Anyone who has ever had a cell phone or flashlight die at exactly the wrong time knows that batteries can be tricky things. We love them because they provide us with guilt-free, relatively inexpensive power—but we don't trust them. And that gives you pause when thinking about battery-run cars. We might love the idea of a clean source of energy, but no one wants to find themselves stuck on the highway at 3 a.m. when their electric car runs out of juice. But Joel Schindall believes he has the solution.
Schindall, an electronics professor at the Massachusetts Institute of Technology, is the associate director of the university's Laboratory for Electromagnetic & Electronic Systems. Researchers there have been working to enhance an energy storage device known as an ultra capacitor in hopes of making all-electric cars viable in the near future.
Ultra capacitors were developed in the 1960s and can currently be found in a wide variety of electronic devices. But they remain relatively expensive to manufacture, and have only recently become competitive in the commercial market. Although ultra capacitors have a long lifetime and are indifferent to temperature change, physical constraints have limited their energy storage until now.
If the MIT scientists are successful in using nanotube structures on ultra capacitors, their development would present the first commercial alternative to conventional batteries since they were invented over 200 years ago. With any luck we may see commercially viable, battery-powered Toyotas (TM) and Fords (F) on the road sooner than that.
Schindall recently spoke with BusinessWeek.com's Christina Pryor from his office in Cambridge, Mass. Edited excerpts of their conversation follow:
First of all, how do capacitors work? If you have two parallel plates that are close to each other and you connect one of them to a positive voltage and one of them to a negative voltage, an electric field forms between the plates that will store electrical energy. The way a capacitor is built today usually is to take two strips of aluminum, separated by what's called dielectric material, or paper, and wrap them up into a cylinder. It winds up looking somewhat like a battery.
If you study electronics, capacitors are one of the first things you learn about. You learn that they store energy but you also learn that they store very little energy compared to a battery, and so no one would really think of using them for a source of power.
An ultra capacitor is a capacitor covered with activated carbon. Is it more efficient than a standard battery? Well, not more than a standard battery yet, but it does hold much more energy than a standard capacitor. In fact, tens of thousands of times more. A super capacitor still holds only about 1/25th of the energy that a battery does. It holds it better in the sense that you can charge it hundreds of thousands of times, and you can't do that with a battery.
If you had a car that was powered by super capacitors instead of batteries—an electric car—you could recharge it in just a few seconds, as fast as you could put gas in your car, instead of the overnight charging that electric cars usually require. But it wouldn't go very far because the old electric cars [had to be recharged too often]. No one would put up with that. Who's going to have charging stations every two to three miles, and who's going to stop every two to three miles?
What makes your super capacitor different? We got interested in studying super capacitors because for hybrid cars, where you do have a gasoline engine and you're using the battery to supplement it, it's potentially quite useful. The advantage is it would last the life of the car, whereas the rechargeable batteries that they use in hybrid cars now, hopefully, are going to last around seven or eight years. But eventually they're going to fail and be expensive to replace. That's where the world was before we started doing our research.
The idea that we came up with is, there's a technique where you can grow nanotubes vertically out from the surface of a sheet of aluminum, almost like the way hair grows from your head, except that this is happening on a very tiny scale. It's almost like a sponge: It's just able to absorb a lot of these charged particles and, in principle, it could produce an ultra capacitor that stores as much charge as a battery does. In other words, a 25-fold improvement.
Now, if that's really successful, it has all the other advantages of a capacitor, meaning that it doesn't involve some of the more dangerous materials that are found in batteries, or wear out like batteries would.
You were quoted in the Boston Globe as saying that 10 years is the cost crossover point where capacitors could become as inexpensive as standard batteries. It could be faster than 10 years if people are optimistic enough to invest a lot of money in it. Ultra capacitors are just beginning to get mainstream, and part of the problem is they're more expensive than a regular battery is they're still a comparatively new product. So the people who would use them say, "Oh, I'll come back as soon as the price is lower,” and the people who build them say, "Well, if you don't buy more of them, I can't build them in large enough quantities to get the price lower.” That's classic with any new technology— frustrating to those of us who are in it but that's just the real world.
Looking to the future, do you think it's possible that some day technology will make all of our cars electric? In some way, you have to have stored energy inside an automobile to make it run. One form of stored energy is gasoline. Another is hydrogen—that's getting a lot of resources right now—and another is electrical energy storage, like a battery.
Part of why I'm willing to take the time to promote this is because I think it deserves more attention on the national level. I think the electric car with the improved nanotube-enhanced ultra capacitor, whether our research leads to it or some other lab does, deserves some intensity of effort because the payoff is relatively fast.
Right now there's a little bit of a shadow over electric vehicles because people think, “Well, they tried that five years ago in California and failed.” I'm saying that perhaps what to me is the main reason it failed could actually be overcome with an improved battery, such as this capacitor battery.
Many drivers will of course be skeptical that a battery-powered car may be more environmentally responsible and still provide driving performance. Do you ever think that a battery-powered car can be as fun to drive as a one with a gas-burning engine? Yes I do. You know there's some history with ED1 in California, and the French have also introduced electric cars. There are battery-powered cars that will accelerate from 0 to 60 miles per hour in something like 3.6 seconds.
You are always trying to strike a balance between power and economy just like in a regular-powered car. An electric motor has a lot of torque and you generally don't have a gear shift involved. They can accelerate quickly and the radio, air conditioning, and styling can be just as sophisticated as today's gasoline-powered cars.
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