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Simulation-based study on CO2-based demand controlled ventilation strategies for multiple zone variable air volume systems
Demand-Controlled Ventilation (DCV) is a ventilation control strategy that provides automatic reduction of outdoor air intake below design rates when the actual occupancy of spaces served by the system is less than design occupancy. This research aimed to propose CO2 and occupancy sensor-based DCV for multiple-zone VAV systems and to evaluate the proposed DCV control strategies with energy simulation and airflow simulation.^ For all three control strategies proposed and developed in this research, CO2 sensors, occupancy-sensors, and airflow measurement were used to calculate the required OA rate to each zone. Those zones without any sensors were assumed to be always occupied at design population.^ The first control strategy used bioeffluent load estimated with steady-state assumption to calculate and dynamically reset system OA rate minimum setpoint by solving the multiple-zone system equations for current conditions ("CO 2-based DR"). The second and third DCV control strategies were developed to reset dynamically the zone primary airflow minimum setpoint to maintain system as a target OA rate and a target system ventilation efficiency respectively ("CO2-based DR+ZDR_Vot" and "CO2-based DR+ZDR_Ev"). The initial zone primary airflow rate for both "CO2-based DR+ZDR" are set as lower values compared to "CO2-based DR". ^ All three proposed DCV control strategies were simulated using both the energy simulation program (EnergyPlus®) and airflow mass balance models (EES – Engineering Equation Solver) for 16 locations. A building simulation model was developed to represent a large classroom/office building with a single path VAV system. Energy savings potentials of these proposed DCV control strategies were estimated by comparing with the baseline case "Without DCV". ^ Based on the simulation results, all three proposed DCV control strategies comply with both ASHRAE Standard 90.1-2010 and ASHRAE Standard 62.1-2010. Either option of CO2-based DR+ ZDR consumes less energy when compared to CO2-based DR and the baseline case. Therefore, control strategies based on these approaches should be considered for CO2-based DCV for multiple zone single duct VAV systems with terminal reheat. Implementation of such control approaches was outside the scope of this research.^
Lin, Xingbin, "Simulation-based study on CO2-based demand controlled ventilation strategies for multiple zone variable air volume systems" (2013). ETD collection for University of Nebraska - Lincoln. AAI3604771.