Solar-Regenerated Desiccant Belt for Direct Indoor Humidity Pumping Through Breathable Insulation Wall

Abstract

A humidity pump is proposed to extract latent load directly from the indoor space using a rotating desiccant-coated belt integrated in the building façade formed of an airgap and a breathable 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 coupled with breathable insulation. The developed model was experimentally validated on a constructed prototype of the system and used to conduct a parametric study for an office space that generates typical latent load of 407 W. The study evaluated the system performance at different belt rotational speeds and shading percentages in three different climates: hot and humid, Mediterranean, and tropical climates. Simulations were performed and optimal operating conditions of the belt were recommended at each hour of an occupancy period to maximize latent load removal. This was achieved by varying the belt rotational speed between 9.6 rph – 19.2 rph while maintaining a shading percentage of 40 %. As a result, the system was capable of extracting 110 W – 456 W of space latent load, which corresponded to 27 % - 112 % of the typical generated latent load of 407 W, while adding 32 W – 195 W of sensible load depending on the climate.