Dhaka, Oct. 10 -- Every night, around 74,000 gallons (280,000 litres) of water are frozen at Norton Audubon Hospital in Louisville.

Instead of relying solely on traditional air conditioning, the hospital now uses 27 massive ice tanks to cool water that circulates through its network of pipes, keeping operating rooms and patient wards at safe, comfortable temperatures.

This system - known as ice thermal energy storage or "ice batteries" - is gaining popularity across the United States as a sustainable way to provide cooling without increasing carbon emissions.

By shifting energy use to nighttime hours when electricity is cheaper and the grid is under less pressure, the technology cuts power demand and costs while easing strain on the gr...