Ultracapacitors: Better than Batteries?
For more than 200 years, batteries have reigned supreme as the technology for storing electricity. But with recent innovations in design and manufacturing, another solution, as old as the battery, is competing for the leadership position.
Back in the 1700s, a Dutch scientist filled a glass jar with water and then covered it with foil to create the first capacitor. In recent years, capacitors have been considered an excellent solution for delivering a quick jolt of electricity needed for operating devices such as computers, cell phones, and televisions. What capacitors have not been known for is the capability to store large amounts of usable energy. That situation is changing.
The storage capability of a capacitor is determined by a variety of factors, including the surface area of its electrodes and the distance between the electrodes. With the recent development of the ultracapacitor, or double-layer capacitor, the surface area of the electrodes has dramatically increased, while the distance between the electrodes has significantly decreased. The result is a new class of high-power, high-energy solutions, chosen by the Society of Manufacturing Engineers as one of the five 2008 innovations having the potential to change manufacturing.
When compared to the traditional battery, the ultracapacitor offers many advantages. It is extremely efficient and compact. It can be charged and discharged rapidly for almost an unlimited number of times. It can operate in harsh environments, in temperatures from minus 50 C to 85 C. It has a long life, with no moving parts, and is virtually maintenance-free. And it’s environmentally safe. Unlike batteries, ultracapacitors do not have hazardous substances that can be released into the environment.
With the introduction of automated manufacturing techniques, ultracapacitors are also becoming a cost-effective choice. Products are available for pennies per farad (the measure of a capacitor’s storage potential). And the price continues to decrease.
As a result of their increased capability and diminishing cost, ultracapacitors have replaced or are being considered to replace batteries in a variety of applications, including industrial lasers, medical equipment, and power electronics.
The Honda FCX hybrid fuel cell vehicle has ultracapacitors that have, according to Honda, given the vehicle a competitive edge in energy efficiency and throttle responsiveness. Ultracapacitors are also being used in vehicles for public transportation around the world, from hybrid gasoline-electric buses in Long Beach, California, to electric buses, trucks, and cars in Russia. In China, electric buses with ultracapacitors operate without power lines. The buses are quickly recharged at each bus stop with electric umbrellas.
In addition, ultracapacitors are being used in bridge power applications to maintain power while backup is restored and to maintain power quality during surges and other disruptive events.
Advances in high-density, nanogate capacitor design and other technological innovations are also making ultracapacitors competitive with the lithium-ion batteries now used for cell phones, laptops, and other applications that require long-lasting, compact solutions.
