Energy Benefits of Liquid Desiccant and Evaporative Cooling-assisted 100% Outdoor Air System (LD-IDECOAS) in an Underground Facilities

Abstract

The application of the liquid desiccant and evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS) in underground spaces was evaluated as an HVAC system to introduce a supplemental amount of outdoor air (OA). If this system replaces the conventional constant air volume (CAV) and variable air volume (VAV) systems, it is determined that it will alleviate environmental problems with the potential of the LD-IDECOAS. The simulation is conducted using TRNSYS 17 and a commercial engineering equation solver program (EES). The thermal load of underground spaces shows a different pattern compared with that of above ground spaces. Maximum cooling and heating loads are relatively small in the underground spaces because of the almost stable temperature condition of the surrounding environment, in comparison to an above ground spaces. As a result, the size of HVAC system in underground spaces can be smaller than those in above ground spaces. So, the energy consumption of the HVAC system applied to the underground building is expected to reduce compared with above ground building. The liquid desiccant (LD) system is consisted of the absorber and regenerator. The regenerator of the LD system was used to treat indoor latent load. The weak solution which was diluted from the dehumidification process in absorber, needs to be regenerated in which it need to heating source for the regeneration. In this study, the solar thermal system and ground source heat pump (GSHP) system are integrated with the LD system in the LD-IDECOAS to supply heating for the desiccant solution. The regeneration heat source was applied to these renewable energy system. The solar thermal system, GSHP system and district heating system operating primary energy saving compared with the conventional gas-boiler in the annual operation. The results show that the integrated systems were more suitable for underground spaces compared with the conventional system. The study is composed of 5 chapters: 1) introduction; 2) system overview; 3) simulation model; 4) simulation results; 5) conclusion. In chapter 1), research background, literature review and objectives are described. For the background, the concept of decoupled system and basic information about LD-IDECOAS are presented. Then, the literature review of the conventional HVAC type of underground space are described. In chapter 2), the system components of LD-IDECOAS used in this study are described in detail with the system configuration and operation mode. In this study, LD system needed to heating source. So the various regeneration heating sources applied to the proposed system. In chapter 3), the details of simulation model is presented. First, the specific information related to the model building is presented. Then the simulation model of each system component is described with the LD-IDECOAS and regenerator heat sources. In chapter 4), the results of the simulation are presented. First, for analyzing the above ground and underground’s seasonal energy consumption of LD-IDECOAS. Second, the annual energy consumption of underground space is compared based on the above ground space. Then, the primary energy consumption of regeneration heating sources compared to conventional heat source. In chapter 5), the conclusion drawn from the research is presented as follows: 1) To analyze the applicability of LD-IDECOAS to underground space, we analyzed system operation energy consumption in case of applying to above ground space and underground space. 2) It was applied to the district heating system, solar thermal system and GSHP system instead of the conventional gas-boiler as the heating heat source for regeneration of summer season and dehumidified solution primary energy was compared and analyzed.