This is one of those great “is it worth it” questions. Certainly you can configure TEG’s into a RMH, and TEG’s reliably generate electricity, but their efficiency is mediocre, meaning they don’t generate much electricity even under optimal circumstances and they don’t come cheap. I looked into this strictly out of curiosity, and the best setup I found could produce 100 watts of electricity by using high temperatures and water cooling and the module was not cheap.
This is not to say that you can’t do it. If you are really interested, or want a robust, reliable power supply when power is out, this might be for you. You might consider Tegmart.com. They have a pretty comprehensive list of modules and equipment, but again, they do not come cheap—just fair warning. If memory serves, we are talking about hundreds of dollars for a 100 watt module.
This would be a very interesting project, and if you decide to do it, please keep us updated, I think it would be VERY interesting to see how things work out.