Super Capacitor 1.0F Aerogel from Tinkering Supplies
This PowerStore Aerogel "B" series 1.0F capacitor is just just what you need to keep your circuits running during power outages and battery changes or to build a "turbo" solar engine. Rated for 2.5v it can accept surges of 3v. It comes in a relatively small 8.5mm by 13.5mm radial package and has a low ESR of 0.4 ohm.