In winter it would work better, not worse. The reason is (most) thermoelectric stuff is harnessing the difference in temperatures to generate electricity, since

In winter it would work better, not worse. The reason is (most) thermoelectric stuff is harnessing the difference in temperatures to generate electricity, since electricity is a difference in potential. Well, electricity can be thought of as a difference in potential, but I'm a bit too tired for a philosophical or scientific debate. ;) If you're familiar with how a Stirling Engine converts a difference in temperature (i.e. heat) into mechanical energy, the vague and general principle will make a lot more sense. http://en.wikipedia.org/wiki/Stirling_engine http://en.wikipedia.org/wiki/Stirling_engine As for the recent KAIST work (linked above) on thermoelectric (TE) generators, according to the following it does work on temperature difference: http://www.kaist.ac.kr/_prog/_board/?code=ed_news&mode=V&no=17562&upr_ntt_no=17562&site_dvs_cd=en&menu_dvs_cd=0601 http://www.kaist.ac.kr/_prog/_board/?code=ed_news&mode=V&no=... > "When using KAIST's TE generator (with a size of 10 cm x 10 cm) for a wearable wristband device, it will produce around 40 mW electric power based on the temperature difference of 31 °F between human skin and the surrounding air." I'm yet to watch these, but there are some videos on the KAIST TE. http://www.youtube.com/watch?v=BlN9lvEzCuw http://www.youtube.com/watch?v=BlN9lvEzCuw http://www.youtube.com/watch?v=9b4wOlc4Do0 http://www.youtube.com/watch?v=9b4wOlc4Do0 My mom won't let me near her hearing aids due to her knowing all too well that I want to take them apart to figure out how they work. My past started with door knobs at the age of three, and some things just never change. ;) Anyhow, I'll have to very roughly guess the power requirements of a "typical" (if there is such a thing) hearing aid. From the following: http://www.audiologyonline.com/articles/battery-consumption-in-wireless-hearing-11899 http://www.audiologyonline.com/articles/battery-consumption-... http://www.audiologyonline.com/ask-the-experts/voltage-of-zinc-air-batteries-477 http://www.audiologyonline.com/ask-the-experts/voltage-of-zi... http://www.rayovac.com/Products/Hearing-Aid-Batteries/Retail-Hearing-Aid-Batteries-10-13-312-675.aspx http://www.rayovac.com/Products/Hearing-Aid-Batteries/Retail... Also I just found and still need to read this study "Siemens Battery Performance In Hearing Instruments" but it looks interesting: http://hearing.siemens.com/Resources/Literature/_Global/training-material/2010%20-%20Battery%20performance.pdf?__blob=publicationFile http://hearing.siemens.com/Resources/Literature/_Global/trai... Our imaginary "typical" hearing aid power requirements are probably somewhere close to this: Capacity: 145 mAh Voltage: 1.4 V Drain: 1.1 mA 1.1 milliamperes = 0.0011 amperes Watts = Amps * Volts Watts = 0.0011 * 1.4 = 0.00154 W = 1.54 mW The KAIST TE can generate 40 mW with a 10cm by 10cm patch, and our mythically "typical" hearing aid only requires 1.54 mW. Some of the pictured TE generators are much smaller, but no specs are given in the abstract or the articles on it. Unfortunately, the paper is paywalled. None the less, creating a battery-less hearing aid with existing tech actually seems doable from a (very rough) power standpoint.