Some ways to run a fridge on solar energy

[Checkthisout]

The spec says ‘up to 150 liters of box’ so that is 5.25 or so cubic feet.

So this draws more watts when running to cool 5 cubic feet than my 20 year old ac 12 cubic foot fridge??

 

[Nevadablue]

That is what the maker says. Danfoss apparently makes good stuff and the $$$ they get for it show. It is specialty equipment and as such demands a premium.
My fridge in the camper pulls something like 600 watts running on 110 volts. It is an absorption unit and they have (had?) their place, but that seems past for most applications. Specialty units…

 

[Nevadablue]

Where are you coming up with 5 cubic feet?

The calcs I ran say 837 btuh for 16 cubic feet. This compressor does ~640.

 

[Checkthisout]

That is what the maker says. Danfoss apparently makes good stuff and the $$$ they get for it show. It is specialty equipment and as such demands a premium.
My fridge in the camper pulls something like 600 watts running on 110 volts. It is an absorption unit and they have (had?) their place, but that seems past for most applications. Specialty units…

Oh I see. It says 18-150 liters. I didn't see that.

Weird. Using another calculator it says 850 btuh is all that's needed for a 16cuf box. *sigh*

 

[Nevadablue]

 

[Nevadablue]

I finally remembered to check the watt meter on the fridge. It has averaged 456 watts per day for the last 17 days. Not sure that can be beat. A 21 cubic foot fridge/freezer running on less power than a 20 watt lightbulb. Knock wood this thing lasts.

 

[Spodek]

For an alternative approach: I unplugged my fridge over a year ago so have been living without one. It took some effort to adjust, learning to ferment and shopping differently, mainly for fresh produce instead of packaged. Also realizing that much of the world and everyone before about a century ago lived without.

 

[Leeds]

For an alternative approach: I unplugged my fridge over a year ago so have been living without one. It took some effort to adjust, learning to ferment and shopping differently, mainly for fresh produce instead of packaged. Also realizing that much of the world and everyone before about a century ago lived without.

A century ago people filled their ice houses in the winter and year round they used that ice to feed their kitchen ice boxes.

Call me lazy but I find electric refrigeration to be so much simpler.

 

[Nevadablue]

For an alternative approach: I unplugged my fridge over a year ago so have been living without one. It took some effort to adjust, learning to ferment and shopping differently, mainly for fresh produce instead of packaged. Also realizing that much of the world and everyone before about a century ago lived without.

Just curious, do you use electricity?

 

[Checkthisout]

For an alternative approach: I unplugged my fridge over a year ago so have been living without one. It took some effort to adjust, learning to ferment and shopping differently, mainly for fresh produce instead of packaged. Also realizing that much of the world and everyone before about a century ago lived without.

Yes but but from late 1800's on, they had daily deliveries of milk, eggs etc along with a horse-pulled cart that carried ice they bought and put in their ice box (refrigerator).

I see your point but canning and shopping become full time jobs.

 

[Tecnodave]

Was a very early adopter of DC compressor referigeration, I have two Grape Solar branded refrigerators that I bought from Home Depot. I bought the first for $800. with a 1 year warranty. It failed at 11 1/2 months and was replaced under warranty. The failure was the breaking of the freezer compartment door, minor but they had no parts so sent me a replacement fridge for free. It was simple to fabricate a Styrofoam “plug” door with the approiate sized holes to achieve balance between referigerator and freezer temp.

These units draw 42 watts at 10-15 volts or 20-30 volts DC or 115 volts AC with the built in power supply.

On average they have a 20% run time over the day 4-5 hours in Coastal California

In a test I sucessfully ran one on a 50 a.h. 12 volt battery and 1 only 50 watt solar panel with a PWM controller, It did just fine but had a hard time with a rare 100 deg F. day

Minimum recommended is 100 a.h. battery and 100 watt solar

The Grape Solar units are now nearly 20 years old and still doing fine, Ive added a third unit which I salvaged from a wrecked late model Volvo Tractor made in Sweden

These run from a 426 amp hour 24 volt bank of Rolls Surette S-530’ L-16 batteries now pushing 20 y.o.

Grape Solar has exited the business but I do see very simular units marketed in other countries for reasonable prices
$900 for a 17 cu. ft. unit in the Phillippines . In America we have a huge power grid so we do not need to have really efficient devices. In third world countries It’s a different story altogether

If anybody still does ammonia referigeration I have the original Dometic dealers diagnostic and repair manual.
This has theory of operation and is a gold mine of rarely available information on adsorption refrigeration .
It’s in Adobe PDF format, PM me and I will email a copy

 

[Spodek]

A century ago people filled their ice houses in the winter and year round they used that ice to feed their kitchen ice boxes.

