A thermal energy storage system that enables the discharge of refrigerated air for cooling cargo or passengers in large compartments, such as the trailer of a semi-truck, for a period of time well in excess of several hours. The thermal energy storage system is able to provide refrigeration without operating a conventional VCC unit, the truck engine, or the TRU diesel APU engine during all or a significant portion of the period of the typical range of time that a 53 foot refrigerated the truck is traveling over the road. The thermal energy storage system includes a phase change material reservoir, a cooling system-to-working fluid heat exchanger in fluid communication with the phase change material reservoir, and a phase change material-to-target heat exchanger in fluid communication with the phase change material reservoir. The phase change material reservoir contains a phase change material, a working fluid and a working fluid-to-phase change material heat exchanger.