ultracapacitor

What is an ultracapacitor?

Capacitors, which used to be known as “condensers” are devices that store energy electric charges and
release them when they are needed. They are very similar to batteries, except for one major difference:
batteries are good at storing energy, but not so good at
releasing power. Capacitors can release a lot of power at
once, but are poor at storing energy. Capacitors were first
developed in 1745 by a German inventor named Ewald Georg
von Kleist. They consist of two plates and a separator. The
plates are charged by a power source and, when the power is
needed, they can send out their entire charge almost
instantaneously.

Researchers at the University of Wisconsin have separated
capacitor development into the following categories:

Traditional electrolytic capacitors (first generation) work by
utilizing two conducting plates (usually made of metals that are
capable of being charged) and a thin film dielectric (insulating
material) as a separator. The amount of capacitance that can
be achieved is described in this simple equation:

The first ultracapacitors (also known as "supercapacitors") were probably developed in the late 1950s.;
These came to be known as an Electric Double Layer (or EDL)
capacitor (second generation). They had the ability to store
more energy than standard capacitors but still suffer (in terms
of energy) when compared to batteries. These devices also
employ two conducting plates and a separator. Both plates
have a certain geometric size (thickness and surface area).
However, they are usually made of a conducting carbon which
generally has a much greater surface area than a metal. When
one of the plates is charged, the ions, which compensate for
the charge on the carbon, are stored in the electrical double
layer near the surface of the pores of the carbon. This distance
is on the order of angstroms. Therefore, distance goes way
down in the formula and capacitance goes way up. Now both
pieces of carbon are effectively each capacitors as one is
storing charge with cations and the other with anions.

Pseudocapacitors (third generation) work by EDL means but
also take advantage of oxidation/reduction reactions at an interface. These oxidation reduction reactions are
like those of batteries. Most pseudocapacitors have been constructed of two transition metal oxides such as
RuOx, NiOx, etc. (the "x" here is meant to imply that the system can be either oxidized or reduces). These
oxides are conductive.

The UW / SolRayo / Enable IPC ultracapacitor is a fourth generation system, combining EDL and an
insulating oxide on top of the carbon. We have some EDL capacity developed because of the porous carbon
supports as well as the potential that is developed on the insulating oxide. The difference here is that most of
our charge is stored by the insulating film of nanoparticulate insulating oxides. Here the charge on the oxide
is developed by a potential determining ion, such as the proton.

Ultracapacitor Products

There are three basic market areas where ultracapacitors are used: consumer electronics, industrial
applications and transportation.

Consumer electronics

Applications in the consumer electronics area include VCRs, CD players, electronic toys, security systems,
computers, scanners, smoke detectors, microwaves, coffee makers, power tools and memory backup.
Several companies are targeting future applications, including laptop and desktop computers (awakening
from sleep mode) and cell phones with added features could require the use of ultracapacitors.

Industrial

Applications in this area include power supplies, industrial automation equipment, power transmission and
distribution and wind turbines.

Transportation

Applications in transportation include hybrid automobiles, aircraft door actuators and rail systems.

Will ultracapacitors replace batteries?

Batteries utilize a chemical reaction to create power. Ultracapacitors do not do this; they simply store
electricity and have the ability to charge and discharge very quickly. In many applications, where charging can
come from another source, they possibly could replace batteries. But they would not replace batteries where
the power generation is required.

(Most of the information above comes from researchers at the University of Wisconsin, in particular Dr. Marc Anderson and
Kevin Leonard).