Fabrication of highly water vapor permeable and selective composite membrane for air dehumidification

Air conditioning is essential for maintaining thermal comfort in indoor environments. In tropical climates, heating ventilation and air conditioning takes up more than 50% of the total energy consumption of a building. Besides removing sensible load, cooling systems have to remove a huge latent load, which accounts for 80-90 % of the total cooling load. Isothermal membrane air dehumidification has attracted much research interest because it is more efficient than conventional solid and liquid desiccants. The working membrane is a crucial part of a membrane air dehumidifier because it determines the efficiency of the water/air separation. In this work, we report the fabrication of a thin film composite membrane for air dehumidification. The membrane was prepared by coating a thin layer of PVA/TEG blend on a flat-sheet thin film composite polymeric substrate. This substrate possesses an asymmetric pore structure allowing a high water vapor permeation rate. Its polyester backing layer provides high mechanical stability to the membrane. The obtained membrane has water vapor permeance of 8800 GPU and selectivity of 2200. Compared with several composite membranes developed for air dehumidification, our membranes possess much higher water vapor permeance. Additionally, the membrane was easily scaled-up for a large-scale multi-sheet membrane module with a total membrane area of 75 m². The membrane module can efficiently dehumidify 145 - 970 m³/h of outdoor air with the percentage of water removal of 20-61%.