How does the ice cooling system work?

I just read an article about buildings in NYC using ice tanks in basements to supplement or reduce the use of traditional cooling systems. The article explained that the ice is frozen at night when energy demand is low, then left to melt during the day to cool the building off. Can anyone be more specific? I'm trying to imagine how this can really perform on par with A/C.

Answer:
The effect comes from the amount of heat that is needed to melt a pound of ice in to one pound of water. The system that I installed ran coils of water and anti-freeze (glycol) inside the ice tanks. The tanks were frozen each night - because electricity for buildings is often cheaper at night than during the day. The ice froze around the coils. The next day we would start a pump that would run the glycol mixture flowing. As the mix ran through the ice tanks, it would melt the ice. Since it used its own heat (from the building) to melt the ice, the mix came out of the ice tanks about 15 degrees colder. That cooler water would then be used to cool the air for the building.
I saw a show that discussed this - they blow air across the ice - cooling the air - apparently it's not efficient enough to be the only source of air cooling as you need a fairly large surface area of ice / air to affect a decent amount of cooling
I've no personal experience with this, but I've been told by those with experience that this technique has also been used to provide cooling for high occupancy/infrequent usage facilities. For example, say you have to design an HVAC system to cool a church or auditorium; an infrequently used structure, but often at maximum capacity when it is used. If you sized the HVAC unit to handle the heat load generated from a large gathering of people, the unit would have to possess greater capacity than would be required the majority of the time, resulting in both high capital equipment cost and inefficiency. With an ice storage system, a cold sink could be created using a smaller HVAC unit while operating at off-peak times, and then used to supplement when needed. I know this wasn't your question, but thought I'd pass is it along anyway, as I found it interesting when told of this.

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