Field Study on Humidification Performance of a Desiccant Air-Conditioning System Combined with a Heat Pump

An overview of solutions for airborne viral transmission reduction related to HVAC systems including liquid desiccant air-scrubbing

The spread of the coronavirus SARS-CoV-2 affects the health of people and the economy worldwide. As air transmits the virus, heating, ventilation and air-conditioning (HVAC) systems in buildings, enclosed spaces and public transport play a significant role in limiting the transmission of airborne pathogens at the expenses of increased energy consumption and possibly reduced thermal comfort. On the other hand, liquid desiccant technology could be adopted as an air scrubber to increase indoor air quality and inactivate pathogens through temperature and humidity control, making them less favourable to the growth, proliferation and infectivity of microorganisms. The objectives of this study are to review the role of HVAC in airborne viral transmission, estimate its energy penalty associated with the adoption of HVAC for transmission reduction and understand the potential of liquid desiccant technology. Factors affecting the inactivation of pathogens by liquid desiccant solutions and possible modifications to increase their heat and mass transfer and sanitising characteristics are also described, followed by an economic evaluation. It is concluded that the liquid desiccant technology could be beneficial in buildings (requiring humidity control or moisture removal in particular when viruses are likely to present) or in high-footfall enclosed spaces (during virus outbreaks).

Desiccant-Assisted Air Conditioning System Relying on Solar and Geothermal Energy during Summer and Winter

At Hamburg University of Technology the combination of an open cycle desiccant-assisted air conditioning system and a geothermal system is investigated in the framework of different research projects for several years. The objective of this study is to investigate the energy efficiency of the overall system and to evaluate the geothermal system during summer and winter mode, based on data measured for a temperate climate region. Monitoring results of the performance for dehumidification and remoistening of supply air are presented. Furthermore, the investigated system is compared to reference air conditioning processes. During summer mode, an average dehumidification efficiency of 1.15 is achieved. The electrical energy savings compared to a conventional reference system sum up to 50% for the investigated cooling period. System operation during winter shows an average moisture recovery efficiency of 0.75. The electrical energy demand for air humidification is reduced by 50% compared to a system with electric isothermal air humidification. The geothermal system is operated efficiently throughout the year for cooling and heating application. Besides the energetic system evaluation, measured data regarding the soil temperature and thermal comfort are presented.