Experimental and theoretical evaluation of the effect of CO(2)-based demand-controlled ventilation strategies on energy consumption

The ASHRAE Standard 62-1989 recommends two approaches for determining ventilation rates for buildings. The first, the Ventilation Rate Procedure, specifies a fixed rate for each building type based on its function. The second, the Air Quality Procedure, allows the use of lower ventilation rates than those mentioned in the Ventilation Rate Procedure, as long as the indoor air quality in the building's zones is maintained at the minimum required level.; This research investigates how the energy consumption in HVAC systems can be reduced based on the ASHRAE's Air Quality Procedure approach. Both the experimental and the theoretical parts of this research are based on the concept that carbon dioxide is a surrogate of indoor air quality that is easily sensed, easily controlled, and has a concentration level directly related to occupancy density.; All experiments were performed in the Joint Center for Energy Management (JCEM) at the Larson Building Systems Laboratory. A full set of experiments was performed to ensure that the setup would operate as expected and to correct all the problems related to laboratory equipment and control. In addition to the base case control strategy (20 cfm/person for office buildings), three other control strategies were evaluated: ON/OFF, linear, and proportional-integral derivative (PID). During these experiments, both the CO₂ setpoint and the temperature were controlled at 900 ppm and 70°F, respectively. The analysis of the experiments revealed that these control strategies consume less outside air, and thus, less energy. An uncertainty analysis was also performed for all the experimental results.; In the theoretical part of this research, a multi-zone contaminant transport model and a contaminant control model were developed. These models were validated using the experimental work. Variable-air volume (VAV) and HVAC equipment models were also developed to determine the energy performance. All four models have been integrated as an IAQ/HVAC model to determine the energy consumption of the control strategies. The energy consumption of each control strategy has been calculated for a number of US cities to reveal savings or penalties.; The sensitivity analysis revealed that the outside air leakage from the outside damper, the use of a temperature economizer, the proportional gain constant (K_p) in the PID control equation, and the CO₂ setpoint can have an impact energy on consumption.