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While ventilation is crucial for ensuring indoor air quality and occupant health, introducing fresh air can lead to increased latent loads due to dehumidification, particularly, in humid climates. The Dedicated Outdoor Air System (DOAS) has gained attention for its ability to supply all fresh air while decoupling latent and sensible loads in buildings. Integrating a desiccant wheel (DW) into the DOAS further enhances its dehumidification performance compared to conventional cooling-based methods. This study proposes a modeling approach leveraging the Julia language and its equation-based acausal modeling framework to analyze the energy performance of DOAS systems, highlighting Julia’s potential in heating, ventilation, and air-conditioning (HVAC) applications. Specifically, we modeled two configurations of DW-based DOAS: one using an active DW and the other using a passive DW. The main modeling components include a desiccant wheel, a thermal network-based office room model considering sensible and latent loads, coils and local controllers. A simulation case study was then conducted to compare the energy performance of the two DOAS configurations over one week during the cooling season in Houston, TX. This study presents a preliminary workflow for HVAC modeling and optimization using a Julia-based symbolic modeling framework, highlighting its potential over conventional methods. The framework is extendable for a further high-fidelity modeling and advanced control analysis of DOAS, and other HVAC equipment and systems.
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Specific energy analysis of using fertilizer-based liquid desiccants to dehumidify indoor plant environments
Controlling humidity in indoor plant environments is crucial to plant growth, but traditional dehumidification methods can be energy intensive. In this study, we evaluate the energy efficiency of a novel dehumidification concept that uses cold concentrated fertilizer solution as a liquid desiccant agent. This closes the water cycle by recovering water vapor for plant fertigation, and eliminates the need for energy-intensive desiccant regeneration. A theoretical transport model is used to conduct a parametric analysis of the specific energy performance of the system in response to desiccant temperature and other operating conditions. Specific energy of dehumidification is defined here as the ratio of the cooling load to the water vapor removal. Minimum specific energy results between 0.16-0.24 Wh/g are achieved at liquid desiccant temperatures between 7-14 °C. These results compare very favorably with other dehumidification technologies on the market, and satisfy new energy efficiency standards for indoor plant cultivation. The vapor flux associated with the minimum specific energy ranged from 1.2-1.6 g/m2/h. Controlling liquid desiccant temperature is shown to be critical to achieving high dehumidification rates at optimal specific energies. These encouraging results suggest that future research and development along this track can contribute to energy efficient greenhouse cultivation for sustainable food production.
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- Award ID(s):
- 2301488
- PAR ID:
- 10525536
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Applied Thermal Engineering
- Volume:
- 238
- Issue:
- C
- ISSN:
- 1359-4311
- Page Range / eLocation ID:
- 121849
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.applthermaleng.2023.121849
