Environmental Engineering Reference
In-Depth Information
Table 10.11 Characteristics of the pyroelectric energy converters working under the pyroelectric
Ericsson cycle
Authors
Material
T
low
(
°
C)
T
high
(
°
C)
E
low
(MVm
−
1
)
E
high
(MVm
−
1
)
f
(Hz)
Electrical
output
ʷ
E
References
0.13 17 Wl
−
1
Olsen
et al.
PLZT
145
178
0.4
3.2
0.42
[
67
]
30 Wl
−
1
cycle
−
1
Olsen
et al.
P(VDF-TrFE)
73/27
23
67
22.5
53
/
/
[
81
]
0.12 10.7 Wl
−
1
Nquyen
et al.
P(VDF-TrFE)
60/40
70.5
85.3
20.2
74
0.053 [
62
]
110 Wl
−
1
Cha et al. P(VDF-TrFE)
56/44
40
100
20
50
1
/
[
80
]
More than 25 years after the work of Olsen and his coworkers, Nquyen et al.
[
62
] built a device similar to that of the Olsen group. In general, the design of the
device was almost identical to that of the Olsen group, with only small differences.
As the pyroelectric material the P(VDF-TrFE) 60/40 polymer was chosen, since it
possesses a low-temperature transition and has a very high dielectric strength. The
polymer
lms were attached to a rectangular supporting structure made of mica
plate and 38 of such pyroelectric elements were put on top of each other. Between
two individual pyroelectric elements Te
fl
on strips were inserted to create a void for
the
ow. To simulate the heat source an electrical heater was used. For the heat
sink a copper tube bent into a helical shape, through which water was
fl
uid
fl
owing, was
applied. A maximum power density of 10.7 W/L of the pyroelectric material was
obtained at a frequency of 0.12 Hz and an oscillating temperature between 70.5 and
85.2
fl
°
C of the working
fl
uid. The pyroelectric material was subjected to a low
eld of 20.2 MVm
−
1
eld of 73.9 MVm
−
1
.An
electric
and to a high electric
ef
ciency of 0.053 % was achieved.
In Table
10.11
, the main characteristics of the above-presented pyroelectric
energy converters working according to the pyroelectric Ericsson cycle are gath-
ered. However, it was only Olsen et al. [
67
] who provided the information about the
absolute power output, which amounted to 30 mW. This means that approximately
1,500 devices presented by Olsen and his coworkers would be needed to power one
50-W light bulb. Nevertheless, with new discoveries in material science and the
further development of the systems design, the performance of the devices could be
improved. Theoretical estimations of the performance of an ideal pyroelectric
energy converter indicate that the device
'
sef
ciency could come close to the Carnot
ef
ciency of a heat engine [
67
].
From the above results, it is obvious that so far research has only tried to prove
the concept of pyroelectric harvesting. For ef
cient pyroelectric energy conversion,
some of the main issues that should be considered in future research and devel-
opment are:
A large temperature span between the heat source and heat sink is required in
order to produce good thermodynamic ef
ciency from the power cycle. As a
result, this may require the layering of pyroelectric materials in the direction of
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