Global Power Technologies
1120 - Class I, Division 2, Group D, T3
(i)
Flammable volatile liquids, flammable gases or vapours are handled, processed,
or used, but in which the liquids, gases, or vapours are normally confined within
closed containers or closed systems from which they can escape only as a result
of accidental rupture or breakdown of the containers or systems or the abnormal
operation of the equipment by which the liquids or gases are handled, processed,
or used or;
(ii)
Hazardous concentration of gases or vapours are normally prevented by positive
mechanical ventilation, but which may become hazardous as the result of failure
or abnormal operation of the ventilation equipment or;
(iii)
The location is adjacent to a Class I, Division 1 location, from which a hazardous
concentration of gases or vapours could be communicated, unless such commu-
nication is prevented by adequate positive pressure ventilation from a source of
clean air, and effective safeguards against ventilation failure are provided.
c)
Group D includes propane, methane, butane.
NOTE: Throughout this manual the words Generator, Thermoelectric Generator, TEG and
Generator System will be used interchangeably.
1 .3 Theory of Operation
A TEG produces electrical power through
the direct conversion of heat energy into
electrical energy. It operates on the same
principle as the thermocouples that are
used for measuring temperatures and in
safety shutoff controls for gas water heat-
ers, home furnaces, etc.. However, the
TEG utilizes semiconducting thermoelec-
tric materials that are much more efficient
and thus permit practical thermoelectric
power sources. A thermocouple consists
of two dissimilar materials (usually in wire
form) which are joined together at one
end. If this junction is heated to a higher
temperature than the other end of the wire,
a voltage will exist across the cooler end.
Further, electrical power will be delivered to
a load placed in the circuit. This process will continue provided that the temperature difference
is maintained. A TEG is a system which provides the means to maintain these required con-
ditions.
Figure 1 illustrates how this is accomplished in the model 1120 TEG. A thermocouple is formed
by a P type and an N type thermoelectric element joined together electrically by a hot junction
electrode. Adjacent thermocouples are joined together electrically by cold junction electrodes.
Eighty thermocouples, each producing 84mV are connected in series so the power unit produc-
es 120 Watts at 6.7 Volts and 18 Amperes.
Figure1
TEG Design
3