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BMW Active Hybrid: X3 EfficientDynamics |
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Page 6 of 6
Broadside Power: Copper Red Super Caps in the Side-Sills.
The Super Caps are within clear sight on the BMW Concept X3 EfficientDynamics,
with tubes glowing copper red integrated in transparent side-sills. This point
of installation ensures optimum results in terms of the car’s lateral and
vertical dynamics as well as the space available.
Together with the Active Transmission, the Super Caps represent the key elements
of the Concept Car. They are able to take up a very high level of electrical energy
within fractions of a second without any losses worth mentioning, delivering that
energy just as quickly and efficiently. So far Super Caps have been used above
all in wind power systems as maintenance-free energy storage units with an unlimited
service life.
The Super Caps featured in the X3 Concept Car measure approximately 50 millimetres
or not quite 2.0´´ in diameter and generate an overall capacity
of 190 kW.
Internal Resistance Reduced to a Minimum: Switching over from Charge to
Discharge without the Slightest Loss of Power.
The only disadvantage of Super Caps versus the electrochemical battery is their
far lower energy density. However, even this drawback is of only theoretical significance,
since the energy density offered by an electrochemical battery today is generally
used only to a very small extent on account of the battery’s service life:
An NiMH battery generates approximately 5 watt-hours per kilogram, as opposed
to roughly 4 watt-hours/kg in the case of a Super Cap.
Another factor is that batteries have a high level of interior resistance dramatically
increasing even further as they are discharged. A high level of interior resistance,
however, means substantial loss of energy when charging, with a lot of the energy
regained through application of the brakes thus being lost and the charge process
lasting longer.
The interior resistance of a Super Cap, by contrast, is virtually zero, regardless
of the current charge level. In practice this means that the cycle from charging
to discharging and back again may be repeated as often as required within a very
short time, Super Caps thus offering all the requirements for use in stop-and-go
traffic, as already described.
The overall capacity of the Super Caps of 190 kW is quite sufficient also for
a car driven very fast and dynamically. And at the same time the driver is able
to drive the car under electric power alone, for example when parking or manoeuvring,
Super Caps again providing adequate energy.
BMW Hybrid Cars: Fifteen Years of Research and Development.
The BMW Group has been working on hybrid drive ever since the early ’90s.
In particular, BMW’s specialists have focused on the development of a disc-shaped
electric motor suitable for automotive use and now featured in the X3 Concept
Car.
In 1991 BMW moreover registered an “Electric Transmission” for patenting
and even built various prototypes. Given the high weight of the batteries and
electrical drive components, the system was however not able to meet the great
demands made by BMW of a automotive concept suitable for the market and
regular use.
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