Direct solar regenerated desiccant dehumidification system for sustainable ventilation in hot and humid climate

Abstract

Conventional vapor-compression cooling for outdoor air dehumidification is energy intensive, especially in hot and humid regions. To reduce energy consumption, desiccant dehumidification wheels and packed beds are integrated with the air conditioning systems. However, these systems have large pressure drops and require external heating sources for regeneration. In this study, a two-stage direct solar-regenerated desiccant dehumidification rotating belt (SR-DDRB) system is proposed. The aim is to sustainably dehumidify the outdoor air while meeting the indoor humidity levels at enhanced indoor air quality and minimal energy. The system was sized, and its operation was optimized using artificial neural network for a case study of a typical office space located in hot and humid climate. The supplied outdoor air flowrate varied between 0.055 kg/s and 0.085 kg/s, which is much higher than the minimum required of 0.0392 kg/s. During months of high humidity, the operating conditions were affected by outdoor air humidity conditions such that higher outdoor air flowrate and bypass factor were achieved at low outdoor humidity, and vice versa. During months of low humidity, the operating conditions were primarily influenced by the outdoor air temperature rather than outdoor air humidity to minimize energy consumption. Over the cooling season and while operating at optimal conditions, the SR-DDRB system was able to meet an indoor relative humidity (RH) of 58 ± 1.5 %. Additionally, it maintained the CO2 concentration of 780 ± 41 ppm, well below the allowable 1,000 ppm, whereas electrical energy consumption was 78.8 kWh over the entire cooling season.