Sizing solar and batteries to run A/C system for a small cabin in California desert

#1
Hi everyone...I'm new here
There are lots of variables here but I'll try to give some info that will help a bit
It gets very, very hot out here. I'm installing a solar system since AC is not an option.
The cabin is 432 sqft (40 sqm).
The hottest temps get to about 117 F (47 C).
The cabin is not well insulated and receives no shade.
I'm wanting to install a mini-split AC heat pump system of 12,000 btu's (1 ton).
Running it during the day is no problem. There is abundant sun here.
My real question is about battery storage.
For other items that will discharge the batteries, it's really very, very little. We use propane for cooking, no microwave, propane frig, etc. We will have a few LED lights and we will laptops/phones during the day.
Does anyone have a similar sized setup?
I've tried running calcs but keep running up against how many hours a day/night the AC will be running.
Thank you all for your help!!
 

Optimist

Not A WuHan Fan
Brass Subscriber
#3
What's your ground temp ten feet down? You put a reservoir that far down, the water will cool. Then you recirculate the water via pump (and DC pumps can be pretty thrifty of power) and air through your radiating surface via fan, and you have a way to cool things somewhat.

I grew up in the Permian Basin. The best designed houses for that area were all adobe. Walls were generally feet thick, with an adobe roof. No A/C was needed in those old ranch houses. Given that your cabin is of modest dimension, doing an adobe external wall and a sod roof might be feasible.

And I hope you like this bunch. There are some sharp folks here.
 

AGreyMan

I’m the kind of G the little homies wanna be like
Brass Subscriber
#4
Hello mg93108, and welcome!

I think member @Red dog may have some insight into your situation. He's off grid in a similar climate. You may need to just make a conservative assumption as to how much power the mini-split will pull, and run your calcs from that number. With my system, I underestimated the power draw of a lot of things, which seems to be a common theme with those going off-grid!

At the risk of derailing the conversation -you specifically asked about battery capacity for night air conditioning- I'll say that I think that Optimist is on to something.

You may wish to explore a cooling method called "earth tubes." Judging from the solar install I had done, it would be a lot cheaper to rent a backhoe and bury two or three 100' runs of 8" PVC 5' underground and run a fan, than it would be to buy more solar panels and battery capacity. Especially in your desert climate, where condensation would not be a big problem, this might be a cost effective way to cool your place.