What with the number of phones set to outnumber humanity sometime this year, the question of how we're going to charge them all is pretty significant where the climate is concerned.
But while scientists still fruitlessly attempt to get their heads around that whole nuclear fusion conundrum, there are a few other ideas floating around.
Researchers at UT Arlington in the States have invented a new form of 'micro windmill', which could theoretically make it possible to charge your phone using the wind.
The tiny windmills (above) built by UT Arlington research associate Smitha Rao and engineering professor J.-C. Chiao are just 1.8mm at their widest point. That's small enough to put about 10 on a single grain of rice. And it might be possible to embed "hundreds" on the outside of a phone case.
Just waving the phone in the air could provide enough power to charge the phone's battery.
It sounds difficult to believe. But if we take a certain amount of this research at face value, it's an amazing concept:
"Rao’s designs blend origami concepts into conventional wafer-scale semiconductor device layouts so complex 3-D moveable mechanical structures can be self-assembled from two-dimensional metal pieces utilizing planar multilayer electroplating techniques that have been optimized by WinMEMS Technologies Co., the Taiwanese fabrication foundry that took an initial interest in Rao’s work."
WinMEMS now has exclusive rights to commercialising the tech, pointing out that a flat - or even solar - panel with thousands of the little blighters could be an incredible way to power homes in the future.