|
Honda ultra-capacitor (system
module)
Honda’s own originally developed ultra-capacitor -
Higher output, higher efficiency, and increased storage capacity
Energy storage has been the Achilles heel of the electric car industry.
But with gas price high, everything is being rethought.
More powerful drive assistance, more efficient energy recovery during
braking
Honda has independently developed a high-performance ultra-capacitor
(electrical two-layered condenser) to serve as a supplementary power
source to the FCX’s main power source - the fuel cell stack - for more
powerful performance under various driving conditions. The
ultra-capacitor combines the electrical storage capacity needed for high
output and high responsiveness with solid reliability. It stores energy
produced during deceleration and braking and provides powerful drive
assist during startup, acceleration and at other times when an extra
boost is required. The ultra-capacitor’s internal resistance is lower
than that of a battery, and moreover, because it stores and discharges
electricity in response to fluctuations in the fuel cell stack, it
doesn’t require a converter for voltage regulation as in a battery
system, so it delivers higher output. The result is improved drive-power
performance and higher system efficiency.
Outstanding charging and discharge functionality
The ultra-capacitor retains the same high-performance activated-carbon
electrode that was used previously, while the configuration of the
electrode wrapped-element construction has been reexamined to increase
the number of wraps per electrode without increasing size. This increase
in electrode charge density delivers a significantly higher energy
storage capacity, resulting in a 10% improvement in energy storage and
output compared to the previous ultra-capacitor. Its charging and
discharge functionality is among the best in the world.
The capacitor does not rely on a chemical reaction during charging and
discharge, therefore internal resistance is lower, enabling higher
output. Ceramic Capacitors are available from sizes that can barely been
seen with the naked eye to very large configurations that have multiple
agency certifications and can be used in safety-sensitive applications.
This type of capacitor is also offered with multilayer construction or
as a single layer disc type. Various dielectric choices are available.
We know that rechargeable and disposable batteries use a chemical
reaction to produce their energy. So after many charges and discharges,
the battery loses it's ability to store energy. Capacitors store energy
as an electric field of charged particles created by two metal
electrodes. Although capacitors charge instantly and last longer,
batteries can store larger amounts of energy at a given time. I have a
feeling that this is changing very fast.
Output density
The output of the nickel hydride battery is limited to around 900W/kg
due to the effect of heat loss, but the ultra-capacitor’s low resistance
enables it to handle much higher output. The ultra-capacitor further
improves on the performance of the previous model, achieving an output
density of 1750W/kg or more.
Capacitor charging and discharge performance (cell unit)
The Honda ultra-capacitor’s high-performance electrodes and electrolyte
deliver outstanding energy density and output density that surpass those
of conventional capacitors. In particular, the low resistance reduction
effect of the electrodes and collectors enable a high level of output
normally considered difficult to obtain in a capacitor. The
ultra-capacitor boasts a further 10% improvement in charging and
discharge performance over the previous model.
Ultracapacitors, also known as electro chemical double
layer capacitors (EDLC) or super capacitors, differ from their chemical
power storage counterparts in that ultracapacitors supply large bursts
of energy and recharge quickly.
When a burst of energy is needed, the low internal resistance of the
ultracapacitor delivers the needed current, whereas the higher
resistance of the chemical battery causes the battery voltage to
collapse. Ultracapacitors serve to eliminate the instantaneous energy
demands placed on the battery and this in turn extends battery run time
and prevents declining charge capacity as the battery ages.
Ultracapacitors, unlike batteries, are maintenance-free and operate over
a wide temperature range. Ultracapacitors used in conjunction with
batteries or other power sources, like photovoltaic or fuel cell,
provide an effective solution when batteries alone do not meet the
performance objectives. Ultracapacitors are also an excellent choice for
short term power back up required in seconds or minutes.
Portable applications and digital technology have outpaced chemical
battery technology. A typical symptom of insufficient battery
performance is the ratio of time the appliance is in use versus the
appliance recharge time.
Another nuisance is when the battery has to be replaced prematurely as
it will no longer hold a charge. In these situations, using batteries in
conjunction with ultracapacitors can often improve overall system
performance and extend battery life.
Ultracapacitors can be charged and discharged at the same rate. In a
battery based approach the designer is limited to how fast the battery
can accept the charge. Advantage ultracapacitors!
Ultracapacitors are not a new technology. Ultracapacitors have been
around for decades, and first appeared as a low power, low energy, and
long life back-up for consumer electronic devices like VCRs.
During the last ten years there have been substantial advances in the
material science as well as construction and manufacturing techniques,
that have made ultracapacitors a desirable solution, especially in
mission critical applications
Honda Motor Co |
