Abstract: A preferred thermal energy storage and delivery unit includes a chamber for containing a phase change material and one or more air channel members which pass through the phase change material for conveying air into heat exchange relationship with the phase change material. The unit also includes a fluid circuit for conveying a thermal potential charging fluid, for example engine coolant or refrigerant, into heat exchange relationship with the phase change material. The unit optionally may include a fluid circuit through which engine coolant passes, and a fluid circuit through which refrigerant passes. In this manner, systems which incorporate the unit and selectively provide heated or cooled air to condition an interior vehicle space are provided. Also described are improved vehicular environmental conditioning systems which include a front HVAC unit and a rear thermal storage apparatus, and which are flexibly operated in a number of environmental conditioning and/or thermal storage modes.