The present book deals with the current problem with energy crisis and the significance to replace fossil fuel with the renewable energy resources like solar, wind, biomass, waste energy etc. One of the main consumption of energy is mainly found the buildings especially in the hot humid area for air conditioning purpose. So, replacing the conventional air conditioning using the liquid desiccant which is solar or renewable energy assisted is underscored. The desiccant categories, properties, way to use, principle of operation and different design the air conditioning which is solar assisted are indicated. The importance of solid and liquid desiccant, the using process and cycle are deals. The solar assisted flat plate collector is used in the liquid desiccant to assist the regeneration process and to increase the performance of the solar collector using nano-fluid is recommended. Finally, the solar collector efficiency and exergy calculation procedure are indicated. And the way toanalysis the absolute humidity reduction and humidity effectiveness are also given for a liquid desiccant used.