In order to reduce summer peak loads, a Californian Utility Company will be providing 2,500 R-410A Ice Energy Storage Units to owners of typically 15-70 kW rooftop air conditioning (AC) systems, common for small to mid-size commercial buildings.
The R-410A Ice Energy Storage Unit is an intelligent distributed energy storage solution that works in conjunction with a direct-expansion AC systems.
On summer afternoons, about a third of Southern California electricity demand comes from AC loads, so that reducing those peaks will help the utility, improving its load factor and its electricity production efficiency, and reducing its costs.
The Ice Energy Storage unit stores energy at night, when electricity generation is more efficient and less expensive, and delivers that energy during peak hours to provide cooling to the building. This allows peak daytime hours to be reduced significantly and, as each system delivers an average reduction of 12 kW peak demand for a minimum of 6 hours daily, 72 kWh will be shifted to off-peak hours. The aim is to reach a total energy storage of 25 MW when the 2,500 units will have been installed, shifting the operation of commercial AC condensing units from peak to off-peak periods..
Operation of the ice energy storage
At night, when temperatures drop and electricity is cheap, each system will freeze around 170 litres of water into a solid block of ice, operating as an integrated high-efficiency AC condensing unit, as thermal efficiency will be higher with lower temperatures.
During the day, when temperatures rise, the AC unit compressor (inefficient at that time, when temperatures are high) will be shut down and the ice will be used to cool the hot refrigerant, slowly melting the ice. The only energy consumed is to run a small pump pushing ice-cold refrigerant through a modified evaporator coil installed in the conventional AC unit.
In total, besides helping to shift peak hours demand, the added ice storage system will significantly reduce the AC unit energy consumption.
Source : here and Manufacturer information