This book introduces the concepts of evaporative cooling and desiccant cooling. Based on some commercially available evaporative coolers, their design structures are illustrated, and some improvements are provided after the comparative experiments are carried out. In order to apply an evaporative cooling efficiently in humid climates, an air dehumidification device should be set prior to the evaporative cooling system, so both desiccant dehumidification and desiccant regeneration are also investigated. Solid and liquid desiccant dehumidification systems are illustrated and classified. Liquid desiccant - potassium formate is used in the experiments due to its many advantages. The dilute solution generated by the air dehumidifier could be regenerated by a novel solar evacuated tube regeneration system. This hybrid evaporative/desiccant cooling system has a huge potential commercial market due to its remarkable energy efficiency and cost effectiveness.