Review of a number of patented thermoelectric refrigerator designs, a photovoltaic-direct/indirect
thermoelectric cooling system, and research studies from the literature are described in the following section. A simple
design was proposed by Beitner (1978) consisting of thermoelectric modules directly powered by an external DC
source and an external thermal sink to dissipate heat to ambient by using natural convection cooling. Reed and Hatcher
(1982) proposed an effective way to enhance the heat dissipation at the hot end of thermoelectric modules by using
the cooling fan. Park (1996) introduced a new design of thermoelectric refrigerator by combining the benefits of super
insulation materials and phase change materials to impart an environmentally benign system that was energy efficient
and could maintain relatively uniform temperature for the extended periods of time with relatively low electrical power
requirements.Gillery and Tex (1999) proposed the design of a thermoelectric refrigerator by employing
evaporating/condensing heat exchanger to improve heat dissipation at hot end of thermoelectric modules. Guo et al.
(2002) proposed a new approach to dissipate heat by using heat pipes for heat conducting and dispersing. In the design
a multi bundle of the heat pipe conducting plates was installed at the cold end of the thermoelectric devices and the
other heat pipe was installed at the hot end of the thermoelectric cooling member with the fin plates or the fin
strips.Riffat et al. (2001) experimentally evaluated two thermoelectric refrigeration systems comprising a 67 litre
cabinet and six thermoelectric modules (type PT-12-40). The special features of this design are: "heat-pipe embedded
fin" heat sink units mounted on the hot side of the thermoelectric modules and an encapsulated phase change material
used as cold heat sink in the prototypes. A mixture of sodium sulphate, potassium chloride and ammonium chloride
with additives to prevent super-cooling was utilized in an encapsulated PCM with a transition temperature point of 7
°C. The experimental results showed that utilization of an encapsulated phase change material was found to improve
the COP of the thermoelectric refrigeration system and a heat pipe-embedded fin could highly transfer the heat from
the hot end of TEM with thermal resistance of 0.012 °C/W and heat capacity of 150 W at vertical position.Omer et al.
(2001) improved the performance of thermoelectric refrigerator of Riffatet al (2001) by integrating a thermal diode
(vertical heat pipe) between the encapsulated phase change material (PCM) and the cold side of thermoelectric
modules. The experimental results showed that the COP of the system could be improved by utilization of PCM at the
cold side of thermoelectric modules and the thermal diodes was also feasible to prevent heat leakage to the PCM in
the event of the power being turned off. Guler and Ahiska (2002) experimentally tested a portable thermoelectric
medical cooling kit consisting of thermoelectric module, cooling fan, and fin. In addition, Microcontrollers LM 35DZ
and 89LV52 were employed in this system for temperature sensor and temperature controller, respectively.