Novel functional materials for energy-efficient indoor moisture control

Abstract

The regulation of the latent load remains a critical problem for built environment control. Unlike the traditional vapor compression system that features high-energy consumption and environmental-unfriendly processes, desiccants represent an alternative air-conditioning method that takes advantage of the low-grade energy, decreases the energy consumption and even employs use of water vapor. However, for a long time, solid desiccants that can be used for built environment control are very limited. Traditional/conventional desiccants, such as silica gel and zeolite, have relatively low water vapor uptake and high energy demand for desorption, which render them unsuitable for energy-efficient humidity control. In the paper, two types of novel functional materials, i.e. metal-organic frameworks (MOFs) and polymer hydrogels (pHyG) developed at DTU are presented. The hygrothermal and sorption properties of these materials are measured. Both MOFs and pHyG have high water vapor uptake and low regeneration temperature and could be used for energy-efficient indoor moisture control. Some examples of the applications of these new materials developed at DTU are presented. We conclude with prospective directions for next generation solid desiccants to promote energy-efficient moisture control from scientific research to practical application. Peer-review under the responsibility of the organizing committee of the ICMB21. The new polymer hydrogel desiccant is prepared by combining hygroscopic materials and hydrophilicity controllable polymers at a molecular level. The water release process can be achieved by a phase separation process, where the polymer in hydrophilic state serving a molecular reservoir is controllably switched to a hydrophobic state, releasing the containing water without any energy-intensive processes such as desorption or dehydration. The maximum water vapor uptake of the polymer hydrogels (pHyG) desiccant can be up to 5.0 g/g at 90% RH.