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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. 

This study employs Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations to investigate interactions between water molecules and Poly(Nisopropylacrylamide) (PNIPAM). DFT reveals preferential water binding sites, with enhanced binding energy observed in the linker zone. Quantum Theory of Atoms in Molecules (QTAIM) and electron localization function (ELF) analyses highlight the roles of hydrogen bonding and steric hindrance. MD simulations unveil temperature-dependent hydration dynamics, with structural transitions marked by changes in the radius of gyration (Rg) and the radial distribution function (RDF), aligning with DFT findings. Our work goes beyond prior studies by combining a DFT, QTAIM and MD simulations approach across different PNIPAM monomer-to-30mer structures. It introduces a systematic quantification of pseudo-saturation thresholds and explores water clustering dynamics with structural specificity, which have not been previously reported in the literature. These novel insights establish a more complete molecular-level picture of PNIPAM hydration behavior and temperature responsiveness, emphasizing the importance of amide hydrogen and carbonyl oxygen sites in hydrogen bonding, which weakens above the lower critical solution temperature (LCST), resulting in increased hydrophobicity and paving the way for understanding water sorption mechanisms, offering guidance for future applications such as dehumidification and atmospheric water harvesting. 

Space cooling constitutes >10% of worldwide electricity consumption and is anticipated to rise swiftly due to intensified heatwaves under emerging climate change. The escalating electricity demand for cooling services will challenge already stressed power grids, especially during peak times of demand. To address this, the adoption of demand response to adjust building energy use on the end-user side becomes increasingly important to adapt future smart buildings with rapidly growing renewable energy sources. However, existing demand response strategies predominantly explore sensible cooling energy as flexible building load while neglecting latent cooling energy, which constitutes significant portions of total energy use of buildings in humid climates. Hence, this paper aims to evaluate the demand response potential by adjusting latent cooling energy through ventilation control for typical medium commercial office buildings in four representative cities across different humid climate zones, i.e., Miami, Huston, Atlanta, and New York in the United States (US). As the first step, the sensible heat ratio, defined as sensible cooling load to total building load (involving both sensible and latent load), in different humid climates are calculated. Subsequently, the strategy to adjust building latent load through ventilation control (LLVC) is explored and implemented for demand response considering the balance of energy shifting, indoor air quality, and energy cost. Results reveal that adjusting building ventilation is capable of achieving 30%–40% Heating, Ventilation, and Air-conditioning (HVAC) cooling demand flexibility during HVAC operation while among this, the latent cooling energy contributes 56% ~ 66.4% to the overall demand flexibility. This work provides a feasible way to improve electricity grid flexibility in humid climates, emphasizing the significant role of adjusting latent cooling energy in building demand response.