Abstract: An improved cold storage refrigeration system and method is presented. A first heat exchanger located in a cold storage unit is connected by means of a series of vertical pipes to a second heat exchanger located below the first heat exchanger within a refrigerated space, forming an integrated tube assembly. To charge the cold storage unit, the tube assembly is operated as the evaporator of a conventional refrigeration circuit. During non-powered cooling, a portion of refrigerant is sealed within the tube assembly. The refrigerant vaporizes in the second heat exchanger and condenses in the first heat exchanger, thereby transferring heat from the refrigerated space to the cold storage unit. Defrosting of the second heat exchanger is accomplished by removing refrigerant from the second heat exchanger and circulating air above 0 degrees centigrade around it.