Dual purpose fridge

[JBP]

Originally Posted by Byrnerc

The numbers help since I intend minimul dehumidification time and the refrigeration time can be assisted with the engine alternator.

The numbers depend a great deal on which fridge you choose and where you are. Adding refrigeration to an old purely insulated ice box could require as much power as CatSketcher says. On the other hand a modern mini fridge like an Engle uses a fraction of that. Mine uses less than 24 Ah/day in 85+ F ambient temperature and it is just a cheap Chinese one. At 70F ambient it uses even less.

[Byrnerc]

Yes JPB, the old uninsulated icebox is the other big problem. I've been trying to figure out how to inject foam insulation around the outside without removing the wood work supporting it. I would drop a mini fridge in except the odd shape prevents that.

[jsanton]

Byrnerc, I think you have a great idea!
Try it out.
I think it’s all in the duty cycle. Thatis, how long it’s allowed to run per whatever time unit.
I’m guessing a cooling plate will get too cold when it’s running since it wants to freeze. I’d bolt a nice size heatsink to it with heat sink compound. Use a cheapo electronic thermostat to control the temp of the heatsink to maybe 60F.
Use a timer to run the fridge setup as above, and the fan that runs air over it for, start at 1 hour/ day and see what you get.
Open the drain on your icebox to ensure the dripping water gets into a sump pump and pumped overboard.
Cooling units take roughly 5A. At least mine does. It runs roughly 50% duty cycle. So, it’s equivalent to 2.5A long term. So, that’s 2.5Ah/day load.
A 100 watt panel creates 8A. The general rule is multiply by 5 hours for a day of insolation on average. So, that’s 40Ah/day supply.
No problem.
The compartment is largely sealed, so no large continuous source of humidity. Temp cycling will bring in a little moisture every day.
I’m an engineer and have studied this area.

[cottonsail]

We have 500 watts of solar, an outback MPPT controller and 8 Trojan T-105 lead acid batteries. This runs 2 Norcold 12 volt refrigerators (one set to freezer temperatures) an "office" sized refrig/freezer and an icemaker. With good sun the system is self sustaining in Florida.

[GordMay]

Originally Posted by jsanton

...
Cooling units take roughly 5A. At least mine does. It runs roughly 50% duty cycle. So, it’s equivalent to 2.5A long term. So, that’s 2.5Ah/day load...

I think:
5A x 24 Hr x 50% Duty = 60 Amp/Hours per day

[pcmm]

Originally Posted by jsanton

Byrnerc, I think you have a great idea!
Try it out.
I think it’s all in the duty cycle. Thatis, how long it’s allowed to run per whatever time unit.
I’m guessing a cooling plate will get too cold when it’s running since it wants to freeze. I’d bolt a nice size heatsink to it with heat sink compound. Use a cheapo electronic thermostat to control the temp of the heatsink to maybe 60F.
Use a timer to run the fridge setup as above, and the fan that runs air over it for, start at 1 hour/ day and see what you get.
Open the drain on your icebox to ensure the dripping water gets into a sump pump and pumped overboard.
Cooling units take roughly 5A. At least mine does. It runs roughly 50% duty cycle. So, it’s equivalent to 2.5A long term. So, that’s 2.5Ah/day load.
A 100 watt panel creates 8A. The general rule is multiply by 5 hours for a day of insolation on average. So, that’s 40Ah/day supply.
No problem.
The compartment is largely sealed, so no large continuous source of humidity. Temp cycling will bring in a little moisture every day.
I’m an engineer and have studied this area.

something is wrong with your maths here.... 2.5a*24hrs is 60Ah per day, not 2.5ah per day... If you are pulling in 40Ah/day supply, you have a 50% (20Ah) deficit. and you haven't even factored in the other items you talked about above.

[pbmaise]

If you recharged desiccant in the hot sun...especially if you make a sort of solar box out of a cooler, you might be able to drive off enough water to reuse desiccant over and over again.

https://www.youtube.com/watch?v=rBXXDo_kaBw