion as the main research goal,based on the two basic conversion methods of solar energy acting on materials,namely,photo-electricity and photo-thermal conversion,through the design and adjustment of the composition,morphology and structure of the material,optimizing the performance of materials in the conversion of solar energy to specific forms,designing devices that are conducive to the directional conversion of solar energy,and constructing different types of solar energy conversion and utilization systems.Three solar energy application systems,namely photo-electric-chemical conversion for photocatalytic degradation of pollutants in water,photothermal conversion for water evaporation and photo-thermoelectric power generation,are studied to explore the efficient conversion and utilization of solar energy.The main research contents of this article are as follows:In terms of photo-electric-chemical conversion and utilization of solar energy,the photocatalytic oxidation of organic pollutants in water using photocatalysts has been extensively studied.In this paper,a assembled photocatalyst suitable for continuous photocatalytic system was designed and constructed.The surface of commercial titanium dioxide photocatalyst was modified with amino groups,and the quartz fiber felt modified with carboxyl groups on the surface was electrostatically stabilized.The quasi-single-layer assembly,after subsequent calcination,carbonizes the organic matter that acts as a bridge to obtain a carbon-connected supported TiO2/quartz fiber felt photocatalyst.In this paper,the effect of the annealing temperature by affecting the degree of carbonization of the material on the photocatalytic performance is explored,and the optimal calcination temperature is obtained.The carbon calcined at the optimal temperature(500?)can not only connect the catalyst and the substrate,solve the problem of difficult separation and recovery of the photocatalyst,but also promote the charge carriers' separation of the photocatalyst and improve the photocatalytic efficiency.Due to the low absorption rate of ultraviolet light by quartz fiber felt,light can be transmitted,refracted,scattered,etc.to achieve coupling transmission,which is conducive to achieving uniform distribution of light on the catalyst.Hydrophilization treatment of TiO2/quartz fiber felt can produce capillary action,so that the pollutants flowing through the sewage can fully contact with the catalyst.Based on this,a continuous photocatalytic reactor designed by capillary action to promote flow is designed to achieve high efficiency continuous-flow photocatalysis to remove pollutants in water.The photocatalytic system constructed in this paper shows a very high purification efficiency on the wastewater from the actual factory,which proves the huge application potential of the photocatalytic system and provides a reference for the application of solar photo-electric-chemical conversion for environmental remediation.In terms of photothermal utilization of solar energy,conversion of solar energy into thermal energy for water evaporation has great potential application value in the desalination of seawater,sewage purification,steam power generation,etc.To improve the efficiency of the photothermal water evaporation system,we must first look for a photothermal conversion material with a high solar absorption rate and a structure conducive to water evaporation.In this paper,the H2Ti3O7 nanobelts were calcined at high temperature in an ammonia atmosphere using a self-template method,and the effects of different nitriding temperatures on photothermal properties were explored.Titanium nitride(TiN)nanobelts are obtained by nitriding at 800?.As a non-noble metal plasmon resonance absorption material,the responding spectrum of TiN to sunlight is broader than the noble metal(such as Au)local surface plasmon resonance material,resulting to higher photothermal conversion efficiency.Due to the local shrinkage during the nitriding process,the TiN nanobelts exhibit a polycrystalline nano-porous structure of nanoparticles,which increases the specific surface area.In addition,the partial oxidation of the surface of enhances the hydrophilicity and enhances the contact between the material and water,which is beneficial for the heat transfer Porous structure is also conducive to the transport of water and steam,thereby speeding up the evaporation rate of water.Further,inspired by the transpiration of plants,the photothermal material is loaded on the surface of the ceramic plate for photothermal conversion to evaporate water,and the capillary action is used to absorb water from the water body and transport it to the photothermal material.As much as possible to reduce the loss of heat to the water body below,the entire photothermal evaporation water device floats on the water surface to achieve local surface heating,thereby constructing an efficient photothermal water evaporation device.The system's efficiency of photothermal evaporation of water under 4 kW/m2 light reached 93.6%,and the distilled water device built by the system was used to achieve efficient desalination of tap water and simulated seawater in a demonstration experiment under real outdoor sunlight.This part of the work provides an efficient and low-cost solution for the large-scale application of photothermal evaporation water.Solar energy utilization system based on coupling of light-heat,heat-electricity and electro-chemical effect.Affected by the periodic changes of solar energy,the conversion of solar energy into other forms of energy for storage has great application value.Assembling high-efficiency photothermal conversion materials on the surface of the thermoelectric device constitutes a photo-thermoelectric power generation device,which can convert solar energy to output electric energy through photothermal-thermoelectric conversion.Compared with photovoltaic power generation and photothermal steam-driven turbine power generation,this power generation device has a simple structure,is flexible and portable,and has low cost.Therefore,in this paper,after exploring a variety of fuels,paraffin was selected as the carbon source,and a layer of ultra-fine carbon nanoparticles was prepared in situ on the surface of the thermoelectric device by flame synthesis to form a photothermal conversion layer.The characterization proved that the composition of as-synthesized carbon nanoparticles are mainly amorphous carbon,and the light absorption layer composed of it has a microscopic pore structure to form an optical "trap".The absorption spectrum confirms that the light absorption layer has an ultra-high absorption performance to full spectrum of sunlight.The in-situ synthesis method achieves close contact between the photothermal material and the thermoelectric device,and improves the heat transfer efficiency.On this basis,a heat dissipation device is installed on the cold-side of the photothermal device,and a plexiglass cover with surface anti-reflection treatment is installed on the hot-side,thereby reducing heat loss and increasing the temperature difference between the cold-side and hot-side,resulting a high-efficiency solar thermoelectric generator.Tests have shown that the power efficiency of the constructed solar thermal-thermoelectric coupling power generation device is 34 times higher than that of the untreated thermoelectric power generation chip.Further,under the real sunlight,the power generation device can drive the electrochemical water splitting to obtain clean hydrogen fuel,and finally convert the solar energy into chemical energy for storage.The power generation device can also drive a small electric fan,which shows its high-power electric output performance.This part of the work provides a new option for household,small,and portable electricity demand occasions,and provides a feasible way for solar energy conversion and storage utilization.