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For a class of mine (specifically, a class on Micro-ElectroMechanical Systems, or MEMS), I'm doing a semester project on a "Thermo-Electric Generator (TEG) for Energy Scavenging." I'm most interested in Ubiquitous Computing applications for such a device, but I'm certain that there are many other possible application spaces. Anyway, this first article will address how they work and a sample application (expect a second follow-up to discuss some technical specifics such as manufacturing and capabilities).

The physical effect being realized is the Seebeck/Peltier effect, in which a temperature difference is converted into a voltage difference, and vice versa. In one operating mode, a voltage is converted into a temperature difference -- this is referred to as the Peltier effect. There are a number of devices that use these for heating and cooling (even for microprocessor cooling). In the other operating mode, a temperature difference is converted into a voltage (referred to as the Seebeck effect), thus generating electrical power. It is the 2nd operating mode that a TEG uses to generate power (see image).

So, wherever there is a temperature difference, there is a chance to use a TEG. On-body applications are a real possibility; this fits nicely in Ubiquitous Computing. A good paper on the subject was written by one of my professors/friends, Dr. Thad Starner. Not only is it possible to use them on-body, a MEMS TEG was created by Seiko to power their Thermic series of wristwatch.

Let's look at the Seiko Thermic (pictured). According to this website, only 500 of these were made (back in 1998), at a cost of 300,000 Yen (or over $2500 USD at the current exchange rate). Seiko also has an informative page about the Thermic. If you take a look at a Scanning Electron Microscope (SEM) picture of the TEG inside the Thermic wristwatch, you can see the P-N junctions stacked vertically (pictured below). I'll explain how these are made, and their capabilities in the next post on the subject.

As a side-note, I'd be interested in acquiring one of these watches. If you're feeling philanthropic, you could buy me one as a gift. Otherwise, I'd be almost as happy if you just notified me when one came up for sale.

NOTE:  This post originally appeared on Hizook.com, which has been transformed into a robotics-centric website.  To preserve all of my original posts, I've transferred the content to my new homepage TravisDeyle.com.  I also encourage you to scope out the new Hizook!