12V Freezer?

[Frood]

Anyone know which uses more power? Same TINY frig used for food versus used for frozen gel packs?

Also, I'd like to hear from people who went that route: using their power for a freezer to supply their cooler. Seems you could store more food and drinks that way, if it works to keep the cooler cold enough.

The math on this doesn't work, since insulation and cooling are never at 100%. The only way this would be useful is if you wanted to put gel packs in a smaller more portable ice chest for day-trips instead of carrying around a big ice chest. Or for putting in a lunch box to keep the items cool.

Your going to be gaining heat in the portable ice chest/lunch box much faster than you are able to cool them off in your portable freezer.

Additionally you are going to be losing quite a bit of storage space because you will have to double up your ice chests and coolers...

The freezer will have to keep running to constantly be re-freezing the gel packs or to keep them frozen. The freezer will be gaining heat constantly as well (although in small amounts). If this was not the case, then you would be able to put some ice in an ice-chest and come back 2 weeks later and have the same amount of ice... I look forward to the day when we can have almost 100% efficient insulation. The more efficient your insulation the less your compressor (heat transfer pump) needs to work to pump excess heat out of your cooler to keep it cold/frozen.

 

[rruff]

The math on this doesn't work

I think Carla is asking the same question I had. There are absolutely *potential* advantages to this system. You can freeze water when you have excess solar, and have a few days of buffer when it's cloudy rather than relying on batteries to do that. A good cooler will insulate better than a good fridge, so that will save energy. You run the freezer primarily when it's sunny and your batteries are topped off. You first freeze the icepacks that have fully melted. Once that is accomplished you can freeze packs that are partially melted; you have a rotation depending on how long the packs have been in the cooler. When you don't have sun you turn the freezer off, and store packs in the cooler.

Freezing water takes a lot of energy... but it gives it back when it melts, 100%. No loss there.

It does take up more space, and you have to shuffle packs back and forth and pay attention to what you are doing.

The other issue is the reduced efficiency of the compressor at lower temperatures. In theory you only need to be just below freezing to make ice, but you probably need a significant delta T in order for the energy to transfer from the pack to the freezer at the max rate the freezer is able to reject it. I'd expect the freezer to run constantly when you are making ice, but the higher the temperature you can do that, the better.

BTW, the most efficient material for this is plain old water. Anything you add to it will reduce the energy capacity of the freeze and melt cycle.

 

[Nomad X]

Using a tiny fridge to supply a cooler with ice is counterproductive. Using a larger fridge as a freezer to the store food and also make ice for a separate smaller cooler makes a lot more sense.

Most of these fridge freezers are very efficient and sip energy. Having more Frozen or cold mass inside the fridge or freezer helps it stay cooler and keeps the compressor from having the kick on more often. So having a larger fridge that is used as a freezer would be more efficient. When you take the gel packs or ice out of the larger freezer you would still have other Frozen items in there to keep that cool, thereby reducing the compressor having to come on and cool the interior again.

A lot of how this works for you is going to depend on your energy generation, interior temperature, air circulation around the fridge, and a few other things.

One thing I could definitively say regarding 12 volt cooling is never buy a thermoelectric cooler heater. They are completely different from a compressor fridge and will eat up your battery and not work nearly as well.

The power required to REfreeze a thawed blue ice block - over and over again - would be insane.

Most freezers are designed to KEEP frozen food frozen, not to freeze room temp items. They are not ice makers.

 

[Frood]

melted. Once that is accomplished you can freeze packs that are partially melted; you have a rotation depending on how long the packs have been in the cooler. When you don't have sun you turn the freezer off, and store packs in the cooler.

Except that you will still need to make ice-packs even when you don't have sun because your ice-packs will need to constantly be refreshed... and you will not necessarily be able to put the ice-packs in the cooler because you are using it to keep other things cold as well, right? Or am I overlooking something very obvious that I'm not seeing?

In the end it I guess what really matters is whether or not what you are doing works for you... because if your process is working for you then that's what matters most.

 

[Happy Camper]

Again. If you have a large enough freezer to where you can have mostly frozen mass (Ice bottles, food, etc) with extra room for "extra" ice bottles that can be put into a smaller cooler, that would be the most efficient way to do what the op asked for originally.

The extra frozen mass in the freezer would allow for it not to work as long or hard on freezing up replacement ice bottles. I would personally freeze ice bottles instead of gel packs. Much more versatile and possible useful.

A small countertop ice maker is an interesting thought as well. They do work quickly. Downside would be that the ice made is usually not very dense. That could also be an upside lol.

 

[AmargosaWayne]

Gel packs can't be used as cold water can be used for first aid purposes.

 

[rruff]

The power required to REfreeze a thawed blue ice block - over and over again - would be insane.

