Abstract: A personal cooling unit, comprising: an air inlet for receiving input air; at least one heat pump having a first surface and a second surface, and being configured to extract heat from the input air at the first surface to generate cooled output air and to transport heat to the second surface; a phase change material in thermal contact with the second surface of the heat pump; and means for conveying the cooled output air to the exterior of the unit;—wherein the phase change material undergoes a temperature-driven phase change from a first phase to a second phase, so that when at least a portion of the phase change material is in the first phase, the phase change material absorbs heat from the second surface until all of the phase change material has changed to the second phase; and wherein the phase change material has a phase transition temperature which is at least about 28° C.