The Effect Of Fresnel Lens Surface Dust On Thermoelectric Output Performance Of HCPVT System

In order to solve the problems of the concentrating loss caused by the dust deposited on the surface of Fresnel lens,the uneven distribution of energy flow on the surface of GaAs battery and the decline of the thermoelectric output performance of the system,this paper took the Fresnel HCPVT system as the research object based on the wind-sand climatic conditions,and according to the different dust deposit characteristics,theoretically analysed and established the prediction model of the electrical output performance of the system,and the concentrating characteristics of the system.The influence of dust deposition on the thermoelectric output performance of the system was studied by experimental research and simulation.By analyzing the mechanism of dust accumulation and its effect on the transmittance of concentrator,the single exponential model of gallium arsenide battery was coupled with the overlapping model of dust accumulation.A single exponential prediction model of tri-junction gallium arsenide battery considering incident angle was established.The model predicted that when DNI was 800 W/m~2,the current of clean was 5.13 A,while the current of 5g/m~2 was 3.76 A,and the difference between before and after dust accumulation was about 26.71%.The transmittance decreases from 92%at clean to about 40%at dust density of 5 g/m~2,and the overall decrease was about 77.9%.The maximum error was about 8%when the theoretical value of transmittance predicted by the model was compared with the measured value.The influence of dust deposition on the transmittance and wavelength of the concentrator was analyzed by the test method of artificial dust distribution.The influence of dust deposition density and particle size on the transmittance and absorbance of Fresnel lens was quantitatively analyzed.The results showed that the transmittance of the lens increased rapidly from 0 to 90%in the 200~400 nm band,and increased slowly to 92%at the wavelength of 400~1000 nm.With the increase of dust density,the transmittance of the lens decreased gradually,from 91.71%in the clean state to 40.29%at the dust density of3.12 g/m~2,the average dust density increased by 1 g/m~2,and the transmittance decreased by about 3.43%.The absorbance of mirror surface with clean and dust-accumulated density of 3.12 g/m~2 was 0.065 and 0.182,respectively.The average dust-accumulated density increased by 1 g/m~2,and the absorbance increased by about 0.031,with an increase of 47.27%.In this paper,a three-dimensional model of dust deposit was established.The influence of dust deposit on the concentrating efficiency of the system,the distribution of energy flow on the surface of the battery and the uniformity of light spot was studied by using Monte Carlo tracing method.At the same time,the influence of dust deposit characteristics and structural parameters on the concentrating performance of the system was analyzed.The results showed that when the dust density was less than 10 g/m~2,the average dust density increased by 1 g/m~2,the energy flux density decreased by 4.77%,and the concentration efficiency decreased by 4.12%.Compared with the concentration efficiency at the incident angle of 0~1°and 1~2°respectively,the concentration efficiency decreased by 22.02%and 28.61%.When the assembly distance was 350 mm~360 mm,the spot uniformity decreases rapidly from 45.3%.The uniformity of spot increased rapidly to about 89%at 360 mm to 380 mm.The influence of dust density on the thermoelectric output performance of the system was studied and analyzed by means of artificial dust distribution.The experimental results showed that the system voltage was almost unchanged with the increase of dust density,while the system current decreased gradually with the increase of dust density.When the dust density was less than 8 g/m~2,the average dust density increased by 1 g/m~2 and the current decreased by 0.23 A;when the dust density was less than 8 g/m~2,the average dust density increased by 1 g/m~2 and the current decreased by 0.23 A.When the degree was greater than 8 g/m~2,the average dust density increased by 1 g/m~2 and the current decreased by 0.11 A.The influence of dust deposition on the thermal performance of the system was greater than that of dust deposition on the electrical performance.The average dust deposition density increased by 1 g/m~2,the thermal power decreased by 6.8%,the thermal efficiency decreased by 6.17%,the electrical efficiency decreased by 5.4%,the electric power decreased by 5.8%,and the power generation decreased by 6.9%.