So this little backpacking gadget was kickstarted successfully back in 2016. It's $250 IIRC and works by tethering it to a tree and letting the drag of moving water spin the blades. It occurs to me that one of the two sites I have been considering for megahab is a river.
Hydro power has many benefits over solar. The first is that it's non-stop. I don't have to put a big expensive battery on-site, (though I'd probably want to) and the turbine itself is underwater while in use, so it's unlikely to be spotted and stolen.
The problem is that this unit has no cable for sending power back to shore. It stores power in an internal battery pack. This means you have to remove it from the water and unscrew the casing to get at the battery and use it to charge your phone or whatever.
This isn't acceptable if I want to use this thing to power, say, an aquarium air compressor. I need it to send power to a battery on land where the air compressor is. It also occurs to me that the output may be enough to power just the air pump, but probably not the heated floor of the habitat as well.
This unit from Canadian company Idenergie is on sale right now for $9,500 (normally $12,500). That's way out of my budget (even the $250 backpacker's turbine is pushing it) but it outputs between 100 and 500 watts depending on water speed.
Even a reliable 100 watts would be more than enough for both the heater and the air pump. It could actually power two pumps in tandem, which I'd want for redundancy's sake. It's also submersible and thus unlikely to be noticed.
I think I can make the battery pack submersible. Putting it in a water tight housing with silicone sealed hull penetration points for the cables ought to suffice. This would prevent it from being noticed and stolen as well.
But then, what to do about the air compressor? Is there some way to emplace it securely on the bottom of a slow moving river, and have it suck air down from the surface using something like a long flexible snorkel tube with a float/buoy at the top to keep it above water level? (and a rain guard).
Perhaps, for example, the battery and inverter could be in the same airtight weighted housing as the air pump. This way the pump could also provide an overpressure in its own housing to guard against leaks, and purge the ongoing buildup of hydrogen gas vented by the battery.
If so, the entire setup could be submerged. The only indication of its presence would be the small floating buoy for the air intake, and the bubbles coming up from the habitat air exhaust:
The longevity of this setup is limited only by the durability of the turbine and the lifespan of the battery. As dwarf hamsters live around 3 years at most, it's conceivably possible to establish a habitat system that will be self-supporting for the entire lifespan of the animal.
A large enough habitat could also conceivably stock three years worth of food, the only limiting factor being spoilage. If that can be overcome, then the duration of submersion would be extended to the entire lifespan of the occupant.
This is achievable only for systems with a single hamster however due to the food requirements doubling if you add another. But then hamsters are antisocial and not to be cohabitated anyways.
A large enough habitat could also conceivably stock three years worth of food, the only limiting factor being spoilage. If that can be overcome, then the duration of submersion would be extended to the entire lifespan of the occupant.
This is achievable only for systems with a single hamster however due to the food requirements doubling if you add another. But then hamsters are antisocial and not to be cohabitated anyways.
