Performance Study Of A Photovoltaic/Thermal Solar Receiver With Volumetric Absorption Combined Spectral Splitter

Concentrating photovoltaic/thermal technology(CPV/T)can effectively reduce the installation cost comparing with traditional photovoltaic systems.And recycling waste heat in the concentrated photovoltaic system can greatly improve the utilization efficiency of sunlight.As the grade of thermal energy obtained from traditional CPV/T systems is limited by the temperature of PV module,spectral beam splitting technology is introduced to solve this problem.The volumetric absorption combined spectral beam splitting technology uses solid based filter and liquid based filter in combination,which has the advantages of good beam spectral splitting effect,low cost and high reliability.However,in current research,there are still some problems in the volume absorption combined spectral beam splitting technology.For example,the poor match between the spectral splitter and photovoltaic cells,unreasonable receiver structure.These cause the lack of uniform illumination on the surface of the receiver,leading to low electrical and thermal efficiency.In this paper,a volumetric absorption combined spectral splitter is designed and optimized.Several combined filters are obtained.The effect of receiver with combined filtering is analyzed by experiments.The structure design and modification of receiver is improved by optical simulation.A prediction of the receiver electrical and thermal efficiency is also finished in this paper.(1)Several combinations of solid based filter and liquid based filter are selected based on the requirements of combined spectral splitter.This aim to solve the problem of poor match between the volumetric absorption combined spectral splitter and Photovoltaic cells.The optical transmittance of solid based filter and liquid based filter is obtained by spectrophotometer.A merit function is introduced to preliminary evaluate the filtering performance of the volumetric absorption combined spectral beam splitter with different combinations.As the receiver is fabricated to work under severe condition for long terms,several reliable experiments are designed based on the IEC62108 standard.Through these investigations,four liquid based filters,such aspropylene glycol,C14 n-alkane,industrial white oil,glycerol/water(1:3)mixture,and two solid based filters including HB600,HB650 are decided.Among these,the combination of HB650 nm filter and glycerol/water(1:3)mixture shows the best filtering performance.which produces market value of 34% theoretically increasing.(2)A solar I-V characteristic test system is used to investigate the effect of combined filters to the electrical and thermal performance of receiver.Electrical experiments,temperature increasing experiment,temperature dropping experiments are designed to investigate the electrical performance,temperature increasing performance and thermal conversion efficiency.The results show that with combined filter technology the electrical efficiency of receiver is decreasing.While heat collecting temperature will improve greatly,and the thermal conversion efficiency is also obviously increasing.(3)A combined spectral beam splitting CPV/T system is designed to analysis the electrical and thermal performance of volumetric absorption combined spectral beam splitter under concentrating conditions.The optical model of designed system is established in LightTools,and the structural parameters are optimized.An optical simulation is finished based on the optimum CPV/T system,and the electrical and thermal efficiency of combined filter is predicted.The result shows the surface illumination uniformity of the filtering receiver achieves above 98%.The total efficiency of 49.53% can be achieved with such a combined filter,in which electrical and thermal efficiency of the receiver are 7% and 42.53% respectively.The market value of receiver obtains 22.7% improvement.