Solar-regenerated desiccant belt for direct indoor humidity pumping through active building façade

Abstract

Indoor humidity management is one of the critical challenges of the built environment. Typical technologies that rely on diluting indoor generated humidity by supplying clean, dehumidified outdoor air are energy intensive. More passive solutions have been suggested to directly remove humidity using hygroscopic materials; however, their performance deteriorated in humid climates. Hence, this study presents a novel solution to regulate indoor air humidity levels using a rotating desiccant-coated belt integrated in the building façade formed of an airgap and a vapor-permeable insulation. The system dries the airgap, creating the gradient needed to drive the indoor moisture outdoors. The belt is regenerated by direct exposure to solar radiation. The external side of the belt is equipped with variable shading mechanism for control of the regeneration temperature. A mathematical model was developed for the proposed system and experimentally validated and used to conduct a parametric study for an office space. The study evaluated the system performance at different belt rotational speeds and shading percentages in three different climates covering a wide range of outdoor conditions to determine its operation conditions. It was found that the system covered between 27 %–112 % of the space latent load while adding 32 W–195 W of sensible load. Lowest speed (9.6 rph–12.8 rph) were needed at high humidity levels and low solar radiation due to the slow regeneration process, whereas highest belt speeds (15.4 rph–19.2 rph) were needed at low humidity levels and high solar radiation where regeneration process was fastest. © 2023 Elsevier B.V.