Solar Sunflowers, an art installation, greets visitors to Mueller's commercial and retail hub off of Interstate 35. The panels power a nightly light display and return power to the grid. When the development is complete, five miles of granite trails will connect the residents to its commercial and retail hubs. Julia Robinson for NPR hide caption

itoggle caption Julia Robinson for NPR

A woman in Senegal charges her cellphone using a port in her solar-powered LED lantern. Bruno Déméocq/Courtesy of Lighting Africa hide caption

itoggle caption Bruno Déméocq/Courtesy of Lighting Africa

Scientists say energy-saving compact fluorescent (left) or light-emitting diode (right) light bulbs can have unsavory health effects. PRNewsFoto/OSRAM SYLVANIA hide caption

itoggle caption PRNewsFoto/OSRAM SYLVANIA