Cecil’s answersays keep the fridge full, since the energy lost from cooling warm air which enters an empty fridge each time it opens, would be worse than the energy lost cooling food or water which is put in to fill up the fridge.
Not so. The fridge needs to remove specific heat from water once, or from air many times, 4.181 kilojoules per kilo of *water *per degree C, and 1.006 per kilo of *air *per degree C. **Density **is 1 kilo per liter of water, and 1.29 grams per liter of air.
So fridge has to remove 4.181 kilojoules per liter of water once, or 0.00130 kilojoules per liter of air many times. This energy for water is 3,200 times the energy for the same volume of air, so storing water is efficient only if it stays for over 3,200 door openings. At 10 per day, that’s 320 days, so the water may be getting moldy. Certainly food (with about the same specific heat and density as water) will be far gone. There are further losses from slightly warming the water or food each time the door opens, and longer door openings as you shift the food around.
A better alternative is to fill empty space in the refrigerator with plastic bags of air: small energy to cool them, and they keep air from leaving the fridge.
This comment does not directly calculate the energy used by the fridge. It will be proportional to the energy removed from water, food or air, so the ratio is right.
I think you’re over my head here, I admit.
But what about the cold temp being radiated by the high moisture items? Water is an efficient thermal mass (for the same reason it takes so much energy initially to cool it), would greatly help cool the relatively warmer air that entered the fridge when door was opened, helping further reduce the working load on the fridge.
Your formulas seem to only take into account the cooling abilities of the fridge’ mechanics, not giving the high h20 thermal mass any credit for aiding in this task.
Because it doesn’t matter. So the high thermal mass objects absorb a bit of heat from the air and help cool the air. But then the high thermal mass objects are slightly warmer, and need to be cooled. So the refrigerator has to add the same amount* of cooling to bring them back down to the original temperature as if it just cooled the air itself and the thermal mass objects didn’t change.
And from the column:
But the energy for making ice would be the same. The whole point was that you want ice, which you are going to get whether or not you have the dispenser. The amount of ice used will be the same (unless you can show some statistics that they are different). Therefore, the ice generation is irrelevant.
*Actually, the Second Law says it will take more energy.