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Distributed Demand-controlled Ventilation for Improving Indoor Air Quality
Start Date 05/01/2007
End Date 04/30/2009
Primary Partner: Syracuse University
Primary Contact: Khalifa, H. Ezzat - Professor
Project Type: CARTI II
Technical Description:
Demand-controlled ventilation (DCV) modulates the amount of fresh air brought into a building based on carbon dioxide (CO2) generated by occupant activities. DCV provides acceptable indoor air quality (IAQ) at higher energy efficiency. In a recent NIST study, it was shown that CO2-based DCV could result in increased levels of other pollutants (e.g., volatile organic carbon compounds) emitted by sources unrelated to occupancy. ASHRAE 62-2004 recommends that ventilation rates be based not only on occupant density, but also floor area (a surrogate for passive emissions) and ventilation efficiency. Significant improvements in IAQ, comfort, and energy efficiency can be achieved by providing fresh air directly to the individual office spaces based on need through distributed demand-controlled ventilations systems (DDCV). This can be achieved by employing hierarchical intelligent control systems that dynamically optimize and regulate fresh air supply to each office/cubicle based on considering both sensed contaminant levels and coupled dynamics among office spaces. This proposal is aimed at the development of practical methods, algorithms, and tools to optimize IAQ through DDCV.
Expected Outcomes:
The results of this work are essential to the development and deployment of novel DDCV systems at the Syracuse Center of Excellence (SyracuseCoE) Headquarters, specifically the Total Indoor Environmental Quality (TIEQ) laboratory, fulfilling the core mission of the SyracuseCoE in the area of intelligent built environmental systems.
Accomplishments:
TC++ models were validated against existing software packages such as TRNFlow. The TC++ model was further used in a study of a DDCV implementation in a model office building. A variety of DDCV scenarios were run utilizing ASHRAE limits and standards. The simulation results show that at the same energy consumption as the ASHRAE Standard case, the DDCV scenario can simultaneously improve both CO2 exposure and VOC exposure.
During the current progress period, in combination with related EPA-funded projects, we investigated the utility of off-the-shelf CO2 sensors for DDCV. We conducted experiments with 16 such CO2 sensors in a sealed calibration chamber, an open cubicle environment, and a closed office. In the experiments conducted in the open cubicle environment, it was found that the CO2 concentrations measured by the sensors are highly sensitive to the location of the sensors relative to the occupants, and thus are unreliable for use as the basis of control decisions. Due to the above-mentioned shortcoming in using off-the-shelf CO2 sensors for control, our current work focuses on DDCV techniques that use known occupancy as the basis for control decisions. The results of preliminary simulations show that for a slight increase in occupant CO2 exposure, an energy consumption improvement of greater than 5% is possible in comparison to CO2-based DDCV.
Benefits:
New innovations in the application of DDCV will provide healthier, more comfortable indoor environments, while at the same time reducing the amount of energy used.
For more information: http://www.ecs.syr.edu/facultystaff.aspx?id=1958
Publications:
D. Demetriou and H. E. Khalifa, " Evaluation of Distributed Environmental Control Systems for Improving IAQ and Reducing Energy Consumption in Office Buildings.” Building Simulation: An International Journal, Vol. 2(3), 2009.
M. Koni, C. Isik, H. E. Khalifa, and H. J. Palanthandalam-Madapusi. "Utility of CO2 Sensors for Distributed Demand Control Ventilation," Healthy Buildings, Syracuse, NY, September 2009.
D. Demetriou and H. E. Khalifa, "Comparison of Distributed Demand Controlled Ventilation in Various United States Climates," Healthy Buildings, Syracuse, NY, September 2009.
D. Demetriou and H. E. Khalifa, "A Fast Executing Model for Whole Building Simulations of Distributed Ventilation Systems," 11th International Conference on Air Distribution in Rooms, Busan, Korea, May 24 - 27, 2009.
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