Ice-based Technology
Air conditioning can be provided more efficiently by using cheaper electricity at night to freeze water into ice, then using the cool of the ice in the afternoon to reduce the electricity needed to handle air conditioning demands. Thermal energy storage using ice makes use of the large heat of fusion of water. One metric ton of water, one cubic meter, can store 334 million joules (MJ) or 317,000 BTUs (93kWh or 26.4 ton-hours). In fact, ice was originally transported from mountains to cities for use as a coolant, and the original definition of a "ton" of cooling capacity (heat flow) was the heat to melt one ton of ice every 24 hours. This is the heat flow one would expect in a 3,000-square-foot (280 m2) house in Boston in the summer. This definition has since been replaced by less archaic units: one ton HVAC capacity = 12,000 BTU/hour (~3.5 kW). Either way, an agreeably small storage facility can hold enough ice to cool a large building for a day or a week, whether that ice is produced by anhydrous ammonia chillers or hauled in by horse-drawn carts.
As such there are developing and developed applications where ice is produced during off peak periods and used for cooling at later time.
Read more about this topic: Thermal Energy Storage
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