Rico, nice idea about a small hydro system on the river.
Or maybe for a homesteader like Kaarina with a woodstove burning much of the time in winter, a little thermoelectric generator might work to generate enough power to charge a mobile phone at least enough for emergency use.
I bought but haven't yet tested an old never-used PowerPot, basically a TEG in a cooking pot. The cooling comes from water in the pot. It doesn't generate much power, 5 watts an hour at best, but it's the back-up to my backup for if when the mains electric is out. It could trickle power into a phone (or a power bank that could then charge the phone) and be no extra work apart from topping up the water in the pot during a cloudy winter period where the woodstove will be burning all day but solar panels won't work.
The basic concept was good but it was a commercial failure, mainly because they marketed it to backpackers not homesteaders and it needs the heat source burning too long to be useful for backpackers, affordable lithium battery banks went on sale much the same time, and the next generation of mobile phones needed higher wattage input so wouldn't charge directly from the pot.
I intend to test it when I'm at the house next week.
