Review on solid desiccant materials for humidity control in buildings

Thermal comfort in buildings is an essential factor for designing energy efficient systems and a cumulative effect resulting from a variety of environmental and personal factors. High moisture content in indoor air can lead to serious health implications for occupants. Dehumidification in buildings is commonly realised by mechanical vapour compression, while desiccant materials with high affinity for water vapour are a promising technology for handling environmental-friendly indoor air conditioning without overcooling and reheating problems. Solid desiccant materials absorb moisture when vapour pressure of the desiccant surface is less than that of the process air until an equilibrium state is achieved between the desiccant and air. Ideally, the solid desiccant is expected to have large water adsorption capacity at its operative temperature and easily regenerated at a lower achievable regeneration temperature. Silica gel and zeolite are the two widely adopted solid desiccants with strong affinity and extensive researches have been conducted to develop solid desiccant materials with better adsorption and regeneration capabilities as well as long stability, such as nanoporous inorganic material, composite and polymeric desiccants. This review summarises recent researches and developments on available solid desiccant materials that can be utilised in built environment for dehumidification purpose.