Economist: Q-CELLS, based in Wolfen, just north of Leipzig, is the world’s biggest maker of the photovoltaic cells used in solar panels. It overtook Sharp of Japan last year and announced big jumps in sales (up 59%) and profits (up 69%) on March 27th. Germany, which is not known for being sunny, seems an unusual place to find this industry leader. But the country leads the world in its installed capacity of renewable energy sources (see chart), and is the third-biggest producer of solar panels, after …