The lowly capacitor has recently made some inroads as a potential replacement for rechargeable electrochemical batteries. What's the potential? Oh..about 5 Volts1. EE Times has the scoop on a new Japanese venture ostensibly trying to commercialize the scheme. And some fracture English here from the inventor of what he calls a capacitor system.
Two things make this intriguing as a technology. One, the huge reduction in size providing a much better energy density, apparently comparable to lithium-ion batteries. Secondly, the speedy recharging makes it a convenient solution (remember this is only an energy storage vehicle).
The cost-driving kicker in the system's ultimate potential may lie in the usual suspect. The U.S. military is actively pursuing the "ultracapacitors" as a discharge medium to achieve a pulsed electromagnetic gun to shoot things out of the sky. A lightning bolt in a can, so to speak.
As a youngster, I distinctly remember being taught that high voltage 1-Farad capacitors could take up the size of a room. As with many of these technologies, child-like optimism for peaceful uses goes hand-in-hand with the art of weaponizing.