Chemistry Reference
In-Depth Information
the hot and cold sides in the heat flow direction, in order to generate the
maximum electric power output and convert thermal energy into electricity
with a high eciency or COP at a reasonably low cost. There has been much
work on investigating the optimisation of thermoelectric devices. Most has
been focused on mathematical modelling for the optimisation of the ther-
mal resistance in power generation
87-89
and refrigeration.
90
Power gene-
ration can be improved compared with that of conventional thermoelectric
devices by modifying the shape of the thermoelectric material.
91,92
Some
research has been conducted on examining the cost of thermoelectric de-
vices because the energy conversion eciency and power generation of such
devices are not yet comparable with those of principal modern generators
such as Rankine cycle steam engines or Stirling engines. Yazawa and
Shakouri
93
suggested the possibility of commercializing thermoelectric
generators by investigating their cost-per-Watt optimisation. Significant
work has also been done to improve the cooling power of refrigeration ap-
plications. Meng et al.
94
suggested a new configuration for a thermoelectric
refrigerator assisted by a thermoelectric generator. The allocation of the
thermoelements in this two-stage combined thermoelectric device was op-
timized to give the highest COP given the number of thermoelements.
Astrain et al.
90
investigated the use of a thermal resistance network to op-
timize the performance of thermoelectric refrigerators. They optimized the
performance of heat dissipation of the thermosyphon system assisted by the
thermoelectric refrigerator by analytical calculations and experiments.
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6.5.4 Applications to Waste Heat Recovery
The energy source of thermoelectric generation is heat itself. Thermoelectric
devices can be installed in various exothermic systems such as heat engines
or catalytic converters in vehicles to recover waste heat and convert it to
electricity. Many people have recently become interested in waste heat re-
covery for automobiles using thermoelectric generators. The heat energy
wasted by hot exhaust gas from a vehicle amounts to 27.7% of the total
energy consumed,
95
and it is known that using exhaust energy from an
automobile engine with a heat exchanger results in fuel savings of up to
34%.
96
BMW and Ford are well-known commercial passenger vehicle com-
panies, and a thermoelectric generator built by Amerigon was attached to
the exhaust gas pipe in their vehicles and produced around 500 W of elec-
tricity from the waste heat.
97
Another interesting application of waste heat
recovery is the cooling of overheated water from a hot spring. Panasonic
developed a thermoelectric generator for use in hot water pipes, which
generated 2.5 W of electricity per 10 cm of pipe.
98
.
6.6 Summary
In this chapter, we have covered various topics in thermoelectrics such as
transport theory, schemes to enhance thermoelectric performance, material
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