Abstract
A desiccant air handling unit is one of the major types of dehumidification handling systems and requires hot water or hot air to regenerate sorption materials. If solar thermal energy is used as the heat source for regeneration, in general, a backup electrical heater, backup boiler, or combined heat and power (CHP) is installed in order to maintain a stable hot water supply. In this study, effective control is proposed for a desiccant air handling system that uses solar thermal energy (flexible control), and its energy performance is compared to that of a traditional control (the fixed control) through a system simulation. The diurnal behavior shows that the system with a fixed control without a backup boiler cannot process the latent load properly (28 GJ of unprocessed latent load for July and August). On the other hand, the system with a flexible control without a backup boiler is able to process required latent heat load. Based on the fact that the fixed control needs a backup boiler to process the latent load, the system with a fixed control with a backup boiler is considered for the energy performance comparison. The simulation results show that the primary energy-based coefficient of performance (hereafter, COP) of the system with a flexible control without a backup boiler reaches 1.56. On the other hand, the primary energy-based COP of the system with a fixed control with a backup boiler reaches only 1.43. This proves that the flexible control contributes to the higher energy performance of the system and maximizes the use of solar thermal energy more than the fixed control.
Highlights
Today, the concept of a net zero energy building (ZEB) is widely recognized, and the popularization and promotion of ZEBs is desired [1,2,3]
This study proposes a desiccant air-handling unit with solar thermal energy without using a backup heater or boiler and evaluates the energy performance of the desiccant air handling system through simulation
This study proposed a new “flexible control” for a desiccant air handling unit, which only uses solar energy for its regenerating heat coil
Summary
The concept of a net zero energy building (ZEB) is widely recognized, and the popularization and promotion of ZEBs is desired [1,2,3]. The indoor thermal load through the outer wall and windows has been decreasing due to the higher performance of insulation [4]. The metabolic rates of humans do not change very much. The constitution of the thermal loads of buildings has changed, the latent load from humans still seems to be relatively large. Global warming is a worldwide issue, thereby increasing the temperature and humidity in some areas of Japan (for example, Nagoya area) [5]. This results in a larger fresh air load.
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