Batteries can't be beat for compact energy storage. Their high energy density makes batteries the perfect choice for cordless electric devices. They do have their negatives, though: they're expensive, they use toxic chemicals, they require long charging times, and they have a limited number of charge-discharge cycles. Oh, and they occasionally start a fire. These limitations are the biggest obstacles to fully electric cars and they make off-grid renewable energy much more costly. I've always told my engineering students that if they're interested in chemistry, they should consider specializing in battery technology. I may be changing my tune on that, thanks to the newest generation of supercapacitors. 

Dr. Jim Zheng of Florida State University has developed a lithium supercapacitor that's the size of a deck of cards and has a capacitance of nearly 400 Farads @ 3.9V. (I did the math and it's a little less than the energy capacity of a rechargeable AA battery.) 

Currently supercaps are used mostly in applications where short bursts of energy are needed and the supercap can recharge quickly. In very low power applications they can replace rechargeable batteries. The new supercaps will cut even deeper into the battery market, working for low-to-medium power and longer duration applications. Don't sell your stock in Duracell just yet, but you might want to invest in supercap technology too.

Do you have a design that might use supercaps instead of batteries? Please tell us about it!

Happy Engineers Week!

^{Image courtesy of Florida State University Photography Services}