Lbs ice per watt

[J.H.]

I use the frozen water bottle method for camping. 3 coolers 2 full of food one full of frozen water bottles and I've had them stay frozen for a week out in a Colman cooler in 90 degree temps
I just placed 2 to 3 frozen bottles in food coolers each day

Yep… the more ya insulate the longer it lasts with no added energy… I didn’t have solar back then in the mid nineties so it wasn’t an option… had to do it the old fashioned way..
my grand parents used to cut ice chunks out of the lakes and store in the mountain caves in the Tenn mountains… it was always cool Underground .. about 50 …..
the ice would last all summer under tarps and hay. Kept their food stored more safely…

 

[Bluedog225]

I'd run the freezer on power supplied by my solar system.

Am I missing something?

I was wondering about efficiency. Starting with water and solar panels. What’s the most efficient method? With a compressor, it comes down to the efficiency of the freezer (compressor type).

Making 10 lbs of ice each day could come in handy.

 

[ricardocello]

I was wondering about efficiency. Starting with ester and solar panels. What’s the most efficient method? With a compressor, it comes down to the efficiency of the freezer (compressor type).

Making 10 lbs of ice each day could come in handy.

Let’s say a freezer compressor has a COP of 1.6 (which seems typical consumer units from what i’ve seen).
See posts #19 and #26.

It physically takes 0.592 kWh to make a 10 lb bag of ice (starting with water at 77F and going down to 5F).
With a freezer with COP of 1.6, it would only take 0.37 kWh to make the bag of ice because it is a heat pump and removes the heat from the water.

So someone on here is probably an expert on freezer efficiency and COP, maybe they can tell us about the most efficient units.

 

[Steve777]

Let’s say a freezer compressor has a COP of 1.6 (which seems typical consumer units from what i’ve seen).
See posts #19 and #26.

It physically takes 0.592 kWh to make a 10 lb bag of ice (starting with water at 77F and going down to 5F).
With a freezer with COP of 1.6, it would only take 0.37 kWh to make the bag of ice because it is a heat pump and removes the heat from the water.

So someone on here is probably an expert on freezer efficiency and COP, maybe they can tell us about the most efficient units.

I'm not sure your math is capturing the real world here.

To make ice from water it takes roughly 0.6 KWH of removed energy from the water (exact amount will vary with the initial temp of the water going in). Refrigeration overall has a COP of 1.6, but that goes down with freezers which work at lower temps than fridges do (and other heat pumps at low temps). Commercial freezers have a COP much closer to 1, and I suspect home freezer do as well (but I have not seen any numbers for home freezer units). In any case COP will vary with the type of compressor and insulation of the individual freezer, and the temp settings.

Heat pumps COP can "create" more KWH of heat than they "burn" because they are just moving the heat from one place to another. But how efficiently they can move that heat depends. When one side is at a low temp the efficiency goes way down; that is why mini splits stop being energy efficient at low outside temps. The same will be true here in trying to move heat out of the ice/water.

It is probably a lot safer to plan for a COP of ~1 on your freezer in making ice, especially if you are trying to bring the ice down to 0F or below.

 

[DIYrich]

I was wondering about efficiency. Starting with water and solar panels. What’s the most efficient method? With a compressor, it comes down to the efficiency of the freezer (compressor type).

Making 10 lbs of ice each day could come in handy.

"Efficient" electricity to convert ice to water: the main energy consumption is moving heat from inside the machine to outside the machine. That relates to the efficiency of the heat pump. Whether you run air over the coils that then freezes the water, or chill the water directly and break the ice off the coil, it is still how "Efficient" is the heat pump. It takes the same number of btu's to freeze one gallon of water.

Some methods may be faster at transferring the heat, and some heat pumps may be optimized for different Temps (chill to 30f vs 0f). In general, larger capacity (btu transfer) is more efficient, and smaller temp differential (higher ending ice temp) is more efficient.

 

[BuffaloTrace]

Using a small pc style fan inside a chest freezer can help speed up the process, but they are basically "sealed" once the lid is closed.

 

[Dadoftheturkeykids]

I don't think there will ever be a market for solar panel direct to fridge considering their low power consumption and intermittent cycling seems like a waste of panel that could be otherwise charging battery or powering continuous loads.

I can imagine a boat or other small space setup working well

 

[HarryN]

Good luck with your storm related challenges.

Prior to having battery back ups and similar things, we used to use dry ice for our cooler when going camping. It is pretty common here.

Just wrap some newspaper around it to keep from accidentally touching it - and wear gloves when handling it to avoid frost bite.

 

[J.H.]

Using a small pc style fan inside a chest freezer can help speed up the process, but they are basically "sealed" once the lid is closed.

Yes…. I have Done it …it’s a great addition……it helps speed up the chilling and balencing the temp through out the space at hand… it doesn’t make it colder overall ,it just makes it evenly the same temp quicker…especially if you put in some new food thats warm/ warmer ..it helps bring it down much quicker.

 

[McKravitts]

It shouldn’t be too hard to build something like this:
View attachment 227588

The geometry of a system like this is critical to make it work.

