chest freezer - energy efficiency tips?

k_man

ariarnia said:

k_man said:

I will try and think of a better explanation, but energy required to heat something, absolutely depends on what the thing is.
The same way as if you open the freezer, and let all the cold air escape and replace with ambient, it only takes a few minutes to cool it back down. But fill with food, at room temperature, it takes many hours, even though it is the same volume of stuff to be cooled.

if you want to then it'll be interesting to read but i think this might just be one of those things my brain can't get around

i just can't see the point of replacing air with air in bottles if those bottles are going to get warmed up anyway when your trying to find something. but i do know that freezer packs work to keep things cold in the car or on picnics. 

i beleve when you say freezers are differnt. my little brain just can't follow the why. 

One last go for tonight 😁
The reason freezer packs (a bit like full bottles) work to cool down your picnic, as they absorb a lot heat from the picnic food (because they stay cold for a long time), and from the cool bag it is in, and the air in the cool bag.
You wouldn't use empty bottles for that purpose, because they don't absorb much heat.

But when you put the freezer packs back in the freezer, all that heat has to be removed, whereas the empty bottles didn't absorb much, so not much has to be removed.
The freezer packs do a good job of cooling stuff, but not a good job of saving energy.

As suggested by @[Deleted User] above, the main point of adding bottles is to prevent the free movement/ replacement of the cold air, and this is reduced in chest freezers Vs uprights anyway.

doodling

Hi,

k_man said:

[...]

As suggested by @[Deleted User] above, the main point of adding bottles is to prevent the free movement/ replacement of the cold air, and this is reduced in chest freezers Vs uprights anyway.

This is the most important point.  In general, with a chest freezer the cold air just sits there if you (gently) open it.  With an upright freezer the cold air flows out of the bottom with warm air replacing it at the top.

Unless you are opening a chest freezer very frequently, the benefit in putting anything in it just to take up space is absolutely tiny.

If you have lots of power cuts then taking up empty space with containers of water will help it stay cooler longer, but that is for an entirely different reason.

ariarnia

I'm just going to keep the freezer full with food and now i'll start telling everyone they can't eat the ice cream because it wastes electricity

Ectophile

Chest freezers are naturally more efficient because the door is on the top.

Hot air rises, and similarly cold air falls. If you open a conventional freezer door, the cold air pours out onto the floor, and is replaced by warm air from the room.

With a chest freezer, when you open the lid, the cold air can't go anywhere. It naturally sits in the freezer until you close it again.

k_man

One final, final (🤪) explanation of why empty bottles are better than full ones to fill space and prevent air replacement in a freezer(or fridge), and save energy.
Note: if the bottles aren't taken out, it doesn't matter.

A thought experiment, I don't suggest doing this, as you may get cold/freezer burns. This holding bottles rather than just taking out, but the effects are comparable, and this gives the feel of what is happening:

Take two bottles, one full, one empty, that are fully cooled down to freezer temperature, out of the freezer.

Hold the empty one in your left hand. Your hand will feel the cold, but not for long, and the bottle will probably stop feeling cold after around 30s.
Heat loss from hand into the bottle is maybe a little fingers worth. The bottle is now warm/at approx ambient temperature.

Hold the full one in your right hand. You hand will really feel the cold, and after 30s your while hand will probably feel very cold, but the full bottle is still at very close to freezer temperature.
Heat loss from hand into bottle is a maybe a full hands worth.

So while the empty one feels warm, it only has a small around of energy added, that then needs to be removed when returned to the freezer*.
The full bottle is still cold, but a lot more energy has been added, so the freezer has a lot more energy to remove*.


Some numbers/details:
The heat capacity of water is approx 4x that of air by mass, but approx 3000x by volume.
Frozen water also has latent heat of phase change when exposed to warmer environments (or pressure), even if its overall temperature is well below freezing, as the exposed surfaces begin to melt.


So the same energy required to heat the empty bottle (ignoring the bottle itself, but that is the same for both, and very low anyway) from -18 to 12°C (and so needs to the be removed by the freezer*), only heats the full bottle by 0.01°C (even ignoring latent heat).

In our thought experiment, we may have added 5 - 10x more energy, so the full bottle may have heated by a whole 0.1°C 😁, to -17.9°C
This is why it still feels cold (while the empty one feels warm), even though much more energy was added.


