Research on hot spot risk of high wattage solar modules

With the rapid increase of solar module wattage from about 300 W to above 650 W, it is important to study the impact of high wattage on the hot spot risk. In this paper we use finite element analysis (FEA) and experiments to analyze the effects of various designs on the hot spot temperature of high wattage solar modules. Design factors include cell size (156.75 mm, 166 mm, 182 mm and 210 mm), the number of cells per bypass diode and cell shape (full cell, half cell and one-third cells). The simulation data is in good agreement with the experiment, and shows a clear trend: increasing the number of cells per bypass diode increases the hotspot temperature at most, increasing cell size leads to a moderate but considerate increase, and cutting a cell into smaller pieces lowers the hot spot temperature under certain conditions. The developed thermal balance model shows that the change in the power density and effective thermal resistance at the hotspot cells are the keys to the trend. This research proves the effectiveness of using finite element analysis (FEA) to study the hotspot risk, and points out a new direction for how to control the hotspot risk of high wattage solar modules with larger solar cells.