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If you own a smartphone or an Apple Watch, you’ve likely experienced the pain of constantly connecting your gear to a charger and configuring (i.e., crippling) your device to extend battery life. Imagine what life would be like if you never had to hunt down that charger and cable again. Clearly, devices that extract energy from the environment are the future.

In my search for ideas on how to tap ambient energy sources, I’ve been studying watch technology. For years, companies such as Seiko and Casio have offered watches that use solar cells to charge an internal capacitor which, in turn, powers miniature motors that move the hands. My inexpensive solar Seiko diver is good for about six months of operation after only a day in direct sunlight. More advanced solar watches feature monitoring of WWV broadcasts for automatic synchronization, as well as GPS satellite monitoring so that local time is always displayed. I’m not sure what percentage of the population actually needs a watch that automatically adjusts to the local time zone, but the underlying energy extraction and transformation technology is impressive.

In my exploration, I’ve also taken apart a few ATMOS clocks, which derive energy from minute changes in atmospheric pressure and temperature, and use that energy to wind a mainspring. Working models of the ATMOS from the ‘50s and ‘60s can be had for less than $400 on eBay.

Then, there’s the ubiquitous mechanical automatic watch from companies ranging from Timex to Rolex. Normal movement of the wearer’s arm causes an internal weight in the watch to rotate, winding the watch spring in the process. The old Timex models are worth studying, if only to see how simple an automatic movement can be made.

Seiko’s line of Kinetic watches use the rotating mechanism to charge a capacitor instead of winding a mainspring. Just as with solar powered watches, the capacitor is used for a power source when the system isn’t being charged. Seiko also offers a spring drive system in which the rotating mechanism both winds a mainspring and charges a capacitor. The capacitor powers a quartz system that replaces the traditional “tic-toc” hairspring mechanism with a smooth, linear, variable brake.

I’ve primarily focused on watches from Seiko and Casio because they are relatively inexpensive and technologically advanced. Companies developing smart watches such as Apple undoubtedly are performing teardowns of their own, with little thought to affordability. One day soon, I expect smart watches and perhaps cell phones will be charger free, extracting energy from a combination of solar, body motion, and perhaps atmospheric changes.  SV