Solar-powered streetlights and parking meters are not hard to find, nor are photovoltaic panels that deliver energy to houses and factories. These advances beg a big question: Will we ever be able to use the sun to power our ubiquitous smartphones and other mobile gadgets instead of plugging them into the grid every night?
The answer depends not only on efficiency gains in photovoltaic cell technology but also on where those cells are placed on our devices and where we store them—many of us keep our smartphones stuffed in a pocket or handbag for much of the day, out of reach of the sun’s energy.
To be sure, there has been some progress. At the World Mobile Congress in Barcelona this year, Japanese cell phone maker Kyocera Corp. for the second year running showed off a prototype of a 12.7-centimeter solar-powered phone. The so-far nameless device allows for a minute of talk time for every three minutes of sunlight—a big improvement over the company’s 2015 predecessor, which offered only 15 minutes for every two hours of solar charging.
To develop the phone Kyocera worked with France-based Sunpartner Technologies, which produces translucent film impregnated with photovoltaic cells. Being see-through, the film can be installed between the LCD display and the touch screen so that the phone can charge more easily while in use. Most previous efforts at solar-powered phones had the cells on the back, meaning that the device had to be facedown to get a charge and that the cells, being external, could more easily be damaged.