Solar panels are an increasingly important source of renewable power that will play an essential role in fighting climate change. They are also complex pieces of technology that become big, bulky sheets of electronic waste at the end of their lives—and right now, most of the world doesn’t have a plan for dealing with that. But we’ll need to develop one soon, because the solar e-waste glut is coming. By 2050, the International Renewable Energy Agency projects that up to 78 million metric tons of solar panels will have reached the end of their life, and that the world will...