Circa 1971, that was the era when radio receivers built around vaccum tubes were not yet phased out. As a kid, I used to watch my dad assemble those bulky contraptions in his lab at home, and used to wonder at one cylindrical shining component on the chassis that stood out tall compared to others. As I later learned, that was the electrolytic capacitor used to filter out AC ripples from the output of Full Wave Rectifier circuit.
Over the years there have been improvements in the design of capacitors and they pack more Farads in smaller size. But nothing parallels the recent introduction of Ultracapacitors.
Ultracapacitors are formed by increasing the effective surface area of the electrodes and by reducing the distance between the electrode and the electrolyte to molecular scale. Both these factors contribute to magnify the Capacitance by several orders of magnitude.
The concept seems very simple, but the feat has been achieved by synthesizing new materials for the electrodes, such as Graphene, that have ultra-large surface area and high electrical conductivity. The separation between the electrode and eletrolyte is reduced by the insertion of nanometer scale layer of materials, such as Barium Strontium Titanate.
For the purpose of comparison, the shining tall capacitor on my dad’s contraption had a capacitance of mere 32 microFarads. However an ultracapacitor of the same size could pack a capacitance of the order of 5000 Farads, or more.
Compared to electrochemical batteries, ultracapacitors pack more power for the same weight and can be charged in seconds instead of hours. They also have longer life and can survive more extreme temperatures. As a result, they have been found to be superior in several applications where electrochemical batteries have ruled supreme in the past.
Ultracapacitors are ideal for applications that require sudden bursts of energy and fast charge cycles, such as, hybrid electric and fuel-cell vehicles, fork lifts carrying heavy load from one place to another, electric flashlight of a camera, electric tools, such as portable drill machine, Energy Harvesters that store electrical energy converted from mechanical movement or vibration, UPSs that smoothen out power fluctuations in the Smart Grid of an electric utility, solar energy converters, and several others.
Do not be surprised if sometime in the future, when on a long drive in your electric car, you will be prompted to charge your car at the nearest fast charge station. Before you have finished your cup of coffee, your car will be fully charged and ready for next leg of your journey. Perhaps, a stack of ultracapacitors under the hood will make it all possible.