A two-stage desiccant dehumidifier has been developed that significantly increases the therrnal coefficient of performance (COP) of desiccant regeneration commercial applications. The first stage is a desiccantimpregnated enthalpy exchange wheel that accomplishes 30% to 50% of the dehumidification task without requiring external, utility-generated heat to reconstitute the desiccant.

Described are the advantages of desiccant dehumidification for commercial facilities, the heat requirement that has made it difficult to develop costeffective commercial applications, and the two-stage desiccant system’s contribution to thermal efficiency. Also described are alternative HVAC systems incorporating two-stage desiccant dehumidification for both new and existing commercial facilities such as office buildings, supermarkets, and restaurants; and the system arrangement, dehumidification process, and regeneration heat requirement and sources in an actual application in a two-story, 90,000 ft² building in Washington, DC.