Freezer/fridge cold battery
I've been learning about freezer to fridge conversions, done for efficiency. Can get very efficient, but they still need to pull power from the battery bank when it's not sunny. I want as small a battery bank as possible, so am thinking about making a cold battery.
The cold battery would be a energy efficient chest freezer, run off an inverter, with the temp turned down as low as possible, and full of jugs of water to freeze (and some frozen food, although there's a risk it will thaw occasionally). It would be the diversion load of the solar charge controller, so would only be powered on when the battery bank is full and the solar power would otherwise be thrown away.
The fridge component is simply an insulated box, perhaps a small dead chest freezer but it could even be a simple cooler. It is physically connected to the cold battery by some form of vent that can be opened and closed, to keep the fridge's temperature cold enough, but not freezing.
One way would be to elevate the cold battery above the fridge, and have a vent connecting them. When the vent was open, warmer air from the fridge would rise to the battery, and cool air from the battery would fill the fridge. A vent control device would wake up every hour or so and check if it needs to adjust the vent.
Or, they could be side-by-side with a fan at the top to move the warm air from fridge to battery, and a bottom vent to draw cold air into the fridge. If the fan kept its vent mostly blocked when not running, a vent control device might not be needed.
The vent control or fan would be the only part of the system that would consume any battery power, and should use much less than a compressor.
There's some simularities to a regular fridge which after all has a freezer compartment, a vent, and a fan. Except I'll bet the cold battery needs to be bigger than a fridge's freezer to store enough ice to get through a cloudy warm week.
Seems like this would be fun to play with building, though a bit unweidly.