Refrigerators have a COP >1 so it takes less energy to freeze the ice than the amount of cooling the ice provides as it melts. It will be working hard (on all the time) while you are freezing the water, but then you turn it off.

Except that you will still need to make ice-packs even when you don't have sun because your ice-packs will need to constantly be refreshed... and you will not necessarily be able to put the ice-packs in the cooler because you are using it to keep other things cold as well, right? Or am I overlooking something very obvious that I'm not seeing?

Let's say you have a cooler that melts 3 lbs of ice per day, and you keep 18 lbs of ice in it. That's a 6 day buffer when it's all frozen. Your fridge/freezer can make 1 lb of ice per hour when it's cranking, so when it's sunny and you have excess solar capacity, you take any unfrozen packs out of the cooler and freeze them. You are basically using ice as your energy storage rather than batteries.

I would only use the unit to make ice to put in the cooler, not to store frozen food.

The extra frozen mass in the freezer would allow for it not to work as long or hard on freezing up replacement ice bottles.

Mass in the freezer only changes the duty cycle, it doesn't change the amount of energy consumed. The compressor will kick on less often, but run for a longer time.

 

[Happy Camper]

Frozen mass will reduce both. Once frozen, that is.

 

[rruff]

Both of what?

 

[Spaceman Spiff]

Refrigerators have a COP >1 so it takes less energy to freeze the ice than the amount of cooling the ice provides as it melts. It will be working hard (on all the time) while you are freezing the water, but then you turn it off.

It takes 334 KJoules to change 1 Kg (1 liter) of 0ºC liquid water into 0ºC solid water (ice).
That same liter of water will absorb 334 KJ of heat changing back to liquid.
There is no free energy lunch; your energy equations have to balance.

There are other losses:
- heat infiltration into the freezer (the insulation is not perfect)
- the compressor gets hot
- coolers have the same heat infiltration problem

Let's say you have a cooler that melts 3 lbs of ice per day, and you keep 18 lbs of ice in it. . . . you take any unfrozen packs out of the cooler and freeze them. You are basically using ice as your energy storage rather than batteries.

Ice packs don't melt serially. At the end of the day all 18 pounds will be 16% melted.

All else being equal, it takes less energy to store food in a refrigerator than to make ice in a freezer for keeping food cold in a cooler.

My biggest b!tch with storing food in a cooler is that it is harder to keep food at a safe temperature.

 

[rruff]

There is no free energy lunch; your energy equations have to balance. All else being equal, it takes less energy to store food in a refrigerator than to make ice in a freezer for keeping food cold in a cooler.

Ice packs don't melt serially. At the end of the day all 18 pounds will be 16% melted.

Yes, as I said the "cost" to freeze the ice is exactly what you get back when it melts. A good cooler is much better insulated than a fridge, so it should take less energy overall... the unknown is the how cold you have to run the fridge to effectively freeze the ice, and what it's COP is at that temp vs at 35F. Based on reviews I see for these cheap refrigerators, it appears that some of them can't even get down below freezing very far.

Yes, good point, the packs don't melt serially... but I figure after your first cloudy spell, you'll have differing stages of frozen-ness. It would be a PITA to manage it and keep them optimized, for sure.

IMO batteries are cheap enough now that it would make more sense to just run the fridge, unless a person had some other reason why they wanted to freeze water.

 

[user 22017]

IMO batteries are cheap enough now that it would make more sense to just run the fridge, unless a person had some other reason why they wanted to freeze water.

I want to avoid lithium because it is harmful to the environment in many ways. I thought a compromise would be a small portable power station to power the 20 liter Alpicool. I might want to learn how to power a frig with a lead acid battery instead, since they are more environmentally friendly.

I thought freezing ice for a cooler might help on cloudy days (no solar).

 

[Spaceman Spiff]

I run a 2.4 cu.ft. fridge, electronic gadgets, LED lights, and a vent fan on 208AH of FLA batteries and 200W solar. Even on very overcast days I can get my batteries back to about 90% and go ~3 days before I have to use another charging method.

IMO best 'bang for your buck' are Sam's Club golf cart batteries: 200AH for ~$200.
If you don't need that much check out 12V marine/trolling motor batteries.

 

[user 22017]

Thanks Spiff!

 

[rruff]

I want to avoid lithium because it is harmful to the environment in many ways. I thought a compromise would be a small portable power station to power the 20 liter Alpicool. I might want to learn how to power a frig with a lead acid battery instead, since they are more environmentally friendly.

