New Optimal Supply Air Temperature and Minimum Zone Air Flow Resetting Strategies for VAV Systems

Nassif, Nabil; Tahmasebi, Mostafa; Ridwana, Iffat; Ebrahimi, Pejman

doi:10.3390/buildings12030348

Cited by 11 publications

(6 citation statements)

References 13 publications

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“…Equations ( 5) and ( 6) can be organized into the simpler expression as shown in equations (7) and (8).…”

Section: Methodsmentioning

confidence: 99%

“…The airflow was assumed to enter the adherent jet zone. From equation (7), the velocity decay coefficient K is only related to the adherent jet zone, and the range of the free jet and transition zone are uniformly attributed to the constant x 0 . In order not to affect the overall data fitting accuracy, point 1 was removed when calculating the velocity decay curve.…”

Section: Validationmentioning

confidence: 99%

“…5 The minimum air volume setting value can affect the total energy consumption of the system. 6,7 At present, the minimum airflow of VAV is usually set to 30%∼50% of the maximum. The research results of Kang et al 8 provide a reference for setting minimum air volume below 20%.…”

Section: Introductionmentioning

confidence: 99%

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An active diffuser control method based on the constant jet throw for improving airflow distribution in variable air volume systems

Song

Zhang

et al. 2023

Indoor and Built Environment

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The air supply of the variable air volume (VAV) system could decrease with indoor load, resulting in reduced indoor comfort. An active diffuser is a good solution, but its adjustment process is often neglected. In most cases, the diffuser maintains the air supply velocity constant by controlling the air supply area. This traditional control method based on constant velocity (CMV) often fails to reach jet throw expectation due to the continuous change of airflow diffusion performance during the adjustment process. In this study, a new control method based on constant jet throw length (CMT) is proposed and applied in two typical rooms (office and conference). The results show that the CMT could increase the throw length in the spreading zone and enhances the airflow at the wall zone and ground zone, providing a more uniform temperature and more comfortable indoor environment. In 40% air volume condition, the air diffusion performance index (ADPI) in the office using CMT has improved from 89.66% to 95.69% compared to CMV, while ADPI in the conference improved from 92.11% to 97.37%. This study can help designers determine the optimal adjustment scheme to improve the adaptability of the active diffuser to the VAV system.

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“…Equations ( 5) and ( 6) can be organized into the simpler expression as shown in equations (7) and (8).…”

Section: Methodsmentioning

confidence: 99%

Section: Validationmentioning

confidence: 99%

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An active diffuser control method based on the constant jet throw for improving airflow distribution in variable air volume systems

Song

Zhang

et al. 2023

Indoor and Built Environment

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“…However, resetting the SAT as a function of OAT may not be the best strategy as there may be zones in cooling even during colder seasons. As a response, Nassif [27] has proposed using zone heating or cooling control loops to reset the supply air temperature. In this strategy, the number of zones in cooling or heating at any time is counted, and the zone value is assigned to be 1 (one) if the zone is in a cooling or dead band.…”

Section: Proposed Supply Air Temperature (Sat) Reset Strategymentioning

confidence: 99%

Solutions to Achieve High-Efficient and Clean Building HVAC Systems

2023

Self Cite

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The building sector accounts for a substantial amount of energy consumption, resulting in higher carbon emissions and environmental impact worldwide. Electrification and energy efficiency in building systems can be the key to decarbonization in buildings. This research proposes new heating and cooling loops consisting of heat pumps to lower natural gas usage in building systems. Typical chillers and boilers in the cooling and heating loops are replaced with heat pumps to serve the loads and maintain thermal comfort in the building. In addition, a new optimal supply air temperature (SAT) reset strategy is also implemented with the proposed configuration for better system performance. A large multi-zone office building is simulated as a case study to measure the conventional system’s electricity and natural gas consumption and the proposed design. Even with heat pumps that use electricity as the energy source, electricity consumption is reduced by 3.3% to 11.8% in different climate zones for the proposed system. On the other hand, 10.2% to 67% lower natural gas is consumed when the proposed system and the optimal SAT reset are utilized. The carbon emission is also reduced by 10.8% to 38% compared to the conventional system. The results show that the proposed design and optimization strategy can lead to significant energy and cost savings in conjunction with lower carbon emissions.

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“…Saloux and Zhang [96] evaluated the impact of a supply air temperature reset strategy based on outdoor air enthalpy for an existing large commercial building; they found that the building cooling load could be decreased by 13%, resulting in a 9% reduction in cooling system electric energy. Nassif et al [107] built upon G36 to develop new strategies to reset supply air temperature and zone minimum airflow rate setpoints for typical VAV systems; the authors showed a potential of 2-6% fan energy decrease and 8-34% heating load reduction. Lu et al [108] compared the performance of G36 for supply air temperature and static difference pressure setpoints with intelligent controllers (optimization-based controller and deep reinforcement-learning-based controller) for a simulated medium-sized office building with a multi-zone variable air volume cooling system.…”

Section: High-performance Control Sequencesmentioning

confidence: 99%

A Critical Perspective on Current Research Trends in Building Operation: Pressing Challenges and Promising Opportunities

Saloux,

Zhang,

Candanedo

2023

Buildings

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Despite the development of increasingly efficient technologies and the ever-growing amount of available data from Building Automation Systems (BAS) and connected devices, buildings are still far from reaching their performance potential due to inadequate controls and suboptimal operation sequences. Advanced control methods such as model-based controls or model-based predictive controls (MPC) are widely acknowledged as effective solutions for improving building operation. Although they have been well-investigated in the past, their widespread adoption has yet to be reached. Based on our experience in this field, this paper aims to provide a broader perspective on research trends on advanced controls in the built environment to researchers and practitioners, as well as to newcomers in the field. Pressing challenges are explored, such as inefficient local controls (which must be addressed in priority) and data availability and quality (not as good as expected, despite the advent of the digital era). Other major hurdles that slow down the large-scale adoption of advanced controls include communication issues with BAS and lack of guidelines and standards tailored for controls. To encourage their uptake, cost-effective solutions and successful case studies are required, which need to be further supported by better training and engagement between the industry and research communities. This paper also discusses promising opportunities: while building modelling is already playing a critical role, data-driven methods and data analytics are becoming a popular option to improve buildings controls. High-performance local and supervisory controls have emerged as promising solutions. Energy flexibility appears instrumental in achieving decarbonization targets in the built environment.

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New Optimal Supply Air Temperature and Minimum Zone Air Flow Resetting Strategies for VAV Systems

Cited by 11 publications

References 13 publications

An active diffuser control method based on the constant jet throw for improving airflow distribution in variable air volume systems

An active diffuser control method based on the constant jet throw for improving airflow distribution in variable air volume systems

Solutions to Achieve High-Efficient and Clean Building HVAC Systems

A Critical Perspective on Current Research Trends in Building Operation: Pressing Challenges and Promising Opportunities

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