IEEE Circuits and Systems Magazine - Q3 2021 - 59

concentration. The values combinations of thermo-EMF
and electrical conductivity in a semiconductor showed
that semiconductor was a significant material to be applied
in TEGs with the efficiency up to 3-4% [9], [10]. Later
A.F. Ioffe wrote that he had predicted such a value already
in 1930. The carriers concentrations, at which the
maximum ZT was maintained, made up 5 1018 - 1 1019 cm−3
at the room temperature. Thus, thermoelectric materials
have to be degenerate semiconductor.
The first TEG prototypes developments were carried
out at the Physical-Technical
Institute in 1938-1940.
The project was supervised by Y.P. Maslakovets. Substances
PbS and Fe were selected as thermocouples
materials. During the time of World War II, TEGs with
electric output power of 12W were industrially fabricated
and provided a life cycle of 400 hours for military
purposes. Heating of TEGs, containing 74 thermocouples,
was carried out on an open campfire. Thus,
movable radio stations power supply was carried
out. Later p-arm of TEG thermocouple was fabricated
based on ZnSb that allows an increase the efficiency
up to 5%. In 1948, the first commercial TEG based on a
kerosene lamp to be used in distant Soviet settlements
was introduced, see Figure 3. Such generators were
widely applied to power household radio performers.
TEGs have a circular structure with a huge radiator
placed on a kerosene lamp glass. Fabricated thermoelements
were based on ZnSb and constantan alloy. The
first conference on thermoelectricity was held in the
USSR in 1955 where the TEG practical devices of that
period were demonstrated.
In his further works A.F. Ioffe and his colleagues established
the efficiency of applying solid solutions to fabricate
TEG thermocouples that enabled the increased
thermoelectric Q-factor ZT by means of reducing thermal
conductivity k and saving thermo-EMF a and electric
conductivity v of basic materials. The values ZT á 1
have been achieved at the room temperature. The results
have been summarized in [11], [12]. It is important
to note that long term efforts to further increase
the parameter ZT failed to change it significantly.
Nanostructured materials, for examples, with superlattices,
quantum wells and dots, quantum wires and
nanocomposites can be promising in increasing ZT
and efficiency that correlates with decreasing thermal
conductivity due to phonon scattering on nanoscale
inhomogeneities.
During the 1970s, research on thermal electricity was
conducted within the framework of aerospace projects
and included both developing TEG industrial manufacturing
and novel thermoelectric materials research.
Later the wide application of TEGs in industries and agriculture
started. Multiple Soviet companies developed
THIRD QUARTER 2021
TEG manufacturing of high power - from 150 W to 1.5 kW
for autonomous energy sources in oil and gas industries
in the Soviet North. Natural fuel has been used as a fuel,
e.g. natural gas. Figure 4 shows TEG GTG -200 manufactured
by Telgen company, Moscow, with the power of
220 W and output voltage 12 V, 24 V and 48 V. The dimensions
are as follows 640 × 550 × 500 mm.
One should note that there are TEGs that convert heat
accumulated as a result of radioactive decay into electric
energy, so called RITEGs. Such energy sources are widely
applied in autonomous radio relay communication
Figure 3. Household thermoelectric generator
kerosene lamp.
fixed on a
Figure 4. TEG GTG -200 manufactured by Telgen company.
IEEE CIRCUITS AND SYSTEMS MAGAZINE
59
IEEE Circuits and Systems Magazine - Q3 2021

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