I thought freezing ice for a cooler might help on cloudy days (no solar)

You can certainly use lead acid if you wish. Much heavier to get the same capacity though. Don't last nearly as long, can't be discharged as far, and you waste a lot of solar to charge them fully as well. Plus flooded ones require maintenance and venting. Freezing water and keeping your food in a cooler will reduce the battery capacity you need.

IMO best 'bang for your buck' are Sam's Club golf cart batteries: 200AH for ~$200.

6V?... so 1200WH?

 

[Spaceman Spiff]

I'm on year 8 with my GC2s, bought in June, 2014.
Two 6V GC2s in series = 12V.

Batteries (like everything else) are going up in price fast. Current price at Sam's Club:
$135 each = two for $270.
I've been contemplating replacing mine even though they still test out good.

 

[Frood]

I want to avoid lithium because it is harmful to the environment in many ways. I thought a compromise would be a small portable power station to power the 20 liter Alpicool. I might want to learn how to power a frig with a lead acid battery instead, since they are more environmentally friendly.

I thought freezing ice for a cooler might help on cloudy days (no solar).

If you recycle the batteries instead of throwing them out then they will re-use the lithium in the future. lead acid doesn't last as long and lead is very bad for the environment as well; at least for people...
https://www.sciencedaily.com/releases/2022/03/220307162011.htmAnd the lithium battery should be usable for many years longer than the lead acid battery...

 

[user 22017]

If you recycle the batteries instead of throwing them out then they will re-use the lithium in the future. lead acid doesn't last as long and lead is very bad for the environment as well; at least for people...

It is estimated that 500,000 gallons of water is used to mine one metric ton of lithium.[9] With the world's leading country in production of lithium being Chile,[10] the lithium mines are in rural areas with an extremely diverse ecosystem.[11] In Chile’s Salar de Atacama, one of the driest places on earth, about 65% of the water is used to mine lithium; leaving many of the local farmers and members of the community to find water elsewhere.[12][13] <snip> The work is in very dangerous conditions with children as young as seven participating.[14] Additionally, it is common for locals to be in conflict with the surrounding lithium mines. There have been many accounts of dead animals and ruined farms in the surrounding areas of many of these mines. In Tagong, a small town in Garzê Tibetan Autonomous Prefecture China, there are records of dead fish and large animals floating down some of the rivers near the Tibetan mines. After further investigation, researchers found that this may have been caused by leakage of evaporation pools that sit for months and sometimes even years.[15]

While lithium ion batteries can be used as a part of sustainable solution, shifting all fossil fuel-powered devices to lithium based batteries might not be the Earth's best option. There is no scarcity yet, but it is a natural resource that can be depleted.[16] According to researchers at Voltswagon, there are about 14 million tons of lithium left, which corresponds to 165 times the production volume in 2018.[17] [Think they meant www.volkswagenag.com]

From:

https://en.wikipedia.org/wiki/Environmental_impacts_of_lithium-ion_batteries

And:

https://www.forbes.com/sites/rrapie...id-and-lithium-ion-batteries/?sh=798f4ee7bf5e
https://ecommons.udayton.edu/cgi/viewcontent.cgi?article=3021&context=stander_posters

 

[user 22017]

If you recycle the batteries instead of throwing them out then they will re-use the lithium in the future. lead acid doesn't last as long and lead is very bad for the environment as well; at least for people...

Frood, Lead is harmful to people, but the recycling process of lead batteries can be safe. That is why government regulations and inspections are vital.

Lead was a serious problem because children ingested it. Paint chips turn to dust and kids got it on their fingers when looking out open windows, crawling/playing on floors, or playing in their dirt yards. Especially around playground equipment where the grass becomes bare dirt (grass was safer). The kids didn't always wash their hands before eating & they ingested lead. Small children who sucked their thumbs ingested it.

When lead harms people and communities due to recycling, it is because the company wasn't following government standards. They were cutting costs.

 

[rruff]

It is estimated that 500,000 gallons of water is used to mine one metric ton of lithium.

Water is a highly renewable resource that ends up recycling itself. Most of the environmental negatives you mention boil down to... yes, there are environmental issues with any industrial process and the countries can manage them as they see fit. Chile can for instance restrict and regulate the mining activity if they feel the environmental costs outweigh the $$$ gained. There are always tradeoffs. I wouldn't bet that the toxic materials in lead acid batteries are more environmentally friendly on a life-cycle basis than LiFe batteries. We've just used them for over 100 years so are familiar with them.

If you really want to minimize the environmentally negative effects of your lifestyle, I'd start with paring all forms of energy use and material consumption to the minimum. Being a van-dwelling vagabond can be a good start. Refrigeration is luxury, not a necessity. It's also quite possible to be motor tramp and live in climates where both heat and cooling of any kind are unnecessary, and drive only a couple thousand miles per year. A bicycle can suffice for short trips... etc.