Development and Benchmarking of a Full-Scale Desiccant Dehumidifier Prototype Utilizing Microwave for Desiccant Regeneration and Inactivation of Airborne Microorganisms

A research team is developing a microwave-powered desiccant dehumidifier that could save energy and improve indoor air quality.

The importance of humidity control in buildings has been established with respect to its contribution to human comfort, indoor air quality, and effects on building materials. Desiccant wheel dehumidification for humidity control in air conditioning systems is receiving significant attention because it has inherent energy-saving potential over many other methods of humidity control in mechanical systems. 

Desiccant requires continual regeneration to maintain its water-removing capacity. A preliminary investigation by project collaborators has shown that microwave energy can provide the same level of drying as conventional heating but using less than 20% of the energy consumed by conventional desiccant regeneration means. The technology has significant market potential if a full-scale prototype can be developed and if the potential energy savings suggested by the preliminary investigation are also realized in full-scale laboratory testing. Microwave has also been shown through past bench scale studies to be effective for inactivation of pathogenic airborne microorganisms. 

Significant facilities exist within the Indoor Environment Center (IEC) and Indoor Aerosol Lab within the Department of Architectural Engineering to develop and undertake full-scale evaluations of heating, ventilation, and air conditioning mechanical systems used in commercial and residential buildings. Additional facilities, specialized capabilities and standard test methods have been developed around these facilities to evaluate inactivation of airborne microorganisms. Development and successful laboratory testing of a full-scale dehumidification system prototype outfitted with microwave regeneration forms the scope of this project. 

Testing will comprise continuous evaluation of moisture-removal capacity per unit of energy (using detailed mass and energy balance methods developed by ASHRAE) and inactivation efficiency across a range of aerosolized challenge airborne microorganisms introduced into the airstreams passing through the desiccant wheel across a range of system variables and dynamic conditions. A number of technical questions must be resolved at the bench scale level in this project to enable successful integration of microwave components into the desiccant dehumidifier system that Munters Corporation will donate to the project. 

The full-scale data collected in the laboratory tests will allow development of realistic economic analysis and energy models including the developed system in new and retrofit installations. Manuscripts detailing various aspects of the project and its outcomes are expected to be publishable in journals targeting aerosol, microwave, and HVAC research. It is expected that patentable intellectual property will be developed during this project. This pilot study will lead to the development of further collaborations amongst the project team that can be supported by successful proposals to government and industry organizations including DOE, ASHRAE and ARPA-E, and others being contemplated.