Sometimes batteries suck. They are expensive, can be dangerous and tricky to handle. And it takes often too long, to load them again.
Think of an experimental board with an Atmel 328 microprocessor (the one that powers Arduino UNO) that should run for an hour or so to do some experiments, like in a classroom for instance. Imagine the teacher having to handle 30 different Lipo-Batteries that have to be charged in advance of the lesson. You get my point.
So there are these fabulous Super-Caps, that are available for not so long. Instead of dealing with micro and nano-Farads, these suddenly are carrying “FARADS”, no nano or micro! You can get an 15 FARAD surface mountable thing at digikey easily.
Of course, compared to real batteries this still is not a lot, but you can actually run something for quite some time from this capacitance. So i just gave it a try. Below you see my custom 328 circuit which runs two LEDs and has no power-saving modes activated whatsoever. Which means, it consumes about 6mA when LEDs are off, and roughly 12mA when they are turned on. I attached a 2.7v 5F SuperCap, which was able to run this guy for 7:30minutes. This translates roughly into 1mAh power, so this device could run a circuit which consumes 1mA for one hour. But of course energy consumption of the 328 could be drastically lower if energy saving modes would be activated when LEDs are off. If you take the 4micro-amp measured here you could run that device for 10 days with that SuperCap.
But for one hour of teaching a 15F Cap combined with a slightly less hungry circuit could be sufficient. And if not – it take just 30seconds to charge the cap from a 3v source again.
Another field where this could be of significant relevance is wearables of course.