Research On Solar Desalination System Based On Compound Parabolic Concentration

The total reserves of water resources on the earth are large but the reserves of fresh water resources are small,so solar desalination can effectively relieve the pressure of global fresh water resources.For the realization of boiling distillation,a seawater desalination system is designed based on the composite parabolic concentrator(CPC)focusing energy supply to achieve efficient steam generation.The system uses CPC components to collect low energy flow density solar light and heat the oil,heat conduction oil is exchanged with atomized raw water in the heat transfer coil of the distiller to produce steam.The steam enters the hot steam chamber of the thermoelectric assembly through the gas-liquid separator under the disturbance of the small fan.Full use of steam latent heat for thermoelectric generation,and then steam into the condenser condensation collection to obtain fresh water? By establishing the mathematical model of heat loss of each part of the system,analyzing the heat loss of each part and analyzing the influence of component structure parameters on the heat loss,designing and optimizing the system for experimental research.The main contents of this thesis are as follows:(1)Based on the analysis of fresh water resources,this paper puts forward the research direction of seawater desalination using CPC heat collection,and finds that: The water resources on the earth are large,but the total amount of fresh water available for human use is small,and the production and living water is scarce.The main components of solar desalination are slot type,tower type,dish type,Fresnel type,CPC and so on.Among them,the advantages of CPC are large receiving angle and no tracking.At present,the solar desalination system is developing rapidly,but there are some problems such as low distillation temperature,scaling of collector and waste heat.(2)By analyzing the heat transfer process of the system and calculating the influence of the structural parameters of the components on the collector performance of the system,found that: The main losses of the system include heat loss of CPC components,heat loss of distiller,heat loss of connecting pipe and heat conduction tank,the thickness of insulation layer of components should be more than 50 mm.Copper with high thermal conductivity can be used in distilled coil and its total length should be more than 14 m.The greater the value coefficient,the greater the temperature difference between the two ends of generator,the better performance of thermoelectric generator,(3)The effect of collector area on the system performance was studied experimentally,found that: The average daily water yield coefficient,fresh water hardness,average heat collection efficiency and average solar energy utilization efficiency of the two-stage CPC system are all superior to those of the three-stage CPC system.The output power of the thermoelectric generating module is affected by the steam generation rate,and the faster the steam generation rate,the greater the output power of the component.(4)The effect of collector inclination angle on system performance was studied experimentally,found that: The parameters of performance coefficient,hardness of fresh water production,average heat collection efficiency and average solar energy utilization efficiency were 45°with the best inclination angle and 20°inclination angle.However,the difference between the parameter values of the three dip angles in the same heat collecting series is small and negligible,which proves that the CPC has good tracking-free characteristics.(5)Experimental study on the difference of system performance in summer and winter,found that: Because of the different sunshine time in summer and winter,the time of boiling vaporization is about 6 h in summer and 5 h in winter.The total water output of the system is in summer is larger than in winter,and the same as the Average water yield coefficient.But because of the higher ambient temperature in summer,the temperature difference between the cold and hot ends of the thermoelectric generator is smaller,that is,the output power of the generator is smaller.The seasonal difference between summer and winter affects the time change of the system's heat utilization rate,but it has little effect on the daily average solar energy heat utilization efficiency.(6)Compared with other solar desalination systems,the system studied in this paper has the advantages of boiling distillation,preventing collector from scaling,steam latent heat generation,and no tracking.However,further research is needed on the surface such as water intake control,system cleaning,reheating structure design and concentrated brine treatment.