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We predicted the impact of desiccant degradation on the performance of an open-cycle desiccant cooling system in ventilation mode using the degradation data on silica gel obtained from a previous study. The degradation data were based on thermal cycling desiccant samples and exposing them to ambient or contaminated air. Depending on the degree of desiccant degradation, the decrease in the thermal coefficient of performance (COP) and the cooling capacity of the system for low-temperature regeneration was 10 percent to 35 percent. The 35 percent loss occurred based on the worst-case desiccant degradation scenario. Under more realistic conditions the loss in system performance is expected to be lower.

We conducted experiments to quantify the effects of thermal cycling and exposure to contamination on solid desiccant materials that may be used in desiccant cooling systems. The source of contamination was cigarette smoke, which is considered one of the worst pollutants in building cooling applications. We exposed five different solid desiccants to 'ambient' and 'contaminated' humid air: silica gel, activated alumina, activated carbon, molecular sieves, and lithium chloride. We obtained the moisture capacity of samples as a function of exposure time. Compared to virgin desiccant samples, the capacity loss caused by thermal cycling with humid ambient air was 10 percent to 30 percent for all desiccants. The capacity loss because of combined effect of thermal cycling with 'smoke-filled' humid air was between 30 percent to 70 percent. The higher losses occurred after four months of experiment time, which is equivalent to four to eight years of field operation. Using a system model and smoke degradation data on silica gel, we predicted that, for low-temperature regeneration, the loss in performance of a ventilation-cycle desiccant cooling system would be between 10 percent to 35 percent, in about eight years, with higher value under worst conditions.