The ultracapacitor is a new way of storing electric energy that will eclipse chemical batteries in the near future. Instead of storing energy electrochemically, it stores it in an electric field. Ultracapacitors have multiple advantages over conventional batteries, including a lifetime of over 10 years, resistance to changes in temperature, shock, overcharging, and discharging efficiency. They require less maintenance than conventional batteries and are light on the environment when disposed because they lack toxic chemicals.
These futuristic batteries have been made since the 1960s, but only in the last decade have they become cost-effective for use in electricity-guzzling tools from the electric car to specialized computers. They are popular for "bridging" applications, in which backup power kicks in as primary systems fail, producing "zero-downtime" power schemes. Because they can't be overcharged, ultracapacitors are ideal for recouping power from things like braking. And they can be recharged in mere minutes. The only downside to ultracapacitors is that they need to be larger than batteries in order to share the same charge.
However, thanks to recent advances at MIT, this will soon change. The amount of charge that an ultracapacitor can hold, per unit weight, is proportional to its internal surface area. Most ultracapacitors use porous carbon to store charge. This carbon, however, is not perfectly porous on the atomic scale, where it has a more obviously chunky structure. Researchers have shown that by using networks of carbon nanotubes, which are only a few atoms wide but tens of thousands of atoms long, surface area-maximizing structures may be built that allow battery volume to be compressed as much as 25 times over. Nanotube-filled ultracapacitors have the potential to surpass conventional batteries in a variety of power-storage applications.
Ultracapacitors, if they become widespread, would signify the first serious departure from the conventional paradigm of electrochemical batteries since they were invented by Volta over 200 years ago.