Sorption vs. separation – Prototype comparison of two approaches to façade-integrated dehumidification

We present a dehumidification concept which reduces building cooling energy loads, achieving higher efficiency comfort conditions and healthier air for hot and humid climates. We demonstrate an alternative to vapor-compression air conditioning, by using sorption-based liquid desiccant and separation-based vacuum membrane methods to manipulate air humidity and velocity. Dry air moving over skin in such climates has been shown to increase the number of thermal comfort hours that do not require cooling, reducing building energy consumption. We have constructed prototypes for each method with design considerations for attachment to the exteriors of buildings that will likely have to consider retrofit solutions due to future rising heat levels. Our lab and field tests yielded promising results, and our theoretical models show dehumidification coefficients of performance higher than equivalently-sized vapor compression systems. The sorption-based system dehumidified better at fan-driven air speed, while the separation-based system performed better at lower air speed. Both prototypes are novel in their mass-exchanger design, compact form-factor, and component-based assembly. This progress suggests that with further research, non-vapor-compression systems, and hybrid vapor-compression/desiccant systems are well-positioned to substantively reduce energy consumption for thermal comfort.