Originally Posted By: UTAlumnus
Quote:
large volumes of loose ice cubes can NEVER go below freezing,


Ice taken from the freezer has to be the same temperature as the inside of the freezer. When you remove it from the freezer, it will not start to melt until the interior of the cube gets up to 32 degrees.

I would advise testing any setup with an out of date bottle of insulin or an empty bottle refilled with water and a thermometer. Another way to test it would be to get one of these weather stations with a remote thermometer that keeps track of the high & low temperature and put the sensor in a plastic bag.


In the case of ice taken from a freezer you are correct. That is why I suggested that bottles of water that have been frozen are not ideal for keeping insulin.

However my original post specifically refers to ice from an ice cube making machine. This is not the same as a freezer.

Ice from an ice machine is at very close to freezing point and starts melting virtually as soon as it is made. If this ice be placed in a large insulated container as I suggested, then it will melt very slowly. Depending on the size of the container, the degree of insulation, and the ambient temperature, some of the ice should last weeks, maybe even months.

Ice made and used as I describe will maintain a well insulated container a very close to freezing point until most of the ice has melted. It can never go detectably below freezing point.

To melt a kilo of ice at freezing point into a kilo of water at freezing point takes about 90 watt hours.
To melt a 1000 kilos of ice therefore takes about 90KWH.
An extremely well insulated container, at freezing point within and located in a cool basement, might have a heat gain of 1KWH a day, so it would take about 90 days for all the ice to melt.
The making of 1000 kilos of ice initially is non trivial, hence the need for an ice maker. Whilst times are normal, about 11 kilos of ice will need replacing each day to keep the container full.
All this entails considerable cost and trouble, but might be worth it for someone whose life depends on insulin or other perishable medicine.
Another option would be an ultra high efficiency DC refrigerator and a PV system to power it. If human life depends on refrigeration it should be duplicated.