Environmental Engineering Reference
In-Depth Information
(c) Calculate the total package volume of this EESU if the packing factor
PF
¼
69%.
(d) Using the volume calculated in (c) and given that the effective package
density, including electronics is
r
EESU
¼
6.2, calculate the total package
mass.
Solution:
(a)
Let the total number of individual cells be
N
c
. Then
t
¼
ð
8
:
854
10
12
Þð
18
:
543
10
3
Þð
5
:
806
10
5
e
0
KA
Þ
C
cell
¼
9
:
732
10
6
¼
0
:
9795
m
F
C
tot
C
cell
¼
30
:
693
0
:
9795
10
6
¼
31
:
335
10
6
N
c
¼
(b)
The electric field in each cell for the stated dimensions is
U
mx
t
¼
9
:
732
10
6
¼
3
:
596
10
8
; r
3
:
596 MV
3,500
E
¼
cm
(c)
Given that the aluminium flash coating on each dielectric slab of thick-
ness,
t
,is1
m
m:
Vol
cell
¼
A
ð
t
þ
1
m
m
Þ¼ð
5
:
806
10
5
Þð
10
:
732
10
6
Þ
¼
62
:
31
10
11
31
:
335
10
6
ð
62
:
31
10
11
N
c
Vol
cell
P
f
Þ
Vol
EESU
¼
¼
0
:
69
0
:
01953 m
3
0
:
69
¼
0
:
0283 m
3
¼
This means a 28.3 L EESU package volume to store 52.22 kWh.
(d)
The package mass of the EESU is therefore
M
EESU
¼
r
EESU
Vol
EESU
¼
4
:
06
ð
28
:
3
Þ¼
114
:
9kg
This example serves to illustrate two important aspects of all ESS. First, it is
possible to realize very large energy storage by the combination of many smaller
cells. In the case of the EESU it required over 31M such cells all parallel con-
nected. Second, combinations of elementary cells are normally arranged into
modules and then modules are connected into packs. Reasonable packing factor for
cells in modules and packs is generally on the order of 70%.