Call me lazy but I find electric refrigeration to be so much simpler.

I was with you before starting. Before doing it, I expected I'd have to spend more effort, time, and money on food, and that things would go bad. I was pleasantly surprised to find the change led to fresher food and the effort was more like taking care of a pet or practicing a craft. I got out what I put in, so value the effort.

The longer I do it, the more what used to feel like effort feels rewarding. My biggest sacrifice is screen time, which has turned out to be a benefit.

 

[Spodek]

Just curious, do you use electricity?

Yes, though I'm in the middle of an experiment disconnecting my apartment in Manhattan from the electric grid. My goal was one month, though, frankly, I didn't know how I'd make it past a couple days. That was May and now I'm in my sixth month. Here's a podcast episode I did on it. I allow myself a cheat: I can plug in my computer and phone at NYU, where I teach, but otherwise I disconnected the circuit connecting my apartment to the grid. I still get hot water from the building.

We've had several rainy days in a row, so haven't gotten to charge my battery, so haven't been able to cook for a few days. Fall vegetables make great salads, though.

 

[Spodek]

Yes but but from late 1800's on, they had daily deliveries of milk, eggs etc along with a horse-pulled cart that carried ice they bought and put in their ice box (refrigerator).

I see your point but canning and shopping become full time jobs.

It's led me to cut back my screen time, which has ended up improving my life.

I've also learned more about traditional cultures, including the Hadza and San, which go back long before the 1800s -- fifty and two hundred thousand years. I haven't canned, but I ferment enough that it's become simple and quick. I live near a farmers market and belong to a CSA, so getting food regularly isn't hard. I also volunteer to help bring farmers markets to underserved communities to replace McDonalds, Starbucks, and delis that extract value and time from them. I'm in this for systemic change.

 

[Mattb4]

It's led me to cut back my screen time, which has ended up improving my life.

I've also learned more about traditional cultures, including the Hadza and San, which go back long before the 1800s -- fifty and two hundred thousand years. I haven't canned, but I ferment enough that it's become simple and quick. I live near a farmers market and belong to a CSA, so getting food regularly isn't hard. I also volunteer to help bring farmers markets to underserved communities to replace McDonalds, Starbucks, and delis that extract value and time from them. I'm in this for systemic change.

Urban and even suburban folks can get by without even owning kitchens. Just walk to the local store, market or eatery. Many can do without owning much household appliances like clothes washers since there is a laundromat or cleaners just down the block. Heavily urban folks don't need cars to get about they just ride Transit and have big things delivered by the stores. Heck even your night time lights can be supplied by all the street lights shining everywhere. Pretty easy to cut down on electric use if someone else supplies things.

If you live in the hive all your needs can be taken care of.

 

[Doggydogworld]

Weird. Using another calculator it says 850 btuh is all that's needed for a 16cuf box. *sigh*

That's just an estimate, of course. Your mileage will vary. Maybe by a lot.

Larger fridges generally use less BTU per cu ft thanks to scaling math. Doubling the length, width and height doubles the door seal length thus doubles warm air infiltration. It quadruples wall surface area through which heat transfers. So you've got 2x of one type of heating and 4x of another. And it's often more like 3x through the walls because larger fridges tend to have thicker/better wall insulation. Meanwhile, that 2-3x higher BTU/hr buys you 8x as many cubic feet!

The other big variables are temperatures inside vs. outside the fridge and how often you put warm items in. Keep the fridge in a cool room (e.g. basement). Vent warm air coming off the (clean) coils up and away from the fridge. Add insulation to the outside walls. Keep it as full as possible while still allowing air to circulate inside, and return food/milk/etc. quickly before it has time to warm up. Push these measures to extremes and that little DC compressor might even run a full size fridge.

 

[AstroBob]

I have a couple of small compressor fridge cooler's that I use for camping. They are both extremely efficient, if a little small for the OP's purposes.
The smaller of the two pulls 20-35 watts when running. When set to maintain <38 degrees, the 24 hour power draw is 135Wh. A 100 watt panel and a small battery will keep it running for a very long time for sure. The larger of the two draws ~220Wh/24hrs. So, at least at my scale, off-grid refrigeration is no problem at all. refrigerant for the smaller unit is r134a. test conditions were 75-80 degrees. The unit was 1/2 full of water jugs.