The energy saving potential of thermo-responsive desiccants for air dehumidification

• Published in: Energy conversion and management Vol. 244; no. C; p. 114520
• Main Authors: Zeng, Yi, Woods, Jason, Cui, Shuang
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.09.2021; Elsevier Science Ltd; Elsevier
• Subjects: Adsorption; Critical temperature; Dehumidification; Desiccant wheel; Desiccants; Energy conservation; Energy consumption; Energy efficiency; Gels; Humidity; Humidity control; Interpenetrating networks; Isotherms; Moisture control; Polymers; Silica; Silica gel; Silicon dioxide; Temperature; Temperature dependence; Thermo-responsive solid desiccant; Water vapor; Energy efficiency; Thermo-responsive solid desiccant; Dehumidification; Desiccant wheel
• DOI: 10.1016/j.enconman.2021.114520
• ISSN: 0196-8904

Traditional desiccant-based dehumidification systems suffer from low energy efficiency due to the desiccant’s fixed affinity to water, meaning it has a single moisture adsorption isotherm regardless of the temperature. We modeled a novel thermo-responsive desiccant with temperature-dependent isotherms in a desiccant wheel model for three representative dehumidification scenarios. These cases show remarkable improvement in moisture removal efficiency of this material because of its switchable water affinity below/above the critical temperature. Our work discusses how to apply and tune the thermo-responsive desiccants for further enhancement in dehumidification performance, depending on application. [Display omitted] •Developed a thermo-responsive desiccant wheel model for air dehumidification.•Demonstrated how and why thermo-responsiveness improves dehumidification efficiency.•Quantified thermo-responsive desiccants’ improvement in dehumidification efficiency.•Provided guidance on desiccant material and system design for air dehumidification. The desiccant wheel is a promising technology for energy-efficient humidity control. However, its overall efficiency—hindered by the desiccant materials’ properties—remains low because traditional desiccants (e.g., silica gels) have a single isotherm regardless of their adsorption temperature. Thermo-responsive materials have been proposed to break this fixed affinity to water vapor, with drastically different adsorption isotherms depending on temperature. Its potential for improving dehumidification efficiency, however, has not been addressed. In this paper, we model the potential of a thermo-responsive interpenetrating polymer network (IPN) desiccant with temperature-dependent adsorption isotherms for energy-efficient dehumidification via a validated transient desiccant wheel model for humidity control of buildings. Thermo-responsive desiccants can improve the dehumidification performance due to their thermo-responsive switchable hydrophilicity below/above the lower critical solution temperature. Our analysis shows that thermo-responsive IPN desiccants can potentially reduce energy consumption by up to 30% compared to silica gels. The savings depend strongly on the critical temperature of the thermo-responsive desiccant and should be higher when the inlet temperatures are expected to be higher.