THERMOELECTRIC POWERED
By John Iovine
For warm summer evenings, I thought it would be cool to have some pool
flowers floating around to create a nice ambience. To make it even cooler, I
wanted to use the sun to power them. I’ve always wanted to work with
thermoelectric effects, so I combined these two desires.
In 1821, Thomas Johann Seebeck discovered the
thermoelectric effect which is the generation of
electric current from heat. He discovered when a
junction of two dissimilar metals are heated
through a temperature gradient, the junction
produces a small but measurable electric current.
By twisting the ends of two dissimilar metal wires
to produce an elongated junction, one can create
a junction that produces a few millivolts.
Inversely, when a voltage is applied to this junction, it creates a temperature difference. This was discovered in
1834 by Jean Charles Peltier and is known as the Peltier
Effect. Together these combined effects are called the
Peltier–Seebeck effect and form the basis of thermo-electric generators (TEG) and thermo-electric cooling
(TEC).
Modern thermoelectric generators use PN junctions
manufactured from semi-conductor materials instead of
dissimilar metals (see Figure 1). However many
thermocouples still use dissimilar metals for their
construction.
There are a number of electronic companies that offer
surplus TEC modules (see Sources). Many TEC modules
■ FIGURE 2.
can be used as TEG modules, although a TEC pressed into
service as a TEG will have a lower efficiency than a TEG
module. However, a TEC still works well enough as a
demonstration model.
■ FIGURE 1.
28
August 2010
Building a Thermoelectric
Generator
To operate a generator, we need to heat one side of
the TEG while simultaneously cooling the opposite side.
This is achieved by securing two aluminum leg
extrusions spring-clamped to each side of the TEG
module. The aluminum legs transfer heat and cold from
the water baths to the module. One aluminum leg
extends down into a hot water bath and the other
