PNNL

Abstract

Variable-air-volume (VAV) systems are used in many office buildings. The minimum air flow rate setting of VAV terminal boxes has significant impacts on energy consumption and indoor air quality. Conventional controls usually have the terminal’s minimum air flow rate at a constant (e.g., 30% or more of the terminal design air flow rate), irrespective of the occupancy status. Such practice may cause problems like excessive simultaneous heating and cooling, under or over ventilation and thermal comfort issues. This paper examines the potential of energy savings from occupancy-based controls (OBCs). The sensed occupancy information, either occupant presence (conventional OBC) or people count (advanced OBC), is used to determine the air flow rate of terminal boxes, the thermostat set points, and the lighting control. Using EnergyPlus, a whole building energy modeling software, the energy savings of OBC strategies are evaluated for representative existing medium office buildings in XXX climate locations in the U.S. The simulation results show that the conventional OBC, based on occupant presence, can save whole building energy use in the range from 8% in Miami (hot climate) to 13% in Chicago (cold climate) while the advanced OBC, based on people counting, can save energy by 11% to 23%. The outdoor-air fraction of the supply air from air-handling units significantly affects the potential energy savings from the advanced OBC strategy. In additional to the energy savings, the advanced OBC satisfies the zone ventilation during all occupied hours over the whole year.