How does thermoelectric generator work

The Seebeck Effect produces an electric current when dissimilar metals are exposed to a variance in temperature. Seebeck effect applications are the foundation of thermoelectric generators TEGs or Seebeck generators which convert heat into energy. The voltage produced by TEGs or Seebeck generators is proportional to the temperature distance across between the two metal junctions.

Thermoelectric generators are solid-state heat engines made of pairs of p-type and n-type elements. The p-type elements are made of semiconductor materials doped such that the charge carriers are positive holes and Seebeck coefficient is positive. The n-type elements are made of semiconductor material doped such that the charge carriers are negative electrons and the Seebeck coefficient is negative. For every hole that migrates into the n-type element, an electron from the n-type element migrates into the p-type element.

Now, back to thermoelectrics! Strictly speaking, thermoelectric generators take a temperature difference and turn it into electrical power. Amazingly, these materials can also be run in reverse! If you put power into a thermoelectric generator you will create a temperature difference. Small mini-fridges, for just a few sodas, use thermoelectric generators to efficiently cool a few drinks.

To understand how thermoelectrics generate the electricity from a temperature difference we have to know a bit about how electrons move in a metal. Metals are good conductors because electrons can move freely within them, similar to a fluid in a pipe. Imagine you have a pipe full of water and you raise one end, what happens? The water will flow down the pipe from the high end to the low end.

This is because when you raised the pipe you increased the potential energy and the water wants to flow downhill. In a thermoelectric material the same thing happens to the fluid-like electrons when you heat it. Heating one end of a thermoelectric material causes the electrons to move away from the hot end toward the cold end.

When the electrons go from the hot side to the cold side this causes an electrical current, which the PowerPot harnesses to charge USB devices. The larger the temperature difference the more electrical current is produced and therefore more power generated. The tricky part about thermoelectric generators is that as you heat the hot side, the cold side of the generator heats up too.

In order to generate power with the a thermoelectric generator you need both a heat source and a way of dissipating heat in order to maintain a temperature difference across the thermoelectric materials.

This is done with no moving parts by heating water in the PowerPot. Water holds several times more heat than aluminum per pound, so it makes a wonderful heatsink. This is why you always need to have something watery in the PowerPot or else it is possible to overheat the thermoelectric generator. This rendering shows temperature distribution in the PowerPot during operation with some parts removed for clarity.

Thermoelectric power is the conversion of a temperature differential directly into electrical power. Thermoelectric power results primarily from two physical effects: the Seebeck effect , and Peltier effect.

The Seebeck effect is named after Thomas J. Seebeck, who first discovered the phenomenon in Seebeck noticed that when a loop comprised of two dissimilar materials was heated on one side, an electromagnetic field was created. He actually discovered the EM field directly with a compass!

He noted that the strength of the electromagnetic field, and therefore the voltage, is proportional to the temperature difference between the hot and cold sides of the material which creates a voltage difference. The magnitude of the Seebeck coefficient S varies with material and temperature of operation.