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ABSTRACT
A dedicated outdoor air system (DOAS) directly supplies occupied zones with 100% outdoor air. Notably, DOAS with a proper operation strategy can provide sufficient ventilation and dehumidification while achieving energy efficiency. In the last decade, there have been efforts to develop advanced control sequences (e.g, optimal or near-optimal control) for DOAS operations. Nevertheless, limited studies have been conducted to analyze the energy-saving potential of implementing such DOAS controls in different climate zones with different DOAS configurations.
For this study, we developed 90 Energy Plus primary school models accommodating different DOAS configurations by changing the type of DOAS system, system sizing and the terminal units, under selected ASHRAE climate zones (i.e., 2A, 3B, 4A, 4C, 6A, and 6B). We used genetic algorithm-based optimization to determine the optimal DOAS SAT that would minimize the operational cost of the system. It was found that optimizing the DOAS SAT control sequence with specific system configurations across all climate zones could save 5-34% in operational costs throughout selected periods (i.e., 4 weeks for heating, cooling, and shoulder seasons, respectively) compared with a typical rule-based control (i.e., outdoor air temperature-based reset control).
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INTRODUCTION
It is acknowledged that improving indoor air quality (IAQ) in buildings is important for better human comfort, health, and even productivity (Dorizas, Assimakopoulos, and Santamouris 2015). The significance has particularly been increased in the post-COVID-19 era. Maintaining good IAQ, however, is likely to require a larger amount of energy consumption (SeppÇnen 2008). In this regard, achieving enhanced IAQ with higher energy efficiency is desirable. For this purpose, dedicated outdoor air systems (DOAS) in buildings has gained considerable attention. Many studies demonstrated that DOAS with proper designs and operations could provide sufficient ventilation and dehumidification while being highly energy efficient (Choi et al. 2023; ASHRAE 2017; Jeong, Mumma, and Bahnfleth 2003; Mumma 2001a).
As defined in the ASHRAE Design Guide for Dedicated Outdoor Air Systems'. "DOAS uses separate equipment to condition all the outdoor air brought into a building for ventilation and delivers it to each occupied space, either directly or in conjunction with local or central heating, ventilation, and air conditioning (HVAC) units serving those same spaces. The local or central HVAC units are used to maintain space temperature (ASHRAE 2017)."...