MIT, light of my life, fire of my brains. My sin, my soul. Em-eye-tee: the tip of the tongue taking a trip of three steps down the palate to tap, at three, on the teeth. Em. Eye. Tee. Or so might russian writer Vladimir Nabokov say if he had as much interest in electric cars as we do. Why? The Lab for Electromagnetic and Electronic Systems (LEES) at the Massachusetts Institute of Technology (MIT) is getting close to a big breakthrough in capacitor technology.
Currently, ultracapacitors can only hold a small fraction of the electrical charge that batteries can hold (about 5%), but they do have many very important advantages over their chemical cousins, such as no battery memory caused by partial discharging, no reduction in capacity with each charge (they last almost forever), and much faster charge-discharge times. If only we could improve their capacity... Well, we're getting there. Read on!The way to increase ultracapacitor capacity is to increase surface area inside of them.
By replacing the porous activated carbon used in ultracapacitors with tightly bunched nanotubes, Schindall believed that the ion-collecting surface area could be increased by as much as five. Since current ultracapacitors can store around 5 percent of the energy in an equivalent-size battery, the addition of nanowires could bring this up to 25 percent. "And you can also operate [the ultracapacitor] at a higher voltage with the nanotubes, and that's about another factor of two in energy," he says. "We are hopeful—we haven't proven it—that we can get up somewhere between 25 and 50 percent of a battery's energy. At that point, it becomes a compelling device for many applications."
This would completely change the game, because batteries in hybrids and electric vehicles are never fully discharged to prolong their life. In fact, there's only about 15% that is used, so an ultracapacitor with 25-50% of battery capacity but no restrictions on full discharge could actually provide more power and a longer range!
They're not quite there yet. Theoretical capacity hasn't been reached in the lab, and even after that it will probably take a few years for enough nanotube-enhanced ultracapacitor to make their way to market, but this is extremely promising (not just for cars, but maybe also as a way to store clean energy from intermittent sources). Thank you MIT!
See also: ::The Economist on Ultracaps and Tribrids, ::EEStor Capacitors- "This could change everything", ::EEStor Ultra Capacitors: The Science Explained, ::Big News: EEStor Says Something, ::Technology Review on EEStor
Photo: Popular Mechanics