Desiccant dehumidification and cooling systems assessment and analysis

Abstract

The objective of this report is to provide a preliminary analysis of the principles, sensitivities, and potential for national energy savings of desiccant cooling and dehumidification systems. The report is divided into four sections. Section I deals with the maximum theoretical performance of ideal desiccant cooling systems. Section II looks at the performance effects of non-ideal behavior of system components. Section III examines the effects of outdoor air properties on desiccant cooling system performance. Section IV analyzes the applicability of desiccant cooling systems to reduce primary energy requirements for providing space conditioning in buildings. A basic desiccation process performs no useful work (cooling). That is, a desiccant material drying air is close to an isenthalpic process. Latent energy is merely converted to sensible energy. Only when heat exchange is applied to the desiccated air is any cooling accomplished. This characteristic is generic to all desiccant cycles and critical to understanding their operation. The analyses of Section I show that desiccant cooling cycles can theoretically achieve extremely high thermal CoP`s (>2). The general conclusion from Section II is that ventilation air processing is the most viable application for the solid desiccant equipment analyzed. The results from the seasonal simulations performed in Section III indicate that, generally, the seasonal performance of the desiccant system does not change significantly from that predicted for outdoor conditions. Results from Section IV show that all of the candidate desiccant systems can save energy relative to standard vapor-compression systems. The largest energy savings are achieved by the enthalpy exchange devise.