Popular Science has just gotten a scoop that I've been waiting for ages to see. Ultracapacitors, which are completely shunned by most auto companies, have been quietly continuing development at small companies and in universities all over the world. The reason they've been so largely ignored is that they hold so much less energy than batteries. The best commercially available ultracaps have about 5% of the energy density of batteries.
Yet they also have tremendous advantages. You can charge them all the way up and all the way down without damaging them (lithium ion batteries stop functioning when charged all the way down.) They contain no chemical reagents and so are thermally stable under all conditions. And they can charge and discharge much faster than batteries.
Popular Science was recently able to visit a lab at MIT working on advanced vehicle technologies. One of these technologies is a nano-tube ultracapacitor that could potentially hold half the charge of a lithium ion battery. And while this alone doesn't sound all that exciting, it's a lot cooler when you realize that most batteries in hybrid cars hardly ever use more than 20% of their charge in order to extend the batteries life.
That's right, 80% of the battery just sits there and never discharges. Ultracapacitors could discharge completely, over and over again, and never need to be replaced.
Unfortunately, after two years of work, the nano-tube capacitors still haven't hit their theoretical capacity. And while it might not take long for them to make capacitors that have competitive energy levels, it will certainly take years, if not decades, to scale the technology up to industrial level.
written by James Jackson, April 05, 2008
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