UC San Diego

Desiccant based dehumidification allows for independent treatment of latent and sensible properties in air conditioning systems and enables the use of energy-saving solar thermal evaporative cooling systems. These systems can reduce dependence on vaporcompression air conditioning which is a significant source of greenhouse gases. Recent research has focused on polymer-based desiccant materials which have higher adsorption capacities than conventional materials such as silica gel and zeolite. Solid desiccant materials used in dehumidification systems are typically utilized in a cycle in which they absorb water vapor from a process air stream and are then regenerated by a source of hot, dry air which evaporates and removes water contained in the material, allowing it to again absorb water from the process air. This research focuses on the development and testing of a hygroscopic salt impregnated, NIPAM hydrogel-based thermo-responsive desiccant material that can be regenerated by elevating the material to its lower critical solution temperature (LCST), enabling a significant energy saving over materials that require regeneration through water evaporation. At this LCST, the water adsorbed by the desiccant becomes insoluble in its NIPAM polymer matrix and is removed through droplet formation induced by gravity. Adsorption and regeneration testing was performed on the material to evaluate the feasibility of using this temperature-sensitive desiccant into a dehumidification system. Testing shows this composite material has a maximum SR of > 2 and analysis indicates improvement in regeneration heat requirements over existing desiccant materials.