For example:
The ammonia solution from the absorber is gravity fed to the generator.
If the absorber is too low relative to the generator, the absorber could flood, if it’s too high gas bubbles from the generator could contaminate the absorber.
Similar considerations should be determined for the relative height of the cooling fins to the evaporator and the relative height of the separator to the absorber.

 

[BuffaloTrace]

Space wise those small ammonia absorber refrigerators are great. 30 days on a standard bbq 20-30lb gal propane bottle and you're set. But terribly inefficient. Lots of waste heat that needs to be exhausted. If I ever do propane in an rv/trailer ever again it's going to run one thing, and that's a generator.

 

[740GLE]

The geometry of a system like this is critical to make it work.

For example:
The ammonia solution from the absorber is gravity fed to the generator.
If the absorber is too low relative to the generator, the absorber could flood, if it’s too high gas bubbles from the generator could contaminate the absorber.
Similar considerations should be determined for the relative height of the cooling fins to the evaporator and the relative height of the separator to the absorber

That’s why it’s important to have your LP fridge nice and level when glamping.

 

[Q-Dog]

This situation is why we installed our battery backup. We had a generator to keep the fridge and freezers cold. But the gas stations don't pump gas when they don't have power.

Living off a generator for a week really isn't that much fun.

 

[Bananaman321]

I can imagine a boat or other small space setup working well

I was referring to the domestic refrigerator I just believed that the added cost and complexity would not outweigh the benefit When most solar generators off-the-shelf accomplish this
Now maybe a 48 V DC based refrigerator that we could avoid the % losses of the inverter. Modern refrigerators aside the compressor are mostly DC based anyways But with this usually comes software dependency

We know how frustrating it is I just had to reflash my electric toothbrush this morning

 

[Citlalatonac]

I wouldn't want any sort of refrigeration that relies on ammonia. Shit's deadly if it goes wrong in the wrong way. I'll take an ease & efficiency L to avoid that.

 

[McKravitts]

I wouldn't want any sort of refrigeration that relies on ammonia. Shit's deadly if it goes wrong in the wrong way. I'll take an ease & efficiency L to avoid that.

A lot of the newer refrigerators use R-170 (ethane), R-290 (propane), R-600 (butane), and R-600A (isobutane). All are highly flammable, and there are instances of refrigerators blowing up.
The manufacturers always find a way to blame it on too much pressure build up and ignore the fire damage.

 

[Recovering EE]

No reason to apologize!
We are all here to share.

...and to learn. Thank you all very much!

 

[Recovering EE]

I wouldn't want any sort of refrigeration that relies on ammonia. Shit's deadly if it goes wrong in the wrong way. I'll take an ease & efficiency L to avoid that.

Little-known fact: The refrigeration system on the international Space Station is Ammonia-based.

A leak can be deadly.

 

[McKravitts]

Little-known fact: The refrigeration system on the international Space Station is Ammonia-based.

A leak can be deadly.

With several thousand Kg of dimethyl hydrazine and nitrogen tetroxide on board as fuel, I doubt if the ammonia in their cooling system worries them too much.

 

[xjaw4]

The geometry of a system like this is critical to make it work.

For example:
The ammonia solution from the absorber is gravity fed to the generator.
If the absorber is too low relative to the generator, the absorber could flood, if it’s too high gas bubbles from the generator could contaminate the absorber.
Similar considerations should be determined for the relative height of the cooling fins to the evaporator and the relative height of the separator to the absorber.

A system that operates in batch mode is possible to build and people have done it.

Home Built IcyBall

On a webpage I can no longer find someone built one that used a solar thermal collector that had a parabolic mirror focused to heat a iron pipe.

 

[OffGridForGood]

Do it yourself refrigeration using propane, heat and pumps...what could Possibly go wrong...be right back...or not.

But to answer the posted question: "lbs of ice per watt",
I looked up a similar question from an online group discussing ice making machines (for hotels etc) and they posted and average 22.58kWh to make 390lbs of ice in 24 hours.
Thats 57.9 Wh per pound of ice.
per watt-hr we get 390lbs / 22,580Wh = 0.0173 lbs of ice per Watt-hour (0.2oz ice per Whr)
maybe better to express in terms of kWh, ie about 17.3 lbs of ice per kWh.

 

[Supervstech]

It shouldn’t be too hard to build something like this:
View attachment 227588

I wonder if a solar lens could be used in leu of the heater for this...

 

[Supervstech]

If you cut open the plastic wrapper the cold can get to the center bottles better.

The heat can escape better... "cold" isnt a thing.

 

[Bananaman321]

Do it yourself refrigeration using propane, heat and pumps...what could Possibly go wrong...be right back...or not.

Propane is a very cheap efficient refrigerant doesn't take very much only a few ounces I'm not scared
It would literally have to almost all leak out at once and get ignited within a short amount of time
Might be a good experiment for the back porch

 

[Supervstech]

Look at us all discussing the best uses of R718
And how best to obtain it.