4. From cell to photovoltaic generator: modularity

Thanks to advances in the semiconductor industry, the unit size of PV cells has increased significantly since their inception. Initially round in the 1970s (diameter 57 mm in RTC-BPX 47 A modules), as shown in Figure 37a, they became square for better tiling of the occupied surface, dominated by typical sizes of 125 mm on a side until 2010. They have now evolved to standards around 157 mm square. With typical energy efficiencies of between 15 and 22%, the maximum unit power of a large crystalline silicon cell is therefore of the order of 5 W. What's more, the voltage V _p delivered by a cell is constrained by the gap energy E _g of the materials; silicon cells typically deliver 0.5 V at the point of maximum power. The result is a very low-voltage, low-power DC generator for most domestic and industrial...