Study On Several Major Issues In Calendering Of Photovoltaic Glass

Photovoltaic glass is an important component of solar cell module,and its quality has an important impact on the performance of solar cell module.Unlike ordinary glass,photovoltaic glass requires high transmittance,low reflectivity,low absorptivity and mildew resistance.It has almost strict requirements on bubbles,stones,patterns,etc.in order to maximize the photovoltaic conversion efficiency of solar cells.Roller calendering is the main method to produce solar photovoltaic glass.Glass calendering belongs to the problem of melt flow and heat transfer with free moving boundary,non-Newtonian and non-isothermal.The forming process is complex.It needs to take into account the factors of material,process,die structure,product performance and so on.The yield of good products in production is very low.It is very important to study and optimize the calendering process of photovoltaic glass for obtaining high quality photovoltaic glass products.In this paper,the key technologies of photovoltaic glass calendering are studied by numerical simulation and experimental testing.The main research results include:(1)The deformation and heat transfer process of photovoltaic glass during calendering are analyzed in detail,and the mathematical model of product forming and temperature field calculation is established.(2)Through the material calculation and experimental test,the viscosity model of the material is determined.With the MSC.Marc software,the modeling process is simulated by reasonable physical model construction and boundary/initial conditions.The distribution of rolling force,temperature field,stress/strain and plate shape change of photovoltaic glass calendering was calculated.(3)The mechanism and model of glass crystallization were studied.Based on the Yuman crystallization model,the corresponding code program was programmed by the secondary development function of MSC.Marc software program to simulate the crystallization behavior of glass.At the same time,the crystallization behavior of photovoltaic glass was experimentally studied,and the simulation results were compared and verified.Thetemperature range of photovoltaic glass crystallization(805 °C~955 °C)was determined.(4)The effects of different pressing rates,melt thickness and initial temperature,calendering speed and temperature on the calendering force and temperature field of glass melt were studied.It was found that the effect of compressive pressure and thickness on rolling force was obvious.The greater the reduction ratio and melt thickness,the greater the rolling force.The calender roll speed and the melt initial temperature have a significant effect on the thickness temperature difference.The higher the calender roll speed and the initial melt temperature,the greater the temperature difference in the thickness direction.At the same time,the actual production measurement of the rolling force and temperature data was carried out,and the simulation and error analysis were compared with the simulation results.