Experimental And Numerical Investigation Of Concentrating Photovoltaic/Thermal Integrated System Based On Fractal Heat Sink

In this paper,Numerical and experimental studies are developed on the heat transfer and flow characteristics and thermal-electrical performance of the concentrating photovoltaic/thermal(PV/T)system based on fractal heat sink.Frensel Lens and water are applied as concentrator and cooling medium in the study,respectively.The first and second thermodynamics law are used to analysis performance of the PV/T integrated system.The concentrating PV/T integrated experimental system with a fractal heat sink are designed and set up.The experimental investigation is performed under the outdoor conditions.The experimental results are given under the same inlet water temperature and solar radiation intensity.It shows that with the increasing of inlet Reynolds number,the electrical power,thermal efficiency,electrical efficiency,overall PV/T energy efficiency,electrical exergy and overall exergy efficiency increase correspondingly.However,the inlet and outlet temperature difference and thermal exergy efficiency decrease with the increasing of inlet Reynolds number.The data shows that the overall energy efficiency range is from 65% to 70%,the overall exergy efficiency range is from9.5% to 10.5%.At the same time,keeping the inlet Reynolds number and solar radiation intensity at the constant value,the electrical power,inlet-outlet temperature difference,electrical efficiency,thermal efficiency,overall PV/T energy efficiency and electrical exergy efficiency all decrease with increasing of inlet temperature.But the thermal exergy efficiency and overall exergy efficiency increase with increasing of inlet temperature.The overall energy efficiency range from 62% to 70%,overall exergy efficiency range from 9.5% to 12%.When the inlet Reynolds number and inlet temperature of water are constant,the thermal efficiency,PV/T overall energy efficiency,thermal exergy efficiency,PV/T overall exergy efficiency,the maximum temperature difference of the battery and inlet-outlet temperature difference of water increase with solar radiation intensity increasing.However,electrical efficiency and electrical exergy efficiency decrease with solar radiation intensity increasing.The overall energy efficiency range from 66% to 74%,overall exergy efficiency range from 10.7% to 11%.Base on the fractal heat sink,develop a three-dimensional geometric model and steady heat transfer mathematical model for a concentrating photovoltaic thermal(PV/T)system.The PV/T integrated system is solved by control-volume method.The PV/T performance are studied under the different inlet parameters of water and solar radiationintensity.The numerical simulation results present that under the same inlet temperature and radiation intensity,with the increase of inlet Reynolds number the electrical efficiency,thermal efficiency,overall energy efficiency,electrical exergy efficiency,thermal exergy efficiency,inlet-outlet pressure difference and overall exergy efficiency increase correspondingly.But the inlet-outlet temperature difference and maximum temperature difference of the battery decrease with the increase of inlet Reynolds number.The overall energy efficiency range from 60% to 63% and the overall exergy efficiency range from 11.1% to 11.2%.Under the same inlet Reynolds number and solar radiation intensity condition,the electrical power,inlet-outlet temperature difference,electrical efficiency,thermal efficiency and overall energy efficiency declined as the inlet temperature rise.However,thermal exergy efficiency and overall exergy efficiency increase as the inlet temperature rise.The overall energy range is from 10% to 90% and overall exergy range is from 10.5% to 11.2%.Finally,keeping the inlet temperature,the inlet Reynolds number as constant,the thermal efficiency,the maximum temperature of battery,inlet-outlet temperature difference,thermal exergy efficiency,overall energy efficiency and overall exergy efficiency rise with the increase of radiation intensity.The overall energy efficiency range from 62% to 71% and overall exergy efficiency range from 11.8% to 12%.Compare the temperature data obtain by simulation and experiment under the same operating condition,it shows that both of them are coincide.The performance of the concentrating PV/T for numerical simulation are compared with the results by experimental investigation.It shows that with the changing of inlet temperature,the radiation intensity the maximum relative error of the overall energy efficiency is 10.06%,maximum relative error of overall exergy efficiency is 11.86%.While the inlet Reynolds number as the only variable,the maximum relative error of the overall energy efficiency is 13.04%,overall exergy efficiency is 13.60%.With the changing of the radiation intensity,the maximum relative error of the overall energy efficiency is 6.63%,overall exergy efficiency is 22.33%.