Environmental Engineering Reference
In-Depth Information
production cells), the 36 s time line crosses right through these VHP cells and also
the very limits of NiMH. Ultra-capacitors lie midway between batteries and the
aluminium electrolytic film and ceramic capacitors (~36
m
s). The Evans Capacitor is
a novel hybrid of tantalum with carbon ultra-cap and is used primarily in pulsed radar
applications.
Example 3:
Clarify what is meant by the United States Advanced Battery Con-
sortium (USABC) goal for high power, lower energy, energy storage system
(LEESS) for power assist hybrid electric vehicles - specifically, the terminology
'Energy over which pulse power goals simultaneously met'. The scenario is this:
Discharge at 20 kW for 10 s (therefore, 20 kW
10 s
!
56 Wh)
●
Charge at 30 kW for 10 s (therefore, 30 kW
10 s
!
83 Wh)
●
Specify the energy window for vehicle use:
E
use
¼
165 Wh
●
Discharge pulse = 56 Wh
Charge pulse = 83 Wh
Energy to meet both power goals
26 Wh
Vehicle energy window = 165Wh
Chg: 56 Wh + 26 Wh = 82 Wh
Dchg: 83 Wh + 26 Wh = 109 Wh
Therefore, the ESS must supply 26 Wh of energy in order to meet a vehicle
energy window of 165 Wh. The following graphic will help clarify this in terms of
hybrid vehicle regeneration and boosting events.
Cumulative energy
(Wh) to Vehicle
Boosting
Time (s)
In use energy window
Regen
10.2.2 Asymmetrical ultra-capacitors
A variant of symmetrical, carbon-carbon electrode ultra-capacitors is the asym-
metrical carbon-nickel super-capacitor. Presently considered for engine cranking