This does suggest that a lot of cold air replacement needs to be avoided, to make it worth ever adding full bottles of freezer packs etc** (at least 3000l of air for every litre bottle added).
As such, as suggested above, opening the freezer less, for shorter times is likely to be better at saving energy than adding anything other than air filled containers.

Ramble over.
And relax.


* the energy used by the freezer, is not the same as the energy removed from the freezer contents (to the room), as it is a heat pump, and uses an amount of energy to move a larger amount between two things. But is proportional.
As another aside the energy added to the room is actually the energy removed from the freezer contents + the energy used by the freezer to do this.


** again as suggested previously, adding more contents to the freezer, or freezer packs has other potential benefits, but can actually use extra energy, rather than save.

badger09

ariarnia said:

I'm just going to keep the freezer full with food and now i'll start telling everyone they can't eat the ice cream because it wastes electricity

😂😂😂
I’m with you on that one. Having just skim read this thread, my thoughts were …freeze empty bottles/boxes😏 seriously?
Either get on and do some batch cooking, using yellow sticker items if possible, stock up on Christmas goodies if you’re that way inclined & can afford it, or load up with staples which can be frozen. But I much prefer @ariarnia’s idea. 

[Deleted User]

badger09 said:

ariarnia said:

I'm just going to keep the freezer full with food and now i'll start telling everyone they can't eat the ice cream because it wastes electricity

😂😂😂
I’m with you on that one. Having just skim read this thread, my thoughts were …freeze empty bottles/boxes😏 seriously?
Either get on and do some batch cooking, using yellow sticker items if possible, stock up on Christmas goodies if you’re that way inclined & can afford it, or load up with staples which can be frozen. But I much prefer @ariarnia’s idea. 

So - your suggestion for saving money is "go and buy lots of things"?

ariarnia

[Deleted User] said:

badger09 said:

ariarnia said:

I'm just going to keep the freezer full with food and now i'll start telling everyone they can't eat the ice cream because it wastes electricity

😂😂😂
I’m with you on that one. Having just skim read this thread, my thoughts were …freeze empty bottles/boxes😏 seriously?
Either get on and do some batch cooking, using yellow sticker items if possible, stock up on Christmas goodies if you’re that way inclined & can afford it, or load up with staples which can be frozen. But I much prefer @ariarnia’s idea. 

So - your suggestion for saving money is "go and buy lots of things"?

makes sense to me. if you can't manage without the freezer completely (so can't turn it off) then it makes more sense to buy things you see reduced now that you know you will to eat than to use the energy running a freezer half full of empty bottles. then the freezer is full (so more efficient) and youve saved time and money by bulk cooking or on the reductions. 

[Deleted User]

ariarnia said:

Deleted_User said:

badger09 said:

ariarnia said:

I'm just going to keep the freezer full with food and now i'll start telling everyone they can't eat the ice cream because it wastes electricity

😂😂😂
I’m with you on that one. Having just skim read this thread, my thoughts were …freeze empty bottles/boxes😏 seriously?
Either get on and do some batch cooking, using yellow sticker items if possible, stock up on Christmas goodies if you’re that way inclined & can afford it, or load up with staples which can be frozen. But I much prefer @ariarnia’s idea. 

So - your suggestion for saving money is "go and buy lots of things"?

makes sense to me. if you can't manage without the freezer completely (so can't turn it off) then it makes more sense to buy things you see reduced now that you know you will to eat than to use the energy running a freezer half full of empty bottles. then the freezer is full (so more efficient) and youve saved time and money by bulk cooking or on the reductions. 

If you can't manage without the freezer completely - as you say, "can't turn it off" - you're going to use the energy anyway.  We're then talking about the cheapest way to keep it full (and therefore running most efficiently).

Everything that you buy to fill it is additional cost that you didn't need.  Money that you might not have.

Buying things that you do not need is completely the opposite of Money Saving.

It makes as much sense as saying to someone trying to save money on their electricity bills "just get some solar panels installed".

ariarnia

Deleted_User said:

Everything that you buy to fill it is additional cost that you didn't need.  Money that you might not have.

Buying things that you do not need is completely the opposite of Money Saving.

we have to eat... so we do need food.

if i can buy something on multi buy or reduced now that i would pay full price for later then that IS money saving. thats one of the reasons my freezer is currently full of christmas food.

i managed to get some cheap sausages and reduced veg so made pigs in blankets, stuffing and some sides that i know will cook okay from frozen so i dont need to buy the stuff at full price later in the month (when everyone will be looking for the same reductions). 

or am i misunderstanding you?