Environmental Engineering Reference
In-Depth Information
Table 10.12 Energy storage system performance goals (US DOE)
Characteristic
Unit
Power assist
Dual mode
Pulse discharge power
kW
25 (18 s)
45 (12 s)
Peak regenerative pulse
power
kW
30 (2 s) min
50 Wh over
10 s
35 (10 s) 97 Wh/pulse
Total available energy
kWh
0.3 at
C
/1
1.5 at 6 kW constant power
Min. round trip energy
efficiency
%
90
88
Cold cranking power at
kW
5
5
30
C(3
2 s pulses
with 10 s rest
intervals each)
Cycle life for specified SOC
increments
#
300 k (7.5
MWh total)
3,750 (22.5 MWh total)
Calendar life
years
15
15
Maximum weight
kg
40
100
Maximum volume
L
32
75 (
<
165 mm height)
Operating voltage limits
(max current
limited to 217 A at any
power level)
V
dc
Max
<
440;
Max
<
440; min
>
0.5 V
mx
min
>
0.55 V
mx
Max allowable self-discharge
rate
Wh/day
50
50
Temperature range:
Operating
C
30 to
þ
52
30 to
þ
52
Survival
46 to
þ
66
46 to
þ
66
advanced batteries for hybrid propulsion must have
P
/
E
>
25 versus only 2-3 for
EV propulsion. The objective is a low cost, high power/energy storage system for
power assist and dual mode hybrids in 2008 and beyond. In their usage, power
assist would be defined as a low storage requirement vehicle that does not have
electric-only range. Dual mode, on the other hand, requires that the battery supply a
large fraction of the power and energy needs. In both cases the ESS life is greater
than 15 years. The goals for ESS for power assist and dual mode are summarized in
Table 10.12.
Characterization tests for the parameters listed in Table 10.12 are standardized
evaluations of static capacity, pulse power, available energy, self-discharge, cold
cranking, thermal performance, energy efficiency and electrochemical impedance
spectroscopy (EIS). EIS will be described in a later section. Impedance modelling
can also be found in Reference 34.
10.6.2 Fuel cell model
The proton exchange membrane (PEM) fuel cell is composed of four basic ele-
ments: the membrane electrode assembly (two each), bipolar plates and the end
plates. The basic construction and repeat units are illustrated in Figure 10.47. It is
