A Flashlight of Fire and Ice

[Daniel Salião Ferreira] may or may not be a Game of Thrones fan, but he does have a fun demo of the Seebeck effect in the form of a flashlight …read more

Jun 6, 2025 - 07:50

[Daniel Salião Ferreira] may or may not be a Game of Thrones fan, but he does have a fun demo of the Seebeck effect in the form of a flashlight powered by fire and ice. The basic idea is to use a thermocouple, but — in this case — he uses a Peltier effect cooler.

The Peltier and Seebeck effects are two sides of the same coin: the Peltier effect creates heating and cooling when current flows through a thermoelectric material. In contrast, the Seebeck effect generates a voltage when there is a temperature gradient. While thermocouples do produce voltage this way, they usually have much lower power output and are useless as heat pumps.

Thermoelectric heat pumps — Peltier devices — use semiconductors, which allow them to reach higher temperature differences when used as a heat pump, and also perform better than a conventional metal thermocouple in reverse operation.

Generating power from waste heat is nothing new. Is it harder to do this with thermocouples? Yes. Yes, it is.