FREQUENTLY ASKED QUESTIONS.

Q:   What is the difference between a Peltier module and a thermoelectric generator (TEG) module?

            A:   They are different names for the same device.


Q:   What happens if the hot and cold sides of a TEG are reversed?

            A:   The polarity of the generated voltage will be reversed.


Q:   What is the relative importance of the heat source and heat sink.

            A:   They are of equal importance.


Q:   What is the difference between a module used for generation and a module used for heat pumping?

            A:   In principle, there is no difference.   Both are constructed from n-type and p-type thermoelectric elements connected in electrical series and disposed in thermal parallel between a heat source and a heat sink.   Every application for either generation or for heat pumping will present application specific challenges.


Q:   I need a thermoelectric module for a generation application.   Where do I start?

            A:   The starting point is always the electrical load requirement, that is, how much electrical power is needed, at what voltage and with what duty cycle.   This is followed by an analysis of the available heat source and heat sink.   What is the available ∆T?


Q: How does TEG module construction impact performance?

            A:   TEGs operate through the intercoupling of thermal and electrical currents in the active thermoelements.   There are actually two subsystems that must be accounted for in a design -- the thermal circuit and the electrical circuit.  Both subsystems are optimized through impedance matching.   For thermal impedance match, the ∆T across the TEG should match the ∆T across parasitic (non-productive) elements.   The TEGs designed by TXL Group have elements with high thermal resistance and a large length to area (L/A) ratio to increase module gradients when thermal energy flux is limited.


Q:   How important is heat sink grease.

            A:   Making a low thermal resistive contact to the heat source and heat sink is always important in thermoelectric applications regardless of whether they are for generation or for heat pumping.   Heat sink grease can be part of a low resistance solution.


Q:   How can I boost the voltage of a thermoelectric generator (TEG)?

            A:   For a given module, voltage can be increased by increasing the temperature difference across the module (that is, increasing the ∆T).  Alternatively, a voltage boost circuit can be used to convert low voltages from the TEG to a higher voltage.


Q:   How can I control the output of a TEG to maintain a set voltage?

            A:   There are three options.   First, if the electrical load is fixed then as long as the temperature across the module is held constant, the output voltage across the load will remain constant.  Second, between the TEG and the load, add a specialized electronic circuit called a regulator.   Third, use a voltage boost circuit to increase voltage from the TEG to a voltage that is higher than the desired output voltage and then use either a battery of the desired voltage or a Zener diode to clamp the output to the desired setpoint voltage.

© 2017 TXL Group, Inc.