Research On The Influence Of Photovoltaic Cell Width On The Daylighting Performance Of Semi-transparent Photovoltaic Window

The energy consumption generated by doors and windows accounts for a large proportion of the total energy consumption of the building env elope,which is a weak link in energy conservation in the envelope structure.Therefore,more and more scholars are conducting research on new energy-saving windows.Since semi-transparent photovoltaic(STPV)windows can not only reduce indoor heat gain and reduce building energy consumption,but also can use photovoltaic power generation,they have received widespread attention.However,the cell coverage rate and cell width of the STPV window will affect the daylight performance.If the cell coverage is too large,the indoor daylight cannot meet the requirements.Otherwise it will cause visual discomfort such as glare.In addition,the same cell coverage rate but different cell width will also affect the daylighting effect.If the cell is too wide,it will cause shadows indoors.Otherwise,it will reduce the efficiency of the module and increase the difficulty and cost of the cutting process.Therefore,it is very important to optimize the cell coverage rate and cell width.In this paper,with the goal of optimal daylight performance,theoretical and experimental researches on the cell width and cell coverage of crystalline silicon STPV windows are carried out.First,based on the illuminance value and Daylight Glare Probability(DGP),the daylighting performance of the STPV windows and ordinary hollow windows are compared through experiments.The experimental results show that compared with ordinary hollow windows,the STPV windows can control the illuminance value at a reasonable level.At the same time,it reduces the DGP and improves the quality of indoor daylighting.Therefore,the use of daylighti ng by the STPV windows is better than that of ordinary hollow windows.Secondly,traditional simulation methods cannot perform dynamic daylighting simulations on semi-transparent photovoltaic windows with the same cell coverage and different cell width.Therefore,this pa per proposes a new method for classifying daylighting simulation,which is to simulate the photovoltaic cell and the transparent glass gap separately,and from the illuminance and DGP using experimental data to verify the accuracy of the method.The results show that,compared with tra ditional simulation methods,the new classification simulation m ethod proposed in this paper has higher accuracy in daylighting simulation,and can reduce the error of illumi nance value by 20% and the error of DGP by 8%.Then,a physical model of the experimental platform was established,and a new simulation method was used to simulate the daylighting characteristics of four STPV windows with the same cell coverage rate and cell widths of 1.0mm,2.5mm,5.0mm and 7.5mm,and using Daylighting Glare Index(DGI),DGP,Daylighting Autonomy(DA)and Useful Daylighting Illuminance(UDI)for comparative analysis.The results show that when the cell coverage is the same,the smaller the cell width,the smaller the DGI and the improved visual comfort.As the cell width increases,the indoor average total DA gradually decreases.Compared with the 7.5mm cell width,the STPV window with a cell width of 2.5mm can increase the proportion of imperceptible glare(DGI<18)by 7%.When the cell width is reduced from 2.5mm to1.0mm.the DGI changes very little.Considering the influence of the cell width on the daylighting quality and the difficulty and cost of the cell cutting process,th e optimal cell width can be determined as 2.5mm.Finally,five types of STPV windows with a cell width of 2.5mm and a cell coverage rate of 20%,30%,40%,50% and 60% were used in different climate region of light such as Lhasa,Xining,Beijing,Changsha and Chongqing.A dynamic daylighting simulation was carried out and the three daylighting indicators of Spatial Daylight Autonomy(s DA),Annual Sunlight Exposure(ASE)and DGP were used for comparative analysis.The results show that the optimal cell coverage decreases with the decrease of the annual average total illuminance value of daylighting.Taking the daylighting characteristics of STPV windows as the optimization goal,the best cell coverage rates for Lhasa,Xining,Beijing,Changsha and Chongqing are 50%,50%,50%,40% and 30%,respectively.