I think everyone knows about “Drinking bird” toy (https://en.wikipedia.org/wiki/Drinking_bird). Here I would like present ”modern”, solid state analog 🙂
We take a Peltier element and put wet rag on one side and big heat sink on the other side.
Water will be evaporating from the rag and it will be cooling.
This creates small (about one degree) temperature difference for several hours.
Using modern DC-DC converter for energy harvesting (like LTC3108) some small electronic device can be powered e.g. clock.
I also believe that it is possible build similar system with ”closed cycle” where water (or perhaps some other coolant circulate inside device). This, however, presents much more serious engineering challenge.
N. E. Zaev’s article about using environmental heat to generate electricity was published somewhere in 1991. According to some internet resources, N.E. Zaev was researching this concept since 1960s, probably in cooperation with P.K. Oshepkov, founder of Public Institute of Energy Inversion. I heard first time about Zaev’s idea of conversion of environmental heat to electricity about ten years ago. Since that time I made a lot of experiments and attempts to build such device without any significant progress. In desperation, I started studding everything related to magnetic properties, BH curves etc. And accidentally, last year a chain of unexpected events was triggered, which brought me to understanding and some experimental results. Here, in this short summary, I am trying to document a path which one have to follow in order to be able understand and build such device.
Full story here: h2e.pdf