ultra efficient frig/freezer

[pengyou]

While I am on this topic (see my other thread) since it seems that it is possible to create a very efficient homemade frig I would like to pursue going one step further and, even though living in the city, I would like to check into getting a 12V system with a solar panel.

Can someone give me an equation (or link to one) that will tell me what size I compressor, evaporator, etc I will need for a given volume of cooling space (given a certain R value for the insulation)? I would like to use the smallest size of hardware possible so that I can minimize the cost of the refrigerating components as well as the solar panel.

[tinknal]

There was a thread here a few months ago about an off-the-gridder using a chest freezer for refrigeration. The reasons were :

1 Cold air is heavier than warm air, so that when you open the refrigerator door the cold air all falls out. The cold air stays in the freezer.

2 Freezers units are much more well built and efficient than refrigeration units.

He just replaced the thermostat with one from a refrigerator.

He was able to run the thing with a solar collector.

[TnAndy]

You're probably not going to find "an equation" as to the components you mention to the size of the cooling capacity.

IF you want to stay with 12v, you can check out Sunfrost ( Google them ) fridge specs, as they are the ones most off grid folks use.....just be prepared for sticker shock.

The other way to go is what tinknal mentions.....using a standard, energy star rated small chest freezer AS a fridge using an external thermostat. Buddy of mine and I did some experimentation with a 7cuft freezer and found you can run it on 200watt/hrs/day. That means a typical 100 watt solar panel with sun 5 hrs/day would run this for 2.5 days without sun.

The external thermostat you use is:

http://kegman.net/9025.html


You will also need an inverter capable of STARTING the motor on the freezer....meaning you will need a decent 1,000w inverter with 1,500w or so surge.....something like this:

INVERTER

Throw in a brand new 7-8cuft energy star rated freezer for 300 bucks or so, and you have a super efficient fridge for 600 bucks.

The batteries/panel(s), etc are pretty much the same whether you go 12v or invert it to 120AC.....and with the inverter, you have some more power options available to you.

[Ramblin Wreck]

I've thought about this as I've read threds on the topic over the years, and I wonder if an efficient DC powered freezer might be a good alternative. You avoid the cost of the inverter and you can always freeze water for use in an ice box. On camping trips, I've had block ice last almost a week in a Coleman type cooler. If you had a well engineered/constructed ice box (and worked to keep the openings/closings to a minimum), block ice might even last over a week.

[Pelenaka]

Hope that this isn't a faux pau but there is a yahoo group that deals with this topic options for energy efficient home refrigeration. RefrigeratorAlternatives is the group's name.
Truthfully the majority of what is discussed is over my head but it is a very informative group. I joined because my number one main reason for being grid tied is refrigeration especially now that we heat with wood. #2 would be the telly.
We did live for over two years with a nonelectric fridge a.k.a. ice box (made ice in a upright freezer). The main trick with this simple technology is to learn to live with less refridgerated food such as room temp/cellar cold apples. For our family of 5 the ice box worked great with a couple of ice blocks formed in small dish pans. My ice box lost out to DH's Grandfather's 1940's Westinghouse. That fridge is really very energy effient since it isn't frost free & has 4" thick walls.

On my own personal to do list is to build myself a super insulated ice box in my cellar using scavanged parts such as fridge racks. I bet that with a really great R value of 30 or more a block of ice would last well over a week. Beware though, the next project you will want to tackle is building an ice house, lol.
Then again I would love to have a Crosley Icy Ball.

~~ pelenaka ~~
http://thirtyfivebyninety.blogspot.c...rn-millie.html