On the ground, solar power has its limitations. Solar cells are not especially efficient. It rains. The sun disappears at night. A space-based solar panel can generate five times the energy of a similar panel on Earth by circumventing both weather and hours lost to darkness. A 2007 study by the National Space Society estimates that a half-mile-wide band of photovoltaics in geosynchronous orbit with Earth could generate the energy equivalent of all the oil remaining on the planet over the course of one year. Though costly, launching working solar satellites is possible today. It’s transmitting the captured energy to Earth that presents a challenge—one that scientists are just starting to work on.